draft-ietf-manet-olsr-10.txt   draft-ietf-manet-olsr-11.txt 
INTERNET-DRAFT Thomas Clausen, Editor INTERNET-DRAFT Thomas Clausen, Editor
IETF MANET Working Group Philippe Jacquet, Editor IETF MANET Working Group Philippe Jacquet, Editor
Expiration: 02 November 2003 Project Hipercom Expiration: 03 Janyary 2003 Project Hipercom
INRIA Rocquencourt, France INRIA Rocquencourt, France
02 May 2003 03 July 2003
Optimized Link State Routing Protocol Optimized Link State Routing Protocol
draft-ietf-manet-olsr-10.txt draft-ietf-manet-olsr-11.txt
Status of this Memo Status of this Memo
This document is a submission by the Mobile Ad Hoc Networking Working This document is a submission by the Mobile Ad Hoc Networking Working
Group of the Internet Engineering Task Force (IETF). Comments should Group of the Internet Engineering Task Force (IETF). Comments should
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Abstract Abstract
This document describes the Optimized Link State Routing (OLSR) This document describes the Optimized Link State Routing (OLSR)
protocol for mobile ad hoc networks. The protocol is an optimization protocol for mobile ad hoc networks. The protocol is an optimization
of the classical link state algorithm tailored to the requirements of of the classical link state algorithm tailored to the requirements of
a mobile wireless LAN. The key concept used in the protocol is that a mobile wireless LAN. The key concept used in the protocol is that
of multipoint relays (MPRs) [1], [2]. MPRs are selected nodes which of multipoint relays (MPRs). MPRs are selected nodes which forward
forward broadcast messages during the flooding process. This broadcast messages during the flooding process. This technique
technique substantially reduces the message overhead as compared to a substantially reduces the message overhead as compared to a classical
classical flooding mechanism, where every node retransmits each flooding mechanism, where every node retransmits each message when it
message when it receives the first copy of the message. In OLSR, receives the first copy of the message. In OLSR, link state
link state information is generated only by nodes elected as MPRs. information is generated only by nodes elected as MPRs. Thus, a
Thus, a second optimization is achieved by minimizing the number of second optimization is achieved by minimizing the number of control
control messages flooded in the network. As a third optimization, an messages flooded in the network. As a third optimization, an MPR
MPR node may chose to report only links between itself and its MPR node may chose to report only links between itself and its MPR
selectors. Hence, as contrary to the classic link state algorithm, selectors. Hence, as contrary to the classic link state algorithm,
partial link state information is distributed in the network. This partial link state information is distributed in the network. This
information is then used by for route calculation. OLSR provides information is then used by for route calculation. OLSR provides
optimal routes (in terms of number of hops). The protocol is optimal routes (in terms of number of hops). The protocol is
particularly suitable for large and dense networks as the technique particularly suitable for large and dense networks as the technique
of MPRs works well in this context. of MPRs works well in this context.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.1. OLSR Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
1.2. OLSR Terminology . . . . . . . . . . . . . . . . . . . . . . . 7 1.2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . . 10
1.4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . . 10 1.4. Multipoint Relays . . . . . . . . . . . . . . . . . . . . . . . 11
1.5. Multipoint Relays . . . . . . . . . . . . . . . . . . . . . . . 11
2. Protocol Functioning . . . . . . . . . . . . . . . . . . . . . . 12 2. Protocol Functioning . . . . . . . . . . . . . . . . . . . . . . 12
2.1. Core Functioning . . . . . . . . . . . . . . . . . . . . . . . 12 2.1. Core Functioning . . . . . . . . . . . . . . . . . . . . . . . 12
2.2. Auxiliary Functioning . . . . . . . . . . . . . . . . . . . . . 14 2.2. Auxiliary Functioning . . . . . . . . . . . . . . . . . . . . . 14
3. Packet Format and Forwarding . . . . . . . . . . . . . . . . . . 15 3. Packet Format and Forwarding . . . . . . . . . . . . . . . . . . 15
3.1. Protocol and Port Number . . . . . . . . . . . . . . . . . . . 16 3.1. Protocol and Port Number . . . . . . . . . . . . . . . . . . . 16
3.2. Main Address . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.2. Main Address . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3. Packet Format . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3. Packet Format . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3.1. Packet Header . . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.1. Packet Header . . . . . . . . . . . . . . . . . . . . . . . . 17
3.3.2. Message Header . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.2. Message Header . . . . . . . . . . . . . . . . . . . . . . . 17
3.4. Packet Processing and Message Flooding . . . . . . . . . . . . 19 3.4. Packet Processing and Message Flooding . . . . . . . . . . . . 19
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13.1. Interoperability Considerations . . . . . . . . . . . . . . . 60 13.1. Interoperability Considerations . . . . . . . . . . . . . . . 60
14. Link Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . 60 14. Link Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . 60
14.1. Local Link Set . . . . . . . . . . . . . . . . . . . . . . . . 61 14.1. Local Link Set . . . . . . . . . . . . . . . . . . . . . . . . 61
14.2. Hello Message Generation . . . . . . . . . . . . . . . . . . . 61 14.2. Hello Message Generation . . . . . . . . . . . . . . . . . . . 61
14.3. Hysteresis Strategy . . . . . . . . . . . . . . . . . . . . . 62 14.3. Hysteresis Strategy . . . . . . . . . . . . . . . . . . . . . 62
14.4. Interoperability Considerations . . . . . . . . . . . . . . . 64 14.4. Interoperability Considerations . . . . . . . . . . . . . . . 64
15. Redundant Topology Information . . . . . . . . . . . . . . . . . 64 15. Redundant Topology Information . . . . . . . . . . . . . . . . . 64
15.1. TC_REDUNDANCY Parameter . . . . . . . . . . . . . . . . . . . 64 15.1. TC_REDUNDANCY Parameter . . . . . . . . . . . . . . . . . . . 64
15.2. Interoperability Considerations . . . . . . . . . . . . . . . 65 15.2. Interoperability Considerations . . . . . . . . . . . . . . . 65
16. MPR Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . 65 16. MPR Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . 65
16.1. MPR_COVERAGE Parameter . . . . . . . . . . . . . . . . . . . . 66 16.1. MPR_COVERAGE Parameter . . . . . . . . . . . . . . . . . . . . 65
16.2. MPR Computation . . . . . . . . . . . . . . . . . . . . . . . 66 16.2. MPR Computation . . . . . . . . . . . . . . . . . . . . . . . 66
16.3. Interoperability Considerations . . . . . . . . . . . . . . . 67 16.3. Interoperability Considerations . . . . . . . . . . . . . . . 67
17. IPv6 Considerations . . . . . . . . . . . . . . . . . . . . . . 67 17. IPv6 Considerations . . . . . . . . . . . . . . . . . . . . . . 67
18. Proposed Values for Constants . . . . . . . . . . . . . . . . . 68 18. Proposed Values for Constants . . . . . . . . . . . . . . . . . 68
18.1. Setting emission interval and holding times . . . . . . . . . 68 18.1. Setting emission interval and holding times . . . . . . . . . 68
18.2. Emission Interval . . . . . . . . . . . . . . . . . . . . . . 68 18.2. Emission Interval . . . . . . . . . . . . . . . . . . . . . . 68
18.3. Holding time . . . . . . . . . . . . . . . . . . . . . . . . . 69 18.3. Holding time . . . . . . . . . . . . . . . . . . . . . . . . . 69
18.4. Message Types . . . . . . . . . . . . . . . . . . . . . . . . 70 18.4. Message Types . . . . . . . . . . . . . . . . . . . . . . . . 70
18.5. Link Types . . . . . . . . . . . . . . . . . . . . . . . . . . 70 18.5. Link Types . . . . . . . . . . . . . . . . . . . . . . . . . . 70
18.6. Neighbor Types . . . . . . . . . . . . . . . . . . . . . . . . 70 18.6. Neighbor Types . . . . . . . . . . . . . . . . . . . . . . . . 70
18.7. Link Hysteresis . . . . . . . . . . . . . . . . . . . . . . . 71 18.7. Link Hysteresis . . . . . . . . . . . . . . . . . . . . . . . 70
18.8. Willingness . . . . . . . . . . . . . . . . . . . . . . . . . 71 18.8. Willingness . . . . . . . . . . . . . . . . . . . . . . . . . 71
18.9. Misc. Constants . . . . . . . . . . . . . . . . . . . . . . . 72 18.9. Misc. Constants . . . . . . . . . . . . . . . . . . . . . . . 72
19. Sequence Numbers . . . . . . . . . . . . . . . . . . . . . . . . 72 19. Sequence Numbers . . . . . . . . . . . . . . . . . . . . . . . . 72
20. Security Considerations . . . . . . . . . . . . . . . . . . . . 72 20. Security Considerations . . . . . . . . . . . . . . . . . . . . 72
20.1. Confidentiality . . . . . . . . . . . . . . . . . . . . . . . 73 20.1. Confidentiality . . . . . . . . . . . . . . . . . . . . . . . 72
20.2. Integrity . . . . . . . . . . . . . . . . . . . . . . . . . . 73 20.2. Integrity . . . . . . . . . . . . . . . . . . . . . . . . . . 73
20.3. Interaction with External Routing Domains . . . . . . . . . . 74 20.3. Interaction with External Routing Domains . . . . . . . . . . 74
20.4. Node Identity . . . . . . . . . . . . . . . . . . . . . . . . 74 20.4. Node Identity . . . . . . . . . . . . . . . . . . . . . . . . 75
21. Flow and congestion control . . . . . . . . . . . . . . . . . . 75 21. Flow and congestion control . . . . . . . . . . . . . . . . . . 75
22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 75 22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 75
23. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 75 23. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 76
24. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 76 24. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 76
25. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 77 25. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 77
26. References . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 26. References . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
1. Introduction 1. Introduction
The Optimized Link State Routing Protocol (OLSR) is developed for The Optimized Link State Routing Protocol (OLSR) is developed for
mobile ad hoc networks. It operates as a table driven, proactive mobile ad hoc networks. It operates as a table driven, proactive
protocol, i.e exchanges topology information with other nodes of the protocol, i.e exchanges topology information with other nodes of the
network regularly. Each node selects a set of its neighbor nodes as network regularly. Each node selects a set of its neighbor nodes as
"multipoint relays" (MPR). In OLSR, only nodes, selected as such "multipoint relays" (MPR). In OLSR, only nodes, selected as such
MPRs, are responsible for forwarding control traffic, intended for MPRs, are responsible for forwarding control traffic, intended for
diffusion into the entire network. MPRs provide an efficient mecha- diffusion into the entire network. MPRs provide an efficient
nism for flooding control traffic by reducing the number of transmis- mechanism for flooding control traffic by reducing the number of
sions required. transmissions required.
Nodes, selected as MPRs, also have a special responsibility when Nodes, selected as MPRs, also have a special responsibility when
declaring link state information in the network. Indeed, the only declaring link state information in the network. Indeed, the only
requirement for OLSR to provide shortest path routes to all destina- requirement for OLSR to provide shortest path routes to all
tions is that MPR nodes declare link-state information for their MPR destinations is that MPR nodes declare link-state information for
selectors. Additional available link-state information may be uti- their MPR selectors. Additional available link-state information may
lized, e.g. for redundancy. be utilized, e.g. for redundancy.
Nodes which have been selected as multipoint relays by some neighbor Nodes which have been selected as multipoint relays by some neighbor
node(s) announce this information periodically in their control mes- node(s) announce this information periodically in their control
sages. Thereby a node announces to the network, that it has reacha- messages. Thereby a node announces to the network, that it has
bility to the nodes which have selected it as an MPR. In route cal- reachability to the nodes which have selected it as an MPR. In route
culation, the MPRs are used to form the route from a given node to calculation, the MPRs are used to form the route from a given node to
any destination in the network. Furthermore, the protocol uses the any destination in the network. Furthermore, the protocol uses the
MPRs to facilitate efficient flooding of control messages in the net- MPRs to facilitate efficient flooding of control messages in the
work. network.
A node selects MPRs from among its one hop neighbors with "symmetri- A node selects MPRs from among its one hop neighbors with
cal", i.e. bi-directional, linkages. Therefore, selecting the route "symmetrical", i.e. bi-directional, linkages. Therefore, selecting
through MPRs automatically avoids the problems associated with data the route through MPRs automatically avoids the problems associated
packet transfer over uni-directional links (such as the problem of with data packet transfer over uni-directional links (such as the
not getting link-layer acknowledgments for data packets at each hop, problem of not getting link-layer acknowledgments for data packets at
for link-layers employing this technique for unicast traffic). each hop, for link-layers employing this technique for unicast
traffic).
OLSR is developed to work independently from other protocols. Like- OLSR is developed to work independently from other protocols.
wise, OLSR makes no assumptions about the underlying link-layer. Likewise, OLSR makes no assumptions about the underlying link-layer.
OLSR inherits the concept of forwarding and relaying from HIPERLAN (a OLSR inherits the concept of forwarding and relaying from HIPERLAN (a
MAC layer protocol) which is standardized by ETSI [3]. The protocol MAC layer protocol) which is standardized by ETSI [3]. The protocol
is developed in the IPANEMA project (part of the Euclid program) and is developed in the IPANEMA project (part of the Euclid program) and
in the PRIMA project (part of the RNRT program). in the PRIMA project (part of the RNRT program).
1.1. Changes 1.1. OLSR Terminology
Major changes from version 09 to version 10
- Designated editors included
- Flow-control section added
- Misc. editorial changes.
1.2. OLSR Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [5]. Addi- document are to be interpreted as described in RFC2119 [5].
tionally, this document uses the following terminology: Additionally, this document uses the following terminology:
node node
A MANET router which implements the Optimized Link State Rout- A MANET router which implements the Optimized Link State
ing protocol as specified in this document. Routing protocol as specified in this document.
OLSR interface OLSR interface
A network device participating in a MANET running OLSR. A A network device participating in a MANET running OLSR. A
node may have several OLSR interfaces, each interface assigned node may have several OLSR interfaces, each interface assigned
an unique IP address. an unique IP address.
non OLSR interface non OLSR interface
A network device, not participating in a MANET running OLSR. A network device, not participating in a MANET running OLSR.
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A multiple OLSR interface node MUST choose one of its OLSR A multiple OLSR interface node MUST choose one of its OLSR
interface addresses as its "main address" (equivalent of interface addresses as its "main address" (equivalent of
"router ID" or "node identifier"). It is of no importance "router ID" or "node identifier"). It is of no importance
which address is chosen, however a node SHOULD always use the which address is chosen, however a node SHOULD always use the
same address as its main address. same address as its main address.
neighbor node neighbor node
A node X is a neighbor node of node Y if node Y can hear node A node X is a neighbor node of node Y if node Y can hear node
X (i.e. a bidirectional link exists between an OLSR inter- X (i.e. a bidirectional link exists between an OLSR
faces on node X and an OLSR interface on Y). interfaces on node X and an OLSR interface on Y).
2-hop neighbor 2-hop neighbor
A node heard by a neighbor. A node heard by a neighbor.
strict 2-hop neighbor strict 2-hop neighbor
a 2-hop neighbor which is not the node itself or a neighbor of a 2-hop neighbor which is not the node itself or a neighbor of
the node, and in addition is a neighbor of a neighbor, with the node, and in addition is a neighbor of a neighbor, with
willingness different from WILL_NEVER, of the node. willingness different from WILL_NEVER, of the node.
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direction. direction.
symmetric 1-hop neighborhood symmetric 1-hop neighborhood
The symmetric 1-hop neighborhood of any node X is the set of The symmetric 1-hop neighborhood of any node X is the set of
nodes which have at least one symmetric link to X. nodes which have at least one symmetric link to X.
symmetric 2-hop neighborhood symmetric 2-hop neighborhood
The symmetric 2-hop neighborhood of X is the set of nodes, The symmetric 2-hop neighborhood of X is the set of nodes,
excluding X itself, which have a symmetric link to the sym- excluding X itself, which have a symmetric link to the
metric 1-hop neighborhood of X. symmetric 1-hop neighborhood of X.
symmetric strict 2-hop neighborhood symmetric strict 2-hop neighborhood
The symmetric 2-hop neighborhood of X is the set of nodes, The symmetric 2-hop neighborhood of X is the set of nodes,
excluding X itself and its neighbors, which have a symmetric excluding X itself and its neighbors, which have a symmetric
link to some symmetric 1-hop neighbor, with willingness dif- link to some symmetric 1-hop neighbor, with willingness
ferent of WILL_NEVER, of X. different of WILL_NEVER, of X.
1.3. Applicability 1.2. Applicability
OLSR is a proactive routing protocol for mobile ad-hoc networks OLSR is a proactive routing protocol for mobile ad-hoc networks
(MANETs). It is well suited to large and dense mobile networks, as (MANETs) [1], [2]. It is well suited to large and dense mobile
the optimization achieved using the MPRs works well in this context. networks, as the optimization achieved using the MPRs works well in
The larger and more dense a network, the more optimization can be this context. The larger and more dense a network, the more
achieved as compared to the classic link state algorithm. OLSR uses optimization can be achieved as compared to the classic link state
hop-by-hop routing, i.e. each node uses its local information to algorithm. OLSR uses hop-by-hop routing, i.e. each node uses its
route packets. local information to route packets.
OLSR is well suited for networks, where the traffic is random and OLSR is well suited for networks, where the traffic is random and
sporadic between a larger set of nodes rather than being almost sporadic between a larger set of nodes rather than being almost
exclusively between a small specific set of nodes. As a proactive exclusively between a small specific set of nodes. As a proactive
protocol, OLSR is also suitable for scenarios where the communicating protocol, OLSR is also suitable for scenarios where the communicating
pairs change over time: no additional control traffic is generated in pairs change over time: no additional control traffic is generated in
this situation since routes are maintained for all known destinations this situation since routes are maintained for all known destinations
at all times. at all times.
1.4. Protocol Overview 1.3. Protocol Overview
OLSR is a proactive routing protocol for mobile ad hoc networks. The OLSR is a proactive routing protocol for mobile ad hoc networks. The
protocol inherits the stability of a link state algorithm and has the protocol inherits the stability of a link state algorithm and has the
advantage of having routes immediately available when needed due to advantage of having routes immediately available when needed due to
its proactive nature. OLSR is an optimization over the classical its proactive nature. OLSR is an optimization over the classical
link state protocol, tailored for mobile ad hoc networks. link state protocol, tailored for mobile ad hoc networks.
OLSR minimizes the overhead from flooding of control traffic by using OLSR minimizes the overhead from flooding of control traffic by using
only selected nodes, called MPRs, to retransmit control messages. only selected nodes, called MPRs, to retransmit control messages.
This technique significantly reduces the number of retransmissions This technique significantly reduces the number of retransmissions
required to flood a message to all nodes in the network. Secondly, required to flood a message to all nodes in the network. Secondly,
OLSR requires only partial link state to be flooded in order to pro- OLSR requires only partial link state to be flooded in order to
vide shortest path routes. The minimal set of link state information provide shortest path routes. The minimal set of link state
required is, that all nodes, selected as MPRs, MUST declare the links information required is, that all nodes, selected as MPRs, MUST
to their MPR selectors. Additional topological information, if declare the links to their MPR selectors. Additional topological
present, MAY be utilized e.g. for redundancy purposes. information, if present, MAY be utilized e.g. for redundancy
purposes.
OLSR MAY optimize the reactivity to topological changes by reducing OLSR MAY optimize the reactivity to topological changes by reducing
the maximum time interval for periodic control message transmission. the maximum time interval for periodic control message transmission.
Furthermore, as OLSR continuously maintains routes to all destina- Furthermore, as OLSR continuously maintains routes to all
tions in the network, the protocol is beneficial for traffic patterns destinations in the network, the protocol is beneficial for traffic
where a large subset of nodes are communicating with another large patterns where a large subset of nodes are communicating with another
subset of nodes, and where the [source, destination] pairs are chang- large subset of nodes, and where the [source, destination] pairs are
ing over time. The protocol is particularly suited for large and changing over time. The protocol is particularly suited for large
dense networks, as the optimization done using MPRs works well in and dense networks, as the optimization done using MPRs works well in
this context. The larger and more dense a network, the more opti- this context. The larger and more dense a network, the more
mization can be achieved as compared to the classic link state algo- optimization can be achieved as compared to the classic link state
rithm. algorithm.
OLSR is designed to work in a completely distributed manner and does OLSR is designed to work in a completely distributed manner and does
not depend on any central entity. The protocol does NOT REQUIRE not depend on any central entity. The protocol does NOT REQUIRE
reliable transmission of control messages: each node sends control reliable transmission of control messages: each node sends control
messages periodically, and can therefore sustain a reasonable loss of messages periodically, and can therefore sustain a reasonable loss of
some such messages. Such losses occur frequently in radio networks some such messages. Such losses occur frequently in radio networks
due to collisions or other transmission problems. due to collisions or other transmission problems.
