draft-ietf-manet-dsr-04.txt   draft-ietf-manet-dsr-05.txt 
IETF MANET Working Group David B. Johnson, Rice University IETF MANET Working Group David B. Johnson, Rice University
INTERNET-DRAFT David A. Maltz, AON Networks INTERNET-DRAFT David A. Maltz, AON Networks
17 November 2000 Yih-Chun Hu, Carnegie Mellon University 2 March 2001 Yih-Chun Hu, Rice University
Jorjeta G. Jetcheva, Carnegie Mellon University Jorjeta G. Jetcheva, Carnegie Mellon University
The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks
<draft-ietf-manet-dsr-04.txt> <draft-ietf-manet-dsr-05.txt>
Status of This Memo Status of This Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 except that the right to all provisions of Section 10 of RFC 2026 except that the right to
produce derivative works is not granted. produce derivative works is not granted.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note Task Force (IETF), its areas, and its working groups. Note
that other groups may also distribute working documents as that other groups may also distribute working documents as
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2. Assumptions 3 2. Assumptions 3
3. DSR Protocol Overview 5 3. DSR Protocol Overview 5
3.1. Basic DSR Route Discovery . . . . . . . . . . . . . . . . 5 3.1. Basic DSR Route Discovery . . . . . . . . . . . . . . . . 5
3.2. Basic DSR Route Maintenance . . . . . . . . . . . . . . . 7 3.2. Basic DSR Route Maintenance . . . . . . . . . . . . . . . 7
3.3. Additional Route Discovery Features . . . . . . . . . . . 8 3.3. Additional Route Discovery Features . . . . . . . . . . . 8
3.3.1. Caching Overheard Routing Information . . . . . . 8 3.3.1. Caching Overheard Routing Information . . . . . . 8
3.3.2. Replying to Route Requests using Cached Routes . 9 3.3.2. Replying to Route Requests using Cached Routes . 9
3.3.3. Preventing Route Reply Storms . . . . . . . . . . 10 3.3.3. Preventing Route Reply Storms . . . . . . . . . . 10
3.3.4. Route Request Hop Limits . . . . . . . . . . . . 12 3.3.4. Route Request Hop Limits . . . . . . . . . . . . 12
3.4. Additional Route Maintenance Features . . . . . . . . . . 12 3.4. Additional Route Maintenance Features . . . . . . . . . . 13
3.4.1. Packet Salvaging . . . . . . . . . . . . . . . . 12 3.4.1. Packet Salvaging . . . . . . . . . . . . . . . . 13
3.4.2. Automatic Route Shortening . . . . . . . . . . . 13 3.4.2. Automatic Route Shortening . . . . . . . . . . . 13
3.4.3. Increased Spreading of Route Error Messages . . . 14 3.4.3. Increased Spreading of Route Error Messages . . . 14
4. Conceptual Data Structures 15 4. Conceptual Data Structures 15
4.1. Route Cache . . . . . . . . . . . . . . . . . . . . . . . 15 4.1. Route Cache . . . . . . . . . . . . . . . . . . . . . . . 15
4.2. Route Request Table . . . . . . . . . . . . . . . . . . . 17 4.2. Route Request Table . . . . . . . . . . . . . . . . . . . 17
4.3. Send Buffer . . . . . . . . . . . . . . . . . . . . . . . 18 4.3. Send Buffer . . . . . . . . . . . . . . . . . . . . . . . 18
4.4. Retransmission Buffer . . . . . . . . . . . . . . . . . . 19 4.4. Retransmission Buffer . . . . . . . . . . . . . . . . . . 19
5. Packet Formats 20 5. DSR Header Format 20
5.1. Destination Options Header . . . . . . . . . . . . . . . 21 5.1. Fixed Portion of DSR Header . . . . . . . . . . . . . . . 21
5.1.1. DSR Route Request Option . . . . . . . . . . . . 22 5.2. Route Request Option . . . . . . . . . . . . . . . . . . 23
5.2. Hop-by-Hop Options Header . . . . . . . . . . . . . . . . 24 5.3. Route Reply Option . . . . . . . . . . . . . . . . . . . 25
5.2.1. DSR Route Reply Option . . . . . . . . . . . . . 25 5.4. Route Error Option . . . . . . . . . . . . . . . . . . . 27
5.2.2. DSR Route Error Option . . . . . . . . . . . . . 27 5.5. Acknowledgment Request Option . . . . . . . . . . . . . . 29
5.2.3. DSR Acknowledgment Option . . . . . . . . . . . . 29 5.6. Acknowledgment Option . . . . . . . . . . . . . . . . . . 30
5.3. DSR Routing Header . . . . . . . . . . . . . . . . . . . 30 5.7. Source Route Option . . . . . . . . . . . . . . . . . . . 31
5.8. Pad1 Option . . . . . . . . . . . . . . . . . . . . . . . 33
5.9. PadN Option . . . . . . . . . . . . . . . . . . . . . . . 34
6. Detailed Operation 33 6. Detailed Operation 35
6.1. General Packet Processing . . . . . . . . . . . . . . . . 33 6.1. General Packet Processing . . . . . . . . . . . . . . . . 35
6.1.1. Originating a Packet . . . . . . . . . . . . . . 33 6.1.1. Originating a Packet . . . . . . . . . . . . . . 35
6.1.2. Adding a DSR Routing Header to a Packet . . . . . 34 6.1.2. Adding a DSR Header to a Packet . . . . . . . . . 35
6.1.3. Receiving a Packet . . . . . . . . . . . . . . . 36 6.1.3. Adding a Source Route Option to a Packet . . . . 36
6.1.4. Processing a Routing Header in a Received Packet 38 6.1.4. Receiving a Packet . . . . . . . . . . . . . . . 36
6.1.5. Processing a Received Source Route Option . . . . 38
6.2. Route Discovery Processing . . . . . . . . . . . . . . . 40 6.2. Route Discovery Processing . . . . . . . . . . . . . . . 40
6.2.1. Originating a Route Request . . . . . . . . . . . 40 6.2.1. Originating a Route Request . . . . . . . . . . . 40
6.2.2. Processing a Received Route Request Option . . . 42 6.2.2. Processing a Received Route Request Option . . . 42
6.2.3. Generating Route Replies using the Route Cache . 43 6.2.3. Generating Route Replies using the Route Cache . 43
6.2.4. Originating a Route Reply . . . . . . . . . . . . 45 6.2.4. Originating a Route Reply . . . . . . . . . . . . 44
6.2.5. Processing a Route Reply Option . . . . . . . . . 46 6.2.5. Processing a Route Reply Option . . . . . . . . . 46
6.3. Route Maintenance Processing . . . . . . . . . . . . . . 47 6.3. Route Maintenance Processing . . . . . . . . . . . . . . 47
6.3.1. Using Network-Layer Acknowledgments . . . . . . . 47 6.3.1. Using Network-Layer Acknowledgments . . . . . . . 47
6.3.2. Using Link Layer Acknowledgments . . . . . . . . 48 6.3.2. Using Link Layer Acknowledgments . . . . . . . . 48
6.3.3. Originating a Route Error . . . . . . . . . . . . 48 6.3.3. Originating a Route Error . . . . . . . . . . . . 48
6.3.4. Processing a Route Error Option . . . . . . . . . 49 6.3.4. Processing a Route Error Option . . . . . . . . . 49
6.3.5. Salvaging a Packet . . . . . . . . . . . . . . . 49 6.3.5. Salvaging a Packet . . . . . . . . . . . . . . . 49
7. Constants 50 7. Constants 50
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believe that portions of the protocol are suitable for implementation believe that portions of the protocol are suitable for implementation
directly within a programmable network interface unit to avoid this directly within a programmable network interface unit to avoid this
overhead on the CPU [13]. Use of promiscuous mode may also increase overhead on the CPU [13]. Use of promiscuous mode may also increase
the power consumption of the network interface hardware, depending the power consumption of the network interface hardware, depending
on the design of the receiver hardware, and in such cases, DSR can on the design of the receiver hardware, and in such cases, DSR can
easily be used without the optimizations that depend on promiscuous easily be used without the optimizations that depend on promiscuous
receive mode, or can be programmed to only periodically switch the receive mode, or can be programmed to only periodically switch the
interface into promiscuous mode. Use of promiscuous receive mode is interface into promiscuous mode. Use of promiscuous receive mode is
entirely optional. entirely optional.
Wireless communication ability between any pair of nodes can at Wireless communication ability between any pair of nodes may at
times not work equally well in both directions, due for example to times not work equally well in both directions, due for example to
differing antenna or propagation patterns or sources of interference differing antenna or propagation patterns or sources of interference
around the two nodes [1, 17]. That is, wireless communications around the two nodes [1, 17]. That is, wireless communications
between each pair of nodes will in many cases be able to operate between each pair of nodes will in many cases be able to operate
bi-directionally, but at times the wireless link between two nodes bi-directionally, but at times the wireless link between two nodes
may be only uni-directional, allowing one node to successfully send may be only uni-directional, allowing one node to successfully send
packets to the other while no communication is possible in the packets to the other while no communication is possible in the
reverse direction. Although many routing protocols operate correctly reverse direction. Although many routing protocols operate correctly
only over bi-directional links, DSR can successfully discover and only over bi-directional links, DSR can successfully discover and
forward packets over paths that contain uni-directional links. forward packets over paths that contain uni-directional links.
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The IP address used by a node using the DSR protocol MAY be assigned The IP address used by a node using the DSR protocol MAY be assigned
by any mechanism (e.g., static assignment or use of DHCP for dynamic by any mechanism (e.g., static assignment or use of DHCP for dynamic
assignment [8]), although the method of such assignment is outside assignment [8]), although the method of such assignment is outside
the scope of this specification. the scope of this specification.
3. DSR Protocol Overview 3. DSR Protocol Overview
3.1. Basic DSR Route Discovery 3.1. Basic DSR Route Discovery
When some node S originates a new packet destined to some other When some source node originates a new packet addressed to some
node D, it places in the header of the packet a source route giving destination node, the source node places in the header of the packet
the sequence of hops that the packet is to follow on its way to a source route giving the sequence of hops that the packet is to
D. Normally, S will obtain a suitable source route by searching follow on its way to the destination. Normally, the sender will
its "Route Cache" of routes previously learned, but if no route is obtain a suitable source route by searching its "Route Cache" of
found in its cache, it will initiate the Route Discovery protocol routes previously learned, but if no route is found in its cache, it
to dynamically find a new route to D. In this case, we call S the will initiate the Route Discovery protocol to dynamically find a new
"initiator" and D the "target" of the Route Discovery. route to this destination node. In this case, we call the source
node the "initiator" and the destination node the "target" of the
Route Discovery.
For example, suppose a node A is attempting to discover a route to For example, suppose a node A is attempting to discover a route to
node E. The Route Discovery initiated by node A in this example node E. The Route Discovery initiated by node A in this example
would proceed as follows: would proceed as follows:
^ "A" ^ "A,B" ^ "A,B,C" ^ "A,B,C,D" ^ "A" ^ "A,B" ^ "A,B,C" ^ "A,B,C,D"
| id=2 | id=2 | id=2 | id=2 | id=2 | id=2 | id=2 | id=2
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| A |---->| B |---->| C |---->| D |---->| E | | A |---->| B |---->| C |---->| D |---->| E |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| | | | | | | |
v v v v v v v v
To initiate the Route Discovery, node A transmits a "Route Request" To initiate the Route Discovery, node A transmits a "Route
message as a single local broadcast packet, which is received by Request" as a single local broadcast packet, which is received by
(approximately) all nodes currently within wireless transmission (approximately) all nodes currently within wireless transmission
range of A, including node B in this example. Each Route Request range of A, including node B in this example. Each Route Request
message identifies the initiator and target of the Route Discovery, identifies the initiator and target of the Route Discovery, and
and also contains a unique request identification (2, in this also contains a unique request identification (2, in this example),
example), determined by the initiator of the Request. Each determined by the initiator of the Request. Each Route Request also
Route Request also contains a record listing the address of each contains a record listing the address of each intermediate node
intermediate node through which this particular copy of the Route through which this particular copy of the Route Request has been
Request message has been forwarded. This route record is initialized forwarded. This route record is initialized to an empty list by the
to an empty list by the initiator of the Route Discovery. In this initiator of the Route Discovery. In this example, the route record
example, the route record initially lists only node A. initially lists only node A.
When another node receives a Route Request (such as node B in this When another node receives this Route Request (such as node B in this
example), if it is the target of the Route Discovery, it returns example), if it is the target of the Route Discovery, it returns
a "Route Reply" message to the initiator of the Route Discovery, a "Route Reply" to the initiator of the Route Discovery, giving
giving a copy of the accumulated route record from the Route Request; a copy of the accumulated route record from the Route Request;
when the initiator receives this Route Reply, it caches this route when the initiator receives this Route Reply, it caches this route
in its Route Cache for use in sending subsequent packets to this in its Route Cache for use in sending subsequent packets to this
destination. Otherwise, if this node receiving the Route Request destination.
has recently seen another Route Request message from this initiator
bearing this same request identification and target address, or if it Otherwise, if this node receiving the Route Request has recently seen
finds that its own address is already listed in the route record in another Route Request message from this initiator bearing this same
the Route Request message, it discards the Request. Otherwise, this request identification and target address, or if this node's own
node appends its own address to the route record in the Route Request address is already listed in the route record in the Route Request,
message and propagates it by transmitting it as a local broadcast this node discards the Request. Otherwise, this node appends its
packet (with the same request identification). In this example, own address to the route record in the Route Request and propagates
node B broadcast the Route Request, which is received by node C; it by transmitting it as a local broadcast packet (with the same
nodes C and D each also broadcast the Request in turn, resulting in a request identification). In this example, node B broadcast the Route
copy of the Request being received by node E. Request, which is received by node C; nodes C and D each also, in
turn, broadcast the Request, resulting in a copy of the Request being
received by node E.
In returning the Route Reply to the initiator of the Route Discovery, In returning the Route Reply to the initiator of the Route Discovery,
such as node E replying back to A in this example, node E will such as in this example, node E replying back to node A, node E will
typically examine its own Route Cache for a route back to A, and if typically examine its own Route Cache for a route back to A, and if
found, will use it for the source route for delivery of the packet found, will use it for the source route for delivery of the packet
containing the Route Reply. Otherwise, E SHOULD perform its own containing the Route Reply. Otherwise, E SHOULD perform its own
Route Discovery for target node A, but to avoid possible infinite Route Discovery for target node A, but to avoid possible infinite
recursion of Route Discoveries, it MUST piggyback this Route Reply on recursion of Route Discoveries, it MUST piggyback this Route Reply
its own Route Request message for A. on the packet containing its own Route Request for A. It is also
possible to piggyback other small data packets, such as a TCP SYN
packet [25], on a Route Request using this same mechanism.
It is also possible to piggyback other small data packets, such as a Node E could instead simply reverse the sequence of hops in the route
TCP SYN packet [26], on a Route Request using this same mechanism.
Node E could also simply reverse the sequence of hops in the route
record that it is trying to send in the Route Reply, and use this record that it is trying to send in the Route Reply, and use this
as the source route on the packet carrying the Route Reply itself. as the source route on the packet carrying the Route Reply itself.
For MAC protocols such as IEEE 802.11 that require a bi-directional For MAC protocols such as IEEE 802.11 that require a bi-directional
frame exchange as part of the MAC protocol [10], this route reversal frame exchange as part of the MAC protocol [10], this route reversal
is preferred as it avoids the overhead of a possible second Route is preferred, as it avoids the overhead of a possible second
Discovery, and it tests the discovered route to ensure it is Route Discovery, and it tests the discovered route to ensure it is
bi-directional before the Route Discovery initiator begins using the bi-directional before the Route Discovery initiator begins using the
route. However, this technique will prevent the discovery of routes route. However, this technique will prevent the discovery of routes
using uni-directional links. In wireless environments where the use using uni-directional links. In wireless environments where the use
of uni-directional links is permitted, such routes may in some cases of uni-directional links is permitted, such routes may in some cases
be more efficient than those with only bi-directional links, or they be more efficient than those with only bi-directional links, or they
may be the only way to achieve connectivity to the target node. may be the only way to achieve connectivity to the target node.
When initiating a Route Discovery, the sending node saves a copy of When initiating a Route Discovery, the sending node saves a copy of
the original packet in a local buffer called the "Send Buffer". The the original packet (that triggered the Discovery) in a local buffer
Send Buffer contains a copy of each packet that cannot be transmitted called the "Send Buffer". The Send Buffer contains a copy of each
by this node because it does not yet have a source route to the packet that cannot be transmitted by this node because it does not
packet's destination. Each packet in the Send Buffer is stamped with yet have a source route to the packet's destination. Each packet in
the time that it was placed into the Buffer and is discarded after the Send Buffer is logically associated with the time that it was
residing in the Send Buffer for some timeout period; if necessary placed into the Send Buffer and is discarded after residing in the
for preventing the Send Buffer from overflowing, a FIFO or other Send Buffer for some timeout period; if necessary for preventing the
replacement strategy MAY also be used to evict packets before they Send Buffer from overflowing, a FIFO or other replacement strategy
expire. MAY also be used to evict packets even before they expire.
While a packet remains in the Send Buffer, the node SHOULD While a packet remains in the Send Buffer, the node SHOULD
occasionally initiate a new Route Discovery for the packet's occasionally initiate a new Route Discovery for the packet's
destination address. However, the node MUST limit the rate at which destination address. However, the node MUST limit the rate at which
such new Route Discoveries for the same address are initiated, since such new Route Discoveries for the same address are initiated, since
it is possible that the destination node is not currently reachable. it is possible that the destination node is not currently reachable.