Also, OLSR does not require sequenced delivery of messages. Each Also, OLSR does not require sequenced delivery of messages. Each
control message contains a sequence number which is incremented for control message contains a sequence number which is incremented for
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Furthermore, OLSR provides support for protocol extensions such as Furthermore, OLSR provides support for protocol extensions such as
sleep mode operation, multicast-routing etc. Such extensions may be sleep mode operation, multicast-routing etc. Such extensions may be
introduced as additions to the protocol without breaking backwards introduced as additions to the protocol without breaking backwards
compatibility with earlier versions. compatibility with earlier versions.
OLSR does not require any changes to the format of IP packets. Thus OLSR does not require any changes to the format of IP packets. Thus
any existing IP stack can be used as is: the protocol only interacts any existing IP stack can be used as is: the protocol only interacts
with routing table management. with routing table management.
1.5. Multipoint Relays 1.4. Multipoint Relays
The idea of multipoint relays is to minimize the overhead of flooding The idea of multipoint relays is to minimize the overhead of flooding
messages in the network by reducing redundant retransmissions in the messages in the network by reducing redundant retransmissions in the
same region. Each node in the network selects a set of nodes in its same region. Each node in the network selects a set of nodes in its
symmetric 1-hop neighborhood which may retransmit its messages. This symmetric 1-hop neighborhood which may retransmit its messages. This
set of selected neighbor nodes is called the "Multipoint Relay" (MPR) set of selected neighbor nodes is called the "Multipoint Relay" (MPR)
set of that node. The neighbors of node N which are *NOT* in its MPR set of that node. The neighbors of node N which are *NOT* in its MPR
set, receive and process broadcast messages but do not retransmit set, receive and process broadcast messages but do not retransmit
broadcast messages received from node N. broadcast messages received from node N.
Each node selects its MPR set from among its one hop symmetric neigh- Each node selects its MPR set from among its one hop symmetric
bors. This set is selected such that it covers (in terms of radio neighbors. This set is selected such that it covers (in terms of
range) all symmetric strict 2-hop nodes. The MPR set of N, denoted radio range) all symmetric strict 2-hop nodes. The MPR set of N,
as MPR(N), is then an arbitrary subset of the symmetric 1-hop neigh- denoted as MPR(N), is then an arbitrary subset of the symmetric 1-hop
borhood of N which satisfies the following condition: every node in neighborhood of N which satisfies the following condition: every node
the symmetric strict 2-hop neighborhood of N must have a symmetric in the symmetric strict 2-hop neighborhood of N must have a symmetric
link towards MPR(N). The smaller a MPR set, the less control traffic link towards MPR(N). The smaller a MPR set, the less control traffic
overhead results from the routing protocol. [2] gives an analysis overhead results from the routing protocol. [2] gives an analysis
and example of MPR selection algorithms. and example of MPR selection algorithms.
Each node maintains information about the set of neighbors that have Each node maintains information about the set of neighbors that have
selected it as MPR. This set is called the "Multipoint Relay Selec- selected it as MPR. This set is called the "Multipoint Relay
tor set" (MPR selector set) of a node. A node obtains this informa- Selector set" (MPR selector set) of a node. A node obtains this
tion from periodic HELLO messages received from the neighbors. information from periodic HELLO messages received from the neighbors.
A broadcast message, intended to be diffused in the whole network, A broadcast message, intended to be diffused in the whole network,
coming from any of the MPR selectors of node N is assumed to be coming from any of the MPR selectors of node N is assumed to be
retransmitted by node N, if N has not received it yet. This set can retransmitted by node N, if N has not received it yet. This set can
change over time (i.e. when a node selects another MPR-set) and is change over time (i.e. when a node selects another MPR-set) and is
indicated by the selector nodes in their HELLO messages. indicated by the selector nodes in their HELLO messages.
2. Protocol Functioning 2. Protocol Functioning
This section outlines the overall protocol functioning. This section outlines the overall protocol functioning.
OLSR is modularized into a "core" of functionality, which is always OLSR is modularized into a "core" of functionality, which is always
required for the protocol to operate, and a set of auxiliary func- required for the protocol to operate, and a set of auxiliary
tions. functions.
The core specifies, in its own right, a protocol able to provide The core specifies, in its own right, a protocol able to provide
routing in a stand-alone MANET. routing in a stand-alone MANET.
Each auxiliary function provides additional functionality, which may Each auxiliary function provides additional functionality, which may
be applicable in specific scenarios. E.g. in case a node is provid- be applicable in specific scenarios. E.g. in case a node is
ing connectivity between the MANET and another routing domain. providing connectivity between the MANET and another routing domain.
All auxiliary functions are compatible, to the extent where any All auxiliary functions are compatible, to the extent where any
(sub)set of auxiliary functions may be implemented with the core. (sub)set of auxiliary functions may be implemented with the core.
Furthermore, the protocol allows heterogeneous nodes, i.e. nodes Furthermore, the protocol allows heterogeneous nodes, i.e. nodes
which implement different subsets of the auxiliary functions, to which implement different subsets of the auxiliary functions, to
coexist in the network. coexist in the network.
The purpose of dividing the functioning of OLSR into a core function- The purpose of dividing the functioning of OLSR into a core
ality and a set of auxiliary functions is to provide a simple and functionality and a set of auxiliary functions is to provide a simple
easy-to-comprehend protocol, and to provide a way of only adding com- and easy-to-comprehend protocol, and to provide a way of only adding
plexity where specific additional functionality is required. complexity where specific additional functionality is required.
2.1. Core Functioning 2.1. Core Functioning
The core functionality of OLSR specifies the behavior of a node, The core functionality of OLSR specifies the behavior of a node,
equipped with OLSR interfaces participating in the MANET and running equipped with OLSR interfaces participating in the MANET and running
OLSR as routing protocol. This includes a universal specification of OLSR as routing protocol. This includes a universal specification of
OLSR protocol messages and their transmission through the network, as OLSR protocol messages and their transmission through the network, as
well as link sensing, topology diffusion and route calculation. well as link sensing, topology diffusion and route calculation.
Specifically, the core is made up from the following components: Specifically, the core is made up from the following components:
Packet Format and Forwarding Packet Format and Forwarding
An universal specification of the packet format and an opti- An universal specification of the packet format and an
mized flooding mechanism serves as the transport mechanism for optimized flooding mechanism serves as the transport mechanism
all OLSR control traffic. for all OLSR control traffic.
Link Sensing Link Sensing
Link Sensing is accomplished through periodic emission of Link Sensing is accomplished through periodic emission of
HELLO messages over the interfaces through which connectivity HELLO messages over the interfaces through which connectivity
is checked. A separate HELLO message is generated for each is checked. A separate HELLO message is generated for each
interface and emitted in correspondence with the provisions in interface and emitted in correspondence with the provisions in
section 7. section 7.
Resulting from Link Sensing is a local link set, describing Resulting from Link Sensing is a local link set, describing
links between "local interfaces" and "remote interfaces" - links between "local interfaces" and "remote interfaces" -
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HELLO message exchange. HELLO message exchange.
Neighbor detection Neighbor detection
Given a network with only single interface nodes, a node may Given a network with only single interface nodes, a node may
deduct the neighbor set directly from the information deduct the neighbor set directly from the information
exchanged as part of link sensing: the "main address" of a exchanged as part of link sensing: the "main address" of a
single interface node is, by definition, the address of the single interface node is, by definition, the address of the
only interface on that node. only interface on that node.
In a network with multiple interface nodes, additional infor- In a network with multiple interface nodes, additional
mation is required in order to map interface addresses to main information is required in order to map interface addresses to
addresses (and, thereby, to nodes). This additional informa- main addresses (and, thereby, to nodes). This additional
tion is acquired through multiple interface declaration (MID) information is acquired through multiple interface declaration
messages, described in section 5. (MID) messages, described in section 5.
MPR Selection and MPR Signaling MPR Selection and MPR Signaling
The objective of MPR selection is for a node to select a sub- The objective of MPR selection is for a node to select a
set of its neighbors such that a broadcast message, retrans- subset of its neighbors such that a broadcast message,
mitted by these selected neighbors, will be received by all retransmitted by these selected neighbors, will be received by
nodes 2 hops away. The MPR set of a node is computed such all nodes 2 hops away. The MPR set of a node is computed such
that it, for each interface, satisfies this condition. The that it, for each interface, satisfies this condition. The
information required to perform this calculation is acquired information required to perform this calculation is acquired
throuth the periodic exchange of HELLO messages, as described throuth the periodic exchange of HELLO messages, as described
in section 6. MPR selection procedures are in section 6. MPR selection procedures are
detailed in section 8.3. detailed in section 8.3.
MPR signaling is provided in correspondence with the provi- MPR signaling is provided in correspondence with the
sions in the section 6. provisions in the section 6.
Topology Control Message Diffusion Topology Control Message Diffusion
Topology Control messages are diffused with the purpose of Topology Control messages are diffused with the purpose of
providing each node in the network with sufficient link-state providing each node in the network with sufficient link-state
information to allow route calculation. Topology Control mes- information to allow route calculation. Topology Control
sages are diffused in correspondence with the provisions in messages are diffused in correspondence with the provisions in
section 9. section 9.
Route Calculation Route Calculation
Given the link state information acquired through periodic Given the link state information acquired through periodic
message exchange, as well as the interface configuration of message exchange, as well as the interface configuration of
the nodes, the routing table for each node can be computed. the nodes, the routing table for each node can be computed.
This is detailed in section 10 This is detailed in section 10
The key notion for these mechanisms is the MPR relationship. The key notion for these mechanisms is the MPR relationship.
skipping to change at page 14, line 39 skipping to change at page 14, line 39
Neighbor detection | 8 Neighbor detection | 8
Topology discovery | 9 Topology discovery | 9
Routing table computation | 10 Routing table computation | 10
Node configuration | 11 Node configuration | 11
2.2. Auxiliary Functioning 2.2. Auxiliary Functioning
In addition to the core functioning of OLSR, there are situations In addition to the core functioning of OLSR, there are situations
where additional functionality is desired. This includes situations where additional functionality is desired. This includes situations
where a node has multiple interfaces, some of which participate in where a node has multiple interfaces, some of which participate in
another routing domain, where the programming interface to the net- another routing domain, where the programming interface to the
working hardware provides additional information in form of link- networking hardware provides additional information in form of link
layer notifications and where it is desired to provide redundant layer notifications and where it is desired to provide redundant
topological information to the network on expense of protocol over- topological information to the network on expense of protocol
head. overhead.
The following table specifies auxiliary functions and their relation The following table specifies auxiliary functions and their relation
to this document. to this document.
Feature | Section Feature | Section
------------------------------+-------------- ------------------------------+--------------
Non-OLSR interfaces | 12 Non-OLSR interfaces | 12
Link-layer notifications | 13 Link-layer notifications | 13
Advanced link sensing | 14 Advanced link sensing | 14
Redundant topology | 15 Redundant topology | 15
Redundant MPR flooding | 16 Redundant MPR flooding | 16
The interpretation of the above table is as follows: if the feature The interpretation of the above table is as follows: if the feature
listed is required, it SHOULD be provided as specified in the corre- listed is required, it SHOULD be provided as specified in the
sponding section. corresponding section.
3. Packet Format and Forwarding 3. Packet Format and Forwarding
OLSR communicates using a unified packet format for all data related OLSR communicates using a unified packet format for all data related
to the protocol. The purpose of this is to facilitate extensibility to the protocol. The purpose of this is to facilitate extensibility
of the protocol without breaking backwards compatibility. This also of the protocol without breaking backwards compatibility. This also
provides an easy way of piggybacking different "types" of information provides an easy way of piggybacking different "types" of information
into a single transmission, and thus for a given implementation to into a single transmission, and thus for a given implementation to
optimize towards utilizing the maximal frame-size, provided by the optimize towards utilizing the maximal frame-size, provided by the
network. These packets are embedded in UDP datagrams for transmis- network. These packets are embedded in UDP datagrams for
sion over the network. The present draft is presented with IPv4 transmission over the network. The present draft is presented with
addresses. Considerations regarding IPv6 are given in section IPv4 addresses. Considerations regarding IPv6 are given in section
17. 17.
Each packet encapsulates one or more messages. The messages share a Each packet encapsulates one or more messages. The messages share a
common header format, which enables nodes to correctly accept and (if common header format, which enables nodes to correctly accept and (if
applicable) retransmit messages of an unknown type. applicable) retransmit messages of an unknown type.
Messages can be flooded onto the entire network, or flooding can be Messages can be flooded onto the entire network, or flooding can be
limited to nodes within a diameter (in terms of number of hops) from limited to nodes within a diameter (in terms of number of hops) from
the originator of the message. Thus transmitting a message to the the originator of the message. Thus transmitting a message to the
neighborhood of a node is just a special case of flooding. When neighborhood of a node is just a special case of flooding. When
flooding any control message, duplicate retransmissions will be elim- flooding any control message, duplicate retransmissions will be
inated locally (i.e. each node maintains a duplicate set to prevent eliminated locally (i.e. each node maintains a duplicate set to
transmitting the same OLSR control message twice) and minimized in prevent transmitting the same OLSR control message twice) and
the entire network through the usage of MPRs as described in later minimized in the entire network through the usage of MPRs as
sections. described in later sections.
Furthermore, a node can examine the header of a message to obtain Furthermore, a node can examine the header of a message to obtain
information on the distance (in terms of number of hops) to the orig- information on the distance (in terms of number of hops) to the
inator of the message. This feature may be useful in situations originator of the message. This feature may be useful in situations
where, e.g., the time information from a received control messages where, e.g., the time information from a received control messages
stored in a node depends on the distance to the originator. stored in a node depends on the distance to the originator.
3.1. Protocol and Port Number 3.1. Protocol and Port Number
Packets in OLSR are communicated using UDP. Port 698 has been Packets in OLSR are communicated using UDP. Port 698 has been
assigned by IANA for exclusive usage by the OLSR protocol. assigned by IANA for exclusive usage by the OLSR protocol.
3.2. Main Address 3.2. Main Address
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Packet Length Packet Length
The length (in bytes) of the packet The length (in bytes) of the packet
Packet Sequence Number Packet Sequence Number
The Packet Sequence Number (PSN) MUST be incremented by one The Packet Sequence Number (PSN) MUST be incremented by one
each time a new OLSR packet is transmitted. "Wrap-around" is each time a new OLSR packet is transmitted. "Wrap-around" is
handled as described in section 19. A separate Packet handled as described in section 19. A separate Packet
Sequence Number is maintained for each interface such that Sequence Number is maintained for each interface such that
packets transmitted over an interface are sequentially enumer- packets transmitted over an interface are sequentially
ated. enumerated.
The IP address of the interface over which a packet was transmitted The IP address of the interface over which a packet was transmitted
is obtainable from the IP header of the packet. is obtainable from the IP header of the packet.
If the packet contains no messages (i.e. the Packet Length is less If the packet contains no messages (i.e. the Packet Length is less
than or equal to the size of the packet header), the packet MUST than or equal to the size of the packet header), the packet MUST
silently be discarded. silently be discarded.
For IPv4 addresses, this implies that packets, where the Packet For IPv4 addresses, this implies that packets, where the Packet
Length < 16 MUST silently be discarded. Length < 16 MUST silently be discarded.
3.3.2. Message Header 3.3.2. Message Header
Message Type Message Type
This field indicates which type of message is to be found in This field indicates which type of message is to be found in
the "MESSAGE" part. Message types in the range of 0-127 are the "MESSAGE" part. Message types in the range of 0-127 are
reserved for messages in this document and in possible exten- reserved for messages in this document and in possible
sions. extensions.
Vtime Vtime
This field indicates for how long time after reception a node This field indicates for how long time after reception a node
MUST consider the information contained in the message as MUST consider the information contained in the message as
valid, unless a more recent update to the information is valid, unless a more recent update to the information is
received. The validity time is represented by its mantissa received. The validity time is represented by its mantissa
(four highest bits of Vtime field) and by its exponent (four (four highest bits of Vtime field) and by its exponent (four
lowest bits of Vtime field). In other words: lowest bits of Vtime field). In other words:
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originally generated this message. This field SHOULD NOT be originally generated this message. This field SHOULD NOT be
confused with the source address from the IP header, which is confused with the source address from the IP header, which is
changed each time to the address of the intermediate interface changed each time to the address of the intermediate interface
which is re-transmitting this message. The Originator Address which is re-transmitting this message. The Originator Address
field MUST *NEVER* be changed in retransmissions. field MUST *NEVER* be changed in retransmissions.
Time To Live Time To Live
This field contains the maximum number of hops a message will This field contains the maximum number of hops a message will
be transmitted. Before a message is retransmitted, the Time be transmitted. Before a message is retransmitted, the Time
To Live MUST be decremented by 1. When a node receives a mes- To Live MUST be decremented by 1. When a node receives a
sage with a Time To Live equal to 0 or 1, the message MUST NOT message with a Time To Live equal to 0 or 1, the message MUST
be retransmitted under any circumstances. Normally, a node NOT be retransmitted under any circumstances. Normally, a
would not receive a message with a TTL of zero. node would not receive a message with a TTL of zero.
Thus, by setting this field, the originator of a message can Thus, by setting this field, the originator of a message can
limit the flooding radius. limit the flooding radius.
Hop Count Hop Count
This field contains the number of hops a message has attained. This field contains the number of hops a message has attained.
Before a message is retransmitted, the Hop Count MUST be Before a message is retransmitted, the Hop Count MUST be
incremented by 1. incremented by 1.
Initially, this is set to '0' by the originator of the mes- Initially, this is set to '0' by the originator of the
sage. message.
Message Sequence Number Message Sequence Number
While generating a message, the "originator" node will assign While generating a message, the "originator" node will assign
a unique identification number to each message. This number a unique identification number to each message. This number
is inserted into the Sequence Number field of the message. is inserted into the Sequence Number field of the message.
The sequence number is increased by 1 (one) for each message The sequence number is increased by 1 (one) for each message
originating from the node. "Wrap-around" is handled as originating from the node. "Wrap-around" is handled as
described in section 19. Message sequence numbers are described in section 19. Message sequence numbers are
used to ensure that a given message is not retransmitted more used to ensure that a given message is not retransmitted more
than once by any node. than once by any node.
3.4. Packet Processing and Message Flooding 3.4. Packet Processing and Message Flooding
Upon receiving a basic packet, a node examines each of the "message Upon receiving a basic packet, a node examines each of the "message
headers". Based on the value of the "Message Type" field, the node headers". Based on the value of the "Message Type" field, the node
can determine the fate of the message. A node may receive the same can determine the fate of the message. A node may receive the same
message several times. Thus, to avoid re-processing of some messages message several times. Thus, to avoid re-processing of some messages
which were already received and processed, each node maintains a which were already received and processed, each node maintains a
Duplicate Set. In this set, the node records information about the Duplicate Set. In this set, the node records information about the
most recently received messages where duplicate processing of a mes- most recently received messages where duplicate processing of a
sage is to be avoided. For such a message, a node records a "Dupli- message is to be avoided. For such a message, a node records a
cate Tuple" (D_addr, D_seq_num, D_retransmitted, D_iface_list, "Duplicate Tuple" (D_addr, D_seq_num, D_retransmitted, D_iface_list,
D_time), where D_addr is the originator address of the message, D_time), where D_addr is the originator address of the message,
D_seq_num is the message sequence number of the message, D_retrans- D_seq_num is the message sequence number of the message,
mitted is a boolean indicating whether the message has been already D_retransmitted is a boolean indicating whether the message has been
retransmitted, D_iface_list is a list of the addresses of the inter- already retransmitted, D_iface_list is a list of the addresses of the
faces on which the message has been received and D_time specifies the interfaces on which the message has been received and D_time
time at which a tuple expires and *MUST* be removed. specifies the time at which a tuple expires and *MUST* be removed.
In a node, the set of Duplicate Tuples are denoted the "Duplicate In a node, the set of Duplicate Tuples are denoted the "Duplicate
set". set".
In this section, the term "Originator Address" will be used for the In this section, the term "Originator Address" will be used for the
main address of the node which sent the message. The term "Sender main address of the node which sent the message. The term "Sender
Interface Address" will be used for the sender address (given in the Interface Address" will be used for the sender address (given in the
IP header of the packet containing the message) of the interface IP header of the packet containing the message) of the interface
which sent the message. The term "Receiving Interface Address" will which sent the message. The term "Receiving Interface Address" will
be used for the address of the interface of the node which received be used for the address of the interface of the node which received
the message. the message.
Thus, upon receiving a basic packet, a node MUST perform the follow- Thus, upon receiving a basic packet, a node MUST perform the
ing tasks for each encapsulated message: following tasks for each encapsulated message:
1 If the packet contains no messages (i.e. the Packet Length is 1 If the packet contains no messages (i.e. the Packet Length is
less than or equal to the size of the packet header), the less than or equal to the size of the packet header), the
packet MUST silently be discarded. packet MUST silently be discarded.
For IPv4 addresses, this implies that packets, where the For IPv4 addresses, this implies that packets, where the
Packet Length < 16 MUST silently be discarded. Packet Length < 16 MUST silently be discarded.
2 If the time to live of the message is less than or equal to 2 If the time to live of the message is less than or equal to
'0' (zero), or if the message was sent by the receiving node '0' (zero), or if the message was sent by the receiving node
skipping to change at page 20, line 49 skipping to change at page 20, line 49
4.1 if there exists a tuple in the duplicate set, where: 4.1 if there exists a tuple in the duplicate set, where:
D_addr == Originator Address, AND D_addr == Originator Address, AND
D_seq_num == Message Sequence Number, D_seq_num == Message Sequence Number,
AND AND
the receiving interface (address) is the receiving interface (address) is
in D_iface_list in D_iface_list
then the message has already been considered for forward- then the message has already been considered for
ing and SHOULD NOT be retransmitted again. forwarding and SHOULD NOT be retransmitted again.
4.2 Otherwise: 4.2 Otherwise:
4.2.1 4.2.1
If the node implements the Message Type of the If the node implements the Message Type of the
message, the message MUST be considered for message, the message MUST be considered for
forwarding according to the specifications for forwarding according to the specifications for
the message type. the message type.
4.2.2 4.2.2
Otherwise, if the node does not implement the Otherwise, if the node does not implement the
Message Type of the message, the message SHOULD Message Type of the message, the message SHOULD
be processed according to the default forward- be processed according to the default
ing algorithm described below. forwarding algorithm described below.
3.4.1. Default Forwarding Algorithm 3.4.1. Default Forwarding Algorithm
The default forwarding algorithm is the following: The default forwarding algorithm is the following:
1 If the sender interface address of the message is not detected 1 If the sender interface address of the message is not detected
to be in the symmetric 1-hop neighborhood of the node, the to be in the symmetric 1-hop neighborhood of the node, the
forwarding algorithm MUST silently stop here (and the message forwarding algorithm MUST silently stop here (and the message
MUST NOT be forwarded). MUST NOT be forwarded).
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D_seq_num == Message Sequence Number D_seq_num == Message Sequence Number
Then the message will be further considered for forwarding if Then the message will be further considered for forwarding if
and only if: and only if:
D_retransmitted is false, AND D_retransmitted is false, AND
the (address of the) interface which received the message the (address of the) interface which received the message
is not included among the addresses in D_iface_list is not included among the addresses in D_iface_list
3 Otherwise, if such an entry doesn't exist, the message is fur- 3 Otherwise, if such an entry doesn't exist, the message is
ther considered for forwarding. further considered for forwarding.
If after those steps, the message is not considered for forwarding, If after those steps, the message is not considered for forwarding,
then the processing of this section stops (i.e. steps 4 to 8 are then the processing of this section stops (i.e. steps 4 to 8 are
ignored), otherwise, if it is still considered for forwarding then ignored), otherwise, if it is still considered for forwarding then
the following algorithm is used: the following algorithm is used:
4 If the sender interface address is an interface address of a 4 If the sender interface address is an interface address of a
MPR selector of this node and if the time to live of the mes- MPR selector of this node and if the time to live of the
sage is greater than '1', the message MUST be retransmitted message is greater than '1', the message MUST be retransmitted
(as described later in steps 6 to 8). (as described later in steps 6 to 8).
5 If an entry in the duplicate set exists, with same Originator 5 If an entry in the duplicate set exists, with same Originator
Address, and same Message Sequence Number, the entry is Address, and same Message Sequence Number, the entry is
updated as follows: updated as follows:
D_time = current time + DUP_HOLD_TIME. D_time = current time + DUP_HOLD_TIME.
The receiving interface (address) is added to The receiving interface (address) is added to
D_iface_list. D_iface_list.
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D_seq_num = Message Sequence Number D_seq_num = Message Sequence Number
D_time = current time + DUP_HOLD_TIME. D_time = current time + DUP_HOLD_TIME.
D_iface_list contains the receiving interface address. D_iface_list contains the receiving interface address.
D_retransmitted is set to true if and only if the message D_retransmitted is set to true if and only if the message
will be retransmitted according to step 4. will be retransmitted according to step 4.
If, and only if, according to step 4, the message must be retransmit- If, and only if, according to step 4, the message must be
ted then: retransmitted then:
6 The TTL of the message is reduced by one. 6 The TTL of the message is reduced by one.
7 The hop-count of the message is increased by one 7 The hop-count of the message is increased by one
8 The message is broadcast on all interfaces (Notice: The 8 The message is broadcast on all interfaces (Notice: The
remaining fields of the message header SHOULD be left unmodi- remaining fields of the message header SHOULD be left
fied.) unmodified.)
3.4.2. Considerations on Processing and Forwarding 3.4.2. Considerations on Processing and Forwarding
It should be noted that processing and forwarding messages are two It should be noted that processing and forwarding messages are two
different actions, conditioned by different rules. Processing different actions, conditioned by different rules. Processing
relates to using the content of the messages, while forwarding is relates to using the content of the messages, while forwarding is
related to retransmitting the same message for other nodes of the related to retransmitting the same message for other nodes of the
network. network.
Notice that this specification includes a description for both the Notice that this specification includes a description for both the
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detection and MPR signaling, detection and MPR signaling,
- TC-messages, performing the task of topology declaration - TC-messages, performing the task of topology declaration
(advertisement of link states). (advertisement of link states).
- MID-messages, performing the task of declaring the presence of - MID-messages, performing the task of declaring the presence of
multiple interfaces on a node. multiple interfaces on a node.
Other message types include those specified in later sections, as Other message types include those specified in later sections, as
well as possible future extensions such as messages enabling power well as possible future extensions such as messages enabling power
conservation / sleep mode, multicast routing, support for unidirec- conservation / sleep mode, multicast routing, support for
tional links, auto-configuration/address assignment etc. unidirectional links, auto-configuration/address assignment etc.
3.5. Message Emission and Jitter 3.5. Message Emission and Jitter
As a basic implementation requirement, synchronization of control As a basic implementation requirement, synchronization of control
messages SHOULD be avoided. As a consequence, OLSR control messages messages SHOULD be avoided. As a consequence, OLSR control messages
SHOULD be emitted such that they avoid synchronization. SHOULD be emitted such that they avoid synchronization.
Emission of control traffic from neighboring nodes may, for various Emission of control traffic from neighboring nodes may, for various
reasons (mainly timer interactions with packet processing), become reasons (mainly timer interactions with packet processing), become
synchronized such that several neighbor nodes attempt to transmit synchronized such that several neighbor nodes attempt to transmit
control traffic simultaneously. Depending on the nature of the control traffic simultaneously. Depending on the nature of the
underlying link-layer, this may or may not lead to collisions and underlying link-layer, this may or may not lead to collisions and
hence message loss - possibly loss of several subsequent messages of hence message loss - possibly loss of several subsequent messages of
the same type. the same type.
To avoid such synchronizations, the following simple strategy for To avoid such synchronizations, the following simple strategy for
emitting control messages is proposed. A node MAY add an amount of emitting control messages is proposed. A node SHOULD add an amount
jitter to the interval at which messages are generated. The jitter of jitter to the interval at which messages are generated. The
must be a random value for each message generated. Thus, for a node jitter must be a random value for each message generated. Thus, for
utilizing jitter: a node utilizing jitter:
Actual message interval = MESSAGE_INTERVAL - jitter Actual message interval = MESSAGE_INTERVAL - jitter
Where jitter is a value, randomly selected from the interval Where jitter is a value, randomly selected from the interval
[0,MAXJITTER] and MESSAGE_INTERVAL is the value of the message inter- [0,MAXJITTER] and MESSAGE_INTERVAL is the value of the message
val specified for the message being emitted (e.g. HELLO_INTERVAL for interval specified for the message being emitted (e.g.
HELLO messages, TC_INTERVAL for TC-messages etc.). HELLO_INTERVAL for HELLO messages, TC_INTERVAL for TC-messages etc.).
Jitter MAY also be introduced when forwarding messages. The follow- Jitter SHOULD also be introduced when forwarding messages. The
ing simple strategy may be adopted: when a message is to be forwarded following simple strategy may be adopted: when a message is to be
by a node, it should be kept in the node during a short period of forwarded by a node, it should be kept in the node during a short
time : period of time :
Keep message period = jitter Keep message period = jitter
Where jitter is a random value in [0,MAXJITTER]. Where jitter is a random value in [0,MAXJITTER].
Notice that when the node sends a control message, the opportunity to Notice that when the node sends a control message, the opportunity to
piggyback other messages (before their keeping period is expired) may piggyback other messages (before their keeping period is expired) may
be taken to reduce the number of packet transmissions. be taken to reduce the number of packet transmissions.
Notice, that a minimal rate of control messages is imposed. A node Notice, that a minimal rate of control messages is imposed. A node
MAY send control messages at a higher rate, if beneficial for a spe- MAY send control messages at a higher rate, if beneficial for a
cific deployment. specific deployment.
4. Information Repositories 4. Information Repositories
Through the exchange of OLSR control messages, each node accumulates Through the exchange of OLSR control messages, each node accumulates
information about the network. This information is stored according information about the network. This information is stored according
to the descriptions in this section. to the descriptions in this section.
4.1. Multiple Interface Association Information Base 4.1. Multiple Interface Association Information Base
For each destination in the network, "Interface Association Tuples" For each destination in the network, "Interface Association Tuples"
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In a node, the set of Interface Association Tuples is denoted the In a node, the set of Interface Association Tuples is denoted the
"Interface Association Set". "Interface Association Set".
4.2. Link Sensing: Local Link Information Base 4.2. Link Sensing: Local Link Information Base
The local link information base stores information about links to The local link information base stores information about links to
neighbors. neighbors.
4.2.1. Link Set 4.2.1. Link Set
A node records a set of "Link Tuples" (L_local_iface_addr, L_neigh- A node records a set of "Link Tuples" (L_local_iface_addr,
bor_iface_addr, L_SYM_time, L_ASYM_time, L_time). L_local_iface_addr L_neighbor_iface_addr, L_SYM_time, L_ASYM_time, L_time).
is the interface address of the local node (i.e. one endpoint of the L_local_iface_addr is the interface address of the local node (i.e.
link), L_neighbor_iface_addr is the interface address of the neighbor one endpoint of the link), L_neighbor_iface_addr is the interface
node (i.e. the other endpoint of the link), L_SYM_time is the time address of the neighbor node (i.e. the other endpoint of the link),
until which the link is considered symmetric, L_ASYM_time is the time L_SYM_time is the time until which the link is considered symmetric,
until which the neighbor interface is considered heard, and L_time L_ASYM_time is the time until which the neighbor interface is
specifies the time at which this record expires and *MUST* be considered heard, and L_time specifies the time at which this record
removed. When L_SYM_time and L_ASYM_time are expired, the link is expires and *MUST* be removed. When L_SYM_time and L_ASYM_time are
considered lost. expired, the link is considered lost.
This information is used when declaring the neighbor interfaces in This information is used when declaring the neighbor interfaces in
the HELLO messages. the HELLO messages.
L_SYM_time is used to decide the Link Type declared for the neighbor L_SYM_time is used to decide the Link Type declared for the neighbor
interface. If L_SYM_time is not expired, the link MUST be declared interface. If L_SYM_time is not expired, the link MUST be declared
symmetric. If L_SYM_time is expired, the link MUST be declared asym- symmetric. If L_SYM_time is expired, the link MUST be declared
metric. If both L_SYM_time and L_ASYM_time are expired, the link asymmetric. If both L_SYM_time and L_ASYM_time are expired, the link
MUST be declared lost. MUST be declared lost.
In a node, the set of Link Tuples are denoted the "Link Set". In a node, the set of Link Tuples are denoted the "Link Set".
4.3. Neighbor Detection: Neighborhood Information Base 4.3. Neighbor Detection: Neighborhood Information Base
The neighborhood information base stores information about neighbors, The neighborhood information base stores information about neighbors,
2-hop neighbors, MPRs and MPR selectors. 2-hop neighbors, MPRs and MPR selectors.
4.3.1. Neighbor Set 4.3.1. Neighbor Set
A node records a set of "neighbor tuples" (N_neighbor_main_addr, A node records a set of "neighbor tuples" (N_neighbor_main_addr,
N_status, N_willingness), describing symmetric neighbors. N_neigh- N_status, N_willingness), describing symmetric neighbors.
bor_main_addr is the main address of a neighbor, N_status specifies N_neighbor_main_addr is the main address of a neighbor, N_status
if the node is NOT_SYM or SYM. N_willingness in an integer between 0 specifies if the node is NOT_SYM or SYM. N_willingness in an integer
and 7, and specifies a nodes willingness to carry traffic on behalf between 0 and 7, and specifies a nodes willingness to carry traffic
of other nodes. on behalf of other nodes.
4.3.2. 2-hop Neighbor Set 4.3.2. 2-hop Neighbor Set
A node records a set of "2-hop tuples" (N_neighbor_main_addr, A node records a set of "2-hop tuples" (N_neighbor_main_addr,
N_2hop_addr, N_time), describing symmetric (and, since MPR links by N_2hop_addr, N_time), describing symmetric (and, since MPR links by
definition are also symmetric, thereby also MPR) links between its definition are also symmetric, thereby also MPR) links between its
neighbors and the symmetric 2-hop neighborhood. N_neighbor_main_addr neighbors and the symmetric 2-hop neighborhood. N_neighbor_main_addr
is the main address of a neighbor, N_2hop_addr is the main address of is the main address of a neighbor, N_2hop_addr is the main address of
a 2-hop neighbor with a symmetric link to N_neighbor_main_addr, and a 2-hop neighbor with a symmetric link to N_neighbor_main_addr, and
N_time specifies the time at which the tuple expires and *MUST* be N_time specifies the time at which the tuple expires and *MUST* be
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main addresses are listed in the MPR Set. main addresses are listed in the MPR Set.
4.3.4. MPR Selector Set 4.3.4. MPR Selector Set
A node records a set of MPR-selector tuples (MS_main_addr, MS_time), A node records a set of MPR-selector tuples (MS_main_addr, MS_time),
describing the neighbors which have selected this node as a MPR. describing the neighbors which have selected this node as a MPR.
MS_main_addr is the main address of a node, which has selected this MS_main_addr is the main address of a node, which has selected this
node as MPR. MS_time specifies the time at which a tuple expires and node as MPR. MS_time specifies the time at which a tuple expires and
*MUST* be removed. *MUST* be removed.
In a node, the set of MPR-selector tuples are denoted the "MPR Selec- In a node, the set of MPR-selector tuples are denoted the "MPR
tor Set". Selector Set".
4.4. Topology Information Base 4.4. Topology Information Base
Each node in the network maintains topology information about the Each node in the network maintains topology information about the
network. This information is acquired from TC-messages and is used network. This information is acquired from TC-messages and is used
for routing table calculations. for routing table calculations.
Thus, for each destination in the network, at least one "Topology Thus, for each destination in the network, at least one "Topology
Tuple" (T_dest_addr, T_last_addr, T_seq, T_time) is recorded. Tuple" (T_dest_addr, T_last_addr, T_seq, T_time) is recorded.
T_dest_addr is the main address of a node, which may be reached in T_dest_addr is the main address of a node, which may be reached in
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T_last_addr is a MPR of T_dest_addr. T_seq is a sequence number, and T_last_addr is a MPR of T_dest_addr. T_seq is a sequence number, and
T_time specifies the time at which this tuple expires and *MUST* be T_time specifies the time at which this tuple expires and *MUST* be
removed. removed.
In a node, the set of Topology Tuples are denoted the "Topology Set". In a node, the set of Topology Tuples are denoted the "Topology Set".
5. Main Addresses and Multiple Interfaces 5. Main Addresses and Multiple Interfaces
For single OLSR interface nodes, the relationship between an OLSR For single OLSR interface nodes, the relationship between an OLSR
interface address and the corresponding main address is trivial: the interface address and the corresponding main address is trivial: the
main address is the OLSR interface address. For multiple OLSR inter- main address is the OLSR interface address. For multiple OLSR
face nodes, the relationship between OLSR interface addresses and interface nodes, the relationship between OLSR interface addresses
main addresses is defined through the exchange of Multiple Interface and main addresses is defined through the exchange of Multiple
Declaration (MID) messages. This section describes how MID messages Interface Declaration (MID) messages. This section describes how MID
are exchanged and processed. messages are exchanged and processed.
Each node with multiple interfaces MUST announce, periodically, Each node with multiple interfaces MUST announce, periodically,
information describing its interface configuration to other nodes in information describing its interface configuration to other nodes in
the network. This is accomplished through flooding a Multiple Inter- the network. This is accomplished through flooding a Multiple
face Declaration message to all nodes in the network through the MPR Interface Declaration message to all nodes in the network through the
flooding mechanism. MPR flooding mechanism.
Each node in the network maintains interface information about the Each node in the network maintains interface information about the
other nodes in the network. This information acquired from MID-mes- other nodes in the network. This information acquired from MID
sages, emitted by nodes with multiple interfaces participating in the messages, emitted by nodes with multiple interfaces participating in
MANET, and is used for routing table calculations. the MANET, and is used for routing table calculations.
Specifically, multiple interface declaration associates multiple Specifically, multiple interface declaration associates multiple
interfaces to a node (and to a main address) through populating the interfaces to a node (and to a main address) through populating the
multiple interface association base in each node. multiple interface association base in each node.
5.1. MID Message Format 5.1. MID Message Format
The proposed format of a MID message is as follows: The proposed format of a MID message is as follows:
0 1 2 3 0 1 2 3
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| OLSR Interface Address | | OLSR Interface Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OLSR Interface Address | | OLSR Interface Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This is sent as the data-portion of the general packet format This is sent as the data-portion of the general packet format
described in section 3.4, with the "Message Type" set to described in section 3.4, with the "Message Type" set to
MID_MESSAGE. The time to live SHOULD be set to 255 (maximum value) MID_MESSAGE. The time to live SHOULD be set to 255 (maximum value)
to diffuse the message into the entire network and Vtime set accord- to diffuse the message into the entire network and Vtime set
ingly to the value of MID_HOLD_TIME, as specified in section accordingly to the value of MID_HOLD_TIME, as specified in section
18.3. 18.3.
OLSR Interface Address OLSR Interface Address
This field contains the address of an OLSR interface of the This field contains the address of an OLSR interface of the
node, excluding the nodes main address (which already indi- node, excluding the nodes main address (which already
cated in the originator address). indicated in the originator address).
All interface addresses other than the main address of the originator All interface addresses other than the main address of the originator
node are put in the MID message. If the maximum allowed message size node are put in the MID message. If the maximum allowed message size
(as imposed by the network) is reached while there are still inter- (as imposed by the network) is reached while there are still
face addresses which have not been inserted into the MID-message, interface addresses which have not been inserted into the MIDmessage,
more MID messages are generated until the entire interface addresses more MID messages are generated until the entire interface addresses
set has been sent. set has been sent.
5.2. MID Message Generation 5.2. MID Message Generation
A MID message is sent by a node in the network to declare its multi- A MID message is sent by a node in the network to declare its
ple interfaces (if any). I.e., the MID message contains the list of multiple interfaces (if any). I.e., the MID message contains the
interface addresses which are associated to its main address. The list of interface addresses which are associated to its main address.
list of addresses can be partial in each MID message (e.g. due to The list of addresses can be partial in each MID message (e.g. due
message size limitations, imposed by the network), but parsing of all to message size limitations, imposed by the network), but parsing of
MID messages describing the interface set from a node MUST be com- all MID messages describing the interface set from a node MUST be
plete within a certain refreshing period (MID_INTERVAL). The infor- complete within a certain refreshing period (MID_INTERVAL). The
mation diffused in the network by these MID messages will help each information diffused in the network by these MID messages will help
node to calculate its routing table. A node which has only a single each node to calculate its routing table. A node which has only a
interface address participating in the MANET (i.e. running OLSR), single interface address participating in the MANET (i.e. running
MUST NOT generate any MID message. OLSR), MUST NOT generate any MID message.
A node with more interfaces, where only one is participating in the A node with more interfaces, where only one is participating in the
MANET and running OLSR (e.g. a node is connected to a wired network MANET and running OLSR (e.g. a node is connected to a wired network
as well as to a MANET) MUST NOT generate any MID messages. as well as to a MANET) MUST NOT generate any MID messages.
A node with more interfaces, where more than one is participating in A node with more interfaces, where more than one is participating in
the MANET and running OLSR MUST generate MID messages as specified. the MANET and running OLSR MUST generate MID messages as specified.
5.3. MID Message Forwarding 5.3. MID Message Forwarding
MID messages are broadcast and retransmitted by the MPRs in order to MID messages are broadcast and retransmitted by the MPRs in order to
diffuse the messages in the entire network. The "default forwarding diffuse the messages in the entire network. The "default forwarding
algorithm" (described in section 3.4) MUST be used for for- algorithm" (described in section 3.4) MUST be used for
warding of MID messages. forwarding of MID messages.
5.4. MID Message Processing 5.4. MID Message Processing
The tuples in the multiple interface association set are recorded The tuples in the multiple interface association set are recorded
with the information that is exchanged through MID messages. with the information that is exchanged through MID messages.