In particular, due to the limited wireless transmission range and the In particular, due to the limited wireless transmission range and the
movement of the nodes in the network, the network may at times become movement of the nodes in the network, the network may at times become
partitioned, meaning that there is currently no sequence of nodes partitioned, meaning that there is currently no sequence of nodes
through which a packet could be forwarded to reach the destination. through which a packet could be forwarded to reach the destination.
Depending on the movement pattern and the density of nodes in the Depending on the movement pattern and the density of nodes in the
network, such network partitions may be rare or may be common. network, such network partitions may be rare or may be common.
If a new Route Discovery was initiated for each packet sent by a If a new Route Discovery was initiated for each packet sent by a
node in such a situation, a large number of unproductive Route node in such a partitioned network, a large number of unproductive
Request packets would be propagated throughout the subset of the Route Request packets would be propagated throughout the subset of
ad hoc network reachable from this node. In order to reduce the the ad hoc network reachable from this node. In order to reduce the
overhead from such Route Discoveries, a node MUST use an exponential overhead from such Route Discoveries, a node MUST use an exponential
back-off algorithm to limit the rate at which it initiates new Route back-off algorithm to limit the rate at which it initiates new Route
Discoveries for the same target. If the node attempts to send Discoveries for the same target. If the node attempts to send
additional data packets to this same node more frequently than this additional data packets to this same destination node more frequently
limit, the subsequent packets SHOULD be buffered in the Send Buffer than this limit, the subsequent packets SHOULD be buffered in the
until a Route Reply is received giving a route to this destination, Send Buffer until a Route Reply is received giving a route to this
but the node MUST NOT initiate a new Route Discovery until the destination, but the node MUST NOT initiate a new Route Discovery
minimum allowable interval between new Route Discoveries for this until the minimum allowable interval between new Route Discoveries
target has been reached. This limitation on the maximum rate of for this target has been reached. This limitation on the maximum
Route Discoveries for the same target is similar to the mechanism rate of Route Discoveries for the same target is similar to the
required by Internet nodes to limit the rate at which ARP Requests mechanism required by Internet nodes to limit the rate at which ARP
are sent for any single target IP address [3]. Requests are sent for any single target IP address [3].
3.2. Basic DSR Route Maintenance 3.2. Basic DSR Route Maintenance
When originating or forwarding a packet using a source route, each When originating or forwarding a packet using a source route, each
node transmitting the packet is responsible for confirming that the node transmitting the packet is responsible for confirming that the
packet has been received by the next hop along the source route; the packet has been received by the next hop along the source route; the
packet SHOULD be retransmitted (up to a maximum number of attempts) packet SHOULD be retransmitted (up to a maximum number of attempts)
until this confirmation of receipt is received. For example, in the until this confirmation of receipt is received. For example, in the
situation shown below, node A has originated a packet for node E situation shown below, node A has originated a packet for node E
using a source route through intermediate nodes B, C, and D: using a source route through intermediate nodes B, C, and D:
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| A |---->| B |---->| C |-- | D | | E | | A |---->| B |---->| C |--x | D | | E |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
In this case, node A is responsible for receipt of the packet at B, In this case, node A is responsible for receipt of the packet at B,
node B is responsible for receipt at C, node C is responsible for node B is responsible for receipt at C, node C is responsible for
receipt at D, and node D is responsible for receipt finally at the receipt at D, and node D is responsible for receipt finally at the
destination E. destination E.
This confirmation of receipt in many cases may be provided at no cost This confirmation of receipt in many cases may be provided at no cost
to DSR, either as an existing standard part of the MAC protocol in to DSR, either as an existing standard part of the MAC protocol in
use (such as the link-level acknowledgement frame defined by IEEE use (such as the link-level acknowledgement frame defined by IEEE
802.11 [10]), or by a "passive acknowledgement" [15] (in which, for 802.11 [10]), or by a "passive acknowledgement" [15] (in which,
example, B confirms receipt at C by overhearing C transmit the packet for example, B confirms receipt at C by overhearing C transmit the
to forward it on to D). If neither of these confirmation mechanisms packet when forwarding it on to D). If neither of these confirmation
are available, the node transmitting the packet can explicitly mechanisms are available, the node transmitting the packet can
request a DSR-specific software acknowledgement be returned by the explicitly request a DSR-specific software acknowledgement be
next hop; this software acknowledgement will normally be transmitted returned by the next hop; this software acknowledgement will normally
directly to the sending node, but if the link between these two nodes be transmitted directly to the sending node, but if the link between
is uni-directional, this software acknowledgement may travel over a these two nodes is uni-directional, this software acknowledgement may
different, multi-hop path. travel over a different, multi-hop path.
If no receipt confirmation is received after the packet has been If no receipt confirmation is received after the packet has been
retransmitted the maximum number of attempts by some hop, this node retransmitted the maximum number of attempts by some hop, this node
SHOULD return a "Route Error" message to the original sender of the SHOULD return a "Route Error" to the original sender of the packet,
packet, identifying the link over which the packet could not be identifying the link over which the packet could not be forwarded.
forwarded. For example, in the example shown above, if C is unable For example, in the example shown above, if C is unable to deliver
to deliver the packet to the next hop D, then C returns a Route Error the packet to the next hop D, then C returns a Route Error to A,
to A, stating that the link from C to D is currently "broken". Node stating that the link from C to D is currently "broken". Node A
A then removes this broken link from its cache; any retransmission then removes this broken link from its cache; any retransmission of
of the original packet can be performed by upper layer protocols the original packet can be performed by upper layer protocols such
such as TCP, if necessary. For sending such a retransmission or as TCP, if necessary. For sending such a retransmission or other
other packets to this same destination E, if A has in its Route Cache packets to this same destination E, if A has in its Route Cache
another route to E (for example, from additional Route Replys from another route to E (for example, from additional Route Replies from
its earlier Route Discovery, or from having overheard sufficient its earlier Route Discovery, or from having overheard sufficient
routing information from other packets), it can send the packet routing information from other packets), it can send the packet
using the new route immediately. Otherwise, it SHOULD perform a new using the new route immediately. Otherwise, it SHOULD perform a new
Route Discovery for this target (subject to the exponential back-off Route Discovery for this target (subject to the exponential back-off
described in Section 3.1). described in Section 3.1).
3.3. Additional Route Discovery Features 3.3. Additional Route Discovery Features
3.3.1. Caching Overheard Routing Information 3.3.1. Caching Overheard Routing Information
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below, node A is using a source route to communicate with node E: below, node A is using a source route to communicate with node E:
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| A |---->| B |---->| C |---->| D |---->| E | | A |---->| B |---->| C |---->| D |---->| E |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
^ ^
| |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| V |---->| W |---->| X |---->| Y |---->| Z | | V |---->| W |---->| X |---->| Y |---->| Z |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
As node C forwards a data packet along the route from A to E, it As node C forwards a data packet along the route from A to E, it
can always add to its cache the presence of the "forward" direction MAY add to its cache the presence of the "forward" direction links
links that it learns from the headers of these packets, from itself that it learns from the headers of these packets, from itself to D
to D and from D to E. However, the "reverse" direction of the links and from D to E. However, the "reverse" direction of the links
identified in the packet headers, from itself back to B and from B to identified in the packet headers, from itself back to B and from B
A, may not work for it since these links might be uni-directional. to A, may not work for it since these links might be uni-directional.
If C knows that the links are in fact bi-directional, for example due If C knows that the links are in fact bi-directional, for example due
to the MAC protocol in use, it could cache them but otherwise SHOULD to the MAC protocol in use, it could cache them but otherwise SHOULD
not. not.
Likewise, node V in the example above is using a different source Likewise, node V in the example above is using a different source
route to communicate with node Z. If node C overhears node X route to communicate with node Z. If node C overhears node X
transmitting a data packet to forward it to Y (from V), node C SHOULD transmitting a data packet to forward it to Y (from V), node C SHOULD
consider whether the links involved can be known to be bi-directional consider whether the links involved can be known to be bi-directional
or not before caching them. If the link from X to C (over which this or not before caching them. If the link from X to C (over which this
data packet was received) can be known to be bi-directional, then C data packet was received) can be known to be bi-directional, then C
could cache the link from itself to X, the link from X to Y, and the MAY cache the link from itself to X, the link from X to Y, and the
link from Y to Z. If all links can be assumed to be bi-directional, link from Y to Z. If all links can be assumed to be bi-directional,
C could also cache the links from X to W and from W to V. Similar C MAY also cache the links from X to W and from W to V. Similar
considerations apply to the routing information that might be learned considerations apply to the routing information that might be learned
from forwarded or otherwise overheard Route Request or Route Reply from forwarded or otherwise overheard Route Request or Route Reply
packets. packets.
3.3.2. Replying to Route Requests using Cached Routes 3.3.2. Replying to Route Requests using Cached Routes
A node receiving a Route Request for which it is not the target, A node receiving a Route Request for which it is not the target,
searches its own Route Cache for a route to the target of the searches its own Route Cache for a route to the target of the
Request. If found, the node generally returns a Route Reply to Request. If found, the node generally returns a Route Reply to the
the initiator itself rather than forwarding the Route Request. In initiator itself rather than forwarding the Route Request. In the
the Route Reply, it sets the route record to list the sequence of Route Reply, this node sets the route record to list the sequence of
hops over which this copy of the Route Request was forwarded to it, hops over which this copy of the Route Request was forwarded to it,
concatenated with its own idea of the route from itself to the target concatenated with the source route to this target obtained from its
from its Route Cache. own Route Cache.
However, before transmitting a Route Reply packet that was generated However, before transmitting a Route Reply packet that was generated
using information from its Route Cache in this way, a node MUST using information from its Route Cache in this way, a node MUST
verify that the resulting route being returned in the Route Reply, verify that the resulting route being returned in the Route Reply,
after this concatenation, contains no duplicate nodes listed in the after this concatenation, contains no duplicate nodes listed in the
route record. For example, the figure below illustrates a case in route record. For example, the figure below illustrates a case in
which a Route Request for target E has been received by node F, and which a Route Request for target E has been received by node F, and
node F already has in its Route Cache a route from itself to E: node F already has in its Route Cache a route from itself to E:
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
skipping to change at page 10, line 18 skipping to change at page 10, line 22
\ / \ /
\ +-----+ / \ +-----+ /
>| C |- >| C |-
+-----+ +-----+
| ^ | ^
v | v |
Route Request +-----+ Route Request +-----+
Route: A - B - C - F | F | Cache: C - D - E Route: A - B - C - F | F | Cache: C - D - E
+-----+ +-----+
The concatenation of the accumulated route from the Route Request and The concatenation of the accumulated route record from the Route
the cached route from F's Route Cache would include a duplicate node Request and the cached route from F's Route Cache would include a
in passing from C to F and back to C. duplicate node in passing from C to F and back to C.
Node F in this case could attempt to edit the route to eliminate Node F in this case could attempt to edit the route to eliminate the
the duplication, resulting in a route from A to B to C to D and on duplication, resulting in a route from A to B to C to D and on to E,
to E, but in this case, node F would not be on the route that it but in this case, node F would not be on the route that it returned
returned in its own Route Reply. DSR Route Discovery prohibits in its own Route Reply. DSR Route Discovery prohibits node F from
node F from returning such a Route Reply from its cache for two returning such a Route Reply from its cache for two reasons. First,
reasons. First, this limitation increases the probability that the this limitation increases the probability that the resulting route
resulting route is valid, since F in this case should have received is valid, since node F in this case should have received a Route
a Route Error if the route had previously stopped working. Second, Error if the route had previously stopped working. Second, this
this limitation means that a Route Error traversing the route is very limitation means that a Route Error traversing the route is very
likely to pass through any node that sent the Route Reply for the likely to pass through any node that sent the Route Reply for the
route (including F), which helps to ensure that stale data is removed route (including node F), which helps to ensure that stale data is
from caches (such as at F) in a timely manner. Otherwise, the next removed from caches (such as at F) in a timely manner. Otherwise,
Route Discovery initiated by A might also be contaminated by a Route the next Route Discovery initiated by A might also be contaminated by
Reply from F containing the same stale route. If the Route Request a Route Reply from F containing the same stale route. If the Route
does not meet these restrictions, the node (node F in this example) Request does not meet these restrictions, the node (node F in this
discards the Route Request rather than replying to it or propagating example) discards the Route Request rather than replying to it or
it. propagating it.
3.3.3. Preventing Route Reply Storms 3.3.3. Preventing Route Reply Storms
The ability for nodes to reply to a Route Request based on The ability for nodes to reply to a Route Request based on
information in their Route Caches, as described in Section 3.3.2, information in their Route Caches, as described in Section 3.3.2,
could result in a possible Route Reply "storm" in some cases. In could result in a possible Route Reply "storm" in some cases. In
particular, if a node broadcasts a Route Request for a target node particular, if a node broadcasts a Route Request for a target node
for which the node's neighbors have a route in their Route Caches, for which the node's neighbors have a route in their Route Caches,
each neighbor may attempt to send a Route Reply, thereby wasting each neighbor may attempt to send a Route Reply, thereby wasting
bandwidth and possibly increasing the number of network collisions in bandwidth and possibly increasing the number of network collisions in
the area. the area.
For example, the figure below shows a situation in which nodes B, C, For example, the figure below shows a situation in which nodes B, C,
D, E, and F all receive A's Route Request for target G, and each have D, E, and F all receive A's Route Request for target G, and each has
the indicated route cached for this target: the indicated route cached for this target:
+-----+ +-----+ +-----+ +-----+
| D |< >| C | | D |< >| C |
+-----+ \ / +-----+ +-----+ \ / +-----+
Cache: C - B - G \ / Cache: B - G Cache: C - B - G \ / Cache: B - G
\ +-----+ / \ +-----+ /
-| A |- -| A |-
+-----+\ +-----+ +-----+ +-----+\ +-----+ +-----+
| | \--->| B | | G | | | \--->| B | | G |
/ \ +-----+ +-----+ / \ +-----+ +-----+
/ \ Cache: G / \ Cache: G
v v v v
+-----+ +-----+ +-----+ +-----+
| E | | F | | E | | F |
+-----+ +-----+ +-----+ +-----+
Cache: F - B - G Cache: B - G Cache: F - B - G Cache: B - G
Normally, they would all attempt to reply from their own Route Normally, these nodes would all attempt to reply from their own
Caches, and would all send their Replys at about the same time since Route Caches, and would all send their Route Replies at about the
they all received the broadcast Route Request at about the same time. same time, since they all received the broadcast Route Request at
Such simultaneous replies from different nodes all receiving the about the same time. Such simultaneous replies from different nodes
Route Request may create packet collisions among some or all of these all receiving the Route Request may create packet collisions among
Replies and may cause local congestion in the wireless network. In some or all of these Replies and may cause local congestion in the
addition, it will often be the case that the different replies will wireless network. In addition, it will often be the case that the
indicate routes of different lengths, as shown in this example. different replies will indicate routes of different lengths, as shown
in this example.
If a node can put its network interface into promiscuous receive If a node can put its network interface into promiscuous receive
mode, it SHOULD delay sending its own Route Reply for a short period, mode, it SHOULD delay sending its own Route Reply for a short period,
while listening to see if the initiating node begins using a shorter while listening to see if the initiating node begins using a shorter
route first. That is, this node SHOULD delay sending its own Route route first. That is, this node SHOULD delay sending its own Route
Reply for a random period d = H * (h - 1 + r), where h is the length Reply for a random period
in number of network hops for the route to be returned in this node's
Route Reply, r is a random number between 0 and 1, and H is a small d = H * (h - 1 + r)
constant delay (at least twice the maximum wireless link propagation
delay) to be introduced per hop. This delay effectively randomizes where h is the length in number of network hops for the route to be
the time at which each node sends its Route Reply, with all nodes returned in this node's Route Reply, r is a random floating point
sending Route Replys giving routes of length less than h sending number between 0 and 1, and H is a small constant delay (at least
their Replys before this node, and all nodes sending Route Replys twice the maximum wireless link propagation delay) to be introduced
giving routes of length greater than h sending their Replys after per hop. This delay effectively randomizes the time at which each
this node. Within the delay period, this node promiscuously receives node sends its Route Reply, with all nodes sending Route Replies
all packets, looking for data packets from the initiator of this giving routes of length less than h sending their Replies before this
Route Discovery destined for the target of the Discovery. If such node, and all nodes sending Route Replies giving routes of length
a data packet received by this node during the delay period uses a greater than h sending their Replies after this node.
source route of length less than or equal to h, this node may infer
that the initiator of the Route Discovery has already received a Within the delay period, this node promiscuously receives all
Route Reply giving an equally good or better route. In this case, packets, looking for data packets from the initiator of this Route
this node SHOULD cancel its delay timer and SHOULD NOT send its Route Discovery destined for the target of the Discovery. If such a data
Reply for this Route Discovery. packet received by this node during the delay period uses a source
route of length less than or equal to h, this node may infer that the
initiator of the Route Discovery has already received a Route Reply
giving an equally good or better route. In this case, this node
SHOULD cancel its delay timer and SHOULD NOT send its Route Reply for
this Route Discovery.
3.3.4. Route Request Hop Limits 3.3.4. Route Request Hop Limits
Each Route Request message contains a "hop limit" that may be used Each Route Request message contains a "hop limit" that may be used
to limit the number of intermediate nodes allowed to forward that to limit the number of intermediate nodes allowed to forward that
copy of the Route Request. This hop limit is implemented using the copy of the Route Request. This hop limit is implemented using the
Time-to-Live (TTL) field in the IP header of the packet carrying Time-to-Live (TTL) field in the IP header of the packet carrying
the Route Request. As the Request is forwarded, this limit is the Route Request. As the Request is forwarded, this limit is
decremented, and the Request packet is discarded if the limit reaches decremented, and the Request packet is discarded if the limit reaches
zero before finding the target. zero before finding the target.
This Route Request hop limit can be used to implement a variety of This Route Request hop limit can be used to implement a variety of
algorithms for controlling the spread of a Route Request during a algorithms for controlling the spread of a Route Request during a
Route Discovery attempt. For example, a node MAY send its first Route Discovery attempt. For example, a node MAY send its first
Route Request attempt for some target node using a hop limit of 1, Route Request attempt for some target node using a hop limit of 1,
such that any node receiving the initial transmission of the Route such that any node receiving the initial transmission of the Route
Request will not forward it to other nodes by rebroadcasting it. Request will not forward the Request to other nodes by rebroadcasting
This form of Route Request is called a "non-propagating" Route it. This form of Route Request is called a "non-propagating"
Request. It provides an inexpensive method for determining if the Route Request. It provides an inexpensive method for determining
target is currently a neighbor of the initiator or if a neighbor if the target is currently a neighbor of the initiator or if a
node has a route to the target cached (effectively using the neighbor node has a route to the target cached (effectively using the
neighbors' Route Caches as an extension of the initiator's own Route neighbors' Route Caches as an extension of the initiator's own Route
Cache). If no Route Reply is received after a short timeout, then a Cache). If no Route Reply is received after a short timeout, then a
"propagating" Route Request (i.e., with no hop limit) MAY be sent. "propagating" Route Request (i.e., with no hop limit) MAY be sent.
Another possible use of the hop limit in a Route Request is to Another possible use of the hop limit in a Route Request is to
implement an "expanding ring" search for the target [13]. For implement an "expanding ring" search for the target [13]. For
example, a node could send an initial non-propagating Route Request example, a node could send an initial non-propagating Route Request
as described above; if no Route Reply is received for it, the node as described above; if no Route Reply is received for it, the node
could initiate another Route Request with a hop limit of 2. For could initiate another Route Request with a hop limit of 2. For
each Route Request initiated, if no Route Reply is received for it, each Route Request initiated, if no Route Reply is received for it,
skipping to change at page 12, line 49 skipping to change at page 13, line 9
Route Request to propagate over the entire network. However, this Route Request to propagate over the entire network. However, this
expanding ring search approach could have the effect of increasing expanding ring search approach could have the effect of increasing
the average latency of Route Discovery, since multiple Discovery the average latency of Route Discovery, since multiple Discovery
attempts and timeouts may be needed before discovering a route to the attempts and timeouts may be needed before discovering a route to the
target node. target node.
3.4. Additional Route Maintenance Features 3.4. Additional Route Maintenance Features
3.4.1. Packet Salvaging 3.4.1. Packet Salvaging
After sending a Route Error message as part of Route Maintenance as After sending a Route Error message as part of Route Maintenance
described in Section 3.2, a node may attempt to "salvage" the data as described in Section 3.2, a node MAY attempt to "salvage" the
packet that caused the Route Error rather than discarding it. To data packet that caused the Route Error rather than discarding the
attempt to salvage a packet, the node sending a Route Error searches packet. To attempt to salvage a packet, the node sending a Route
its own Route Cache for a route from itself to the destination of the Error searches its own Route Cache for a route from itself to the
packet causing the Error. If such a route is found, the node may destination of the packet causing the Error. If such a route is
salvage the packet after returning the Route Error by replacing the found, the node MAY salvage the packet after returning the Route
original source route on the packet with the route from its Route Error by replacing the original source route on the packet with the
Cache. The node then forwards the packet to the next node indicated route from its Route Cache. The node then forwards the packet to the
along this source route. For example, in the situation shown in the next node indicated along this source route. For example, in the
example of Section 3.2, if node C has another route cached to node E, situation shown in the example of Section 3.2, if node C has another
it can salvage the packet by applying this route to the packet rather route cached to node E, it can salvage the packet by replacing the
than discarding the packet. original route in the packet with this new route from its own Route
Cache, rather than discarding the packet.
When salvaging a packet in this way, a count is maintained in the When salvaging a packet in this way, a count is maintained in the
packet of the number of times that it has been salvaged, to prevent a packet of the number of times that it has been salvaged, to prevent a
single packet from being salvaged endlessly. Otherwise, it could be single packet from being salvaged endlessly. Otherwise, it could be
possible for the packet to enter a routing loop, as different nodes possible for the packet to enter a routing loop, as different nodes
repeatedly salvage the packet and replace the source route on the repeatedly salvage the packet and replace the source route on the
packet with routes to each other. packet with routes to each other.
3.4.2. Automatic Route Shortening 3.4.2. Automatic Route Shortening
Source routes in use may be automatically shortened if one or more Source routes in use MAY be automatically shortened if one or more
intermediate hops in the route become no longer necessary. This intermediate hops in the route become no longer necessary. This
mechanism of automatically shortening routes in use is somewhat mechanism of automatically shortening routes in use is somewhat
similar to the use of passive acknowledgements. In particular, if a similar to the use of passive acknowledgements [15]. In particular,
node is able to overhear a packet carrying a source route (e.g., by if a node is able to overhear a packet carrying a source route (e.g.,
operating its network interface in promiscuous receive mode), then by operating its network interface in promiscuous receive mode), then
this node examines the unused portion of that source route. If this this node examines the unused portion of that source route. If this
node is not the intended next hop for the packet but is named in node is not the intended next hop for the packet but is named in
the later unused portion of the packet's source route, then it can the later unused portion of the packet's source route, then it can
infer that the intermediate nodes before itself in the source route infer that the intermediate nodes before itself in the source route
are no longer needed in the route. For example, the figure below are no longer needed in the route. For example, the figure below
illustrates an example in which node D has overheard a data packet illustrates an example in which node D has overheard a data packet
being transmitted from B to C, for later forwarding to D and to E: being transmitted from B to C, for later forwarding to D and to E:
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| A |---->| B |---->| C | | D | | E | | A |---->| B |---->| C | | D | | E |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
\ ^ \ ^
\ / \ /
--------------------- ---------------------
In this case, this node (node D) returns a "gratuitous" Route Reply In this case, this node (node D) returns a "gratuitous" Route Reply
message to the original sender of the packet (node A). The Route to the original sender of the packet (node A). The Route Reply
Reply gives the shorter route as the concatenation of the portion of gives the shorter route as the concatenation of the portion of the
the original source route up through the node that transmitted the original source route up through the node that transmitted the
overheard packet (node B), plus the suffix of the original source overheard packet (node B), plus the suffix of the original source
route beginning with the node returning the gratuitous Route Reply route beginning with the node returning the gratuitous Route Reply
(node D). In this example, the route returned in the gratuitous Route (node D). In this example, the route returned in the gratuitous Route
Reply message sent from D to A gives the new route as the sequence of Reply message sent from D to A gives the new route as the sequence of
hops from A to B to D to E. hops from A to B to D to E.
3.4.3. Increased Spreading of Route Error Messages 3.4.3. Increased Spreading of Route Error Messages
When a source node receives a Route Error for a data packet that When a source node receives a Route Error for a data packet that
it originated, this source node propagates this Route Error to its it originated, this source node propagates this Route Error to its
neighbors by piggybacking it on its next Route Request. In this way, neighbors by piggybacking it on its next Route Request. In this way,
stale information in the caches of nodes around this source node will stale information in the caches of nodes around this source node will
not generate Route Replys that contain the same invalid link for not generate Route Replies that contain the same invalid link for
which this source node received the Route Error. which this source node received the Route Error.
For example, in the situation shown in the example of Section 3.2, For example, in the situation shown in the example of Section 3.2,
node A learns from the Route Error message from C, that the link from node A learns from the Route Error message from C, that the link
C to D is currently broken. It thus removes this link from its own from C to D is currently broken. It thus removes this link from
Route Cache and initiates a new Route Discovery (if it doesn't have its own Route Cache and initiates a new Route Discovery (if it has
another route to E in its Route Cache). On the Route Request packet no other route to E in its Route Cache). On the Route Request
initiating this Route Discovery, node A piggybacks a copy of this packet initiating this Route Discovery, node A piggybacks a copy
Route Error message, ensuring that the Route Error message spreads of this Route Error, ensuring that the Route Error spreads well to
well to other nodes, and guaranteeing that any Route Reply that it other nodes, and guaranteeing that any Route Reply that it receives
receives (including those from other node's Route Caches) in response (including those from other node's Route Caches) in response to this
to this Route Request does not contain a route that assumes the Route Request does not contain a route that assumes the existence of
existence of this broken link. this broken link.
4. Conceptual Data Structures 4. Conceptual Data Structures
This document describes the DSR protocol in terms of a number of This document describes the operation of the DSR protocol in terms
conceptual data structures. This section describes each of these of a number of conceptual data structures. This section describes
data structures and provides an overview of its use in the protocol. each of these data structures and provides an overview of its use
In an implementation of the protocol, these data structures MAY be in the protocol. In an implementation of the protocol, these data
implemented in any manner consistent with the external behavior structures MAY be implemented in any manner consistent with the
described in this document. external behavior described in this document.
4.1. Route Cache 4.1. Route Cache
All routing information needed by a node participating in an ad hoc All routing information needed by a node participating in an ad hoc
network using DSR is stored in a Route Cache. Each node in the network using DSR is stored in that node's Route Cache. Each node in
network maintains its own Route Cache. A node adds information the network maintains its own Route Cache. A node adds information
to its Route Cache as it learns of new links between nodes in the to its Route Cache as it learns of new links between nodes in the
ad hoc network; for example, a node may learn of new links when it ad hoc network; for example, a node may learn of new links when it
receives a packet carrying either a Route Reply or a DSR Routing receives a packet carrying either a Route Reply or a DSR Routing
header. Likewise, a node removes information from its Route Cache as header. Likewise, a node removes information from its Route Cache as
it learns that existing links in the ad hoc network have broken; for it learns that existing links in the ad hoc network have broken; for
example, a node may learn of a broken link when it receives a packet example, a node may learn of a broken link when it receives a packet
carrying a Route Error or through the link-layer retransmission carrying a Route Error or through the link-layer retransmission
mechanism reporting a failure in forwarding a packet to its next-hop mechanism reporting a failure in forwarding a packet to its next-hop
destination. destination.
skipping to change at page 15, line 40 skipping to change at page 15, line 40
external to this DSR network. Such external networks may, for external to this DSR network. Such external networks may, for
example, be the Internet, or may be other ad hoc networks routed example, be the Internet, or may be other ad hoc networks routed
with a routing protocol other than DSR. Such external networks may with a routing protocol other than DSR. Such external networks may
also be other DSR networks that are treated as external networks also be other DSR networks that are treated as external networks
in order to improve scalability. The complete handling of such in order to improve scalability. The complete handling of such
external networks is beyond the scope of this document. However, external networks is beyond the scope of this document. However,
this document specifies a minimal set of requirements and features this document specifies a minimal set of requirements and features
necessary to allow nodes only implementing this specification to necessary to allow nodes only implementing this specification to
interoperate correctly with nodes implementing interfaces to such interoperate correctly with nodes implementing interfaces to such
external networks. This minimal set of requirements and features external networks. This minimal set of requirements and features
involve the First Hop External (F) and Last Hop External (L) bits in involve the First Hop External (F) and Last Hop External (L)
a DSR Routing Header and a DSR Route Reply option, and the addition bits in a Source Route option (Section 5.7) and a Route Reply
of an External flag bit tagging each node in the Route Cache, copied option (Section 5.3) in a packet's DSR header (Section 5). These
from the First Hop External (F) and Last Hop External (L) bits in the requirements also include the addition of an External flag bit
Routing header or Route Reply from which the link to this node was tagging each node in the Route Cache, copied from the First Hop
External (F) and Last Hop External (L) bits in the Source Route
option or Route Reply option from which the link to this node was
learned. learned.
The Route Cache SHOULD support storing more than one route to each The Route Cache SHOULD support storing more than one route to each
destination. In searching the Route Cache for a route to some destination. In searching the Route Cache for a route to some
destination node, the Route Cache is indexed by destination node destination node, the Route Cache is indexed by destination node
address. address. The following properties describe this searching function
on a Route Cache:
- Each implementation of DSR at any node MAY choose any appropriate - Each implementation of DSR at any node MAY choose any appropriate
strategy and algorithm for searching its Route Cache and strategy and algorithm for searching its Route Cache and
selecting a "best" route to the destination from among those selecting a "best" route to the destination from among those
found. For example, a node MAY choose to select the shortest found. For example, a node MAY choose to select the shortest
route to the destination (the shortest sequence of hops), or it route to the destination (the shortest sequence of hops), or it
MAY use an alternate metric to select the route from the Cache. MAY use an alternate metric to select the route from the Cache.
- However, if there are multiple cached routes to a destination, - However, if there are multiple cached routes to a destination,
the selection of routes when searching the Route Cache SHOULD the selection of routes when searching the Route Cache SHOULD
prefer routes that do not have the External flag set on any prefer routes that do not have the External flag set on any node.
node. This will prefer routes that lead directly to the target This preference will select routes that lead directly to the
node instead of routes that attempt to reach the target via any target node over routes that attempt to reach the target via any
external networks connected to the DSR ad hoc network. external networks connected to the DSR ad hoc network.
- In addition, any route selected when searching the Route Cache - In addition, any route selected when searching the Route Cache
MUST NOT have the External bit set for any nodes other than MUST NOT have the External bit set for any nodes other than
possibly the first node, the last node, or both; the External bit possibly the first node, the last node, or both; the External bit
MUST NOT be set for any intermediate hops in the route selected. MUST NOT be set for any intermediate hops in the route selected.
An implementation of a Route Cache MAY provide a fixed capacity for An implementation of a Route Cache MAY provide a fixed capacity
the cache, or the cache size MAY be variable. for the cache, or the cache size MAY be variable. The following
properties describe the management of available space within a node's
Route Cache:
- Each implementation of DSR at each node MAY choose any - Each implementation of DSR at each node MAY choose any
appropriate policy for managing the entries in its Route Cache, appropriate policy for managing the entries in its Route Cache,
such as when limited cache capacity requires a choice of which such as when limited cache capacity requires a choice of which
entries to retain in the cache. For example, a node MAY chose a entries to retain in the Cache. For example, a node MAY chose a
"least recently used" (LRU) cache replacement policy, in which "least recently used" (LRU) cache replacement policy, in which
the entry last used longest ago is discarded from the cache if a the entry last used longest ago is discarded from the cache if a
decision needs to be made to allow space in the cache for some decision needs to be made to allow space in the cache for some
new entry being added. new entry being added.
- However, the Route Cache replacement policy SHOULD allow routes - However, the Route Cache replacement policy SHOULD allow routes
to be categorized based upon "preference", where routes with a to be categorized based upon "preference", where routes with a
higher preferences are less likely to be removed from the cache. higher preferences are less likely to be removed from the cache.
For example, a node could prefer routes for which it initiated For example, a node could prefer routes for which it initiated
a Route Discovery over routes that it learned as the result of a Route Discovery over routes that it learned as the result of
promiscuous snooping on other packets. In particular, a node promiscuous snooping on other packets. In particular, a node
SHOULD prefer routes that it is presently using over those that SHOULD prefer routes that it is presently using over those that
it is not. it is not.
Any suitable data structure organization, consistent with this Any suitable data structure organization, consistent with this
specification, MAY be used to implement the Route Cache in any node. specification, MAY be used to implement the Route Cache in any node.
For example, the following two types of organization are possible: For example, the following two types of organization are possible:
- In DSR, the route returned in each Route Reply that is received - In DSR, the route returned in each Route Reply that is received
by the initiator of a Route Discovery (or that is learned from by the initiator of a Route Discovery (or that is learned from
the header of overhead packets, as described in Section 6.1.3) the header of overhead packets, as described in Section 6.1.4)
represents a complete path (a sequence of links) leading to the represents a complete path (a sequence of links) leading to the
destination node. By caching each of these paths separately, destination node. By caching each of these paths separately,
a "path cache" organization for the Route Cache can be formed. a "path cache" organization for the Route Cache can be formed.
A path cache is very simple to implement and easily guarantees A path cache is very simple to implement and easily guarantees
that all routes are loop-free, since each individual route from that all routes are loop-free, since each individual route from
a Route Reply or Route Request or used in a packet is loop-free. a Route Reply or Route Request or used in a packet is loop-free.
To search for a route in a path cache data structure, the sending To search for a route in a path cache data structure, the sending
node can simply search its Route Cache for any path (or prefix of node can simply search its Route Cache for any path (or prefix of
a path) that leads to the intended destination node. a path) that leads to the intended destination node.
This type of organization for the Route Cache in DSR has This type of organization for the Route Cache in DSR has
been extensively studied through simulation [5, 11, 19] and been extensively studied through simulation [5, 11, 18] and
through implementation of DSR in a mobile outdoor testbed under through implementation of DSR in a mobile outdoor testbed under
significant workload [20, 21]. significant workload [19, 20, 20].