Upon receiving a MID message, the "validity time" MUST be computed Upon receiving a MID message, the "validity time" MUST be computed
from the Vtime field of the message header (as described in section from the Vtime field of the message header (as described in section
3.3.2). The Multiple Interface Association Information Base 3.3.2). The Multiple Interface Association Information Base
SHOULD then be updated as follows: SHOULD then be updated as follows:
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set where: set where:
I_iface_addr == interface address, AND I_iface_addr == interface address, AND
I_main_addr == originator address, I_main_addr == originator address,
then the holding time of that tuple is set to: then the holding time of that tuple is set to:
I_time = current time + validity time. I_time = current time + validity time.
2.2 Otherwise, a new tuple is recorded in the interface asso- 2.2 Otherwise, a new tuple is recorded in the interface
ciation set where: association set where:
I_iface_addr = interface address, I_iface_addr = interface address,
I_main_addr = originator address, I_main_addr = originator address,
I_time = current time + validity time. I_time = current time + validity time.
5.5. Resolving a Main Address from an Interface Address 5.5. Resolving a Main Address from an Interface Address
In general, the only part of OLSR requiring use of "interface In general, the only part of OLSR requiring use of "interface
addresses" is link sensing. The remaining parts of OLSR operate on addresses" is link sensing. The remaining parts of OLSR operate on
nodes, uniquely identified by their "main addresses" (effectively, nodes, uniquely identified by their "main addresses" (effectively,
the main address of a node is its "node id" - which for convenience the main address of a node is its "node id" - which for convenience
corresponds to the address of one of its interfaces). In a network corresponds to the address of one of its interfaces). In a network
with only single interface nodes, the main address of a node will, by with only single interface nodes, the main address of a node will, by
definition, be equal to the interface address of the node. In net- definition, be equal to the interface address of the node. In
works with multiple interface nodes operating within a common OLSR networks with multiple interface nodes operating within a common OLSR
area, it is required to be able to map any interface address to the area, it is required to be able to map any interface address to the
corresponding main address. corresponding main address.
The exchange of MID messages provides a way in which interface infor- The exchange of MID messages provides a way in which interface
mation is acquired by nodes in the network. This permits identifica- information is acquired by nodes in the network. This permits
tion of a nodes "main address", given one of its interface addresses. identification of a nodes "main address", given one of its interface
addresses.
Given an interface address: Given an interface address:
1 if there exists some tuple in the interface association set 1 if there exists some tuple in the interface association set
where: where:
I_iface_addr == interface address I_iface_addr == interface address
then the result of the main address search is the originator then the result of the main address search is the originator
address I_main_addr of the tuple. address I_main_addr of the tuple.
2 Otherwise, the result of the main address search is the inter- 2 Otherwise, the result of the main address search is the
face address itself. interface address itself.
6. HELLO Message Format and Generation 6. HELLO Message Format and Generation
A common mechanism is employed for populating the local link informa- A common mechanism is employed for populating the local link
tion base and the neighborhood information base, namely periodic information base and the neighborhood information base, namely
exchange of HELLO messages. Thus this section describes the general periodic exchange of HELLO messages. Thus this section describes the
HELLO message mechanism, followed by a description of link sensing general HELLO message mechanism, followed by a description of link
and topology detection, respectively. sensing and topology detection, respectively.
6.1. HELLO Message Format 6.1. HELLO Message Format
To accommodate for link sensing, neighborhood detection and MPR To accommodate for link sensing, neighborhood detection and MPR
selection signalling, as well as to accommodate for future exten- selection signalling, as well as to accommodate for future
sions, an approach similar to the overall packet format is taken. extensions, an approach similar to the overall packet format is
Thus the proposed format of a HELLO message is as follows: taken. Thus the proposed format of a HELLO message is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Htime | Willingness | | Reserved | Htime | Willingness |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Code | Reserved | Link Message Size | | Link Code | Reserved | Link Message Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Interface Address | | Neighbor Interface Address |
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C is specified in section 18. C is specified in section 18.
Willingness Willingness
This field specifies the willingness of a node to carry and This field specifies the willingness of a node to carry and
forward traffic for other nodes. forward traffic for other nodes.
A node with willingness WILL_NEVER (see section 18.8, for A node with willingness WILL_NEVER (see section 18.8, for
willingness constants) MUST never be selected as MPR by any willingness constants) MUST never be selected as MPR by any
node. A node with willingness WILL_ALWAYS MUST always be node. A node with willingness WILL_ALWAYS MUST always be
selected as MPR. By default, a node SHOULD advertise a will- selected as MPR. By default, a node SHOULD advertise a
ingness of WILL_DEFAULT. willingness of WILL_DEFAULT.
Link Code Link Code
This field specifies informations about the link between the This field specifies informations about the link between the
interface of the sender and the following list of neighbor interface of the sender and the following list of neighbor
interfaces. It also specifies informations about the status interfaces. It also specifies informations about the status
of the neighbor. of the neighbor.
Link codes, not known by a node, are silently discarded. Link codes, not known by a node, are silently discarded.
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end of the message). end of the message).
Neighbor Interface Address Neighbor Interface Address
An address of the interface of a neighbor node. An address of the interface of a neighbor node.
6.1.1. Link Code as Link Type and Neighbor Type 6.1.1. Link Code as Link Type and Neighbor Type
This document only specifies processing of Link Codes < 16. This document only specifies processing of Link Codes < 16.
If the Link Code value is less or equal to 15, then it MUST be inter- If the Link Code value is less or equal to 15, then it MUST be
preted as holding two different fields, of two bits each: interpreted as holding two different fields, of two bits each:
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
+-------+-------+-------+-------+-------+-------+-------+-------+ +-------+-------+-------+-------+-------+-------+-------+-------+
| 0 | 0 | 0 | 0 | Neighbor Type | Link Type | | 0 | 0 | 0 | 0 | Neighbor Type | Link Type |
+-------+-------+-------+-------+-------+-------+-------+-------+ +-------+-------+-------+-------+-------+-------+-------+-------+
The following four "Link Types" are REQUIRED by OLSR: The following four "Link Types" are REQUIRED by OLSR:
- UNSPEC_LINK - indicating that no specific information about - UNSPEC_LINK - indicating that no specific information about
the links is given. the links is given.
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Note that an implementation should be careful in not confusing Link Note that an implementation should be careful in not confusing Link
Type with Neighbor Type nor the constants (confusing SYM_NEIGH with Type with Neighbor Type nor the constants (confusing SYM_NEIGH with
SYM_LINK for instance). SYM_LINK for instance).
A link code advertising: A link code advertising:
Link Type == SYM_LINK AND Link Type == SYM_LINK AND
Neighbor Type == NOT_NEIGH Neighbor Type == NOT_NEIGH
is invalid, and any links adverticed as such MUST be silently dis- is invalid, and any links adverticed as such MUST be silently
carded without any processing. discarded without any processing.
Likewise a Neighbor Type field advertising a numerical value which is Likewise a Neighbor Type field advertising a numerical value which is
not one of the constants SYM_NEIGH, MPR_NEIGH, NOT_NEIGH, is invalid, not one of the constants SYM_NEIGH, MPR_NEIGH, NOT_NEIGH, is invalid,
and any links adverticed as such MUST be silently discarded without and any links adverticed as such MUST be silently discarded without
any processing. any processing.
6.2. HELLO Message Generation 6.2. HELLO Message Generation
This involves transmitting the Link Set, the Neighbor Set and the MPR This involves transmitting the Link Set, the Neighbor Set and the MPR
Set. In principle, a HELLO message serves three independent tasks: Set. In principle, a HELLO message serves three independent tasks:
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- MPR selection signaling - MPR selection signaling
Three tasks are all are based on periodic information exchange within Three tasks are all are based on periodic information exchange within
a nodes neighborhood, and serve the common purpose of "local topology a nodes neighborhood, and serve the common purpose of "local topology
discovery". A HELLO message is therefore generated based on the discovery". A HELLO message is therefore generated based on the
information stored in the Local Link Set, the Neighbor Set and the information stored in the Local Link Set, the Neighbor Set and the
MPR Set from the local link information base. MPR Set from the local link information base.
A node must perform link sensing on each interface, in order to A node must perform link sensing on each interface, in order to
detect links between the interface and neighbor interfaces. Further- detect links between the interface and neighbor interfaces.
more, a node must advertise its entire symmetric 1-hop neighborhood Furthermore, a node must advertise its entire symmetric 1-hop
on each interface in order to perform neighbor detection. Hence, for neighborhood on each interface in order to perform neighbor
a given interface, a HELLO message will contain a list of links on detection. Hence, for a given interface, a HELLO message will
that interface (with associated link types), as well as a list of the contain a list of links on that interface (with associated link
entire neighborhood (with an associated neighbor types). types), as well as a list of the entire neighborhood (with an
associated neighbor types).
The Vtime field is set such that it corresponds to the value of the The Vtime field is set such that it corresponds to the value of the
node's NEIGHB_HOLD_TIME parameter. The Htime field is set such that node's NEIGHB_HOLD_TIME parameter. The Htime field is set such that
it corresponds to the value of the node's HELLO_INTERVAL parameter it corresponds to the value of the node's HELLO_INTERVAL parameter
(see section 18.3). (see section 18.3).
The Willingness field is set such that it corresponds to the node's The Willingness field is set such that it corresponds to the node's
willingness to forward traffic on behalf of other nodes (see section willingness to forward traffic on behalf of other nodes (see section
18.8). A node MUST advertise the same willingness on all 18.8). A node MUST advertise the same willingness on all
interfaces. interfaces.
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Link Type = ASYM_LINK Link Type = ASYM_LINK
1.3 Otherwise, if L_ASYM_time < current time (expired) AND 1.3 Otherwise, if L_ASYM_time < current time (expired) AND
L_SYM_time < current time (expired) L_SYM_time < current time (expired)
Link Type = LOST_LINK Link Type = LOST_LINK
2 The Neighbor Type is set according to the following: 2 The Neighbor Type is set according to the following:
2.1 If the main address, corresponding to L_neigh- 2.1 If the main address, corresponding to
bor_iface_addr, is included in the MPR set: L_neighbor_iface_addr, is included in the MPR set:
Neighbor Type = MPR_NEIGH Neighbor Type = MPR_NEIGH
2.2 Otherwise, if the main address, corresponding to L_neigh- 2.2 Otherwise, if the main address, corresponding to
bor_iface_addr, is included in the neighbor set: L_neighbor_iface_addr, is included in the neighbor set:
2.2.1 2.2.1
if N_status == SYM if N_status == SYM
Neighbor Type = SYM_NEIGH Neighbor Type = SYM_NEIGH
2.2.2 2.2.2
Otherwise, if N_status == NOT_SYM Otherwise, if N_status == NOT_SYM
Neighbor Type = NOT_NEIGH Neighbor Type = NOT_NEIGH
For each tuple in the Neighbor Set, for which no L_neigh- For each tuple in the Neighbor Set, for which no
bor_iface_addr from an associated link tuple has been advertised by L_neighbor_iface_addr from an associated link tuple has been
the previous algorithm, N_neighbor_main_addr is advertised with: advertised by the previous algorithm, N_neighbor_main_addr is
advertised with:
- Link Type = UNSPEC_LINK, - Link Type = UNSPEC_LINK,
- Neighbor Type set as described in step 2 above - Neighbor Type set as described in step 2 above
For a node with a single OLSR interface, the main address is simply For a node with a single OLSR interface, the main address is simply
the address of the OLSR interface. I.e. for a node with a single the address of the OLSR interface. I.e. for a node with a single
OLSR interface, the main address, corresponding to L_neigh- OLSR interface, the main address, corresponding to
bor_iface_addr is simply L_neighbor_iface_addr. L_neighbor_iface_addr is simply L_neighbor_iface_addr.
A HELLO message can be partial (e.g. due to message size limita- A HELLO message can be partial (e.g. due to message size
tions, imposed by the network), the rule being the following, on each limitations, imposed by the network), the rule being the following,
interface: each link and each neighbor node MUST be cited at least on each interface: each link and each neighbor node MUST be cited at
once within a predetermined refreshing period, REFRESH_INTERVAL. To least once within a predetermined refreshing period,
keep track of fast connectivity changes, a HELLO message must be sent REFRESH_INTERVAL. To keep track of fast connectivity changes, a
at least every HELLO_INTERVAL period, smaller than or equal to HELLO message must be sent at least every HELLO_INTERVAL period,
REFRESH_INTERVAL. smaller than or equal to REFRESH_INTERVAL.
Notice that for limiting the impact from loss of control messages, it Notice that for limiting the impact from loss of control messages, it
is desirable that a message (plus the generic packet header) can fit is desirable that a message (plus the generic packet header) can fit
into a single MAC frame. into a single MAC frame.
6.3. HELLO Message Forwarding 6.3. HELLO Message Forwarding
Each HELLO message generated is broadcast by the node on one inter- Each HELLO message generated is broadcast by the node on one
face to its neighbors. HELLO messages MUST never be forwarded. interface to its neighbors. HELLO messages MUST never be forwarded.
6.4. HELLO Message Processing 6.4. HELLO Message Processing
A node processes incoming HELLO messages for the purpose of conduct- A node processes incoming HELLO messages for the purpose of
ing link sensing (detailed in section 7), neighbor detection conducting link sensing (detailed in section 7), neighbor
and MPR selector set population (detailed in section 8) detection and MPR selector set population (detailed in section
8)
7. Link Sensing 7. Link Sensing
Link sensing populates the local link information base. Link sensing Link sensing populates the local link information base. Link sensing
is exclusively concerned with OLSR interface addresses and the abil- is exclusively concerned with OLSR interface addresses and the
ity to exchange packets between such OLSR interfaces. ability to exchange packets between such OLSR interfaces.
The mechanism for link sensing is the periodic exchange of HELLO The mechanism for link sensing is the periodic exchange of HELLO
messages. messages.
7.1. Populating the Link Set 7.1. Populating the Link Set
The Link Set is populated with information on links to neighbor The Link Set is populated with information on links to neighbor
nodes. The process of populating this set is denoted "link sensing" nodes. The process of populating this set is denoted "link sensing"
and is performed using HELLO message exchange, updating a local link and is performed using HELLO message exchange, updating a local link
information base in each node. information base in each node.
Each node should detect the links between itself and neighbor nodes. Each node should detect the links between itself and neighbor nodes.
Uncertainties over radio propagation may make some links unidirec- Uncertainties over radio propagation may make some links
tional. Consequently, all links MUST be checked in both directions unidirectional. Consequently, all links MUST be checked in both
in order to be considered valid. directions in order to be considered valid.
A "link" is described by a pair of interfaces: a local and a remote A "link" is described by a pair of interfaces: a local and a remote
interface. interface.
For the purpose of link sensing, each neighbor node (more specifi- For the purpose of link sensing, each neighbor node (more
cally, the link to each neighbor) has an associated status of either specifically, the link to each neighbor) has an associated status of
"symmetric" or "asymmetric". "Symmetric" indicates, that the link to either "symmetric" or "asymmetric". "Symmetric" indicates, that the
that neighbor node has been verified to be bi-directional, i.e. it link to that neighbor node has been verified to be bi-directional,
is possible to transmit data in both directions. "Asymmetric" indi- i.e. it is possible to transmit data in both directions.
cates that HELLO messages from the node have been heard (i.e. commu- "Asymmetric" indicates that HELLO messages from the node have been
nication from the neighbor node is possible), however it is not con- heard (i.e. communication from the neighbor node is possible),
firmed that this node is also able to receive messages (i.e. commu- however it is not confirmed that this node is also able to receive
nication to the neighbor node is not confirmed). messages (i.e. communication to the neighbor node is not confirmed).
The information, acquired through and used by the link sensing, is The information, acquired through and used by the link sensing, is
accumulated in the link set. accumulated in the link set.
7.1.1. HELLO Message Processing 7.1.1. HELLO Message Processing
The "Originator Address" of a HELLO message is the main address of The "Originator Address" of a HELLO message is the main address of
the node, which has emitted the message. the node, which has emitted the message.
Upon receiving a HELLO message, a node SHOULD update its Link Set. Upon receiving a HELLO message, a node SHOULD update its Link Set.
skipping to change at page 39, line 20 skipping to change at page 39, line 20
section 5. section 5.
The mechanism for neighbor detection is the periodic exchange of The mechanism for neighbor detection is the periodic exchange of
HELLO messages. HELLO messages.
8.1. Populating the Neighbor Set 8.1. Populating the Neighbor Set
A node maintains a set of neighbor tuples, based on the link tuples. A node maintains a set of neighbor tuples, based on the link tuples.
This information is updated according to changes in the Link Set. This information is updated according to changes in the Link Set.
The Link Set keeps the information about the links, while the Neigh- The Link Set keeps the information about the links, while the
bor Set keeps the information about the neighbors. There is a clear Neighbor Set keeps the information about the neighbors. There is a
association between those two sets, since a node is a neighbor of clear association between those two sets, since a node is a neighbor
another node if and only if there is at least one link between the of another node if and only if there is at least one link between the
two nodes. two nodes.
In any case, the formal correspondence between links and neighbors is In any case, the formal correspondence between links and neighbors is
defined as follows: defined as follows:
The "associated neighbor tuple" of a link tuple, is, if it The "associated neighbor tuple" of a link tuple, is, if it
exists, the neighbor tuple where: exists, the neighbor tuple where:
N_neighbor_main_addr == main address of N_neighbor_main_addr == main address of
L_neighbor_iface_addr L_neighbor_iface_addr
The "associated link tuples" of a neighbor tuple, are all the The "associated link tuples" of a neighbor tuple, are all the
link tuples, where: link tuples, where:
N_neighbor_main_addr == main address of N_neighbor_main_addr == main address of
L_neighbor_iface_addr L_neighbor_iface_addr
The Neighbor Set MUST be populated by maintaining the proper corre- The Neighbor Set MUST be populated by maintaining the proper
spondence between link tuples and associated neighbor tuples, as fol- correspondence between link tuples and associated neighbor tuples, as
lows: follows:
Creation Creation
Each time a link appears, that is, each time a link tuple is Each time a link appears, that is, each time a link tuple is
created, the associated neighbor tuple MUST be created, if it created, the associated neighbor tuple MUST be created, if it
doesn't already exist, with the following values: doesn't already exist, with the following values:
N_neighbor_main_addr = main address of N_neighbor_main_addr = main address of
L_neighbor_iface_addr L_neighbor_iface_addr
(from the link tuple) (from the link tuple)
In any case, the N_status MUST then be computed as described In any case, the N_status MUST then be computed as described
in the next step in the next step
Update Update
Each time a link changes, that is, each time the information Each time a link changes, that is, each time the information
of a link tuple is modified, the node MUST ensure that the of a link tuple is modified, the node MUST ensure that the
N_status of the associated neighbor tuple respects the prop- N_status of the associated neighbor tuple respects the
erty: property:
If the neighbor has any associated link tuple which indi- If the neighbor has any associated link tuple which
cates a symmetrical link (i.e. with L_SYM_time >= cur- indicates a symmetrical link (i.e. with L_SYM_time >=
rent time), then current time), then
N_status is set to SYM N_status is set to SYM
else N_status is set to NOT_SYM else N_status is set to NOT_SYM
Removal Removal
Each time a link is deleted, that is, each time a link tuple Each time a link is deleted, that is, each time a link tuple
is removed, the associated neighbor tuple MUST be removed if is removed, the associated neighbor tuple MUST be removed if
it has no longer any associated link tuples. it has no longer any associated link tuples.
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- if the Originator Address is the N_neighbor_main_addr from a - if the Originator Address is the N_neighbor_main_addr from a
neighbor tuple included in the Neighbor Set: neighbor tuple included in the Neighbor Set:
then, the neighbor tuple SHOULD be updated as follows: then, the neighbor tuple SHOULD be updated as follows:
N_willingness = willingness from the HELLO message N_willingness = willingness from the HELLO message
8.2. Populating the 2-hop Neighbor Set 8.2. Populating the 2-hop Neighbor Set
The 2-hop neighbor set describes the set of nodes which have a sym- The 2-hop neighbor set describes the set of nodes which have a
metric link to a symmetric neighbor. This information set is main- symmetric link to a symmetric neighbor. This information set is
tained through periodic exchange of HELLO messages as described in maintained through periodic exchange of HELLO messages as described
this section. in this section.
8.2.1. HELLO Message Processing 8.2.1. HELLO Message Processing
The "Originator Address" of a HELLO message is the main address of The "Originator Address" of a HELLO message is the main address of
the node, which has emitted the message. the node, which has emitted the message.
Upon receiving a HELLO message from a symmetric neighbor, a node Upon receiving a HELLO message from a symmetric neighbor, a node
SHOULD update its 2-hop Neighbor Set. Notice, that a HELLO message SHOULD update its 2-hop Neighbor Set. Notice, that a HELLO message
MUST neither be forwarded nor be recorded in the duplicate set. MUST neither be forwarded nor be recorded in the duplicate set.
Upon receiving a HELLO message, the "validity time" MUST be computed Upon receiving a HELLO message, the "validity time" MUST be computed
from the Vtime field of the message header (see section 3.3.2). from the Vtime field of the message header (see section 3.3.2).
If the Originator Address is the main address of a L_neigh- If the Originator Address is the main address of a
bor_iface_addr from a link tuple included in the Link Set with L_neighbor_iface_addr from a link tuple included in the Link Set with
L_SYM_time >= current time (not expired) L_SYM_time >= current time (not expired)
(in other words: if the Originator Address is a symmetric neighbor) (in other words: if the Originator Address is a symmetric neighbor)
then the 2-hop Neighbor Set SHOULD be updated as follows: then the 2-hop Neighbor Set SHOULD be updated as follows:
1 for each address (henceforth: 2-hop neighbor address), listed 1 for each address (henceforth: 2-hop neighbor address), listed
in the HELLO message with Neighbor Type equal to SYM_NEIGH or in the HELLO message with Neighbor Type equal to SYM_NEIGH or
MPR_NEIGH: MPR_NEIGH:
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among its symmetric 1-hop neighborhood. The symmetric links with among its symmetric 1-hop neighborhood. The symmetric links with
MPRs are advertised with Link Type MPR_NEIGH instead of SYM_NEIGH in MPRs are advertised with Link Type MPR_NEIGH instead of SYM_NEIGH in
HELLO messages. HELLO messages.
The MPR set MUST be calculated by a node in such a way that it, The MPR set MUST be calculated by a node in such a way that it,
through the neighbors in the MPR-set, can reach all symmetric strict through the neighbors in the MPR-set, can reach all symmetric strict
2-hop neighbors. (Notice that a node, a, which is a direct neighbor 2-hop neighbors. (Notice that a node, a, which is a direct neighbor
of another node, b, is not also a strict 2-hop neighbor of node b). of another node, b, is not also a strict 2-hop neighbor of node b).
This means that the union of the symmetric 1-hop neighborhoods of the This means that the union of the symmetric 1-hop neighborhoods of the
MPR nodes contains the symmetric strict 2-hop neighborhood. MPR set MPR nodes contains the symmetric strict 2-hop neighborhood. MPR set
recalculation should occur when changes are detected in the neighbor- recalculation should occur when changes are detected in the
hood or in the 2-hop neighborhood. neighborhood or in the 2-hop neighborhood.
MPRs are computed per interface, the union of the MPR sets of each MPRs are computed per interface, the union of the MPR sets of each
interface make up the MPR set for the node. interface make up the MPR set for the node.
While it is not essential that the MPR set is minimal, it is While it is not essential that the MPR set is minimal, it is
essential that all strict 2-hop neighbors can be reached through the essential that all strict 2-hop neighbors can be reached through the
selected MPR nodes. A node SHOULD select an MPR set such that any selected MPR nodes. A node SHOULD select an MPR set such that any
strict 2-hop neighbor is covered by at least one MPR node. This strict 2-hop neighbor is covered by at least one MPR node. This
ensures that the overhead of the protocol is kept at a minimum. ensures that the overhead of the protocol is kept at a minimum.
skipping to change at page 43, line 36 skipping to change at page 43, line 36
(on the local node) has a link to any one interface of (on the local node) has a link to any one interface of
the neighbor node. the neighbor node.
2-hop neighbors reachable from an interface 2-hop neighbors reachable from an interface
the list of 2-hop neighbors of the node that can be the list of 2-hop neighbors of the node that can be
reached from neighbors of this interface. reached from neighbors of this interface.
MPR set of an interface MPR set of an interface
a (sub)set of the neighbors of an interface with a will- a (sub)set of the neighbors of an interface with a
ingness different from WILL_NEVER, selected such that willingness different from WILL_NEVER, selected such that
through these selected nodes, all strict 2-hop neighbors through these selected nodes, all strict 2-hop neighbors
reachable from that interface are reachable. reachable from that interface are reachable.
N: N:
N is the subset of neighbors of the node, which are N is the subset of neighbors of the node, which are
neighbor of the interface I. neighbor of the interface I.
N2: N2:
The set of two-hop neighbors reachable from the interface The set of two-hop neighbors reachable from the interface
I, excluding: I, excluding:
(i) the nodes only reachable by members of N with will- (i) the nodes only reachable by members of N with
ingness WILL_NEVER willingness WILL_NEVER
(ii) the node performing the computation (ii) the node performing the computation
(iii) (iii)
all the symmetric neighbors: the nodes for which all the symmetric neighbors: the nodes for which
there exists a symmetric link to this node on some there exists a symmetric link to this node on some
interface. interface.
D(y): D(y):
The degree of an one hop neighbor node y (where y is a The degree of an one hop neighbor node y (where y is a
member of N), is defined as the number of symmetric member of N), is defined as the number of symmetric
neighbors of node y, EXCLUDING all the members of N and neighbors of node y, EXCLUDING all the members of N and
EXCLUDING the node performing the computation. EXCLUDING the node performing the computation.
The proposed heuristic is as follows: The proposed heuristic is as follows:
1 Start with an MPR set made of all members of N with N_willing- 1 Start with an MPR set made of all members of N with
ness equal to WILL_ALWAYS N_willingness equal to WILL_ALWAYS
2 Calculate D(y), where y is a member of N, for all nodes in N. 2 Calculate D(y), where y is a member of N, for all nodes in N.
3 Add to the MPR set those nodes in N, which are the *only* 3 Add to the MPR set those nodes in N, which are the *only*
nodes to provide reachability to a node in N2. I.e. if node nodes to provide reachability to a node in N2. I.e. if node
b in N2 can be reached only through a symmetric link to node a b in N2 can be reached only through a symmetric link to node a
in N, then add node a to the MPR set. Remove the nodes from in N, then add node a to the MPR set. Remove the nodes from
N2 which are now covered by a node in the MPR set. N2 which are now covered by a node in the MPR set.
4 While there exist nodes in N2 which are not covered by at 4 While there exist nodes in N2 which are not covered by at
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other interfaces on node 'a'. other interfaces on node 'a'.
8.4. Populating the MPR Selector Set 8.4. Populating the MPR Selector Set
The MPR selector set of a node, n, is populated by the main addresses The MPR selector set of a node, n, is populated by the main addresses
of the nodes which have selected n as MPR. MPR selection is signaled of the nodes which have selected n as MPR. MPR selection is signaled
through HELLO messages. through HELLO messages.
8.4.1. HELLO Message Processing 8.4.1. HELLO Message Processing
Upon receiving a HELLO message, if a node finds one of its own inter- Upon receiving a HELLO message, if a node finds one of its own
face addresses in the list with a Neighbor Type equal to MPR_NEIGH, interface addresses in the list with a Neighbor Type equal to
information from the HELLO message must be recorded in the MPR Selec- MPR_NEIGH, information from the HELLO message must be recorded in the
tor Set. MPR Selector Set.
The "validity time" MUST be computed from the Vtime field of the mes- The "validity time" MUST be computed from the Vtime field of the
sage header (see section 3.3.2). The MPR Selector Set SHOULD message header (see section 3.3.2). The MPR Selector Set
then be updated as follows: SHOULD then be updated as follows:
1 If there exists no MPR selector tuple with: 1 If there exists no MPR selector tuple with:
MS_main_addr == Originator Address MS_main_addr == Originator Address
then a new tuple is created with: then a new tuple is created with:
MS_main_addr = Originator Address MS_main_addr = Originator Address
2 The tuple (new or otherwise) with 2 The tuple (new or otherwise) with
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MS_time = current time + validity time. MS_time = current time + validity time.
Deletion of MPR selector tuples occurs in case of expiration of the Deletion of MPR selector tuples occurs in case of expiration of the
timer or in case of link breakage as described in the "Neighborhood timer or in case of link breakage as described in the "Neighborhood
and 2-hop Neighborhood Changes". and 2-hop Neighborhood Changes".
8.5. Neighborhood and 2-hop Neighborhood Changes 8.5. Neighborhood and 2-hop Neighborhood Changes
A change in the neighborhood is detected when: A change in the neighborhood is detected when:
- The L_SYM_time field of a link tuple expires. This is consid- - The L_SYM_time field of a link tuple expires. This is
ered as a neighbor loss if the link described by the expired considered as a neighbor loss if the link described by the
tuple was the last link with a neighbor node (on the contrary, expired tuple was the last link with a neighbor node (on the
a link with an interface may break while a link with another contrary, a link with an interface may break while a link with
interface of the neighbor node remains without being observed another interface of the neighbor node remains without being
as a neighborhood change). observed as a neighborhood change).
- A new link tuple is inserted in the Link Set with a non- - A new link tuple is inserted in the Link Set with a non
expired L_SYM_time or a tuple with expired L_SYM_time is modi- expired L_SYM_time or a tuple with expired L_SYM_time is
fied so that L_SYM_time becomes non-expired. This is consid- modified so that L_SYM_time becomes non-expired. This is
ered as a neighbor appearance if there was previously no link considered as a neighbor appearance if there was previously no
tuple describing a link with the corresponding neighbor node. link tuple describing a link with the corresponding neighbor
node.
A change in the 2-hop neighborhood is detected when a 2-hop neighbor A change in the 2-hop neighborhood is detected when a 2-hop neighbor
tuple expires or is deleted according to section 8.2. tuple expires or is deleted according to section 8.2.
The following processing occurs when changes in the neighborhood or The following processing occurs when changes in the neighborhood or
the 2-hop neighborhood are detected: the 2-hop neighborhood are detected:
- In case of neighbor loss, all 2-hop tuples with N_neigh- - In case of neighbor loss, all 2-hop tuples with
bor_main_addr == Main Address of the neighbor MUST be deleted. N_neighbor_main_addr == Main Address of the neighbor MUST be
deleted.
- In case of neighbor loss, all MPR selector tuples with - In case of neighbor loss, all MPR selector tuples with
MS_main_addr == Main Address of the neighbor MUST be deleted MS_main_addr == Main Address of the neighbor MUST be deleted
- The MPR set MUST be re-calculated when a neighbor appearance - The MPR set MUST be re-calculated when a neighbor appearance
or loss is detected, or when a change in the 2-hop neighbor- or loss is detected, or when a change in the 2-hop
hood is detected. neighborhood is detected.
- An additional HELLO message MAY be sent when the MPR set - An additional HELLO message MAY be sent when the MPR set
changes. changes.
9. Topology Discovery 9. Topology Discovery
The link sensing and neighbor detection part of the protocol basi- The link sensing and neighbor detection part of the protocol
cally offers, to each node, a list of neighbors with which it can basically offers, to each node, a list of neighbors with which it can
communicate directly and, in combination with the Packet Format and communicate directly and, in combination with the Packet Format and
Forwarding part, an optimized flooding mechanism through MPRs. Based Forwarding part, an optimized flooding mechanism through MPRs. Based
on this, topology information is disseminated through the network. on this, topology information is disseminated through the network.
The present section describes what part of the information given by The present section describes what part of the information given by
the link sensing and neighbor detection is disseminated to the entire the link sensing and neighbor detection is disseminated to the entire
network and how it is used to construct routes. network and how it is used to construct routes.
Routes are constructed through advertised links and links with neigh- Routes are constructed through advertised links and links with
bors. A node must at least disseminate links between itself and the neighbors. A node must at least disseminate links between itself and
nodes in its MPR-selector set, in order to provide sufficient infor- the nodes in its MPR-selector set, in order to provide sufficient
mation to enable routing. information to enable routing.
9.1. TC Message Format 9.1. TC Message Format
The proposed format of a TC message is as follows: The proposed format of a TC message is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ANSN | Reserved | | ANSN | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 48, line 9 skipping to change at page 48, line 9
This is sent as the data-portion of the general message format with This is sent as the data-portion of the general message format with
the "Message Type" set to TC_MESSAGE. The time to live SHOULD be set the "Message Type" set to TC_MESSAGE. The time to live SHOULD be set
to 255 (maximum value) to diffuse the message into the entire network to 255 (maximum value) to diffuse the message into the entire network
and Vtime set accordingly to the value of TOP_HOLD_TIME, as specified and Vtime set accordingly to the value of TOP_HOLD_TIME, as specified
in section 18.3. in section 18.3.
Advertised Neighbor Sequence Number (ANSN) Advertised Neighbor Sequence Number (ANSN)
A sequence number is associated with the advertised neighbor A sequence number is associated with the advertised neighbor
set. Every time a node detects a change in its advertised set. Every time a node detects a change in its advertised
neighbor set, it increments this sequence number ("Wrap- neighbor set, it increments this sequence number ("Wraparound"
around" is handled as described in section 19). This is handled as described in section 19). This number
number is sent in this ANSN field of the TC message to keep is sent in this ANSN field of the TC message to keep track of
track of the most recent information. When a node receives a the most recent information. When a node receives a TC
TC message, it can decide on the basis of this Advertised message, it can decide on the basis of this Advertised
Neighbor Sequence Number, whether or not the received informa- Neighbor Sequence Number, whether or not the received
tion about the advertised neighbors of the originator node is information about the advertised neighbors of the originator
more recent than what it already has. node is more recent than what it already has.
Advertised Neighbor Main Address Advertised Neighbor Main Address
This field contains the main address of a neighbor node. All This field contains the main address of a neighbor node. All
main addresses of the advertised neighbors of the Originator main addresses of the advertised neighbors of the Originator
node are put in the TC message. If the maximum allowed mes- node are put in the TC message. If the maximum allowed
sage size (as imposed by the network) is reached while there message size (as imposed by the network) is reached while
are still advertised neighbor addresses which have not been there are still advertised neighbor addresses which have not
inserted into the TC-message, more TC messages will be gener- been inserted into the TC-message, more TC messages will be
ated until the entire advertised neighbor set has been sent. generated until the entire advertised neighbor set has been
Extra main addresses of neighbor nodes may be included, if sent. Extra main addresses of neighbor nodes may be included,
redundancy is desired. if redundancy is desired.
Reserved Reserved
This field is reserved, and MUST be set to "0000000000000000" This field is reserved, and MUST be set to "0000000000000000"
for compliance with this document. for compliance with this document.
9.2. Advertised Neighbor Set 9.2. Advertised Neighbor Set
A TC message is sent by a node in the network to declare a set of A TC message is sent by a node in the network to declare a set of
links, called advertised link set which MUST include at least the links, called advertised link set which MUST include at least the
links to all nodes of its MPR Selector set, i.e., the neighbors which links to all nodes of its MPR Selector set, i.e., the neighbors which
have selected the sender node as a MPR. have selected the sender node as a MPR.
If, for some reason, it is required to distribute redundant TC infor- If, for some reason, it is required to distribute redundant TC
mation, refer to section 15. information, refer to section 15.
The sequence number (ANSN) associated with the advertised neighbor The sequence number (ANSN) associated with the advertised neighbor
set is also sent with the list. The ANSN number MUST be incremented set is also sent with the list. The ANSN number MUST be incremented
when links are removed from the advertised neighbor set; the ANSN when links are removed from the advertised neighbor set; the ANSN
number SHOULD be incremented when links are added to the advertised number SHOULD be incremented when links are added to the advertised
neighbor set. neighbor set.
9.3. TC Message Generation 9.3. TC Message Generation
In order to build the topology information base, each node, which has In order to build the topology information base, each node, which has
been selected as MPR, broadcasts Topology Control (TC) messages. TC been selected as MPR, broadcasts Topology Control (TC) messages. TC
messages are flooded to all nodes in the network and take advantage messages are flooded to all nodes in the network and take advantage
of MPRs. MPRs enable a better scalability in the distribution of of MPRs. MPRs enable a better scalability in the distribution of
topology information [1]. topology information [1].
The list of addresses can be partial in each TC message (e.g. due to The list of addresses can be partial in each TC message (e.g. due to
message size limitations, imposed by the network), but parsing of all message size limitations, imposed by the network), but parsing of all
TC messages describing the advertised link set of a node MUST be com- TC messages describing the advertised link set of a node MUST be
plete within a certain refreshing period (TC_INTERVAL). The informa- complete within a certain refreshing period (TC_INTERVAL). The
tion diffused in the network by these TC messages will help each node information diffused in the network by these TC messages will help
calculate its routing table. each node calculate its routing table.
When the advertised link set of a node becomes empty, it SHOULD still When the advertised link set of a node becomes empty, it SHOULD still
send (empty) TC-messages during the a duration equal to the "validity send (empty) TC-messages during the a duration equal to the "validity
time" (typically, this will be equal to TC_HOLD_TIME) of its previ- time" (typically, this will be equal to TC_HOLD_TIME) of its
ously emitted TC-messages, in order to invalidate the previous TC- previously emitted TC-messages, in order to invalidate the previous
messages. It SHOULD then stop sending TC-messages until some node is TC-messages. It SHOULD then stop sending TC-messages until some node
inserted in its advertised link set. is inserted in its advertised link set.
A node MAY transmit additional TC-messages to increase its reactive- A node MAY transmit additional TC-messages to increase its
ness to link failures. When a change to the MPR selector set is reactiveness to link failures. When a change to the MPR selector set
detected and this change can be attributed to a link failure, a TC- is detected and this change can be attributed to a link failure, a
message SHOULD be transmitted after a shorter interval than TC_INTER- TC-message SHOULD be transmitted after a shorter interval than
VAL. TC_INTERVAL.
9.4. TC Message Forwarding 9.4. TC Message Forwarding
TC messages are broadcast and retransmitted by the MPRs in order to TC messages are broadcast and retransmitted by the MPRs in order to
diffuse the messages in the entire network. TC messages MUST be for- diffuse the messages in the entire network. TC messages MUST be
warded according to the "default forwarding algorithm". forwarded according to the "default forwarding algorithm".
9.5. TC Message Processing 9.5. TC Message Processing
Upon receiving a TC message, the "validity time" MUST be computed Upon receiving a TC message, the "validity time" MUST be computed
from the Vtime field of the message header (see section 3.3.2). from the Vtime field of the message header (see section 3.3.2).
The topology set SHOULD then be updated as follows (using section The topology set SHOULD then be updated as follows (using section
19 for comparison of ANSN): 19 for comparison of ANSN):
1 If the sender interface (NB: not originator) of this message 1 If the sender interface (NB: not originator) of this message
is not in the symmetric 1-hop neighborhood of this node, the is not in the symmetric 1-hop neighborhood of this node, the
message MUST be discarded. message MUST be discarded.
2 If there exist some tuple in the topology set where: 2 If there exist some tuple in the topology set where:
T_last_addr == originator address AND T_last_addr == originator address AND
T_seq > ANSN, T_seq > ANSN,
then further processing of this TC message MUST NOT be per- then further processing of this TC message MUST NOT be
formed and the message MUST be silently discarded (case: mes- performed and the message MUST be silently discarded (case:
sage received out of order). message received out of order).
3 All tuples in the topology set where: 3 All tuples in the topology set where:
T_last_addr == originator address AND T_last_addr == originator address AND
T_seq < ANSN T_seq < ANSN
MUST be removed from the topology set. MUST be removed from the topology set.
4 For each of the advertised neighbor main address received in 4 For each of the advertised neighbor main address received in
skipping to change at page 51, line 11 skipping to change at page 51, line 11
T_seq = ANSN, T_seq = ANSN,
T_time = current time + validity time. T_time = current time + validity time.
10. Routing Table Calculation 10. Routing Table Calculation
Each node maintains a routing table which allows it to route data, Each node maintains a routing table which allows it to route data,
destined for the other nodes in the network. The routing table is destined for the other nodes in the network. The routing table is
based on the information contained in the link set and the topology based on the information contained in the link set and the topology
set. Therefore, if any of these sets are changed, the routing table set. Therefore, if any of these sets are changed, the routing table
is re-calculated to update the route information about each destina- is recalculated to update the route information about each
tion in the network. The route entries are recorded in the routing destination in the network. The route entries are recorded in the
table in the following format: routing table in the following format:
1. R_dest_addr R_next_addr R_dist R_iface_addr 1. R_dest_addr R_next_addr R_dist R_iface_addr
2. R_dest_addr R_next_addr R_dist R_iface_addr 2. R_dest_addr R_next_addr R_dist R_iface_addr
3. ,, ,, ,, ,, 3. ,, ,, ,, ,,
Each entry in the table consists of R_dest_addr, R_next_addr, R_dist, Each entry in the table consists of R_dest_addr, R_next_addr, R_dist,
and R_iface_addr. Such entry specifies that the node identified by and R_iface_addr. Such entry specifies that the node identified by
R_dest_addr is estimated to be R_dist hops away from the local node, R_dest_addr is estimated to be R_dist hops away from the local node,
that the symmetric neighbor node with interface address R_next_addr that the symmetric neighbor node with interface address R_next_addr
is the next hop node in the route to R_dest_addr, and that this sym- is the next hop node in the route to R_dest_addr, and that this
metric neighbor node is reachable through the local interface with symmetric neighbor node is reachable through the local interface with
the address R_iface_addr. Entries are recorded in the routing table the address R_iface_addr. Entries are recorded in the routing table
for each destination in the network for which a route is known. All for each destination in the network for which a route is known. All
the destinations, for which a route is broken or only partially the destinations, for which a route is broken or only partially
known, are not recorded in the table. known, are not recorded in the table.