- Alternatively, a "link cache" organization could be used for the - Alternatively, a "link cache" organization could be used for the
Route Cache, in which each individual link in the routes returned Route Cache, in which each individual link (hop) in the routes
in Route Reply packets (or otherwise learned from the header of returned in Route Reply packets (or otherwise learned from the
overhead packets) is added to a unified graph data structure of header of overhead packets) is added to a unified graph data
this node's current view of the network topology. To search structure of this node's current view of the network topology.
for a route in link cache, the sending node must use a more To search for a route in link cache, the sending node must use
complex graph search algorithm, such as the well-known Dijkstra's a more complex graph search algorithm, such as the well-known
shortest-path algorithm, to find the current best path through Dijkstra's shortest-path algorithm, to find the current best path
the graph to the destination node. Such an algorithm is more through the graph to the destination node. Such an algorithm is
difficult to implement and may require significantly more CPU more difficult to implement and may require significantly more
time to execute. CPU time to execute.
However, a link cache organization is more powerful than a However, a link cache organization is more powerful than a
path cache organization, in its ability to effectively utilize path cache organization, in its ability to effectively utilize
all of the potential information that a node might learn about all of the potential information that a node might learn about
the state of the network: links learned from different Route the state of the network: links learned from different Route
Discoveries or from the header of any overheard packets can be Discoveries or from the header of any overheard packets can be
merged together to form new routes in the network, but this merged together to form new routes in the network, but this
is not possible in a path cache due to the separation of each is not possible in a path cache due to the separation of each
individual path in the cache. individual path in the cache.
skipping to change at page 17, line 47 skipping to change at page 17, line 51
through detailed simulation [9]. through detailed simulation [9].
The choice of data structure organization to use for the Route Cache The choice of data structure organization to use for the Route Cache
in any DSR implementation is a local matter for each node and affects in any DSR implementation is a local matter for each node and affects
only performance; any reasonable choice of organization for the Route only performance; any reasonable choice of organization for the Route
Cache does not affect either correctness or interoperability. Cache does not affect either correctness or interoperability.
4.2. Route Request Table 4.2. Route Request Table
The Route Request Table records information about Route Requests that The Route Request Table records information about Route Requests that
were recently originated or forwarded by this node. The table is have been recently originated or forwarded by this node. The table
indexed by IP address. is indexed by IP address.
The Route Request Table on a node records the following information The Route Request Table on a node records the following information
about nodes to which this node has initiated a Route Request: about nodes to which this node has initiated a Route Request:
- The time that this node last originated a Route Discovery for - The time that this node last originated a Route Request for that
that target node. target node.
- The number of consecutive Route Requests initiated for this - The number of consecutive Route Requests initiated for this
target since receiving a valid Route Reply giving a route to that target since receiving a valid Route Reply giving a route to that
target node. target node.
- The remaining amount of time before which this node MAY next - The remaining amount of time before which this node MAY next
attempt at a Route Discovery for that target node. attempt at a Route Discovery for that target node.
- The Time-to-Live (TTL) field used in the IP header of last Route - The Time-to-Live (TTL) field used in the IP header of last Route
Request initiated by this node for that target node. Request initiated by this node for that target node.
skipping to change at page 18, line 32 skipping to change at page 18, line 35
- A FIFO cache of size REQUEST_TABLE_IDS entries containing the - A FIFO cache of size REQUEST_TABLE_IDS entries containing the
Identification value and target address from the most recent Identification value and target address from the most recent
Route Requests received by this node from that initiator node. Route Requests received by this node from that initiator node.
Nodes SHOULD use an LRU policy to manage the entries in their Route Nodes SHOULD use an LRU policy to manage the entries in their Route
Request Table. Request Table.
The number of Identification values to retain in each Route Request The number of Identification values to retain in each Route Request
Table entry, REQUEST_TABLE_IDS, MUST NOT be unlimited, since, Table entry, REQUEST_TABLE_IDS, MUST NOT be unlimited, since,
in the worst case, when a node crashes and reboots, the first in the worst case, when a node crashes and reboots, the first
REQUEST_TABLE_IDS Route Requests it initiates could appear to be REQUEST_TABLE_IDS Route Discoveries it initiates after rebooting
duplicates to the other nodes in the network. could appear to be duplicates to the other nodes in the network.
In addition, a node SHOULD base its initial Identification value,
used for Route Discoveries after rebooting, on a battery backed-up
clock or other persistent memory device, in order to help avoid any
possible such delay in successfully discovering new routes after
rebooting; if no such source of initial Identification value is
available, a node SHOULD base its initial Identification value after
rebooting on a random number.
4.3. Send Buffer 4.3. Send Buffer
The Send Buffer of some node is a queue of packets that cannot be The Send Buffer of a node implementing DSR is a queue of packets that
transmitted by that node because it does not yet have a source cannot be sent by that node because it does not yet have a source
route to each respective packet's destination. Each packet in the route to each such packet's destination. Each packet in the Send
Send Buffer is stamped with the time that it is placed into the Buffer is logically associated with the time that it was placed into
Buffer, and SHOULD be removed from the Send Buffer and discarded the Buffer, and SHOULD be removed from the Send Buffer and silently
SEND_BUFFER_TIMEOUT seconds after initially being placed in the discarded SEND_BUFFER_TIMEOUT seconds after initially being placed in
Buffer. If necessary, a FIFO strategy SHOULD be used to evict the Buffer. If necessary, a FIFO strategy SHOULD be used to evict
packets before they timeout to prevent the buffer from overflowing. packets before they timeout to prevent the buffer from overflowing.
Subject to the rate limiting defined in Section 6.2, a Route Subject to the rate limiting defined in Section 6.2, a Route
Discovery SHOULD be initiated as often as possible for the Discovery SHOULD be initiated as often as possible for the
destination address of any packets residing in the Send Buffer. destination address of any packets residing in the Send Buffer.
4.4. Retransmission Buffer 4.4. Retransmission Buffer
The Retransmission Buffer of a node is a queue of packets sent by The Retransmission Buffer of a node implementing DSR is a queue
this node that are awaiting the receipt of an acknowledgment from the of packets sent by this node that are awaiting the receipt of an
next hop in the source route (Section 5.3). acknowledgment from the next hop in the source route (Section 5.7).
For each packet in the Retransmission Buffer, a node maintains (1) a For each packet in the Retransmission Buffer, a node maintains (1) a
count of the number of retransmissions and (2) the time of the last count of the number of retransmissions and (2) the time of the last
retransmission. retransmission.
Packets are removed from the buffer when an acknowledgment Packets are removed from the Retransmission Buffer when an
is received, or when the number of retransmissions exceeds acknowledgment is received or when the number of retransmissions
DSR_MAXRXTSHIFT. In the later case, the removal of the packet from exceeds DSR_MAXRXTSHIFT. In the later case, the removal of the
the Retransmission Buffer SHOULD result in a Route Error being packet from the Retransmission Buffer SHOULD result in a Route Error
returned to the original source of the packet (Section 6.3). being returned to the original source of the packet (Section 6.3).
5. Packet Formats 5. DSR Header Format
Dynamic Source Routing makes use of four options carrying control The Dynamic Source Routing protocol makes use of a special header
information that can be piggybacked in any existing IP packet. The carrying control information that can be included in any existing IP
mechanism used to represent these options in a packet is based on packet. This DSR header in a packet contains a small fixed-sized,
the design of the Hop-by-Hop and Destination Options mechanisms in 4-octet portion, followed by a sequence of zero or more DSR options
IPv6 [7]. The ability to generate and process such options must carrying optional information. The end of the sequence of DSR
be added to an IPv4 protocol stack. Specifically, the Protocol options in the DSR header is implied by total length of the DSR
field in the IP header is used to indicate that a Hop-by-Hop Options header.
extension header or Destination Options extension header follows the
IP header, and the Next Header field in the extension header is used
to indicate the type of protocol header (such as a transport layer
header) following the extension header.
In addition, DSR makes use of one additional header type, to carry The DSR header is inserted in the packet following the packet's IP
the source route for a packet. This DSR Routing header is based on header, before any following header such as a traditional (e.g., TCP
the design of the Routing header defined for IPv6 [7]. DSR defines or UDP) transport layer header. Specifically, the Protocol field
a new value for the Routing Type field to distinguish a DSR Routing in the IP header is used to indicate that a DSR header follows the
header from other types of Routing headers. IP header, and the Next Header field in the DSR header is used to
indicate the type of protocol header (such as a transport layer
header) following the DSR header.
For IPv6, all extension headers are a multiple of 8 bytes in length. The total length of the DSR header (and thus the total, combined
However, for use in IPv4 packets, all extension headers only MUST be length of all DSR options present) MUST be a multiple of 4 octets.
a multiple of 4 bytes long. This requirement preserves the alignment This requirement preserves the alignment of any following headers in
of any following extension headers and of any additional header the packet.
(e.g., a TCP header [26]) following the last extension header.
5.1. Destination Options Header 5.1. Fixed Portion of DSR Header
The Destination Options extension header is used to carry optional The fixed portion of the DSR header is used to carry information that
information that needs to be examined only by a packet's destination must be present in any DSR header. This fixed portion of the DSR
node(s). The Destination Options extension header is identified by header has the following format:
a Next Header (or Protocol) value of 60 in the immediately preceding
header [7], and has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | | | Next Header | Reserved | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. . . .
. Options . . Options .
. . . .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Next Header Next Header
8-bit selector. Identifies the type of header immediately 8-bit selector. Identifies the type of header immediately
following the Destination Options header. Uses the same values following the DSR header. Uses the same values as the IPv4
as the IPv4 Protocol field [27]. Protocol field [26].
Hdr Ext Len Reserved
8-bit unsigned integer. Length of the Destination Options Sent as 0; ignored on reception.
header in 4-octet units, not including the first 8 octets.
Payload Length
The length of the DSR header, excluding the 4-octet fixed
portion. The value of the Payload Length field defines the
total length of all options carried in the DSR header.
Options Options
Variable-length field, of length such that the complete Variable-length field; the length of the Options field is
Destination Options header is an integer multiple of 4 octets specified by the Payload Length field in this DSR header.
long. Contains one or more TLV-encoded options. Contains one or more pieces of optional information (DSR
options), encoded in type-length-value (TLV) format (with the
exception of the Pad1 option, described in Section 5.8).
The following destination option type is used by the DSR protocol: The placement of DSR options following the fixed portion of the DSR
header MAY be padded for alignment. However, due to the typically
limited available wireless bandwidth in ad hoc networks, this padding
is not required, and receiving nodes MUST NOT expect options within
a DSR header to be aligned. A node inserting a DSR header into
a packet MUST set the Don't Fragment (DF) bit in the packet's IP
header.
- DSR Route Request option (Section 5.1.1) The following types of DSR options are defined in this document for
use within a DSR header:
5.1.1. DSR Route Request Option - Route Request option (Section 5.2)
The DSR Route Request destination option is encoded in - Route Reply option (Section 5.3)
type-length-value (TLV) format as follows:
- Route Error option (Section 5.4)
- Acknowledgement Request option (Section 5.5)
- Acknowledgement option (Section 5.6)
- Source Route option (Section 5.7)
- Pad1 option (Section 5.8)
- PadN option (Section 5.9)
5.2. Route Request Option
The Route Request DSR option is encoded 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Identification | | Option Type | Opt Data Len | Identification |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target Address | | Target Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[1] | | Address[1] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[2] | | Address[2] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[n] | | Address[n] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IP fields: IP fields:
Source Address Source Address
MUST be set to the address of the node originating this packet. MUST be set to the address of the node originating this packet.
Intermediate nodes that repropagate the Route Request MUST not Intermediate nodes that retransmit the packet to propagate the
change this field. Route Request MUST NOT change this field.
Destination Address Destination Address
MUST be set to the limited broadcast address (255.255.255.255). MUST be set to the IP limited broadcast address
(255.255.255.255).
Hop Limit (TTL) Hop Limit (TTL)
Can be varied from 1 to 255, for example to implement MAY be varied from 1 to 255, for example to implement
non-propagating Route Requests and Route Request expanding-ring non-propagating Route Requests and Route Request expanding-ring
searches (Section 3.3.4). searches (Section 3.3.4).
Route Request fields: Route Request fields:
Option Type Option Type
???. The top three bits of this Option Type value are equal to 2
011, meaning that a node that does not understand this option
MUST discard the packet, and that the Option Data may change
en-route [7].
Option Length Opt Data Len
8-bit unsigned integer. Length of the option, in octets, 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. excluding the Option Type and Opt Data Len fields.
Identification Identification
A unique value generated by the initiator (original sender) of A unique value generated by the initiator (original sender) of
the Route Request. Nodes initiating a Route Request generate the Route Request. Nodes initiating a Route Request generate
a new Identification value for each Route Request, for example a new Identification value for each Route Request, for example
based on a sequence number counter of all Route Requests based on a sequence number counter of all Route Requests
initiated by the node. initiated by the node.
This value allows a receiving node to determine whether it This value allows a receiving node to determine whether it
has recently seen a copy of this Route Request: if this has recently seen a copy of this Route Request: if this
Identification value is found by this receiving node in its Identification value is found by this receiving node in its
Route Request Table (in the cache of Identification values Route Request Table (in the cache of Identification values
in the entry there for this initiating node), this receiving in the entry there for this initiating node), this receiving
node MUST discard the Route Request. When propagating a Route node MUST discard the Route Request. When propagating a Route
Request, this field MUST be copied from the received copy of Request, this field MUST be copied from the received copy of
the Route Request being forwarded. the Route Request being propagated.
Target Address Target Address
The address of the node that is the target of the Route The address of the node that is the target of the Route
Request. Request.
Address[1..n] Address[1..n]
Address[i] is the address of the i-th hop recorded in the Address[i] is the address of the i-th hop recorded in the Route
Route Request option. The number of addresses present in this Request option. The address given in the Source Address field
field is indicated by the Option Length field in the option in the IP header is the address of the initiator of the Route
(n = (Option Length - 6) / 4). Each node repropagating the Discovery and MUST NOT be listed in the Address[i] fields; the
Route Request adds its own address to this list, increasing the address given in Address[1] is thus the address of the first
Option Length value by 4. node on the path after the initiator. The number of addresses
present in this field is indicated by the Opt Data Len field in
the option (n = (Opt Data Len - 2) / 4). Each node propagating
the Route Request adds its own address to this list, increasing
the Opt Data Len value by 4 octets.
The DSR Route Request destination option MUST NOT appear more than The Route Request option MUST NOT appear more than once within a DSR
once within any single Destination Options extension header. header.
5.2. Hop-by-Hop Options Header 5.3. Route Reply Option
The Hop-by-Hop Options extension header is used to carry optional The Route Reply DSR option is encoded as follows:
information that must be examined by every node along a packet's
delivery path. The Hop-by-Hop Options extension header is identified
by a Protocol value of 0 in the IP header [7], and has the following
format:
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
+-+-+-+-+-+-+-+-+
| Option Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | | | Opt Data Len |L| Reserved | Identification |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
. .
. Options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Next Header
8-bit selector. Identifies the type of header immediately
following the Hop-by-Hop Options header. Uses the same values
as the IPv4 Protocol field [27].
Hdr Ext Len
8-bit unsigned integer. Length of the Hop-by-Hop Options
header in 4-octet units, not including the first 8 octets.
Options
Variable-length field, of length such that the complete
Hop-by-Hop Options header is an integer multiple of 4 octets
long. Contains one or more TLV-encoded options.
If present in an IP packet, the Hop-by-Hop Options extension header
MUST appear in the packet immediately following the IP header.
The following hop-by-hop option types are used by the DSR protocol:
- DSR Route Reply option (Section 5.2.1)
- DSR Route Error option (Section 5.2.2)
- DSR Acknowledgment option (Section 5.2.3)
5.2.1. DSR Route Reply Option
The DSR Route Reply hop-by-hop option is encoded in type-length-value
(TLV) format as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |L| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[1] | | Address[1] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[2] | | Address[2] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[n] | | Address[n] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IP fields:
Source Address
Set to the address of the node sending the Route Reply.
In the case of a node sending a reply from its Route
Cache (Section 3.3.2) or sending a gratuitous Route Reply
(Section 3.4.2), this address can differ from the address that
was the target of the Route Discovery.
Destination Address
MUST be set to the address of the source node of the route
being returned. Copied from the Source Address field of the
Route Request generating the Route Reply, or in the case of a
gratuitous Route Reply, copied from the Source Address field of
the data packet triggering the gratuitous Reply.
Route Reply fields:
Option Type Option Type
???. The top three bits of this Option Type value are equal to 3
000, meaning that a node that does not understand this option
SHOULD ignore this option and continue processing the packet,
and that the Option Data does not change en-route [7].
Option Length Opt Data Len
8-bit unsigned integer. Length of the option, in octets, 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. excluding the Option Type and Opt Data Len fields.
Last Hop External (L) Last Hop External (L)
Set to indicate that the last node indicated by the Route Reply Set to indicate that the last node indicated by the Route
is actually in a network external to the DSR network; the exact Reply (Address[n]) is actually in a network external to the
sequence of hops leading to it outside the DSR network are not DSR network; the exact sequence of hops leading to it outside
represented in the Route Reply. Nodes caching this hop in the DSR network is not represented in the Route Reply. Nodes
their Route Cache MUST flag the cached hop with the External caching this hop in their Route Cache MUST flag the cached hop
flag. Such hops MUST NOT be returned in a cached Route Reply with the External flag. Such hops MUST NOT be returned in a
generated from this Route Cache entry, and selection of routes cached Route Reply generated from this Route Cache entry, and
from the Route Cache to route a packet being sent SHOULD prefer selection of routes from the Route Cache to route a packet
routes that contain no nodes flagged as External. being sent SHOULD prefer routes that contain no hops flagged as
External.
Reserved Reserved
Sent as 0; ignored on reception. Sent as 0; ignored on reception.
Identification
Copied from the Identification field of the Route Request for
which this Reply is sent in response. Sent as 0 if the Route
Reply is not sent in response to a Route Request (a gratuitous
Route Reply).
Address[1..n] Address[1..n]
The source route being returned by the Route Reply, indicating The source route being returned by the Route Reply. The route
a route from the node with address Address[1] to the node with indicates a sequence of hops, originating at the source node
address Address[n]. The number of addresses present in this specified in the Destination Address field of the IP header
field is indicated by the Option Length field in the option of the packet carrying the Route Reply, through each of the
(n = (Option Length - 1) / 4). Address[i] nodes in the order listed in the Route Reply,
ending with the destination node indicated by Address[n].
The number of addresses present in the Address[1..n]
field is indicated by the Opt Data Len field in the option
(n = (Opt Data Len - 3) / 4).
A DSR Route Reply destination option MAY appear one or more times A Route Reply option MAY appear one or more times within a DSR
within a single Hop-by-Hop Options extension header. header.
5.2.2. DSR Route Error Option 5.4. Route Error Option
The DSR Route Error hop-by-hop option is encoded in type-length-value The Route Error DSR option is encoded as follows:
(TLV) format 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Error Type |Reservd|Salvage| | Option Type | Opt Data Len | Error Type |Reservd|Salvage|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Source Address | | Error Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Destination Address | | Error Destination Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unreachable Node Address | . .
. Type-Specific Information .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type Option Type
???. The top three bits of this Option Type value are equal to 4
000, meaning that a node that does not understand this option
SHOULD ignore this option and continue processing the packet,
and that the Option Data does not change en-route [7].
Option Length Opt Data Len
8-bit unsigned integer. Length of the option, in octets, 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. excluding the Option Type and Opt Data Len fields.
For the current definition of the DSR Route Error option, this For the current definition of the Route Error option,
field MUST be set to 13. Extensions to the DSR Route Error this field MUST be set to 10, plus the size of any
option format may be included after the fixed portion of the Type-Specific Information present in the Route Error. Further
DSR Route Error option specified above. The presence of such extensions to the Route Error option format may also be
extensions will be indicated by the Option Length field. When included after the Type-Specific Information portion of the
the Option Length is greater than 13 octets, the remaining Route Error option specified above. The presence of such
octets are interpreted as extensions. Currently, no extensions extensions will be indicated by the Opt Data Len field.
have been defined. When the Opt Data Len is greater than that required for
the fixed portion of the Route Error plus the necessary
Type-Specific Information as indicated by the Option Type
value in the option, the remaining octets are interpreted as
extensions. Currently, no such further extensions have been
defined.
Error Type Error Type
The type of error encountered. Currently, the following type The type of error encountered. Currently, the following type
value is defined: value is defined:
NODE_UNREACHABLE 1 1 = NODE_UNREACHABLE
Other values of the Error Type field are reserved for future Other values of the Error Type field are reserved for future
use. use.
Reservd Reservd
Reserved. Sent as 0; ignored on reception. Reserved. Sent as 0; ignored on reception.
Salvage Salvage
A 4-bit unsigned integer. Copied from the Salvage field in the A 4-bit unsigned integer. Copied from the Salvage field in the
DSR Routing header of the packet triggering the Route Error, Source Route option of the packet triggering the Route Error,
incremented by the node returning the Route Error. incremented by the node returning the Route Error.
Error Source Address Error Source Address
The address of the node originating the Route Error (e.g., the The address of the node originating the Route Error (e.g., the
node that attempted to forward a packet and discovered the link node that attempted to forward a packet and discovered the link
failure). failure).
Error Destination Address Error Destination Address
The address of the node to which the Route Error must The address of the node to which the Route Error must be
be delivered (e.g., the node that generated the routing delivered For example, when the Error Type field is set to
information claiming that the hop Error Source Address to NODE_UNREACHABLE, this field will be set to the address of the
Unreachable Node Address was a valid hop). node that generated the routing information claiming that the
hop from the Error Source Address to Unreachable Node Address
(specified in the Type-Specific Information) was a valid hop.
Type-Specific Information
Information specific to the Error Type of this Route Error
message.
Currently, the Type-Specific Information field is defined only for
Route Error messages of type NODE_UNREACHABLE. In this case, the
Type-Specific Information field is defined as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unreachable Node Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Unreachable Node Address Unreachable Node Address
The address of the node that was found to be unreachable The address of the node that was found to be unreachable
(the next hop neighbor to which the node with address (the next hop neighbor to which the node with address
Error Source Address was attempting to transmit the packet). Error Source Address was attempting to transmit the packet).
A DSR Route Error destination option MAY appear one or more times A Route Error option MAY appear one or more times within a DSR
within a single Hop-by-Hop Options extension header. header.
5.2.3. DSR Acknowledgment Option 5.5. Acknowledgment Request Option
The DSR Acknowledgment hop-by-hop option is encoded in The Acknowledgment Request DSR option is encoded as follows:
type-length-value (TLV) format 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Identification | | Option Type | Opt Data Len | Identification |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACK Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACK Destination Address | | ACK Request Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type Option Type
???. The top three bits of this Option Type value are equal to 5
000, meaning that a node that does not understand this option
SHOULD ignore this option and continue processing the packet,
and that the Option Data does not change en-route [7].
Option Length Opt Data Len
8-bit unsigned integer. Length of the option, in octets, 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. excluding the Option Type and Opt Data Len fields.
Identification Identification
Copied from the Identification field of the DSR Routing header The Identification field is set to a unique nonzero value and
of the packet being acknowledged. is copied into the Identification field of the Acknowledgement
option when returned by the node receiving the packet over this
ACK Source Address hop.
The address of the node originating the DSR Acknowledgment.
ACK Destination Address ACK Request Source Address
The address of the node to which the DSR Acknowledgment is to The address of the node requesting the acknowledgment.
be delivered.
A DSR Acknowledgement destination option MAY appear one or more times An Acknowledgement Request option MUST NOT appear more than once
within a single Hop-by-Hop Options extension header. within a DSR header.
5.3. DSR Routing Header 5.6. Acknowledgment Option
As specified for IPv6 [7], a Routing header is used by a source to The Acknowledgment DSR option is encoded as follows:
list one or more intermediate nodes to be "visited" on the way to
a packet's destination. This function is similar to IPv4's Loose
Source and Record Route option, but the Routing header does not
record the route taken as the packet is forwarded. The specific
processing steps required to implement the Routing header must be
added to an IPv4 protocol stack. The Routing header is identified by
a Next Header value of 43 in the immediately preceding header, and
has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Segments Left | | Option Type | Opt Data Len | Identification |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | ACK Source Address |
. . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. type-specific data . | ACK Destination Address |
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The type-specific data for a Routing Header carrying a DSR Source Option Type
Route is:
6
Opt Data Len
8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Opt Data Len fields.
Identification
Copied from the Identification field of the Acknowledgement
Request option of the packet being acknowledged.
ACK Source Address
The address of the node originating the acknowledgment.
ACK Destination Address
The address of the node to which the acknowledgment is to be
delivered.
An Acknowledgement option MAY appear one or more times within a DSR
header.
5.7. Source Route Option
The Source Route DSR option is encoded 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|L| Reserved |Salvage| Identification | | Option Type | Opt Data Len |F|L|Reservd|Salvage| Segs Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[1] | | Address[1] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[2] | | Address[2] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address[n] | | Address[n] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Routing header fields:
Next Header
8-bit selector. Identifies the type of header immediately
following the Routing header.
Hdr Ext Len Option Type
8-bit unsigned integer. Length of the Routing header in
4-octet units, not including the first 8 octets.
Routing Type
???
Segments Left 7
Number of route segments remaining, i.e., number of explicitly Opt Data Len
listed intermediate nodes still to be visited before reaching
the final destination.
Type-specific fields: 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Opt Data Len fields. For the
format of the Source Route option defined here, this field
MUST be set to the value (n * 4) + 2, where n is the number of
addresses present in the Address[i] fields.
First Hop External (F) First Hop External (F)
Set to indicate that the first node indicated by the Routing Set to indicate that the first node indicated by the Source
header is actually in a network external to the DSR network; Route option is actually in a network external to the DSR
the exact sequence of hops leading from it outside the DSR network; the exact sequence of hops leading from it outside the
network are not represented in the Routing header. Nodes DSR network are not represented in the Source Route option.
caching this hop in their Route Cache MUST flag the cached Nodes caching this hop in their Route Cache MUST flag the
hop with the External flag. Such hops MUST NOT be returned cached hop with the External flag. Such hops MUST NOT be
in a Route Reply generated from this Route Cache entry, and returned in a Route Reply generated from this Route Cache
selection of routes from the Route Cache to route a packet entry, and selection of routes from the Route Cache to route
being sent SHOULD prefer routes that contain no hops flagged as a packet being sent SHOULD prefer routes that contain no hops
External. flagged as External.
Last Hop External (L) Last Hop External (L)
Set to indicate that the last hop indicated by the Routing Set to indicate that the last hop indicated by the Source Route
header is actually in a network external to the DSR network; option is actually in a network external to the DSR network;
the exact sequence of hops leading to it outside the DSR the exact sequence of hops leading to it outside the DSR
network are not represented in the Routing header. Nodes network are not represented in the Source Route option. Nodes
caching this hop in their Route Cache MUST flag the cached caching this hop in their Route Cache MUST flag the cached
hop with the External flag. Such hops MUST NOT be returned hop with the External flag. Such hops MUST NOT be returned
in a Route Reply generated from this Route Cache entry, and in a Route Reply generated from this Route Cache entry, and
selection of routes from the Route Cache to route a packet selection of routes from the Route Cache to route a packet
being sent SHOULD prefer routes that contain no hops flagged as being sent SHOULD prefer routes that contain no hops flagged as
External. External.
Reserved Reserved
Sent as 0; ignored on reception. Sent as 0; ignored on reception.
Salvage Salvage
A 4-bit unsigned integer. Count of number of times that A 4-bit unsigned integer. Count of number of times that
this packet has been salvaged as a part of DSR routing this packet has been salvaged as a part of DSR routing
(Section 3.4.1). (Section 3.4.1).
Identification Segments Left (Segs Left)
Used to request that a DSR Acknowledgement option be returned Number of route segments remaining, i.e., number of explicitly
to this transmitting node for this hop. The special value of 0 listed intermediate nodes still to be visited before reaching
indicates that no DSR Acknowledgement is requested. Otherwise, the final destination.
the Identification field is set to a unique nonzero number
by this node transmitting the packet and is copied into the
Identification field of the DSR Acknowledgement option when
returned by the node receiving the packet over this hop.
Address[1..n] Address[1..n]
The sequence of addresses of the source route. In routing The sequence of addresses of the source route. In routing
and forwarding the packet, the source route is processed as and forwarding the packet, the source route is processed as
described in Sections 6.1.2 and 6.1.4. described in Sections 6.1.3 and 6.1.5.
When forwarding a packet along a DSR source route using a Source
Route option in the packet's DSR header, the Source Address field in
the packet's IP header is always set to the address of the packet's
ultimate destination. A node receiving a packet containing a DSR
header with a Source Route option MUST examine the indicated source
route to determine if it is the intended next hop for the packet and
determine how to forward the packet, as defined in Sections 6.1.4
and 6.1.5.
5.8. Pad1 Option
The Pad1 DSR option is encoded as follows:
+-+-+-+-+-+-+-+-+
| Option Type |
+-+-+-+-+-+-+-+-+
Option Type
0
A Pad1 option MAY be included in the Options field of a DSR header
in order to align subsequent DSR options, but such alignment is
not required and MUST NOT be expected by nodes receiving packets
containing a DSR header.
The total length of a DSR header, indicated by the Payload Length
field in the DSR header MUST be a multiple of 4 octets. When
building a DSR header in a packet, sufficient Pad1 or PadN options
MUST be included in the Options field of the DSR header to make the
total length a multiple of 4 octets.
If more than one consecutive octet of padding is being inserted in
the Options field of a DSR header, the PadN option, described next,
SHOULD be used, rather than multiple Pad1 options.
Note that the format of the Pad1 option is a special case; it does
not have an Opt Data Len or Option Data field.
5.9. PadN Option
The PadN DSR option is encoded as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - -
| Option Type | Opt Data Len | Option Data
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - -
Option Type
1
Opt Data Len
8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Opt Data Len fields.
Option Data
A number of zero valued octets equal to the Opt Data Len.
A PadN option MAY be included in the Options field of a DSR header
in order to align subsequent DSR options, but such alignment is
not required and MUST NOT be expected by nodes receiving packets
containing a DSR header.
The total length of a DSR header, indicated by the Payload Length
field in the DSR header MUST be a multiple of 4 octets. When
building a DSR header in a packet, sufficient Pad1 or PadN options
MUST be included in the Options field of the DSR header to make the
total length a multiple of 4 octets.
6. Detailed Operation 6. Detailed Operation
6.1. General Packet Processing 6.1. General Packet Processing
6.1.1. Originating a Packet 6.1.1. Originating a Packet
When originating any packet, a node using DSR routing MUST perform When originating any packet, a node using DSR routing MUST perform
the following sequence of steps: the following sequence of steps:
skipping to change at page 33, line 30 skipping to change at page 35, line 30
- If the packet contains a Route Request option, then replace the - If the packet contains a Route Request option, then replace the
IP Destination Address field with the IP "limited broadcast" IP Destination Address field with the IP "limited broadcast"
address (255.255.255.255) [3]. address (255.255.255.255) [3].
- Else, this node must have a route to the Destination Address - Else, this node must have a route to the Destination Address
of the packet (since otherwise a Route Request would have of the packet (since otherwise a Route Request would have
been added to the packet). If the length of this route is been added to the packet). If the length of this route is
greater than 1 hop, or if the node determines to request a DSR greater than 1 hop, or if the node determines to request a DSR
network-layer acknowledgement from the first hop of the route, network-layer acknowledgement from the first hop of the route,
then insert a DSR Routing header into the packet, as described then insert a DSR header as described in Section 6.1.2, and
in Section 6.1.2. The source route in the packet is initialized insert a Source Route option, as described in Section 6.1.3. The
from the route to the Destination Address found in the Route source route in the packet is initialized from the route to the
Cache. Destination Address found in the Route Cache.
- Transmit the packet to the address given in the IP
Destination Address, using Route Maintenance to retransmit the
packet if necessary, as described in Section 6.3.
6.1.2. Adding a DSR Routing Header to a Packet
The design of the DSR Routing header is based on the design of a - Transmit the packet to the address given in the next hop, using
Routing header in IPv6 [7]. A node originating a packet adds a Route Maintenance to retransmit the packet if necessary, as
DSR Routing header to the packet, if necessary, in order to carry described in Section 6.3.
the source route of hops from this originating node to the final
destination address of the packet. Specifically, the node adding the
DSR Routing header constructs the Routing header and modifies the IP
packet according to the following sequence of steps:
- A DSR Routing header, as described in Section 5.3, is created 6.1.2. Adding a DSR Header to a Packet
and added to the packet after the IP header and any Hop-by-Hop
Options header that may already be in the packet, but before any
Destination Options header (e.g., containing a DSR Route Reply
option) that may be present.
- The number of Address fields to include in the DSR Routing A node originating a packet adds a DSR header to the packet, if
header (n) is the number of intermediate nodes in the source necessary, to carry information needed by the routing protocol. A
route for the packet (i.e., excluding address of the originating packet MUST NOT contain more than one DSR header. A DSR header is
node and the final destination address of the packet). The added to a packet by performing the following sequence of steps
Segments Left field in the DSR Routing header is initialized (these steps assume that the packet contains no other headers that
equal to n. MUST be located in the packet before the DSR header):
- The Source Address from the IP header is copied into Address[n] - Insert a DSR header after the IP header but before any other
in the DSR Routing header. header that may be present.
- The first hop of the source route for the packet is copied into - Set the Next Header field of the DSR header to the Protocol
the Source Address field in the IP header. number field of the packet's IP header.
- The remaining hops of the source route for the packet are copied - Set the Protocol field of the packet's IP header to the Protocol
into sequential Address[i] fields in the DSR routing header, number assigned for a DSR header (???).
for i = 1, 2, ..., n-1.
- The First Hop External (F) bit in the Routing header is copied 6.1.3. Adding a Source Route Option to a Packet
from the External bit flagging the first hop node in the source
route for the packet, as indicated in the Route Cache.
- The Last Hop External (L) bit in the Routing header is copied A node originating a packet adds a Source Route option to the packet,
from the External bit flagging the last hop node in the source if necessary, in order to carry the source route of hops from this
route for the packet, as indicated in the Route Cache. originating node to the final destination address of the packet.
Specifically, the node adding the Source Route option constructs
the Source Route option and modifies the IP packet according to the
following sequence of steps:
- All other fields in the type-specific data in the DSR Routing - A Source Route option, as described in Section 5.7, is created
header are initialized to 0. and appended to the DSR header in the packet (a DSR header is
added, as described in Section 6.1.2, if not already present).
- The Routing Type field in the DSR Routing header is initialized - The number of Address[i] fields to include in the DSR Source
to ???. Route option (n) is the number of intermediate nodes in the
source route for the packet (i.e., excluding address of the
originating node and the final destination address of the
packet). The Segments Left field in the DSR Source Route option
is initialized equal to n.
- The Hdr Ext Len field in the DSR Routing header is initialized - The Destination Address from the IP header is copied into
to 4. Address[n] in the DSR Source Route option.