The routing table is updated when a change is detected in either: The routing table is updated when a change is detected in either:
- the link set, - the link set,
- the neighbor set, - the neighbor set,
- the 2-hop neighbor set, - the 2-hop neighbor set,
- the topology set, - the topology set,
- the Multiple Interface Association Information Base, - the Multiple Interface Association Information Base,
More precisely, the routing table is re-calculated in case of neigh- More precisely, the routing table is recalculated in case of neighbor
bor appearance or loss, when a 2-hop tuple is created or removed,when appearance or loss, when a 2-hop tuple is created or removed,when a
a topology tuple is created or removed or when multiple interface topology tuple is created or removed or when multiple interface
association information changes. The update of this routing informa- association information changes. The update of this routing
tion does not generate or trigger any messages to be transmitted, information does not generate or trigger any messages to be
neither in the network, nor in the 1-hop neighborhood. transmitted, neither in the network, nor in the 1-hop neighborhood.
To construct the routing table of node X, a shortest path algorithm To construct the routing table of node X, a shortest path algorithm
is run on the directed graph containing the arcs X -> Y where Y is is run on the directed graph containing the arcs X -> Y where Y is
any symmetric neighbor of X (with Neighbor Type equal to SYM), the any symmetric neighbor of X (with Neighbor Type equal to SYM), the
arcs Y -> Z where Y is a neighbor node with willingness different of arcs Y -> Z where Y is a neighbor node with willingness different of
WILL_NEVER and there exists an entry in the 2-hop Neighbor set with Y WILL_NEVER and there exists an entry in the 2-hop Neighbor set with Y
as N_neighbor_main_addr and Z as N_2hop_addr, and the arcs U -> V, as N_neighbor_main_addr and Z as N_2hop_addr, and the arcs U -> V,
where there exists an entry in the topology set with V as T_dest_addr where there exists an entry in the topology set with V as T_dest_addr
and U as T_last_addr. and U as T_last_addr.
The following procedure is given as an example to calculate (or re- The following procedure is given as an example to calculate (or
calculate) the routing table : recalculate) the routing table :
1 All the entries from the routing table are removed. 1 All the entries from the routing table are removed.
2 The new routing entries are added starting with the symmetric 2 The new routing entries are added starting with the symmetric
neighbors (h=1) as the destination nodes. I.e. for each neighbors (h=1) as the destination nodes. I.e. for each
neighbor tuple in the neighbor set where: neighbor tuple in the neighbor set where:
N_status = SYM N_status = SYM
(there is a symmetric link to the neighbor), and for each (there is a symmetric link to the neighbor), and for each
skipping to change at page 52, line 44 skipping to change at page 52, line 44
R_iface_addr = L_local_iface_addr of the R_iface_addr = L_local_iface_addr of the
associated link tuple. associated link tuple.
If in the above, no R_dest_addr is equal to the main address If in the above, no R_dest_addr is equal to the main address
of the neighbor, then another new routing entry with MUST be of the neighbor, then another new routing entry with MUST be
added, with: added, with:
R_dest_addr = main address of the neighbor; R_dest_addr = main address of the neighbor;
R_next_addr = L_neighbor_iface_addr of one of the R_next_addr = L_neighbor_iface_addr of one of the
associated link tuple with L_time >= cur- associated link tuple with L_time >=
rent time; current time;
R_dist = 1; R_dist = 1;
R_iface_addr = L_local_iface_addr of the R_iface_addr = L_local_iface_addr of the
associated link tuple. associated link tuple.
3 for each node in N2, i.e a 2-hop neighbor which is not a 3 for each node in N2, i.e a 2-hop neighbor which is not a
neighbor node or the node itself, and such that there exist at neighbor node or the node itself, and such that there exist at
least one entry in the 2-hop neighbor set where N_neigh- least one entry in the 2-hop neighbor set where
bor_main_addr correspond to a neighbor node with willingness N_neighbor_main_addr correspond to a neighbor node with
different of WILL_NEVER, one selects one 2-hop tuple and cre- willingness different of WILL_NEVER, one selects one 2-hop
ates one entry in the routing table with: tuple and creates one entry in the routing table with:
R_dest_addr = the main address of the two hop neighbor; R_dest_addr = the main address of the two hop neighbor;
R_next_addr = the R_next_addr of the entry in the R_next_addr = the R_next_addr of the entry in the
routing table with: routing table with:
R_dest_addr == N_neighbor_main_addr R_dest_addr == N_neighbor_main_addr
of the 2-hop tuple; of the 2-hop tuple;
R_dist = 2; R_dist = 2;
skipping to change at page 53, line 36 skipping to change at page 53, line 36
of the 2-hop tuple; of the 2-hop tuple;
3 The new route entries for the destination nodes h+1 hops away 3 The new route entries for the destination nodes h+1 hops away
are recorded in the routing table. The following procedure are recorded in the routing table. The following procedure
MUST be executed for each value of h, starting with h=2 and MUST be executed for each value of h, starting with h=2 and
incrementing it by 1 each time. The execution will stop if no incrementing it by 1 each time. The execution will stop if no
new entry is recorded in an iteration. new entry is recorded in an iteration.
3.1 For each topology entry in the topology table, if its 3.1 For each topology entry in the topology table, if its
T_dest_addr does not correspond to R_dest_addr of any T_dest_addr does not correspond to R_dest_addr of any
route entry in the routing table AND its T_last_addr cor- route entry in the routing table AND its T_last_addr
responds to R_dest_addr of a route entry whose R_dist is corresponds to R_dest_addr of a route entry whose R_dist
equal to h, then a new route entry MUST be recorded in is equal to h, then a new route entry MUST be recorded in
the routing table (if it does not already exist) where: the routing table (if it does not already exist) where:
R_dest_addr = T_dest_addr; R_dest_addr = T_dest_addr;
R_next_addr = R_next_addr of the recorded R_next_addr = R_next_addr of the recorded
route entry where: route entry where:
R_dest_addr == T_last_addr R_dest_addr == T_last_addr
R_dist = h+1; and R_dist = h+1; and
R_iface_addr = R_iface_addr of the recorded R_iface_addr = R_iface_addr of the recorded
route entry where: route entry where:
R_dest_addr == T_last_addr. R_dest_addr == T_last_addr.
3.2 Several topology entries may be used to select a next hop 3.2 Several topology entries may be used to select a next hop
R_next_addr for reaching the node R_dest_addr. When h=1, R_next_addr for reaching the node R_dest_addr. When h=1,
ties should be broken such that nodes with highest will- ties should be broken such that nodes with highest
ingness and MPR selectors are preferred as next hop. willingness and MPR selectors are preferred as next hop.
4 For each entry in the multiple interface association base 4 For each entry in the multiple interface association base
where there exists a routing entry such that: where there exists a routing entry such that:
R_dest_addr == I_main_addr (of the multiple interface R_dest_addr == I_main_addr (of the multiple interface
association entry) association entry)
AND there is no routing entry such that: AND there is no routing entry such that:
R_dest_addr == I_iface_addr R_dest_addr == I_iface_addr
skipping to change at page 55, line 24 skipping to change at page 55, line 24
11.3. Data Packet Forwarding 11.3. Data Packet Forwarding
OLSR itself does not perform packet forwarding. Rather, it maintains OLSR itself does not perform packet forwarding. Rather, it maintains
the routing table in the underlying operating system, which is the routing table in the underlying operating system, which is
assumed to be forwarding packets as specified in RFC1812. assumed to be forwarding packets as specified in RFC1812.
12. Non OLSR Interfaces 12. Non OLSR Interfaces
A node MAY be equipped with multiple interfaces, some of which do not A node MAY be equipped with multiple interfaces, some of which do not
participate in the OLSR MANET. These non-OLSR interfaces may be participate in the OLSR MANET. These non OLSR interfaces may be
point to point connections to other singular hosts or may connect to point to point connections to other singular hosts or may connect to
separate networks. separate networks.
In order to provide connectivity from the OLSR MANET interface(s) to In order to provide connectivity from the OLSR MANET interface(s) to
these non-OLSR interface(s), a node SHOULD be able to inject external these non OLSR interface(s), a node SHOULD be able to inject external
route information to the OLSR MANET. route information to the OLSR MANET.
Injecting routing information from the OLSR MANET to non-OLSR inter- Injecting routing information from the OLSR MANET to non OLSR
faces is outside the scope of this specification. It should be interfaces is outside the scope of this specification. It should be
clear, however, that the routing information for the OLSR MANET can clear, however, that the routing information for the OLSR MANET can
be extracted from the topology table (see section 4.4) or be extracted from the topology table (see section 4.4) or
directly from the routing table of OLSR, and SHOULD be injected onto directly from the routing table of OLSR, and SHOULD be injected onto
the non-OLSR interfaces following whatever mechanism (routing proto- the non OLSR interfaces following whatever mechanism (routing
col, static configuration etc.) is provided on these interfaces. protocol, static configuration etc.) is provided on these interfaces.
An example of such a situation could be where a node is equipped with An example of such a situation could be where a node is equipped with
a fixed network (e.g. an Ethernet) connecting to a larger network a fixed network (e.g. an Ethernet) connecting to a larger network
running, as well as a wireless network interface running OLSR. running, as well as a wireless network interface running OLSR.
Notice that this is a different case from that of "multiple inter- Notice that this is a different case from that of "multiple
faces", where all the interfaces are participating in the MANET interfaces", where all the interfaces are participating in the MANET
through running the OLSR protocol. through running the OLSR protocol.
In order to provide this capability of injecting external routing In order to provide this capability of injecting external routing
information into an OLSR MANET, a node with such non-MANET interfaces information into an OLSR MANET, a node with such non-MANET interfaces
periodically issues a Host and Network Association (HNA) message, periodically issues a Host and Network Association (HNA) message,
containing sufficient information for the recipients to construct an containing sufficient information for the recipients to construct an
appropriate routing table. appropriate routing table.
12.1. HNA Message Format 12.1. HNA Message Format
skipping to change at page 56, line 27 skipping to change at page 56, line 27
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Address | | Network Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Netmask | | Netmask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This is sent as the data part of the general packet format with the This is sent as the data part of the general packet format with the
"Message Type" set to HNA_MESSAGE, the TTL field set to 255 and Vtime "Message Type" set to HNA_MESSAGE, the TTL field set to 255 and Vtime
set accordingly to the value of HNA_HOLD_TIME, as specified in sec- set accordingly to the value of HNA_HOLD_TIME, as specified in
tion 18.3. section 18.3.
Network Address Network Address
The network address of the associated network The network address of the associated network
Netmask Netmask
The netmask, corresponding to the network address immediately The netmask, corresponding to the network address immediately
above. above.
12.2. Host and Network Association Information Base 12.2. Host and Network Association Information Base
Each node maintains information concerning which nodes may act as Each node maintains information concerning which nodes may act as
"gateways" to associated hosts and networks by recording "association "gateways" to associated hosts and networks by recording "association
tuples" (A_gateway_addr, A_network_addr, A_netmask, A_time), where tuples" (A_gateway_addr, A_network_addr, A_netmask, A_time), where
A_gateway_addr is the address of a OLSR interface of the gateway, A_gateway_addr is the address of a OLSR interface of the gateway,
A_network_addr and A_netmask specify the network address and netmask A_network_addr and A_netmask specify the network address and netmask
of a network, reachable through this gateway, and A_time specifies of a network, reachable through this gateway, and A_time specifies
the time at which this tuple expires and hence *MUST* be removed. the time at which this tuple expires and hence *MUST* be removed.
The set of all association tuples in a node is called the "associa- The set of all association tuples in a node is called the
tion set". "association set".
It should be noticed, that the HNA-message can be considered as a It should be noticed, that the HNA-message can be considered as a
"generalized version" of the TC-message: the originator of both the "generalized version" of the TC-message: the originator of both the
HNA- and TC-messages announce "reachability" to some other host(s). HNA- and TC-messages announce "reachability" to some other host(s).
In the TC-message, no netmask is required, since all reachability is In the TC-message, no netmask is required, since all reachability is
announced on a per-host basis. In HNA-messages, announcing reacha- announced on a per-host basis. In HNA-messages, announcing
bility to an address sequence through a network- and netmask address reachability to an address sequence through a network- and netmask
is typically preferred over announcing reachability to individual address is typically preferred over announcing reachability to
host addresses. individual host addresses.
An important difference between TC- and HNA-messages is, that a TC An important difference between TC- and HNA-messages is, that a TC
message may have a canceling effect on previous information (if the message may have a canceling effect on previous information (if the
ANSN is incremented), whereas information in HNA-messages is removed ANSN is incremented), whereas information in HNA-messages is removed
only upon expiration. only upon expiration.
12.3. HNA Message Generation 12.3. HNA Message Generation
A node with associated hosts and/or networks SHOULD periodically gen- A node with associated hosts and/or networks SHOULD periodically
erate a Host and Network Association (HNA) message, containing pairs generate a Host and Network Association (HNA) message, containing
of (network address, netmask) corresponding to the connected hosts pairs of (network address, netmask) corresponding to the connected
and networks. HNA-messages SHOULD be transmitted periodically every hosts and networks. HNA-messages SHOULD be transmitted periodically
HNA_INTERVAL. The Vtime is set accordingly to the value of every HNA_INTERVAL. The Vtime is set accordingly to the value of
HNA_HOLD_TIME, as specified in section 18.3. HNA_HOLD_TIME, as specified in section 18.3.
A node without any associated hosts and/or networks SHOULD NOT gener- A node without any associated hosts and/or networks SHOULD NOT
ate HNA-messages. generate HNA-messages.
12.4. HNA Message Forwarding 12.4. HNA Message Forwarding
Upon receiving a HNA message, and thus following the rules of section Upon receiving a HNA message, and thus following the rules of section
3, in this version of the specification, the message MUST be 3, in this version of the specification, the message MUST be
forwarded according to section 3.4. forwarded according to section 3.4.
12.5. HNA Message Processing 12.5. HNA Message Processing
In this section, the term "originator address" is used to designate In this section, the term "originator address" is used to designate
skipping to change at page 59, line 22 skipping to change at page 59, line 22
then the routing entry is modified as follows: then the routing entry is modified as follows:
R_dest_addr = A_network_addr/A_netmask R_dest_addr = A_network_addr/A_netmask
R_next_addr = the next hop on the path R_next_addr = the next hop on the path
from the node to A_gateway_addr from the node to A_gateway_addr
R_dist = dist to A_gateway_addr R_dist = dist to A_gateway_addr
R_next_addr and R_iface_addr MUST be set to the same val- R_next_addr and R_iface_addr MUST be set to the same
ues as the tuple from the routing set with R_dest_addr == values as the tuple from the routing set with R_dest_addr
A_gateway_addr. == A_gateway_addr.
12.7. Interoperability Considerations 12.7. Interoperability Considerations
Nodes, which do not implement support for non-OLSR interfaces, can Nodes, which do not implement support for non OLSR interfaces, can
coexist in a network with nodes which do implement support for non- coexist in a network with nodes which do implement support for non
OLSR interfaces: the generic packet format and message forwarding OLSR interfaces: the generic packet format and message forwarding
(section 3) ensures that HNA messages are correctly for- (section 3) ensures that HNA messages are correctly
warded by all nodes . Nodes which implement support for non-OLSR forwarded by all nodes . Nodes which implement support for non OLSR
interfaces may thus transmit and process HNA messages according to interfaces may thus transmit and process HNA messages according to
this section. this section.
Nodes, which do not implement support for non-OLSR interfaces can not Nodes, which do not implement support for non OLSR interfaces can not
take advantage of the functionality specified in this section, how- take advantage of the functionality specified in this section,
ever will forward HNA messages correctly, as specified in section however will forward HNA messages correctly, as specified in section
3. 3.
13. Link Layer Notification 13. Link Layer Notification
OLSR is designed not to impose or expect any specific information OLSR is designed not to impose or expect any specific information
from the link layer. However, if information from the link-layer from the link layer. However, if information from the link-layer
describing link breakage is available, a node MAY use this as describing link breakage is available, a node MAY use this as
described in this section. described in this section.
If link layer information describing connectivity to neighboring If link layer information describing connectivity to neighboring
skipping to change at page 60, line 22 skipping to change at page 60, line 21
Each link tuple in the local link set SHOULD, in addition to what is Each link tuple in the local link set SHOULD, in addition to what is
described in section 4.2, include a L_LOST_LINK_time field. described in section 4.2, include a L_LOST_LINK_time field.
L_LOST_LINK_time is a timer for declaring a link as lost when an L_LOST_LINK_time is a timer for declaring a link as lost when an
established link becomes pending. (Notice, that this is a subset of established link becomes pending. (Notice, that this is a subset of
what is recommended in section 14, thus link hysteresis what is recommended in section 14, thus link hysteresis
and link layer notifications can coexist). and link layer notifications can coexist).
HELLO message generation should consider those new fields as follows: HELLO message generation should consider those new fields as follows:
1 if L_LOST_LINK_time is not expired, the link is advertised 1 if L_LOST_LINK_time is not expired, the link is advertised
with a link type of LOST_LINK. In addition, it is not consid- with a link type of LOST_LINK. In addition, it is not
ered as a symmetrical link in the updates of the associated considered as a symmetrical link in the updates of the
neighbor tuple (see section 8.1). associated neighbor tuple (see section 8.1).
2 if the link to a neighboring symmetric or asymmetric interface 2 if the link to a neighboring symmetric or asymmetric interface
is broken, the corresponding link tuple is modified: is broken, the corresponding link tuple is modified:
L_LOST_LINK_time and L_time are set to current time + L_LOST_LINK_time and L_time are set to current time +
NEIGHB_HOLD_TIME. NEIGHB_HOLD_TIME.
3 this is considered as a link loss and the appropriate process- 3 this is considered as a link loss and the appropriate
ing described in section 8.5 should be performed. processing described in section 8.5 should be
performed.
13.1. Interoperability Considerations 13.1. Interoperability Considerations
Link layer notifications provide, for a node, an additional criterion Link layer notifications provide, for a node, an additional criterion
by which a node may determine if a link to a neighbor node is lost. by which a node may determine if a link to a neighbor node is lost.
Once a link is detected as lost, it is advertised, in accordance with Once a link is detected as lost, it is advertised, in accordance with
the provisions described in the previous sections of this specifica- the provisions described in the previous sections of this
tion. specification.
14. Link Hysteresis 14. Link Hysteresis
Established links should be as reliable as possible to avoid data Established links should be as reliable as possible to avoid data
packet loss. This implies that link sensing should be robust against packet loss. This implies that link sensing should be robust against
bursty loss or transient connectivity between nodes. Hence, to bursty loss or transient connectivity between nodes. Hence, to
enhance the robustness of the link sensing mechanism, the following enhance the robustness of the link sensing mechanism, the following
implementation recommendations SHOULD be considered. implementation recommendations SHOULD be considered.
14.1. Local Link Set 14.1. Local Link Set
Each link tuple in the local link set SHOULD, in addition to what is Each link tuple in the local link set SHOULD, in addition to what is
described in section 4.2, include a L_link_pending field, a described in section 4.2, include a L_link_pending field, a
L_link_quality field, and a L_LOST_LINK_time field. L_link_pending L_link_quality field, and a L_LOST_LINK_time field. L_link_pending
is a boolean value specifying if the link is considered pending (i.e. is a boolean value specifying if the link is considered pending (i.e.
the link is not considered established). L_link_quality is a dimen- the link is not considered established). L_link_quality is a
sionless number between 0 and 1 describing the quality of the link. dimensionless number between 0 and 1 describing the quality of the
L_LOST_LINK_time is a timer for declaring a link as lost when an link. L_LOST_LINK_time is a timer for declaring a link as lost when
established link becomes pending. an established link becomes pending.
14.2. Hello Message Generation 14.2. Hello Message Generation
HELLO message generation should consider those new fields as follows: HELLO message generation should consider those new fields as follows:
1 if L_LOST_LINK_time is not expired, the link is advertised 1 if L_LOST_LINK_time is not expired, the link is advertised
with a link type of LOST_LINK. with a link type of LOST_LINK.
2 otherwise, if L_LOST_LINK_time is expired and L_link_pending 2 otherwise, if L_LOST_LINK_time is expired and L_link_pending
is set to "true", the link SHOULD NOT be advertised at all; is set to "true", the link SHOULD NOT be advertised at all;
3 otherwise, if L_LOST_LINK_time is expired and L_link_pending 3 otherwise, if L_LOST_LINK_time is expired and L_link_pending
is set to "false", the link is advertised as described previ- is set to "false", the link is advertised as described
ously in section 6. previously in section 6.
A node considers that it has a symmetric link for each link tuple A node considers that it has a symmetric link for each link tuple
where: where:
1 L_LOST_LINK_time is expired, AND 1 L_LOST_LINK_time is expired, AND
2 L_link_pending is "false", AND 2 L_link_pending is "false", AND
3 L_SYM_time is not expired. 3 L_SYM_time is not expired.
skipping to change at page 62, line 17 skipping to change at page 62, line 17
does not modify the function of any other fields in the link tuples. does not modify the function of any other fields in the link tuples.