- Next Header field in the DSR Routing header is set equal to the - The first hop of the source route for the packet is copied into
current value in the Protocol field in the IP header (or the the Destination Address field in the IP header.
Next Header field in the preceding extension header), and the
Protocol field (or preceding Next Header field) is set equal
to 43 to indicate a Routing header extension header [7].
6.1.3. Receiving a Packet - The remaining hops of the source route for the packet are copied
into sequential Address[i] fields in the Source Route option,
for i = 1, 2, ..., n-1.
When a node receives any packet, it MUST process the packet according - The First Hop External (F) bit in the Source Route option is
to the following sequence of steps: copied from the External bit flagging the first hop node in the
source route for the packet, as indicated in the Route Cache.
- If the Destination Address in the packet's IP header does not - The Last Hop External (L) bit in the Source Route option is
match any of this receiving node's own IP address(s), then the copied from the External bit flagging the last hop node in the
processing of this packet depends on whether the packet contains source route for the packet, as indicated in the Route Cache.
a DSR Routing header:
* If the packet contains a DSR Routing header, then discard the 6.1.4. Receiving a Packet
packet.
* Else, if the packet contains a Hop-by-Hop Options extension When a node receives any packet containing a DSR header, it MUST
header (if present, this MUST immediately follow the packet's process the packet according to the following sequence of steps:
IP header), then process the options contained in the
Hop-by-Hop Options extension header. Forward the packet
using normal IP forwarding proceedures and do not process the
packet further.
- Examine and process each of the extension headers (if any) in - If the Destination Address in the packet's IP header matches
the packet in the order in which they occur in the packet. By one of this receiving node's own IP address(es), remove the DSR
dispatching on the Protocol field in the packet's IP header, header and all the included DSR options in the header, and pass
and subsequently dispatching on the Next Header field of each the rest of the packet to the network layer.
encountered extension header, the appropriate protocol module is
executed by the receiving node for each extension header.
- If a Hop-by-Hop Options extension header or Destination Options - Examine and process each of the options (if any) in the DSR
extension headers is encountered in processing the packet, the header in the order in which they occur in the packet, skipping
receiving node MUST process any options given in this header in over any Pad1 or PadN options.
the order in which they occur in the Options field within the
option.
Any DSR routing information carried in a packet SHOULD be examined Any DSR routing information carried in a packet SHOULD be examined
and reflected in the node's Route Cache, even if the options in and reflected in the node's Route Cache, even if the options in
the packet are not otherwise processed as described above. In the packet are not otherwise processed as described above. In
particular, the following routing information SHOULD be handled in particular, the following routing information SHOULD be handled in
this way: this way:
- In a DSR Route Request option, the accumulated route record, - In a Route Request option, the accumulated route record,
represented by the IP Source Address of the packet and by the represented by the IP Source Address of the packet and by the
sequence of Address[i] entries in the Route Request option SHOULD sequence of Address[i] entries in the Route Request option SHOULD
be added to the node's Route Cache. be added to the node's Route Cache.
- In a DSR Route Reply option, the route record being returned, - In a Route Reply option, the route record being returned,
represented by the sequence of Address[i] entries in the Route represented by the sequence of Address[i] entries in the Route
Request option and by the Destination Address in the packet's IP Request option and by the Destination Address in the packet's IP
header SHOULD be added to the node's Route Cache. header SHOULD be added to the node's Route Cache.
- In a DSR Acknowledgement option, the single link from the - In an Acknowledgement option, the single link from the
ACK Source Address to the ACK Destination Address SHOULD be added ACK Source Address to the ACK Destination Address SHOULD be added
to the node's Route Cache. to the node's Route Cache.
- In a DSR Route Error option, the single link from the - In a Route Error option, the single link from the
Error Source Address to the Unreachable Node Address MUST be Error Source Address to the Unreachable Node Address MUST
removed from the node's Route Cache. be removed from the node's Route Cache.
- In a DSR Routing header, the indicated source route SHOULD be - In a Source Route option, the indicated source route SHOULD
added to the node's Route Cache, subject to the conditions be added to the node's Route Cache, subject to the conditions
identified in Section 3.3.1. The full sequence of hops in the identified in Section 3.3.1. The full sequence of hops in the
DSR Routing header is as follows: DSR Source Route option is as follows:
* The Source Address in the packet's IP header is the first hop * The Source Address in the packet's IP header is the first hop
(the sender of the packet). (the sender of the packet).
* Let n equal Hdr Ext Len. This is the number of addresses in
the Routing header. Let i equal n minus Segments Left.
* The sequence of hops * The sequence of hops
Address[1], Address[2], ..., Address[i] Address[1], Address[2], ..., Address[n]
follow immediately after the IP Source Address in the source follow immediately after the IP Source Address in the source
route. route, where n is the number of addresses in the packet, or
(Opt Data Len - 2) / 4.
* The Destination Address in the packet's IP header follows
immediately next in the source route.
* The sequence of hops
Address[i+1], Address[i+2], ..., Address[n]
follow next in the source route. The address Address[n] * The Destination Address in the packet's IP header is the
above is the final hop in the source route. final destination of the packet and is the last hop of the
source route.
In addition to the processing of received packets described above, a In addition to the processing of received packets described above, a
node SHOULD examine the packet to determine if the receipt of this node SHOULD examine the packet to determine if the receipt of this
packet indicates an opportunity for automatic route shortening, as packet indicates an opportunity for automatic route shortening, as
described in Section 3.4.2. If the received packet satisfies the described in Section 3.4.2. If the received packet satisfies the
tests described there, then this node SHOULD perform the following tests described there, then this node SHOULD perform the following
sequence of steps: sequence of steps:
- Return a gratuitous Route Reply to the IP Source Address of the - Return a gratuitous Route Reply to the IP Source Address of the
packet, as described in Section 3.4.2. packet, as described in Section 3.4.2.
- Discard the received packet, since the packet has been received - Discard the received packet, since the packet has been received
before its normal traversal of the packet's source route would before its normal traversal of the packet's source route would
have caused it to reach this receiving node. Another copy of have caused it to reach this receiving node. Another copy of
the packet will normally arrive at this node as indicated in the packet will normally arrive at this node as indicated in
the packet's source route; discarding this initial copy of the the packet's source route; discarding this initial copy of the
packet, which triggered the gratuitous Route Reply, will prevent packet, which triggered the gratuitous Route Reply, will prevent
the duplication of this packet that would otherwise occur. the duplication of this packet that would otherwise occur.
6.1.4. Processing a Routing Header in a Received Packet 6.1.5. Processing a Received Source Route Option
A Routing header in a packet is not examined or processed until the
packet reaches the node identified in the Destination Address field
in the packet's IP header. In that node, dispatching on the Protocol
field in the packet's IP header (or the Next Header field in the
preceding extension header) causes the Routing header module in that
node's IP implementation to be invoked. The node then examines the
Routing Type field in the Routing header to determine the specific
type of processing for that type of Routing header. The processing
for a Routing header here in general follows the procedures specified
for IPv6 Routing headers, and the processing specifically for a DSR
Routing header in general follows the general procedures specified
for a Type 0 Routing header in IPv6 [7].
If, while processing a received packet, a node encounters a Routing
header with an unrecognized Routing Type value, the required behavior
of the node depends on the value of the Segments Left field, as
follows:
- If Segments Left is 0, the node MUST ignore the Routing header
and proceed to process the next header in the packet, whose type
is identified by the Next Header field in the Routing header.
- If Segments Left is non-zero, the node MUST discard the packet If a received packet contains a DSR header with a DSR Source Route
and send an ICMP Parameter Problem, Code 0, message [24] to option, the Source Route option MUST be examined and processed (even
the packet's Source Address, pointing to the unrecognized though this node is not indicated in the Destination Address field of
Routing Type. the packet's IP header).
If, after processing a Routing header in a received packet, an If, after processing a Source Route option in a received packet, an
intermediate node determines that the packet is to be forwarded onto intermediate node determines that the packet is to be forwarded onto
a link whose link MTU is less than the size of the packet, the node a link whose link MTU is less than the size of the packet, the node
MUST discard the packet and send an ICMP Packet Too Big message to MUST discard the packet and send an ICMP Packet Too Big message to
the packet's Source Address [24]. the packet's Source Address [23].
A DSR Routing header is identified by a Routing Type value of ??? A Source Route option in a DSR header for IPv4 is processed according
in the Routing header. A DSR Routing header for IPv4 is processed to the following sequence of steps:
according to the following sequence of steps:
- If the value of the Segments Left field in the Routing header - If the value of the Segments Left field in the Source Route
equals 0, then proceed to process the next header in the packet, option equals 0, then remove the Source Route option from the DSR
whose type is identified by the Next Header field in the Routing header.
header. Do not process the Routing header further.
- Else, let n equal Hdr Ext Len. This is the number of addresses - Else, let n equal (Opt Data Len - 2) / 4. This is the number of
in the Routing header. addresses in the Source Route option.
- If the value of the Segments Left field is greater than n, then - If the value of the Segments Left field is greater than n, then
send an ICMP Parameter Problem, Code 0, message [24] to the IP send an ICMP Parameter Problem, Code 0, message [23] to the IP
Source Address, pointing to the Segments Left field, and discard Source Address, pointing to the Segments Left field, and discard
the packet. Do not process the Routing header further. the packet. Do not process the Source Route option further.
- Else, decrement the value of the Segments Left field by 1. Let i - Else, decrement the value of the Segments Left field by 1. Let i
equal n minus Segments Left. This is the index of the next equal n minus Segments Left. This is the index of the next
address to be visited in the Address vector. address to be visited in the Address vector.
- If Address[i] or the IP Destination Address is a multicast - If Address[i] or the IP Destination Address is a multicast
address, then discard the packet. Do not process the Routing address, then discard the packet. Do not process the Source
header further. Route option further.
- Else, swap the IP Destination Address and Address[i].
- Forward the packet to the IP address specified in the - Forward the packet to the IP address specified in the Address[i]
Destination Address field of the IP header, following normal IP field of the IP header, following normal IP forwarding
forwarding procedures, including checking and decrementing the procedures, including checking and decrementing the Time-to-Live
Time-to-Live (TTL) field in the packet's IP header [25, 3]. In (TTL) field in the packet's IP header [24, 3]. In this
this forwarding of the packet, the next hop node (identified by forwarding of the packet, the next hop node (identified by
the Destination Address) MUST be treated as a direct neighbor Address[i]) MUST be treated as a direct neighbor node; the
node; the transmission to that next node MUST be done in a single transmission to that next node MUST be done in a single IP
IP forwarding hop, without Route Discovery and without searching forwarding hop, without Route Discovery and without searching the
the Route Cache. Route Cache.
- In forwarding the packet, perform Route Maintenance for the next - In forwarding the packet, perform Route Maintenance for the next
hop of the packet, by verifying that the packet was received by hop of the packet, by verifying that the packet was received by
that next hop, as described in Section 6.3. that next hop, as described in Section 6.3.
Multicast addresses must not appear in a DSR Routing header or in Multicast addresses MUST NOT appear in a Source Route option or in
the IP Destination Address field of a packet carrying a DSR Routing the IP Destination Address field of a packet carrying a Source Route
header. option in a DSR header.
6.2. Route Discovery Processing 6.2. Route Discovery Processing
Route Discovery is the mechanism by which a node S wishing to send a Route Discovery is the mechanism by which a node S wishing to send a
packet to a destination node D obtains a source route to D. Route packet to a destination node D obtains a source route to D. Route
Discovery is used only when S attempts to send a packet to D and Discovery is used only when S attempts to send a packet to D and
does not already know a route to D. The node initiating a Route does not already know a route to D. The node initiating a Route
Discovery is known as the "initiator" of the Route Discovery, and the Discovery is known as the "initiator" of the Route Discovery, and the
destination node for which the Route Discovery is initiated is known destination node for which the Route Discovery is initiated is known
as the "target" of the Route Discovery. as the "target" of the Route Discovery.
Route Discovery operates entirely on demand, with a node initiating Route Discovery operates entirely on demand, with a node initiating
Route Discovery based on its own origination of new packets for Route Discovery based on its own origination of new packets for
some destination address to which it does not currently know a some destination address to which it does not currently know a
route. Route Discovery does not depend on any periodic or background route. Route Discovery does not depend on any periodic or background
exchange of routing information or neighbor node detection at any exchange of routing information or neighbor node detection at any
layer in the network protocol stack at any node. layer in the network protocol stack at any node.
The Route Discovery procedure utilizes two types of messages, a DSR The Route Discovery procedure utilizes two types of messages, a Route
Route Request (Section 5.1.1) and a DSR Route Reply (Section 5.2.1), Request (Section 5.2) and a Route Reply (Section 5.3), to actively
to actively search the ad hoc network for a route to the desired search the ad hoc network for a route to the desired destination.
destination. These DSR messages MAY be carried in any type of IP These DSR messages MAY be carried in any type of IP packet, through
packet, through use of extension headers as described in Section 5: use of the DSR header as described in Section 5.
a Route Request is carried in a Destination options extension header,
and a Route Reply is carried in a Hop-by-Hop options extension
header.
A Route Discovery for a destination SHOULD NOT be initiated unless A Route Discovery for a destination address SHOULD NOT be initiated
the initiating node has a packet in the Send Buffer requiring unless the initiating node has a packet in its Send Buffer requiring
delivery to that destination. A Route Discovery for a given target delivery to that destination. A Route Discovery for a given target
node MUST NOT be initiated unless permitted by the rate-limiting node MUST NOT be initiated unless permitted by the rate-limiting
information contained in the Route Request Table. After each information contained in the Route Request Table. After each
Route Discovery attempt, the interval between successive Route Route Discovery attempt, the interval between successive Route
Discoveries for this target must be doubled, up to a maximum of Discoveries for this target MUST be doubled, up to a maximum of
MAX_REQUEST_PERIOD. MAX_REQUEST_PERIOD, until a valid Route Reply is received for this
target.
6.2.1. Originating a Route Request 6.2.1. Originating a Route Request
A node initiating a Route Discovery for some target creates and A node initiating a Route Discovery for some target creates and
initializes a DSR Route Request option in some IP packet. This initializes a Route Request option in a DSR header in some IP packet.
MAY be a separate IP packet, used only to carry this Route Request This MAY be a separate IP packet, used only to carry this Route
option, or the node MAY include the Route Request option in some Request option, or the node MAY include the Route Request option
existing packet it needs to send to the target node (e.g., the IP in some existing packet it needs to send to the target node (e.g.,
packet originated by this node, that caused the node to attempt Route the IP packet originated by this node, that caused the node to
Discovery for the destination address of the packet). attempt Route Discovery for the destination address of the packet).
The Route Request option MUST be included in a DSR header in the
The Route Request option MUST be included in a Destination Options packet. To initialize the Route Request option, the node performs
extension header in the packet. To initialize the Route Request the following sequence of steps:
option, the node performs the following sequence of steps:
- The Option Type in the option MUST be set to the value ???. - The Option Type in the option MUST be set to the value 2.
- The Option Length field in the option MUST be set to the value 6. - The Opt Data Len field in the option MUST be set to the value 6.
The total size of the Route Request option when initiated is The total size of the Route Request option when initiated
8 octets; the Option Length field excludes the size of the is 8 octets; the Opt Data Len field excludes the size of the
Option Type and Option Length fields themselves. Option Type and Opt Data Len fields themselves.
- The Identification field in the option MUST be set to a new - The Identification field in the option MUST be set to a new
value, different from that used for other Route Requests recently value, different from that used for other Route Requests recently
initiated by this node. For example, each node MAY maintain a initiated by this node. For example, each node MAY maintain a
single counter value for generating a new Identification value single counter value for generating a new Identification value
for each Route Request it initiates. for each Route Request it initiates.
- The Target Address field in the option MUST be set to the IP - The Target Address field in the option MUST be set to the IP
address that is the target of this Route Discovery. address that is the target of this Route Discovery.
skipping to change at page 42, line 5 skipping to change at page 41, line 53
next attempt at a Route Discovery for that target node. next attempt at a Route Discovery for that target node.
These values MUST be used to implement an exponential back-off These values MUST be used to implement an exponential back-off
algorithm to limit the rate at which this node initiates new algorithm to limit the rate at which this node initiates new
Route Discoveries for the same target address. Until a valid Route Discoveries for the same target address. Until a valid
Route Reply is received for this target node address, the timeout Route Reply is received for this target node address, the timeout
between consecutive Route Discovery initiations for this target between consecutive Route Discovery initiations for this target
node SHOULD increase by doubling the timeout value on each new node SHOULD increase by doubling the timeout value on each new
initiation. initiation.
The behavior of a node processing a packet containing both a Routing The behavior of a node processing a packet containing DSR header with
Header and a Route Request Destination option is unspecified. both a Source Route option and a Route Request option is unspecified.
Packets SHOULD NOT contain both a Routing Header and a Route Request
Destination option. [This is not exactly true: A Route Request
option appearing in the second Destination Options header that IPv6
allows after the Routing Header would probably do-what-you-mean,
though we have not triple-checked it yet. Namely, it would allow the
originator of a route discovery to unicast the request to some other
node, where it would be released and begin the flood fill. We call
this a Route Request Blossom since the unicast portion of the path
looks like a stem on the blossoming flood-fill of the request.]
Packets containing a Route Request Destination option SHOULD NOT be Packets SHOULD NOT contain both a Source Route option and a Route
retransmitted, SHOULD NOT request an explicit DSR Acknowledgment by Request option.
setting the R bit, SHOULD NOT expect a passive acknowledgment, and
SHOULD NOT be placed in the Retransmission Buffer. The repeated Packets containing a Route Request option SHOULD NOT be
transmission of packets containing a Route Request Destination option retransmitted, SHOULD NOT request a DSR acknowledgment by including
is controlled solely by the logic described in this section. an Acknowledgement Request option, SHOULD NOT expect a passive
acknowledgment, and SHOULD NOT be placed in the Retransmission
Buffer. The repeated transmission of packets containing a Route
Request option is controlled solely by the logic described in this
section.
6.2.2. Processing a Received Route Request Option 6.2.2. Processing a Received Route Request Option
When a node receives a packet containing a Route Request option, the When a node receives a packet containing a Route Request option, the
node MUST process the option according to the following sequence of node MUST process the option according to the following sequence of
steps: steps:
- If the Target Address field in the Route Request matches this - If the Target Address field in the Route Request matches this
node's own IP address, then the node SHOULD return a Route Reply node's own IP address, then the node SHOULD return a Route Reply
to the initiator of this Route Request (the Source Address in the to the initiator of this Route Request (the Source Address in the
IP header of the packet), as described in Section 6.2.4. The IP header of the packet), as described in Section 6.2.4. The
source route for this reply is the sequence of hops source route for this reply is the sequence of hops
initiator, Address[1], Address[2], ..., Address[n], target initiator, Address[1], Address[2], ..., Address[n], target
where initiator is the address of the initiator of this Route where initiator is the address of the initiator of this Route
Request, each Address[i] is an address from the Route Request, Request, each Address[i] is an address from the Route Request,
and target is the target of the Route Request (the Target Address and target is the target of the Route Request (the Target Address
field in the Route Request). field in the Route Request).
The node MUST then continue processing the packet normally, The node MUST then continue processing the rest of the packet
including any following options or extension headers in the normally. The node in this case MUST NOT retransmit the Route
packet. The node MUST NOT retransmit the Route Request to Request to propagate it to other nodes. Do not process the Route
propagate it to other nodes. Do not process the Route Request Request option further.
option further.
- Else, the node MUST examine the route recorded in the Route - Else, the node MUST examine the route recorded in the Route
Request option (the IP Source Address field and the sequence of Request option (the IP Source Address field and the sequence of
Address[i] fields) to determine if this node's own IP address Address[i] fields) to determine if this node's own IP address
already appears in this list of addresses. If so, the node MUST already appears in this list of addresses. If so, the node MUST
discard the entire packet carrying the Route Request option. discard the entire packet carrying the Route Request option.
- Else, the node MUST search its Route Request Table for an entry - Else, the node MUST search its Route Request Table for an entry
for the initiator of this Route Request (the IP Source Address for the initiator of this Route Request (the IP Source Address
field). If such an entry is found in the table, the node MUST field). If such an entry is found in the table, the node MUST
search the cache of Identification values of recently received search the cache of Identification values of recently received
Route Requests in that table entry, to determine if an entry Route Requests in that table entry, to determine if an entry
is present in the cache matching the Identification value is present in the cache matching the Identification value
and target node address in this Route Request. If such an and target node address in this Route Request. If such an
(Identification, target address) entry is found in this cache in (Identification, target address) entry is found in this cache in
this entry in the Route Request Table, then the node MUST discard this entry in the Route Request Table, then the node MUST discard
the entire packet carrying the Route Request option. the entire packet carrying the Route Request option.
- Else, this node SHOULD repropagate this Route Request. If it - Else, this node SHOULD further process the Route Request
does so, the node MUST do so according to the following sequence according to the following sequence of steps:
of steps:
* Add an entry for this Route Request in its cache of * Add an entry for this Route Request in its cache of
(Identification, target address) values of recently received (Identification, target address) values of recently received
Route Requests. Route Requests.
* Create a copy of this entire packet and perform the following * Create a copy of this entire packet and perform the following
steps on the copy of the packet. steps on the copy of the packet.
* Append this node's own IP address to the list of Address[i] * Append this node's own IP address to the list of Address[i]
values in the Route Request, and increase the value of the values in the Route Request, and increase the value of the
Option Length field in the Route Request by 4 (the size of an Opt Data Len field in the Route Request by 4 (the size of an
IP address). IP address).
* This node SHOULD search its own Route Cache for a route * This node SHOULD search its own Route Cache for a route
(from itself, as if it were the source of a packet) to the (from itself, as if it were the source of a packet) to the
target of this Route Request. If such a route is found in target of this Route Request. If such a route is found in
its Route Cache, then this node SHOULD follow the procedure its Route Cache, then this node SHOULD follow the procedure
outlined in Section 6.2.3 to return a "cached Route Reply" outlined in Section 6.2.3 to return a "cached Route Reply"
to the initiator of this Route Request, if permitted by the to the initiator of this Route Request, if permitted by the
restrictions specified there. restrictions specified there.
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- Send a Route Reply to the initiator of the Route Request, using - Send a Route Reply to the initiator of the Route Request, using
the procedure defined in Section 6.2.4. The initiator of the the procedure defined in Section 6.2.4. The initiator of the
Route Request is indicated in the Source Address field in the Route Request is indicated in the Source Address field in the
packet's IP header. packet's IP header.
6.2.4. Originating a Route Reply 6.2.4. Originating a Route Reply
A node originates a Route Reply in order to reply to a received and A node originates a Route Reply in order to reply to a received and
processed Route Request, according to the procedures described in processed Route Request, according to the procedures described in
Sections 6.2.2 and 6.2.3. The Route Reply is returned in a DSR Route Sections 6.2.2 and 6.2.3. The Route Reply is returned in a Route
Reply option (Section 5.2.1). The Route Reply option MAY be returned Reply option (Section 5.3). The Route Reply option MAY be returned
to the initiator of the Route Request in a separate IP packet, used to the initiator of the Route Request in a separate IP packet, used
only to carry this Route Reply option, or it MAY be included in any only to carry this Route Reply option, or it MAY be included in any
other IP packet being sent to this address. other IP packet being sent to this address.
The Route Reply option MUST be included in a Hop-by-Hop Options The Route Reply option MUST be included in a DSR header in the packet
extension header in the packet returned to the initiator. To returned to the initiator. To initialize the Route Reply option, the
initialize the Route Reply option, the node performs the following node performs the following sequence of steps:
sequence of steps:
- The Option Type in the option MUST be set to the value ???. - The Option Type in the option MUST be set to the value 3.
- The Option Length field in the option MUST be set to the value - The Opt Data Len field in the option MUST be set to the value
(n * 4) + 1, where n is the number of addresses in the source (n * 4) + 3, where n is the number of addresses in the source
route being returned (excluding the Route Discovery initiator route being returned (excluding the Route Discovery initiator
node's address). node's address).
- The Last Hop External (L) bit in the option MUST be initialized - The Last Hop External (L) bit in the option MUST be initialized
to 0. to 0.
- The Reserved field in the option MUST be initialized to 0. - The Reserved field in the option MUST be initialized to 0.
- The Route Request Identifier MUST be initialized to the
Identifier field of the Route Request that this reply is sent in
response to.
- The sequence of addresses of the source route are copied into - The sequence of addresses of the source route are copied into
the Address[i] fields of the option. Address[1] MUST be set the Address[i] fields of the option. Address[1] MUST be set
to the first hop of the route after the initiator of the Route to the first hop of the route after the initiator of the Route
Discovery, Address[n] MUST be set to the last hop of the source Discovery, Address[n] MUST be set to the last hop of the source
route (the address of the target node), and each other Address[i] route (the address of the target node), and each other Address[i]
MUST be set to the next address in sequence in the source route MUST be set to the next address in sequence in the source route
being returned. being returned.
The Destination Address field in the IP header of the packet carrying The Destination Address field in the IP header of the packet carrying
the Route Reply option MUST be set to the address of the initiator the Route Reply option MUST be set to the address of the initiator
of the Route Discovery (i.e., for a Route Reply being returned in of the Route Discovery (i.e., for a Route Reply being returned in
response to some Route Request, the IP Source Address of the Route response to some Route Request, the IP Source Address of the Route
Request). Request).
After creating and initializing the DSR Route Reply option and After creating and initializing the Route Reply option and the IP
the IP packet containing it, send the Route Reply, jittered by packet containing it, send the Route Reply. In sending the Route
T milliseconds, where T is a uniformly distributed random number Reply from this node (but not from nodes forwarding the Route Reply),
between 0 and BROADCAST_JITTER. this node SHOULD delay the rely by a small jitter period chosen
randomly between 0 and BROADCAST_JITTER milliseconds.
If the MAC layer above which DSR is operating requires
bidirectionality for unidirectional transmissions, the Route
Reply MUST be sent by reversing the sequence of hops that are stored
in it.
If sending a Route Reply to the originator of the Route Request If sending a Route Reply to the originator of the Route Request
requires performing a Route Discovery, the Route Reply hop-by-hop requires performing a Route Discovery, the Route Reply Option MUST
option MUST be piggybacked on the packet that contains the Route be piggybacked on the packet that contains the Route Request. This
Request. This piggybacking prevents a loop wherein the target of the piggybacking prevents a loop wherein the target of the new Route
new Route Request (which was itself the originator of the original Request (which was itself the originator of the original Route
Route Request) must do another Route Request in order to return its Request) must do another Route Request in order to return its Route
Route Reply. Reply.
If sending the Route Reply to the originator of the Route Request If sending the Route Reply to the originator of the Route Request
does not require performing Route Discovery, a node SHOULD send a does not require performing Route Discovery, a node SHOULD send a
unicast Route Reply in response to every received Route Request unicast Route Reply in response to every received Route Request
targeted at it. targeted at it.
6.2.5. Processing a Route Reply Option 6.2.5. Processing a Route Reply Option
Upon receiving a Route Reply, a node SHOULD extract the source route Upon receiving a Route Reply, a node SHOULD extract the source route
from the Route Reply and add this routing information to its Route from the Route Reply and add this routing information to its Route
skipping to change at page 47, line 19 skipping to change at page 47, line 19
such that it can no longer use its route to D because a link along such that it can no longer use its route to D because a link along
the route no longer works. When Route Maintenance indicates a source the route no longer works. When Route Maintenance indicates a source
route is broken, S can attempt to use any other route it happens to route is broken, S can attempt to use any other route it happens to
know to D, or can invoke Route Discovery again to find a new route know to D, or can invoke Route Discovery again to find a new route
for subsequent packets to D. Route Maintenance for this route is for subsequent packets to D. Route Maintenance for this route is
used only when S is actually sending packets to D. used only when S is actually sending packets to D.
When forwarding a packet, a node MUST attempt to receive an When forwarding a packet, a node MUST attempt to receive an
acknowledgement for the packet from the next hop. If no acknowledgement for the packet from the next hop. If no
acknowledgement is received, the node SHOULD return a Route Error to acknowledgement is received, the node SHOULD return a Route Error to
the IP Source Address of the packet, as described in Section 6.3.3 the IP Source Address of the packet, as described in Section 6.3.3.
A node's algorithm for deciding whether or not to return a Route
Error MUST NOT allow any node to attempt to send an unbounded number
of packets along a broken link without receiving a Route Error.
6.3.1. Using Network-Layer Acknowledgments 6.3.1. Using Network-Layer Acknowledgments
When a node retransmits a packet or has no other way to ensure When a node retransmits a packet or has no other way to ensure
successful delivery of a packet to the next hop, it SHOULD request successful delivery of a packet to the next hop, it MUST request a
a network-layer acknowledgement by placing a non-zero value in the network-layer acknowledgement by placing inserting an Acknowledgement
Identification field of the DSR Routing header. Such a value MUST Request the DSR header. The Identification value contained in that
be unique over all packets delivered to the same next hop which are header MUST be unique over all packets delivered to the same next hop
either unacknowledged or recently acknowledged. which are either unacknowledged or recently acknowledged.
A node receiving a DSR Routing header with a non-zero value in the A node receiving an Acknowledgement Request MUST send an
Identification field MUST send an acknowledgement to the previous hop acknowledgement to the previous hop by performing the following
by performing the following sequence of steps: sequence of steps:
- Create a packet and set the IP Source Address to the address - Create a packet and set the IP Source Address to the address
of this node, the IP Destination Address to the address of the of this node, the IP Destination Address to the address of the
previous hop, and the IP Protocol field to the protocol number previous hop, and the IP Protocol field to the protocol number
reserved for Hop-by-Hop Options extension headers. reserved for DSR headers.
- Set the Hop-by-Hop Options extension header's Next Header field - Set the DSR header's Next Header field to be the "No Next Header"
to be the "No Next Header" value. Set the Header Extension value.
Length to the size of a DSR Acknowledgement Option.
- Set the DSR Acknowledgement option's Option Type field to - Set the Acknowledgement option's Option Type field to 6, and the
the Option Type reserved for DSR Acknowledgements, and the Opt Data Len field to 10.
Option Length field to 10.
- Copy the Identification field from the Routing Header into - Copy the Identification field from the Acknowledgement Request
the Identification field in the DSR Acknowledgement Option. option into the Identification field in the Acknowledgement
Set the ACK Source Address field in the option to be the IP option. Set the ACK Source Address field in the option to be the
Source Address and the ACK Destination Address field to the IP IP Source Address and the ACK Destination Address field to the IP
Destination Address. Destination Address.
- Send the packet as described in Section 6.1.1. - Send the packet as described in Section 6.1.1.
6.3.2. Using Link Layer Acknowledgments 6.3.2. Using Link Layer Acknowledgments
If explicit failure notifications are provided by the link layer, If explicit failure notifications are provided by the link layer,
then all packets are assumed to be correctly received by the then all packets are assumed to be correctly received by the
next hop, and a Route Error is sent only when an explicit failure next hop, and a Route Error is sent only when an explicit failure
notification is made from the link layer. notification is made from the link layer.
Nodes receiving a packet without a Routing Header do not need to send Nodes receiving a packet without an Acknowledgement Request Option
an explicit Acknowledgment to the packet's originator, since the do not need to send an explicit Acknowledgment to the packet's
link layer will notify the originator if the packet was not received originator, since the link layer will notify the originator if the
properly. packet was not received properly.
6.3.3. Originating a Route Error 6.3.3. Originating a Route Error
When a node is unable to verify successful delivery of a packet to When a node is unable to verify successful delivery of a packet to
the next hop after a maximum number of retransmission attempts, the next hop after a maximum number of retransmission attempts,
a node SHOULD send a Route Error to the IP Source Address of the a node SHOULD send a Route Error to the IP Source Address of the
packet. When sending a Route Error for a packet containing either a packet. In addition, a node's algorithm for deciding whether or not
DSR Route Error option or a DSR Acknowledgement option, a node SHOULD to return a Route Error MUST NOT allow any node to attempt to send
add these options to it's Route Error, subject to some limit on an unbounded number of packets along a broken link without receiving
a Route Error. When sending a Route Error for a packet containing
either a Route Error option or an Acknowledgement option, a node
SHOULD add these options to its Route Error, subject to some limit on
lifetime. Specifically, we define the "salvage count" of an option lifetime. Specifically, we define the "salvage count" of an option
to be the sum of one plus the salvage count recorded in the DSR to be the sum of one plus the salvage count recorded in the Source
Routing header plus the sum of the salvage counts of any DSR Route Route option plus the sum of the salvage counts of any Route Errors
Errors preceding that option. preceding that option.
A node transmitting a Route Error MUST follow the following steps: A node transmitting a Route Error MUST follow the following steps:
- Create a packet and set the IP Source Address to the address of - Create a packet and set the IP Source Address to the address of
this node, the IP Destination Address to the address IP Source this node, the IP Destination Address to the address IP Source
Address of the packet experiencing the error. Address of the packet experiencing the error.
- Insert a Hop-by-Hop Options Header into the packet. - Insert a DSR header into the packet.
- Add a Route Error Option, setting the Error Type to - Add a Route Error Option, setting the Error Type to
NODE_UNREACHABLE, the Reserved bits to 0, the Salvage value to NODE_UNREACHABLE, the Reserved bits to 0, the Salvage value to
one plus the Salvage value from the DSR Routing header, and the one plus the Salvage value from the DSR Source Route option, and
Unreachable Node Address to the address of the next hop. Set the Unreachable Node Address to the address of the next hop. Set
the Error Source Address to the IP Source Address and the Error the Error Source Address to the IP Source Address and the Error
Destination to the IP Destination Address. Destination to the IP Destination Address.
- The node MAY append each DSR Route Error and DSR Acknowledgement, - The node MAY append each Route Error and Acknowledgement
in order, from the packet experiencing the error, though it MUST option, in order, from the packet experiencing the error,
exclude options with salvage counts greater than 15. though it MUST exclude options with salvage counts greater
than MAX_SALVAGE_TIMES.
- Send the packet as described in Section 6.1.1. - Send the packet as described in Section 6.1.1.
6.3.4. Processing a Route Error Option 6.3.4. Processing a Route Error Option
A node receiving a Route Error MUST process it as follows: A node receiving a Route Error MUST process it as follows:
- Delete all routes from the Route Cache that have a link from the - Delete all routes from the Route Cache that have a link from the
Route Error Source Address to the Unreachable Node Address. Route Error Source Address to the Unreachable Node Address.