14.3. Hysteresis Strategy 14.3. Hysteresis Strategy
The link between a node and some of its neighbor interfaces might be The link between a node and some of its neighbor interfaces might be
"bad", i.e. from time to time let HELLOs pass through only to fade "bad", i.e. from time to time let HELLOs pass through only to fade
out immediately after. In this case, the neighbor information base out immediately after. In this case, the neighbor information base
would contain a bad link for at least "validity time". The following would contain a bad link for at least "validity time". The following
hysteresis strategy SHOULD be adopted to counter this situation. hysteresis strategy SHOULD be adopted to counter this situation.
For each neighbor interface NI heard by interface I, the L_link_qual- For each neighbor interface NI heard by interface I, the
ity field of the corresponding Link Tuple determines the establish- L_link_quality field of the corresponding Link Tuple determines the
ment of the link. The value of L_link_quality is compared to two establishment of the link. The value of L_link_quality is compared
thresholds HYST_THRESHOLD_HIGH, HYST_THRESHOLD_LOW, fixed between 0 to two thresholds HYST_THRESHOLD_HIGH, HYST_THRESHOLD_LOW, fixed
and 1 and such that HYST_THRESHOLD_HIGH >= HYST_THRESHOLD_LOW. between 0 and 1 and such that HYST_THRESHOLD_HIGH >=
HYST_THRESHOLD_LOW.
The L_link_pending field is set according to the following: The L_link_pending field is set according to the following:
1 if L_link_quality > HYST_THRESHOLD_HIGH: 1 if L_link_quality > HYST_THRESHOLD_HIGH:
L_link_pending = false L_link_pending = false
L_LOST_LINK_time = current time - 1 (expired) L_LOST_LINK_time = current time - 1 (expired)
2 otherwise, if L_link_quality < HYST_THRESHOLD_LOW: 2 otherwise, if L_link_quality < HYST_THRESHOLD_LOW:
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L_link_pending and L_LOST_LINK_time remain unchanged. L_link_pending and L_LOST_LINK_time remain unchanged.
The condition for considering a link established is thus stricter The condition for considering a link established is thus stricter
than the condition for dropping a link. Notice thus, that a link can than the condition for dropping a link. Notice thus, that a link can
be dropped based on either timer expiration (as described in section be dropped based on either timer expiration (as described in section
7) or on L_link_quality dropping below HYST_THRESHOLD_LOW. 7) or on L_link_quality dropping below HYST_THRESHOLD_LOW.
Also notice, that even if a link is not considered as established by Also notice, that even if a link is not considered as established by
the link hysteresis, the link tuples are still updated for each the link hysteresis, the link tuples are still updated for each
received HELLO message (as described in section 7). Specif- received HELLO message (as described in section 7).
ically, this implies that, regardless of whether or not the link hys- Specifically, this implies that, regardless of whether or not the
teresis considers a link as "established", tuples in the link set do link hysteresis considers a link as "established", tuples in the link
not expire except as determined by the L_time field of the link set do not expire except as determined by the L_time field of the
tuples. link tuples.
As a basic implementation requirement, an estimation of the link As a basic implementation requirement, an estimation of the link
quality must be maintained and stored in the L_link_quality field. quality must be maintained and stored in the L_link_quality field.
If some measure of the signal/noise level on a received message is If some measure of the signal/noise level on a received message is
available (e.g. as a link layer notification), then it can be used available (e.g. as a link layer notification), then it can be used
as estimation after normalization. as estimation after normalization.
If no signal/noise information or other link quality information is If no signal/noise information or other link quality information is
available from the link layer, an algorithm such as the following can available from the link layer, an algorithm such as the following can
be utilized (it is an exponentially smoothed moving average of the be utilized (it is an exponentially smoothed moving average of the
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+ HYST_SCALING. + HYST_SCALING.
When an OLSR packet emitted by NI is lost by I, the instability When an OLSR packet emitted by NI is lost by I, the instability
rule is applied: rule is applied:
L_link_quality = (1-HYST_SCALING)*L_link_quality. L_link_quality = (1-HYST_SCALING)*L_link_quality.
The loss of OLSR packet is detected by tracking the missing Packet The loss of OLSR packet is detected by tracking the missing Packet
Sequence Numbers on a per interface basis and by "long period of Sequence Numbers on a per interface basis and by "long period of
silence" from a node. A "long period of silence may be detected silence" from a node. A "long period of silence may be detected
thus: if no OLSR packet has been received on interface I from inter- thus: if no OLSR packet has been received on interface I from
face NI during HELLO emission interval of interface NI (computed from interface NI during HELLO emission interval of interface NI (computed
the Htime field in the last HELLO message received from NI), a loss from the Htime field in the last HELLO message received from NI), a
of an OLSR packet is detected. loss of an OLSR packet is detected.
14.4. Interoperability Considerations 14.4. Interoperability Considerations
Link hysteresis determines, for a node, the criteria at which a link Link hysteresis determines, for a node, the criteria at which a link
to a neighbor node is accepted or rejected. Nodes in a network may to a neighbor node is accepted or rejected. Nodes in a network may
have different criteria, according to e.g. the nature of the media have different criteria, according to e.g. the nature of the media
over which they are communicating. Once a link is accepted, it is over which they are communicating. Once a link is accepted, it is
advertised, in accordance with the provisions described in the previ- advertised, in accordance with the provisions described in the
ous sections of this specification. previous sections of this specification.
15. Redundant Topology Information 15. Redundant Topology Information
In order to provide redundancy to topology information base, the In order to provide redundancy to topology information base, the
advertised link set of a node MAY contain links to neighbor nodes advertised link set of a node MAY contain links to neighbor nodes
which are not in MPR selector set of the node. The advertised link which are not in MPR selector set of the node. The advertised link
set MAY contain links to the whole neighbor set of the node. The set MAY contain links to the whole neighbor set of the node. The
minimal set of links that any node MUST advertise in its TC messages minimal set of links that any node MUST advertise in its TC messages
is the links to the nodes MPR selectors. The advertised link set can is the links to the nodes MPR selectors. The advertised link set can
be built according to the following rule based on a local parameter be built according to the following rule based on a local parameter
called TC_REDUNDANCY parameter. called TC_REDUNDANCY parameter.
15.1. TC_REDUNDANCY Parameter 15.1. TC_REDUNDANCY Parameter
The parameter TC_REDUNDANCY specifies, for the local node, the amount The parameter TC_REDUNDANCY specifies, for the local node, the amount
of information that MAY be included in the TC messages. The parame- of information that MAY be included in the TC messages. The
ter SHOULD be interpreted as follows: parameter SHOULD be interpreted as follows:
- if the TC_REDUNDANCY parameter of the node is 0, then the - if the TC_REDUNDANCY parameter of the node is 0, then the
advertised link set of the node set is limited to the MPR advertised link set of the node set is limited to the MPR
selector set (as described in section 8.3), selector set (as described in section 8.3),
- if the TC_REDUNDANCY parameter of the node is 1, then the - if the TC_REDUNDANCY parameter of the node is 1, then the
advertised link set of the node is the union of its MPR set advertised link set of the node is the union of its MPR set
and its MPR selector set, and its MPR selector set,
- if the TC_REDUNDANCY parameter of the node is 2, then the - if the TC_REDUNDANCY parameter of the node is 2, then the
advertised link set of the node is the full neighbor link set. advertised link set of the node is the full neighbor link set.
A node with willingness equal to WILL_NEVER SHOULD have TC_REDUNDANCY A node with willingness equal to WILL_NEVER SHOULD have TC_REDUNDANCY
also equal to zero. also equal to zero.
15.2. Interoperability Considerations 15.2. Interoperability Considerations
A TC message is sent by a node in the network to declare a set of A TC message is sent by a node in the network to declare a set of
links, called advertised link set which MUST include at least the links, called advertised link set which MUST include at least the
links to all nodes of its MPR Selector set, i.e., the neighbors which links to all nodes of its MPR Selector set, i.e., the neighbors which
have selected the sender node as a MPR. This is sufficient informa- have selected the sender node as a MPR. This is sufficient
tion to ensure that routes can be computed in accordance with section information to ensure that routes can be computed in accordance with
10. section 10.
The provisions in this section specifies how additional information The provisions in this section specifies how additional information
may be declared, as specified through a TC_REDUNDANCY parameter. may be declared, as specified through a TC_REDUNDANCY parameter.
TC_REDUNDANCY = 0 implies that the information declared corresponds TC_REDUNDANCY = 0 implies that the information declared corresponds
exactly to the MPR Selector set, identical to section 9. Other exactly to the MPR Selector set, identical to section 9. Other
values of TC_REDUNDANCY specifies additional information to be values of TC_REDUNDANCY specifies additional information to be
declared, i.e. the contents of the MPR Selector set is always declared, i.e. the contents of the MPR Selector set is always
declared. Thus, nodes with different values of TC_REDUNDANCY may declared. Thus, nodes with different values of TC_REDUNDANCY may
coexist in a network: control messages are carried by all nodes in coexist in a network: control messages are carried by all nodes in
accordance with section 3, and all nodes will receive at accordance with section 3, and all nodes will receive at
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nodes, thus additional links are diffused to the network. nodes, thus additional links are diffused to the network.
While, in general, a minimal MPR set provides the least overhead, While, in general, a minimal MPR set provides the least overhead,
there are situations in which overhead can be traded off for other there are situations in which overhead can be traded off for other
benefits. E.g. a node can may decide to increase its MPR coverage benefits. E.g. a node can may decide to increase its MPR coverage
if it observes many changes in its neighbor information base caused if it observes many changes in its neighbor information base caused
by mobility, while otherwise keeping a low MPR coverage. by mobility, while otherwise keeping a low MPR coverage.
16.1. MPR_COVERAGE Parameter 16.1. MPR_COVERAGE Parameter
The MPR coverage is defined by a single local parameter, MPR_COVER- The MPR coverage is defined by a single local parameter,
AGE, specifying by how many MPR nodes any strict 2-hop node should be MPR_COVERAGE, specifying by how many MPR nodes any strict 2-hop node
covered. MPR_COVERAGE=1 specifies that the overhead of the protocol should be covered. MPR_COVERAGE=1 specifies that the overhead of the
is kept at a minimum and causes the MPR selection to operate as protocol is kept at a minimum and causes the MPR selection to operate
described in section 8.3.1. MPR_COVERAGE=m ensures that, if as described in section 8.3.1. MPR_COVERAGE=m ensures that,
possible, a node selects its MPR set such that all strict 2-hop nodes if possible, a node selects its MPR set such that all strict 2-hop
for an interface are reachable through at least m MPR nodes on that nodes for an interface are reachable through at least m MPR nodes on
interface. MPR_COVERAGE can assume any integer value > 0. The that interface. MPR_COVERAGE can assume any integer value > 0. The
heuristic MUST be applied per interface, I. The MPR set for a node heuristic MUST be applied per interface, I. The MPR set for a node
is the union of the MPR sets found for each interface. is the union of the MPR sets found for each interface.
Notice that MPR_COVERAGE can be tuned locally without affecting the Notice that MPR_COVERAGE can be tuned locally without affecting the
consistency of the protocol. I.e. nodes in a network may operate consistency of the protocol. I.e. nodes in a network may operate
with different values of MPR_COVERAGE. with different values of MPR_COVERAGE.
16.2. MPR Computation 16.2. MPR Computation
Using MPR coverage, the MPR selection heuristics is extended from Using MPR coverage, the MPR selection heuristics is extended from
that described in the section 8.3.1 by one definition: that described in the section 8.3.1 by one definition:
Poorly covered node: Poorly covered node:
A poorly covered node is a node in N2 which is covered by less A poorly covered node is a node in N2 which is covered by less
than MPR_COVERAGE nodes in N. than MPR_COVERAGE nodes in N.
The proposed heuristic for selecting MPRs is then as follows: The proposed heuristic for selecting MPRs is then as follows:
1 Start with an MPR set made of all members of N with willing- 1 Start with an MPR set made of all members of N with
ness equal to WILL_ALWAYS willingness equal to WILL_ALWAYS
2 Calculate D(y), where y is a member of N, for all nodes in N. 2 Calculate D(y), where y is a member of N, for all nodes in N.
3 Select as MPRs those nodes in N which cover the poorly covered 3 Select as MPRs those nodes in N which cover the poorly covered
nodes in N2. The nodes are then removed from N2 for the rest nodes in N2. The nodes are then removed from N2 for the rest
of the computation. of the computation.
4 While there exist nodes in N2 which are not covered by at 4 While there exist nodes in N2 which are not covered by at
least MPR_COVERAGE nodes in the MPR set: least MPR_COVERAGE nodes in the MPR set:
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nodes in N2. The nodes are then removed from N2 for the rest nodes in N2. The nodes are then removed from N2 for the rest
of the computation. of the computation.
4 While there exist nodes in N2 which are not covered by at 4 While there exist nodes in N2 which are not covered by at
least MPR_COVERAGE nodes in the MPR set: least MPR_COVERAGE nodes in the MPR set:
4.1 For each node in N, calculate the reachability, i.e. the 4.1 For each node in N, calculate the reachability, i.e. the
number of nodes in N2 which are not yet covered by at number of nodes in N2 which are not yet covered by at
least MPR_COVERAGE nodes in the MPR set, and which are least MPR_COVERAGE nodes in the MPR set, and which are
reachable through this one hop neighbor; reachable through this one hop neighbor;
4.2 Select as a MPR the node with highest willingness among 4.2 Select as a MPR the node with highest willingness among
the nodes in N with non-zero reachability. In case of the nodes in N with non-zero reachability. In case of
multiple choice select the node which provides reachabil- multiple choice select the node which provides
ity to the maximum number of nodes in N2. In case of reachability to the maximum number of nodes in N2. In
multiple nodes providing the same amount of reachability, case of multiple nodes providing the same amount of
select the node as MPR whose D(y) is greater. Remove the reachability, select the node as MPR whose D(y) is
nodes from N2 which are now covered by MPR_COVERAGE nodes greater. Remove the nodes from N2 which are now covered
in the MPR set. by MPR_COVERAGE nodes in the MPR set.
5 A node's MPR set is generated from the union of the MPR sets 5 A node's MPR set is generated from the union of the MPR sets
for each interface. As an optimization, process each node, y, for each interface. As an optimization, process each node, y,
in the MPR set in increasing order of N_willingness. If all in the MPR set in increasing order of N_willingness. If all
nodes in N2 are still covered by at least MPR_COVERAGE nodes nodes in N2 are still covered by at least MPR_COVERAGE nodes
in the MPR set excluding node y, and if N_willingness of node in the MPR set excluding node y, and if N_willingness of node
y is smaller than WILL_ALWAYS, then node y MAY be removed from y is smaller than WILL_ALWAYS, then node y MAY be removed from
the MPR set. the MPR set.
When the MPR set has been computed, all the corresponding main When the MPR set has been computed, all the corresponding main
addresses are stored in the MPR Set. addresses are stored in the MPR Set.
16.3. Interoperability Considerations 16.3. Interoperability Considerations
The MPR set of a node MUST, according to section 8.3, be cal- The MPR set of a node MUST, according to section 8.3, be
culated by a node in such a way that it, through the neighbors in the calculated by a node in such a way that it, through the neighbors in
MPR-set, can reach all symmetric strict 2-hop neighbors. This is the MPR-set, can reach all symmetric strict 2-hop neighbors. This is
achieved by the heuristics in this section, for all values of achieved by the heuristics in this section, for all values of
MPR_COVERAGE > 0. MPR_COVERAGE is a local parameter for each node. MPR_COVERAGE > 0. MPR_COVERAGE is a local parameter for each node.
Setting this parameter affects only the amount of redundancy in part Setting this parameter affects only the amount of redundancy in part
of the network. of the network.
Notice that for MPR_COVERAGE=1, the heuristics in this section is Notice that for MPR_COVERAGE=1, the heuristics in this section is
identical to the heuristics specified in the section 8.3.1. identical to the heuristics specified in the section 8.3.1.
Nodes with different values of MPR_COVERAGE may coexist in a network: Nodes with different values of MPR_COVERAGE may coexist in a network:
control messages are carried by all nodes in accordance with section control messages are carried by all nodes in accordance with section
3, and all nodes will receive at least the link-state infor- 3, and all nodes will receive at least the link-state
mation required to construct routes as described in sections 9 information required to construct routes as described in sections
and 10. #REF:td and 10.
17. IPv6 Considerations 17. IPv6 Considerations
All the operations and parameters described in this document used by All the operations and parameters described in this document used by
OLSR for IP version 4 are the same as those used by OLSR for IP ver- OLSR for IP version 4 are the same as those used by OLSR for IP
sion 6. To operate with IP version 6, the only required change is to version 6. To operate with IP version 6, the only required change is
replace the IPv4 addresses with IPv6 address. The minimum packet and to replace the IPv4 addresses with IPv6 address. The minimum packet
message sizes (under which there is rejection) should be adjusted and message sizes (under which there is rejection) should be adjusted
accordingly, considering the greater size of IPv6 addresses. accordingly, considering the greater size of IPv6 addresses.
18. Proposed Values for Constants 18. Proposed Values for Constants
This section list the values for the constants used in the descrip- This section list the values for the constants used in the
tion of the protocol. description of the protocol.
18.1. Setting emission intervals and holding times 18.1. Setting emission intervals and holding times
The proposed constant for C is the following: The proposed constant for C is the following:
C = 1/16 seconds (equal to 0.0625 seconds) C = 1/16 seconds (equal to 0.0625 seconds)
C is a scaling factor for the "validity time" calculation ("Vtime" C is a scaling factor for the "validity time" calculation ("Vtime"
and "Htime" fields in message headers, see section 18.3). and "Htime" fields in message headers, see section 18.3).
The "validity time" advertisement is designed such that nodes in a The "validity time" advertisement is designed such that nodes in a
network may have different and individually tuneable emission inter- network may have different and individually tuneable emission
vals, while still interoperate fully. For protocol functioning and intervals, while still interoperate fully. For protocol functioning
interoperability to work: and interoperability to work:
- the advertised holding time MUST always be greater than the - the advertised holding time MUST always be greater than the
refresh interval of the advertised information. Moreover, it refresh interval of the advertised information. Moreover, it
is recommended that the relation between the interval (from is recommended that the relation between the interval (from
section 18.2), and the hold time is kept as specified section 18.2), and the hold time is kept as specified
in section 18.3, to allow for reasonable packet loss. in section 18.3, to allow for reasonable packet loss.
- the constant C SHOULD be set to the suggested value. In order - the constant C SHOULD be set to the suggested value. In order
to achieve interoperability, C MUST be the same on all nodes. to achieve interoperability, C MUST be the same on all nodes.
- the emission intervals (section 18.2), along with the - the emission intervals (section 18.2), along with the
advertised holding times (subject to the above constraints) advertised holding times (subject to the above constraints)
MAY be selected on a per node basis. MAY be selected on a per node basis.
Note that the timer resolution of a given implementation might not be Note that the timer resolution of a given implementation might not be
sufficient to wake up the system on precise refresh times or on pre- sufficient to wake up the system on precise refresh times or on
cise expire times: the implementation SHOULD round up the 'validity precise expire times: the implementation SHOULD round up the
time' ("Vtime" and "Htime" of packets) to compensate for coarser 'validity time' ("Vtime" and "Htime" of packets) to compensate for
timer resolution, at least in the case where "validity time" could be coarser timer resolution, at least in the case where "validity time"
shorter than the sum of emission interval and maximum expected timer could be shorter than the sum of emission interval and maximum
error. expected timer error.
18.2. Emission Intervals 18.2. Emission Intervals
HELLO_INTERVAL = 2 seconds
HELLO_INTERVAL = 2 seconds
REFRESH_INTERVAL = 2 seconds REFRESH_INTERVAL = 2 seconds
TC_INTERVAL = 5 seconds TC_INTERVAL = 5 seconds
MID_INTERVAL = TC_INTERVAL MID_INTERVAL = TC_INTERVAL
HNA_INTERVAL = TC_INTERVAL HNA_INTERVAL = TC_INTERVAL
18.3. Holding Time 18.3. Holding Time
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field and b the integer represented by the four lowest bits of the field and b the integer represented by the four lowest bits of the
field. field.
Notice, that for the previous proposed value of C, (1/16 seconds), Notice, that for the previous proposed value of C, (1/16 seconds),
the values, in seconds, expressed by the formula above can be stored, the values, in seconds, expressed by the formula above can be stored,
without loss of precision, in binary fixed point or floating point without loss of precision, in binary fixed point or floating point
numbers with at least 8 bits of fractional part. This corresponds numbers with at least 8 bits of fractional part. This corresponds
with NTP time-stamps and single precision IEEE Standard 754 floating with NTP time-stamps and single precision IEEE Standard 754 floating
point numbers. point numbers.