- If the Hop-by-Hop option following the Route Error is a DSR - If the option following the Route Error is an Acknowledgement
Acknowledgement or DSR Route Error option sent by this node or Route Error option sent by this node (that is, with
(that is, with Acknowledgement or Error Source Address equal to Acknowledgement or Error Source Address equal to this node's
this node's address), copy the Hop-by-Hop options following the address), copy the DSR options following the current Route
current Route Error into a new packet with IP Source Address Error into a new packet with IP Source Address equal to this
equal to this node's own IP address and IP Destination Address node's own IP address and IP Destination Address equal to the
equal to the Acknowledgement or Error Destination Address. Acknowledgement or Error Destination Address. Transmit this
Transmit this packet as described in Section 6.1.1, with the packet as described in Section 6.1.1, with the salvage count in
salvage count in the DSR Routing header set to the Salvage value the Source Route option set to the Salvage value of the Route
of the Route Error. Error.
6.3.5. Salvaging a Packet 6.3.5. Salvaging a Packet
When a node is unable to verify successful delivery of a packet When a node is unable to verify successful delivery of a packet
to the next hop after a maximum number of retransmission attempts to the next hop after a maximum number of retransmission attempts
and has transmitted a Route Error to the sender, it MAY attempt to and has transmitted a Route Error to the sender, it MAY attempt to
salvage the packet by examining its route cache. If the node can salvage the packet by examining its route cache. If the node can
find a route to the packet's IP Destination Address in its own Route find a route to the packet's IP Destination Address in its own Route
Cache, then this node replaces the packet's Routing header with a new Cache, then this node replaces the packet's Source Route option
Routing Header in the same way as described in Section 6.1.2, except with a new Source Route option in the same way as described in
that Address[1] MUST be set to the address of this node and the Section 6.1.3, except that Address[1] MUST be set to the address of
Salvage field MUST be set to 1 plus the value of the Salvage field in this node and the Salvage field MUST be set to 1 plus the value of
the Routing Header that caused the error. the Salvage field in the Source Route option that caused the error.
7. Constants 7. Constants
BROADCAST_JITTER 10 milliseconds BROADCAST_JITTER 10 milliseconds
MAX_ROUTE_LEN 15 nodes MAX_ROUTE_LEN 15 nodes
MAX_SALVAGE_TIMES 15 salvages
Route Cache Route Cache
ROUTE_CACHE_TIMEOUT 300 seconds ROUTE_CACHE_TIMEOUT 300 seconds
Send Buffer Send Buffer
SEND_BUFFER_TIMEOUT 30 seconds SEND_BUFFER_TIMEOUT 30 seconds
Route Request Table Route Request Table
REQUEST_TABLE_SIZE 64 nodes REQUEST_TABLE_SIZE 64 nodes
REQUEST_TABLE_IDS 16 identifiers REQUEST_TABLE_IDS 16 identifiers
MAX_REQUEST_REXMT 16 retransmissions MAX_REQUEST_REXMT 16 retransmissions
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NONPROP_REQUEST_TIMEOUT 30 milliseconds NONPROP_REQUEST_TIMEOUT 30 milliseconds
Retransmission Buffer Retransmission Buffer
DSR_RXMT_BUFFER_SIZE 50 packets DSR_RXMT_BUFFER_SIZE 50 packets
Retransmission Timer Retransmission Timer
DSR_MAXRXTSHIFT 2 DSR_MAXRXTSHIFT 2
8. IANA Considerations 8. IANA Considerations
This document proposes the use in IPv4 of the Destination Options This document proposes the use of a DSR header, which requires an IP
extension header, the Hop-by-Hop Options extension header, and Protocol number.
Routing header, which were originally defined for IPv6 [7]. The
Next Header values indicating these three extension header types (60,
0, and 43, respectively) must therefore be reserved within the IPv4
Protocol number space. In addition, the "No Next Header" type value
of 69, defined for IPv6, must also be defined for use in IPv4. Other
protocols in IPv4 wishing to use these IPv6-style extension headers
can also make use of these Protocol number assignments.
For use within a Destination Options extension header, this document
defines one new type of destination option, which must be assigned an
Option Type value:
- DSR Route Request option, described in Section 5.1.1. The top
three bits of this Option Type value MUST be 011.
For use within a Hop-by-Hop Options extension header, this document
defines three new types of hop-by-hop options, each of which must be
assigned an Option Type value:
- DSR Route Reply option, described in Section 5.2.1. The top
three bits of this Option Type value MUST be 000.
- DSR Route Error option, described in Section 5.2.2. The top
three bits of this Option Type value MUST be 000.
- DSR Acknowledgment option, described in Section 5.2.3. The top
three bits of this Option Type value MUST be 000.
For use within a Routing header, this document defines one new type
of routing header, which must be assigned an Routing Type value:
- DSR Routing Header, defined in Section 5.3. In addition, this document proposes use of the value "No Next Header"
(originally defined for use in IPv6) within an IPv4 packet, to
indicate that no further header follows a DSR header.
9. Security Considerations 9. Security Considerations
This document does not specifically address security concerns. This This document does not specifically address security concerns. This
document does assume that all nodes participating in the DSR protocol document does assume that all nodes participating in the DSR protocol
do so in good faith and without malicious intent to corrupt the do so in good faith and without malicious intent to corrupt the
routing ability of the network. In mission-oriented environments routing ability of the network. In mission-oriented environments
where all the nodes participating in the DSR protocol share a where all the nodes participating in the DSR protocol share a
common goal that motivates their participation in the protocol, the common goal that motivates their participation in the protocol, the
communications between the nodes can be encrypted at the physical communications between the nodes can be encrypted at the physical
skipping to change at page 53, line 16 skipping to change at page 53, line 16
When designing DSR, we had to determine at what layer within When designing DSR, we had to determine at what layer within
the protocol hierarchy to implement ad hoc network routing. We the protocol hierarchy to implement ad hoc network routing. We
considered two different options: routing at the link layer (ISO considered two different options: routing at the link layer (ISO
layer 2) and routing at the network layer (ISO layer 3). Originally, layer 2) and routing at the network layer (ISO layer 3). Originally,
we opted to route at the link layer for several reasons: we opted to route at the link layer for several reasons:
- Pragmatically, running the DSR protocol at the link layer - Pragmatically, running the DSR protocol at the link layer
maximizes the number of mobile nodes that can participate in maximizes the number of mobile nodes that can participate in
ad hoc networks. For example, the protocol can route equally ad hoc networks. For example, the protocol can route equally
well between IPv4 [25], IPv6 [7], and IPX [28] nodes. well between IPv4 [24], IPv6 [7], and IPX [27] nodes.
- Historically [12, 13], DSR grew from our contemplation of - Historically [12, 13], DSR grew from our contemplation of
a multi-hop propagating version of the Internet's Address a multi-hop propagating version of the Internet's Address
Resolution Protocol (ARP) [23], as well as from the routing Resolution Protocol (ARP) [22], as well as from the routing
mechanism used in IEEE 802 source routing bridges [22]. These mechanism used in IEEE 802 source routing bridges [21]. These
are layer 2 protocols. are layer 2 protocols.
- Technically, we designed DSR to be simple enough that it could - Technically, we designed DSR to be simple enough that it could
be implemented directly in the firmware inside wireless network be implemented directly in the firmware inside wireless network
interface cards [12, 13], well below the layer 3 software within interface cards [12, 13], well below the layer 3 software within
a mobile node. We see great potential in this for DSR running a mobile node. We see great potential in this for DSR running
inside a cloud of mobile nodes around a fixed base station, inside a cloud of mobile nodes around a fixed base station,
where DSR would act to transparently extend the coverage range where DSR would act to transparently extend the coverage range
to these nodes. Mobile nodes that would otherwise be unable to these nodes. Mobile nodes that would otherwise be unable
to communicate with the base station due to factors such as to communicate with the base station due to factors such as
distance, fading, or local interference sources could then reach distance, fading, or local interference sources could then reach
the base station through their peers. the base station through their peers.
Ultimately, however, we decided to specify and to implement [20] Ultimately, however, we decided to specify and to implement [19]
DSR as a layer 3 protocol, since this is the only layer at which we DSR as a layer 3 protocol, since this is the only layer at which we
could realistically support nodes with multiple network interfaces of could realistically support nodes with multiple network interfaces of
different types forming an ad hoc network. different types forming an ad hoc network.
Appendix B. Implementation and Evaluation Status Appendix B. Implementation and Evaluation Status
The DSR protocol has been implemented under the FreeBSD 2.2.7 The DSR protocol has been implemented under the FreeBSD 2.2.7
operating system running on Intel x86 platforms. FreeBSD is based operating system running on Intel x86 platforms. FreeBSD is based
on a variety of free software, including 4.4 BSD Lite from the on a variety of free software, including 4.4 BSD Lite from the
University of California, Berkeley. For the environments in which University of California, Berkeley. For the environments in which
skipping to change at page 54, line 22 skipping to change at page 54, line 22
protocol specified in this draft. protocol specified in this draft.
During the 7 months from August 1998 to February 1999, we designed During the 7 months from August 1998 to February 1999, we designed
and implemented a full-scale physical testbed to enable the and implemented a full-scale physical testbed to enable the
evaluation of ad hoc network performance in the field, in a actively evaluation of ad hoc network performance in the field, in a actively
mobile ad hoc network under realistic communication workloads. mobile ad hoc network under realistic communication workloads.
The last week of February and the first week of March included The last week of February and the first week of March included
demonstrations of this testbed to a number of our sponsors and demonstrations of this testbed to a number of our sponsors and
partners, including Lucent Technologies, Bell Atlantic, and DARPA. partners, including Lucent Technologies, Bell Atlantic, and DARPA.
A complete description of the testbed is available as a Technical A complete description of the testbed is available as a Technical
Report [20]. Report [19].
The software was ported to FreeBSD 3.3, and a preliminary version The software was ported to FreeBSD 3.3, and a preliminary version
of Quality of Service (QoS) support was added. A demonstration of of Quality of Service (QoS) support was added. A demonstration of
this modified version of DSR was presented in July 2000. Those QoS this modified version of DSR was presented in July 2000. Those QoS
features are not included in this draft, and will be added later in a features are not included in this draft, and will be added later in a
seprate draft on top of the base protocol specified here. separate draft on top of the base protocol specified here.
The DSR protocol has been extensively studied using simulation; we The DSR protocol has been extensively studied using simulation; we
have implemented DSR in the ns-2 simulator [5, 19] and conducted have implemented DSR in the ns-2 simulator [5, 18] and conducted
evaluations of different caching strategies documented in this evaluations of different caching strategies documented in this
draft [9]. draft [9].
Several independant groups have also used DSR as a platform for their Several independent groups have also used DSR as a platform for their
own research, or and as a basis of comparison between ad hoc network own research, or and as a basis of comparison between ad hoc network
routing protocols. routing protocols.
Acknowledgements Acknowledgements
The protocol described in this draft has been designed and developed The protocol described in this draft has been designed and developed
within the Monarch Project, a research project at Rice University and within the Monarch Project, a research project at Rice University and
Carnegie Mellon University which is developing adaptive networking Carnegie Mellon University which is developing adaptive networking
protocols and protocol interfaces to allow truly seamless wireless protocols and protocol interfaces to allow truly seamless wireless
and mobile node networking [14, 6]. and mobile node networking [14, 6].
skipping to change at page 57, line 26 skipping to change at page 57, line 26
[16] Phil Karn. MACA---A new channel access method for packet radio. [16] Phil Karn. MACA---A new channel access method for packet radio.
In ARRL/CRRL Amateur Radio 9th Computer Networking Conference, In ARRL/CRRL Amateur Radio 9th Computer Networking Conference,
pages 134--140, September 1990. pages 134--140, September 1990.
[17] Gregory S. Lauer. Packet-radio routing. In Routing in [17] Gregory S. Lauer. Packet-radio routing. In Routing in
Communications Networks, edited by Martha E. Steenstrup, Communications Networks, edited by Martha E. Steenstrup,
chapter 11, pages 351--396. Prentice-Hall, Englewood Cliffs, chapter 11, pages 351--396. Prentice-Hall, Englewood Cliffs,
New Jersey, 1995. New Jersey, 1995.
[18] S.B. Lee, A. Gahng-Seop, X. Zhang, and A.T. Campbell. INSIGNIA: [18] David A. Maltz, Josh Broch, Jorjeta Jetcheva, and David B.
An IP-Based Quality of Service Framework for Mobile Ad Hoc
Networks. Journal of Parallel and Distributed Computing,
60(4):374--406, April 2000.
[19] David A. Maltz, Josh Broch, Jorjeta Jetcheva, and David B.
Johnson. The effects of on-demand behavior in routing protocols Johnson. The effects of on-demand behavior in routing protocols
for multi-hop wireless ad hoc networks. IEEE Journal on for multi-hop wireless ad hoc networks. IEEE Journal on
Selected Areas of Communications, 17(8):1439--1453, August 1999. Selected Areas of Communications, 17(8):1439--1453, August 1999.
[20] David A. Maltz, Josh Broch, and David B. Johnson. Experiences [19] David A. Maltz, Josh Broch, and David B. Johnson. Experiences
designing and building a multi-hop wireless ad hoc network designing and building a multi-hop wireless ad hoc network
testbed. Technical Report CMU-CS-99-116, School of Computer testbed. Technical Report CMU-CS-99-116, School of Computer
Science, Carnegie Mellon University, Pittsburgh, Pennsylvania, Science, Carnegie Mellon University, Pittsburgh, Pennsylvania,
March 1999. March 1999.
[21] David A. Maltz, Josh Broch, and David B. Johnson. Quantitative [20] David A. Maltz, Josh Broch, and David B. Johnson. Lessons from
lessons from a full-scale multi-hop wireless ad hoc network a full-scale multihop wireless ad hoc network testbed. IEEE
testbed. In Proceedings of the IEEE Wireless Communications and Personal Communications, 8(1):8--15, February 2001.
Networking Conference, September 2000.
[22] Radia Perlman. Interconnections: Bridges and Routers. [21] Radia Perlman. Interconnections: Bridges and Routers.
Addison-Wesley, Reading, Massachusetts, 1992. Addison-Wesley, Reading, Massachusetts, 1992.
[23] David C. Plummer. An Ethernet address resolution protocol: [22] David C. Plummer. An Ethernet address resolution protocol:
Or converting network protocol addresses to 48.bit Ethernet Or converting network protocol addresses to 48.bit Ethernet
addresses for transmission on Ethernet hardware. RFC 826, addresses for transmission on Ethernet hardware. RFC 826,
November 1982. November 1982.
[24] J. B. Postel, editor. Internet Control Message Protocol. [23] J. B. Postel, editor. Internet Control Message Protocol.
RFC 792, September 1981. RFC 792, September 1981.
[25] J. B. Postel, editor. Internet Protocol. RFC 791, September [24] J. B. Postel, editor. Internet Protocol. RFC 791, September
1981. 1981.
[26] J. B. Postel, editor. Transmission Control Protocol. RFC 793, [25] J. B. Postel, editor. Transmission Control Protocol. RFC 793,
September 1981. September 1981.
[27] Joyce K. Reynolds and Jon Postel. Assigned numbers. RFC 1700, [26] Joyce K. Reynolds and Jon Postel. Assigned numbers. RFC 1700,
October 1994. See also http://www.iana.org/numbers.html. October 1994. See also http://www.iana.org/numbers.html.
[28] Paul Turner. NetWare communications processes. NetWare [27] Paul Turner. NetWare communications processes. NetWare
Application Notes, Novell Research, pages 25--91, September Application Notes, Novell Research, pages 25--91, September
1990. 1990.
Chair's Address Chair's Address
The MANET Working Group can be contacted via its current chairs: The MANET Working Group can be contacted via its current chairs:
M. Scott Corson Phone: +1 301 405-6630 M. Scott Corson Phone: +1 301 405-6630
Institute for Systems Research Email: corson@isr.umd.edu Institute for Systems Research Email: corson@isr.umd.edu
University of Maryland University of Maryland
skipping to change at page 60, line 18 skipping to change at page 60, line 18
David B. Johnson Phone: +1 713 348-3063 David B. Johnson Phone: +1 713 348-3063
Rice University Fax: +1 713 348-5930 Rice University Fax: +1 713 348-5930
Computer Science Department, MS 132 Email: dbj@cs.rice.edu Computer Science Department, MS 132 Email: dbj@cs.rice.edu
6100 Main Street 6100 Main Street
Houston, TX 77005-1892 Houston, TX 77005-1892
USA USA
David A. Maltz Phone: +1 650 688-3128 David A. Maltz Phone: +1 650 688-3128
AON Networks Fax: +1 650 688-3119 AON Networks Fax: +1 650 688-3119
3045 Park Blvd. Email: dmaltz@cs.cmu.com 3045 Park Blvd. Email: dmaltz@cs.cmu.edu
Palo Alto, CA 94306 Palo Alto, CA 94306
USA USA
Yih-Chun Hu Phone: +1 412 268-3075 Yih-Chun Hu Phone: +1 412 268-3075
Carnegie Mellon University Fax: +1 412 268-5576 Rice University Fax: +1 412 268-5576
Computer Science Department Email: yihchun@cs.cmu.edu Computer Science Department, MS 132 Email: yihchun@cs.cmu.edu
5000 Forbes Avenue 6100 Main Street
Pittsburgh, PA 15213-3891 Houston, TX 77005-1892
USA USA
Jorjeta G. Jetcheva Phone: +1 412 268-3053 Jorjeta G. Jetcheva Phone: +1 412 268-3053
Carnegie Mellon University Fax: +1 412 268-5576 Carnegie Mellon University Fax: +1 412 268-5576
Computer Science Department Email: jorjeta@cs.cmu.edu Computer Science Department Email: jorjeta@cs.cmu.edu
5000 Forbes Avenue 5000 Forbes Avenue
Pittsburgh, PA 15213-3891 Pittsburgh, PA 15213-3891
USA USA
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