Given one of the above holding times, a way of computing the man- Given one of the above holding times, a way of computing the
tissa/exponent representation of a number T (of seconds) is the fol- mantissa/exponent representation of a number T (of seconds) is the
lowing: following:
- find the largest integer 'b' such that: T/C >= 2^b - find the largest integer 'b' such that: T/C >= 2^b
- compute the expression 16*(T/(C*(2^b))-1), which may not be a - compute the expression 16*(T/(C*(2^b))-1), which may not be a
integer, and round it up. This results in the value for 'a' integer, and round it up. This results in the value for 'a'
- if 'a' is equal to 16: increment 'b' by one, and set 'a' to 0 - if 'a' is equal to 16: increment 'b' by one, and set 'a' to 0
- now, 'a' and 'b' should be integers between 0 and 15, and the - now, 'a' and 'b' should be integers between 0 and 15, and the
field will be a byte holding the value a*16+b field will be a byte holding the value a*16+b
For instance, for values of 2 seconds, 6 seconds, 15 seconds, and 30 For instance, for values of 2 seconds, 6 seconds, 15 seconds, and 30
seconds respectively, a and b would be: (a=0,b=5), (a=8,b=6), seconds respectively, a and b would be: (a=0,b=5), (a=8,b=6),
(a=14,b=7) and (a=14,b=8) respectively. (a=14,b=7) and (a=14,b=8) respectively.
18.4. Message Types 18.4. Message Types
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WILL_ALWAYS = 7 WILL_ALWAYS = 7
The willingness of a node may be set to any integer value from 0 to The willingness of a node may be set to any integer value from 0 to
7, and specifies how willing a node is to be forwarding traffic on 7, and specifies how willing a node is to be forwarding traffic on
behalf of other nodes. Nodes will, by default, have a willingness behalf of other nodes. Nodes will, by default, have a willingness
WILL_DEFAULT. WILL_NEVER indicates a node which does not wish to WILL_DEFAULT. WILL_NEVER indicates a node which does not wish to
carry traffic for other nodes, e.g. due to resource constraints carry traffic for other nodes, e.g. due to resource constraints
(e.g. low on battery). WILL_ALWAYS indicates that a node always (e.g. low on battery). WILL_ALWAYS indicates that a node always
should be selected to carry traffic on behalf of other nodes, e.g. should be selected to carry traffic on behalf of other nodes, e.g.
due to resource abundance (e.g. permanent power supply, high-capac- due to resource abundance (e.g. permanent power supply, high
ity interfaces to other nodes). capacity interfaces to other nodes).
A node may dynamically change its willingness as its conditions A node may dynamically change its willingness as its conditions
change. change.
One possible application would, for example, be for a node, connected One possible application would, for example, be for a node, connected
to a permanent power supply and with fully charged batteries, to to a permanent power supply and with fully charged batteries, to
advertise a willingness of WILL_ALWAYS. Upon being disconnected from advertise a willingness of WILL_ALWAYS. Upon being disconnected from
the permanent power supply (e.g. a PDA being taken out of its charg- the permanent power supply (e.g. a PDA being taken out of its
ing cradle), a willingness of WILL_DEFAULT is advertised. As battery charging cradle), a willingness of WILL_DEFAULT is advertised. As
capacity is drained, the willingness would be further reduced. First battery capacity is drained, the willingness would be further
to the intermediate value between WILL_DEFAULT and WILL_LOW, then to reduced. First to the intermediate value between WILL_DEFAULT and
WILL_LOW and finally to WILL_NEVER, when the battery capacity of the WILL_LOW, then to WILL_LOW and finally to WILL_NEVER, when the
node does no longer support carrying foreign traffic. battery capacity of the node does no longer support carrying foreign
traffic.
18.9. Misc. Constants 18.9. Misc. Constants
TC_REDUNDANCY = 0 TC_REDUNDANCY = 0
MPR COVERAGE = 1 MPR COVERAGE = 1
MAXJITTER = HELLO_INTERVAL / 4 MAXJITTER = HELLO_INTERVAL / 4
19. Sequence Numbers 19. Sequence Numbers
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Sequence numbers are used in OLSR with the purpose of discarding Sequence numbers are used in OLSR with the purpose of discarding
"old" information, i.e. messages received out of order. However "old" information, i.e. messages received out of order. However
with a limited number of bits for representing sequence numbers, with a limited number of bits for representing sequence numbers,
wrap-around (that the sequence number is incremented from the maximum wrap-around (that the sequence number is incremented from the maximum
possible value to zero) will occur. To prevent this from interfering possible value to zero) will occur. To prevent this from interfering
with the operation of the protocol, the following MUST be observed. with the operation of the protocol, the following MUST be observed.
The term MAXVALUE designates in the following the largest possible The term MAXVALUE designates in the following the largest possible
value for a sequence number. value for a sequence number.
The sequence number S1 is said to be "greater than" the sequence num- The sequence number S1 is said to be "greater than" the sequence
ber S2 iff: number S2 iff:
S1 > S2 AND S1 - S2 <= MAXVALUE/2 OR S1 > S2 AND S1 - S2 <= MAXVALUE/2 OR
S2 > S1 AND S2 - S1 > MAXVALUE/2 S2 > S1 AND S2 - S1 > MAXVALUE/2
Thus when comparing two messages, it is possible - even in the pres- Thus when comparing two messages, it is possible - even in the
ence of wrap-around - to determine which message contains the most presence of wrap-around - to determine which message contains the
recent information. most recent information.
20. Security Considerations 20. Security Considerations
Currently, OLSR does does not specify any special security measures. Currently, OLSR does does not specify any special security measures.
As a proactive routing protocol, OLSR makes a target for various As a proactive routing protocol, OLSR makes a target for various
attacks. The various possible vulnerability are discussed in this attacks. The various possible vulnerability are discussed in this
section. section.
20.1. Confidentiality 20.1. Confidentiality
Being a proactive protocol, OLSR periodically diffuses topological Being a proactive protocol, OLSR periodically diffuses topological
information. Hence, if used in an unprotected wireless network, the information. Hence, if used in an unprotected wireless network, the
network topology is revealed to anyone who listens to OLSR control network topology is revealed to anyone who listens to OLSR control
messages. messages.
In situations where the confidentiality of the network topology is of In situations where the confidentiality of the network topology is of
importance, regular cryptographic techniques can be applied to ensure importance, regular cryptographic techniques such as exchange of OLSR
that control traffic can be read and interpreted by only those autho- control traffic messages encrypted by pgp [9] or by encrypted by some
rized to do so. shared secret key can be applied to ensure that control traffic can
be read and interpreted by only those authorized to do so.
20.2. Integrity 20.2. Integrity
In OLSR, each node is injecting topological information into the net- In OLSR, each node is injecting topological information into the
work through transmitting HELLO messages and, for some nodes, TC mes- network through transmitting HELLO messages and, for some nodes, TC
sages. If some nodes for some reason, malicious or malfunction, messages. If some nodes for some reason, malicious or malfunction,
inject invalid control traffic, network integrity may be compromised. inject invalid control traffic, network integrity may be compromised.
Therefore, message authentication is recommended. Therefore, message authentication is recommended.
Different such situations may occur, for instance: Different such situations may occur, for instance:
1 a node generates TC (or HNA) messages, advertising links to 1 a node generates TC (or HNA) messages, advertising links to
non-neighbor nodes: non-neighbor nodes:
2 a node generates TC (or HNA) messages, pretending to be 2 a node generates TC (or HNA) messages, pretending to be
another node, another node,
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6 a node does not broadcast control messages, 6 a node does not broadcast control messages,
7 a node does not select multipoint relays correctly. 7 a node does not select multipoint relays correctly.
8 a node forwards broadcast control messages unaltered, but does 8 a node forwards broadcast control messages unaltered, but does
not forward unicast data traffic; not forward unicast data traffic;
9 a node "replays" previously recorded control traffic from 9 a node "replays" previously recorded control traffic from
another node. another node.
Authenticated signatures on control messages (for situation 2, 4 and Authentication of the originator node for control messages (for
5) and on the individual links announced in the control messages (for situation 2, 4 and 5) and on the individual links announced in the
situation 1 and 3) may be used as a countermeasure. However to pre- control messages (for situation 1 and 3) may be used as a
vent nodes from repeating old (and correctly authenticated) informa- countermeasure. However to prevent nodes from repeating old (and
tion (situation 9) temporal information is required, allowing a node correctly authenticated) information (situation 9) temporal
to positively identify such delayed messages. information is required, allowing a node to positively identify such
delayed messages.
Signatures and other required security information may be transmitted Signatures and other required security information may be transmitted
as a separate OLSR message type, thereby allowing that "secured" and as a separate OLSR message type, thereby allowing that "secured" and
"unsecured" nodes can coexist in the same network, if desired. "unsecured" nodes can coexist in the same network, if desired.
An important consideration is, that all control messages in OLSR are
transmitted either to all nodes in the neighborhood (HELLO messages)
or broadcast to all nodes in the network (e.g. TC messages). I.e.
a control message in OLSR is always a point-to-multipoint
transmission. It is therefore important that the authentication
mechanism employed permits that any receiving node can validate the
authenticity of a message. As an analogy, given a block of text,
signed by a PGP private key, then anyone with the corresponding
public key can verify the authenticiy of the text.
20.3. Interaction with External Routing Domains 20.3. Interaction with External Routing Domains
OLSR does, through the HNA messages specified in section 12, OLSR does, through the HNA messages specified in section 12,
provide a basic mechanism for injecting external routing information provide a basic mechanism for injecting external routing information
to the OLSR domain. Section 12 also specifies that routing to the OLSR domain. Section 12 also specifies that routing
information can be extracted from the topology table or the routing information can be extracted from the topology table or the routing
table of OLSR and, potentially, injected into an external domain if table of OLSR and, potentially, injected into an external domain if
the routing protocol governing that domain permits. the routing protocol governing that domain permits.
Other than as described in the section 20.2, when operating Other than as described in the section 20.2, when operating
nodes, connecting OLSR to an external routing domain, care MUST be nodes, connecting OLSR to an external routing domain, care MUST be
taken not to allow potentially insecure and un-trustworthy informa- taken not to allow potentially insecure and un-trustworthy
tion to be injected from the OLSR domain to external routing domains. information to be injected from the OLSR domain to external routing
Care MUST be taken to validate the correctness of information prior domains. Care MUST be taken to validate the correctness of
to it being injected as to avoid polluting routing tables with information prior to it being injected as to avoid polluting routing
invalid information. tables with invalid information.
A recommended way of extending connectivity from an existing routing A recommended way of extending connectivity from an existing routing
domain to an OLSR routed MANET is to assign an IP prefix (under the domain to an OLSR routed MANET is to assign an IP prefix (under the
authority of the nodes/gateways connecting the MANET with the exiting authority of the nodes/gateways connecting the MANET with the exiting
routing domain) exclusively to the OLSR MANET area, and to configure routing domain) exclusively to the OLSR MANET area, and to configure
the gateways statically to advertise routes to that IP sequence to the gateways statically to advertise routes to that IP sequence to
nodes in the existing routing domain. nodes in the existing routing domain.
20.4. Node Identity 20.4. Node Identity
OLSR does not make any assumption about node addresses, other than OLSR does not make any assumption about node addresses, other than
that each node is assumed to have an unique IP addresses. Therefore, that each node is assumed to have an unique IP addresses. Therefore,
no special considerations can be made about the applicability of no special considerations can be made about the applicability of
IPsec authentication headers or key exchange mechanisms. IPsec authentication headers or key exchange mechanisms.
21. Flow and congestion control 21. Flow and congestion control
Due to its proactive nature, the OLSR protocol has a natural control Due to its proactive nature, the OLSR protocol has a natural control
over the flow of its control traffic. Nodes transmits control mes- over the flow of its control traffic. Nodes transmits control
sage at predetermined rates fixed by predefined refresh intervals. message at predetermined rates fixed by predefined refresh intervals.
In certain options some control messages may be intentionnaly sent in Furthermore the MPR optimization greatly saves on control overhead,
advance of their deadline(TC or Hello messages) in order to increase and this is done on two sides. First, the packets that advertize the
the reactiveness of the protocol against certain events. This may topology are much shorter since only MPR selectors may be advertized.
cause a small, temporary and local increase of control traffic. Second, the cost of flooding this information is greatly reduced
since only MPR nodes forward the broadcast packets. In dense
networks, the reduction of control traffic can be of several orders
of magnitude compared to routing protocols using classical flooding
(such as OSPF) [10]. This feature naturally provides more bandwidth
for useful data traffic and pushes further the frontier of
congestion. Since the control traffic is continuous and periodic, it
keeps more stable the quality of the links used in routing, where
reactive protocols, with bursty floodings for route discoveries and
repairs, may damage the link qualities for short times by causing
numerous collisions on those links, possibly provoking route repair
cascades. However, in certain OLSR options, some control messages
may be intentionnaly sent in advance of their deadline(TC or Hello
messages) in order to increase the reactiveness of the protocol
against topology changes. This may cause a small, temporary and
local increase of control traffic.
22. IANA Considerations 22. IANA Considerations
OLSR defines a "Message Type" field for control messages. A new reg- OLSR defines a "Message Type" field for control messages. A new
istry is to be created for the values for this Message Type field, registry is to be created for the values for this Message Type field,
and the following values assigned: and the following values assigned:
Message Type Value Message Type Value
-------------------- ----- -------------------- -----
HELLO_MESSAGE 1 HELLO_MESSAGE 1
TC_MESSAGE 2 TC_MESSAGE 2
MID_MESSAGE 3 MID_MESSAGE 3
HNA_MESSAGE 4 HNA_MESSAGE 4
Future values in the range 5-127 of the Message Type can be allocated Future values in the range 5-127 of the Message Type can be allocated
using standards action [7]. using standards action [7].
Additionally, values in the range 128-255 are reserved for pri- Additionally, values in the range 128-255 are reserved for
vate/local use. private/local use.
23. Acknowledgments 23. Acknowledgments
The authors would like to thank Joseph Macker The authors would like to thank Joseph Macker
<macker@itd.nrl.navy.mil> and his team, including Justin Dean <macker@itd.nrl.navy.mil> and his team, including Justin Dean
<jdean@itd.nrl.navy.mil>, for their valuable suggestions on the <jdean@itd.nrl.navy.mil>, for their valuable suggestions on the
advanced neighbor sensing mechanism and other various aspects of the advanced neighbor sensing mechanism and other various aspects of the
protocol, including careful review of the protocol specification. protocol, including careful review of the protocol specification.
The authors would also like to thank Christopher Dearlove The authors would also like to thank Christopher Dearlove
<chris.dearlove@baesystems.com> for valuable input on the MPR selec- <chris.dearlove@baesystems.com> for valuable input on the MPR
tion heuristics and for careful reviews of the protocol specifica- selection heuristics and for careful reviews of the protocol
tion. specification.
24. Contributors 24. Contributors
During the development of this specification, the following list of During the development of this specification, the following list of
people contributed. The contributors are listed alphabetically. people contributed. The contributors are listed alphabetically.
Cedric Adjih, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Le Cedric Adjih, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Le
Chesnay Cedex, France, Phone: +33 1 3963 5215, Email: Chesnay Cedex, France, Phone: +33 1 3963 5215, Email:
Cedric.Adjih@inria.fr Cedric.Adjih@inria.fr
skipping to change at page 76, line 27 skipping to change at page 76, line 42
Philippe Jacquet, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Philippe Jacquet, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153
Le Chesnay Cedex, France, Phone: +33 1 3963 5263, Email: Le Chesnay Cedex, France, Phone: +33 1 3963 5263, Email:
Philippe.Jacquet@inria.fr Philippe.Jacquet@inria.fr
Anis Laouiti, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Le Anis Laouiti, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Le
Chesnay Cedex, France, Phone: +33 1 3963 508832, Email: Chesnay Cedex, France, Phone: +33 1 3963 508832, Email:
Anis.Laouiti@inria.fr Anis.Laouiti@inria.fr
Pascale Minet, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Le Pascale Minet, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Le
Chesnay Cedex, France, Phone: +33 1 3963 508832, Email: Pas- Chesnay Cedex, France, Phone: +33 1 3963 508832, Email:
cale.Minet@inria.fr Pascale.Minet@inria.fr
Paul Muhlethaler, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Paul Muhlethaler, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153
Le Chesnay Cedex, France, Phone: +33 1 3963 5278, Email: Paul.Muh- Le Chesnay Cedex, France, Phone: +33 1 3963 5278, Email:
lethaler@inria.fr Paul.Muhlethaler@inria.fr
Amir Qayyum, Center for Advanced Research in Engineering Pvt. Ltd., Amir Qayyum, Center for Advanced Research in Engineering Pvt. Ltd.,
19, Ataturk Avenue, Islamabad, Pakistan, Phone: +92-51-2874115, 19, Ataturk Avenue, Islamabad, Pakistan, Phone: +92-51-2874115,
Email: amir@carepvtltd.com Email: amir@carepvtltd.com
Laurent Viennot, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Laurent Viennot, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153
Le Chesnay Cedex, France, Phone: +33 1 3963 5225, Email: Lau- Le Chesnay Cedex, France, Phone: +33 1 3963 5225, Email:
rent.Viennot@inria.fr Laurent.Viennot@inria.fr
25. Authors' Addresses 25. Authors' Addresses
Thomas Heide Clausen, Project HIPERCOM, INRIA Rocquencourt, BP 105, Thomas Heide Clausen, Project HIPERCOM, INRIA Rocquencourt, BP 105,
78153 Le Chesnay Cedex, France, Phone: +33 1 3963 5133, Email: 78153 Le Chesnay Cedex, France, Phone: +33 1 3963 5133, Email:
Thomas.Clausen@inria.fr Thomas.Clausen@inria.fr
Philippe Jacquet, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153 Philippe Jacquet, Project HIPERCOM, INRIA Rocquencourt, BP 105, 78153
Le Chesnay Cedex, France, Phone: +33 1 3963 5263, Email: Le Chesnay Cedex, France, Phone: +33 1 3963 5263, Email:
Philippe.Jacquet@inria.fr Philippe.Jacquet@inria.fr
26. References 26. References
1. P. Jacquet, P. Minet, P. Muhlethaler, N. Rivierre. Increasing 1. P. Jacquet, P. Minet, P. Muhlethaler, N. Rivierre. Increasing
reliability in cable free radio LANs: Low level forwarding in reliability in cable free radio LANs: Low level forwarding in
HIPERLAN. Wireless Personal Communications, 1996 HIPERLAN. Wireless Personal Communications, 1996
2. A. Qayyum, L. Viennot, A. Laouiti. Multipoint relaying: An effi- 2. A. Qayyum, L. Viennot, A. Laouiti. Multipoint relaying: An
cient technique for flooding in mobile wireless networks. 35th efficient technique for flooding in mobile wireless networks. 35th
Annual Hawaii International Conference on System Sciences Annual Hawaii International Conference on System Sciences
(HICSS'2001). (HICSS'2001).
3. ETSI STC-RES10 Committee. Radio equipment and systems: HIPERLAN 3. ETSI STC-RES10 Committee. Radio equipment and systems: HIPERLAN
type 1, functional specifications ETS 300-652, ETSI, June 1996 type 1, functional specifications ETS 300-652, ETSI, June 1996
4. Philippe Jacquet and Laurent Viennot, Overhead in Mobile Ad-hoc Net- 4. P. Jacquet and L. Viennot, Overhead in Mobile Ad-hoc Network
work Protocols, INRIA research report RR-3965, 2000 Protocols, INRIA research report RR-3965, 2000
5. S. Bradner. Key words for use in RFCs to Indicate Requirement Lev- 5. S. Bradner. Key words for use in RFCs to Indicate Requirement
els. Request for Comments (Best Current Practice) 2119, Internet Levels. Request for Comments (Best Current Practice) 2119,
Engineering Task Force, March 1997. Internet Engineering Task Force, March 1997.
6. T. Clausen, G. Hansen, L. Christensen and G. Behrmann. The 6. T. Clausen, G. Hansen, L. Christensen and G. Behrmann. The
Optimized Link State Routing Protocol, Evaluation through Experi- Optimized Link State Routing Protocol, Evaluation through
ments and Simulation. IEEE Symposium on "Wireless Personal Mobile Experiments and Simulation. IEEE Symposium on "Wireless Personal
Communications", September 2001. Mobile Communications", September 2001.
7. T. Clausen, P. Jacquet, A. Laouiti, P. Muhlethaler, A. Qayyum 7. T. Clausen, P. Jacquet, A. Laouiti, P. Muhlethaler, A. Qayyum
and L. Viennot. Optimized Link State Routing Protocol. IEEE and L. Viennot. Optimized Link State Routing Protocol. IEEE
INMIC Pakistan 2001. INMIC Pakistan 2001.
8. T. Narten and H. Alvestrand. Guidelines for Writing an IANA Con- 8. T. Narten and H. Alvestrand. Guidelines for Writing an IANA
siderations Section in RFCs. Request for Comments (Best Current Considerations Section in RFCs. Request for Comments (Best Current
Practice) 2434, Internet Engineering Task Force, October 1998. Practice) 2434, Internet Engineering Task Force, October 1998.
9. D. Atkins, W. Stallings and P. Zimmermann, PGP Message Exchange
Formats. Request for Comments (Informational) 1991, August 1996.
10. P. Jacquet, A. Laouiti, P. Minet, L. Viennot. Performance
analysis of OLSR multipoint relay flooding in two ad hoc wireless
network models, INRIA research report RR-4260, 2001.
Reference [5] and [7] are normative; all others are informative. Reference [5] and [7] are normative; all others are informative.
 End of changes. 

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