draft-ietf-roll-trickle-mcast-01.txt   draft-ietf-roll-trickle-mcast-02.txt 
ROLL J. Hui ROLL J. Hui
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track R. Kelsey Intended status: Standards Track R. Kelsey
Expires: January 14, 2013 Silicon Labs Expires: April 22, 2013 Silicon Labs
July 13, 2012 October 19, 2012
Multicast Forwarding Using Trickle Multicast Protocol for Low power and Lossy Networks (MPL)
draft-ietf-roll-trickle-mcast-01 draft-ietf-roll-trickle-mcast-02
Abstract Abstract
Low power and Lossy Networks (LLNs) are typically composed of This document specifies the Multicast Protocol for Low power and
resource constrained nodes communicating over links that have dynamic Lossy Networks (MPL) that provides IPv6 multicast forwarding in
characteristics. Memory constraints coupled with temporal variations constrained networks. MPL avoids the need to construct or maintain
in link connectivity makes the use of topology maintenance to support any multicast forwarding topology, disseminating messages to all MPL
IPv6 multicast challenging. This document describes the use of forwarders in an MPL domain. MPL uses the Trickle algorithm to drive
Trickle to efficiently forward multicast messages without the need packet transmissions for both control and data-plane packets.
for topology maintenance. Specific Trickle parameter configurations allow MPL to trade between
dissemination latency and transmission efficiency.
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Trickle Multicast Parameters . . . . . . . . . . . . . . . . . 7 4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 7
5. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 9 4.1. MPL Option . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Trickle Multicast Option . . . . . . . . . . . . . . . . . 9 4.2. ICMPv6 MPL Message . . . . . . . . . . . . . . . . . . . . 8
5.2. Trickle ICMPv6 Message . . . . . . . . . . . . . . . . . . 10 4.2.1. MPL Window . . . . . . . . . . . . . . . . . . . . . . 9
5.2.1. Sequence List . . . . . . . . . . . . . . . . . . . . 11 5. MPL Forwarder Behavior . . . . . . . . . . . . . . . . . . . . 11
6. Trickle Multicast Forwarder Behavior . . . . . . . . . . . . . 12 5.1. Multicast Packet Dissemination . . . . . . . . . . . . . . 11
6.1. Managing Sliding Windows . . . . . . . . . . . . . . . . . 12 5.1.1. Trickle Parameters and Variables . . . . . . . . . . . 12
6.2. Trickle Timers . . . . . . . . . . . . . . . . . . . . . . 12 5.1.2. Proactive Propagation . . . . . . . . . . . . . . . . 12
6.3. Trickle Multicast Option Processing . . . . . . . . . . . 13 5.1.3. Reactive Propagation . . . . . . . . . . . . . . . . . 13
6.4. Trickle ICMP Processing . . . . . . . . . . . . . . . . . 13 5.2. Sliding Windows . . . . . . . . . . . . . . . . . . . . . 13
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 5.3. Transmission of MPL Multicast Packets . . . . . . . . . . 15
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 5.4. Reception of MPL Multicast Packets . . . . . . . . . . . . 16
9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 5.5. Transmission of ICMPv6 MPL Messages . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.6. Reception of ICMPv6 MPL Messages . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . . 18 6. MPL Parameters . . . . . . . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . . 18 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
9. Security Considerations . . . . . . . . . . . . . . . . . . . 22
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
10.1. Normative References . . . . . . . . . . . . . . . . . . . 23
10.2. Informative References . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
The resource constraints of Low power and Lossy Networks (LLNs) may Low power and Lossy Networks typically operate with strict resource
preclude the use of existing IPv6 multicast forwarding mechanisms. constraints in communication, computation, memory, and energy. Such
Such networks are typically constrained in resources (limited channel resource constraints may preclude the use of existing IPv6 multicast
capacity, processing power, energy capacity, memory). In particular topology and forwarding mechanisms. Traditional IP multicast
memory constraints may limit nodes to maintaining state for only a forwarding typically relies on topology maintenance mechanisms to
small subset of neighbors. Limited channel and energy capacity forward multicast messages to all subscribers of a multicast group.
require protocols to remain efficient and robust even in dense However, maintaining such topologies in LLNs is costly and may not be
topologies. feasible given the available resources.
Traditional IP multicast forwarding typically relies on topology Memory constraints may limit devices to maintaining links/routes to
maintenance mechanisms to efficiently forward multicast messages to one or a few neighbors. For this reason, the Routing Protocol for
the intended destinations. In some cases, topology maintenance LLNs (RPL) specifies both storing and non-storing modes [RFC6550].
involves maintaining multicast trees to reach all subscribers of a The latter allows RPL routers to maintain only one or a few default
multicast group. Maintaining such topologies is difficult especially routes towards a LLN Border Router (LBR) and use source routing to
when memory constraints are such that nodes can only maintain a forward packets away from the LBR. For the same reasons, a LLN
default route. Dynamic properties of wireless networks can make device may not be able to maintain a multicast forwarding topology
control traffic prohibitively expensive. In wireless environments, when operating with limited memory.
topology maintenance may involve selecting a connected dominating set
used to forward multicast messages to all nodes in an administrative
domain. However, existing mechanisms often require two-hop topology
information, which is more state than a LLN node may be able to
handle.
This document describes the use of Trickle for IPv6 multicast Furthermore, the dynamic properties of wireless networks can make the
forwarding in LLNs. Trickle provides a mechanism for controlled, cost of maintaining a multicast forwarding topology prohibitively
density-aware flooding without the need to maintain a forwarding expensive. In wireless environments, topology maintenance may
topology [RFC6206]. involve selecting a connected dominating set used to forward
multicast messages to all nodes in an administrative domain.
However, existing mechanisms often require two-hop topology
information and the cost of maintaining such information grows
polynomially with network density.
1.1. Requirements Language This document specifies the Multicast Protocol for Low power and
Lossy Networks (MPL), which provides IPv6 multicast forwarding in
constrained networks. MPL avoids the need to construct or maintain
any multicast forwarding topology, disseminating multicast messages
to all MPL forwarders in an MPL domain. By using the Trickle
algorithm [RFC6206], MPL requires only small, constant state for each
MPL device that initiates disseminations. The Trickle algorithm also
allows MPL to be density-aware, allowing the communication rate to
scale logarithmically with density.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Terminology The following terms are used throughout this document:
Trickle Multicast Message A IPv6 multicast datagram that includes a
Trickle Multicast option in the IPv6 Hop-by-Hop
Options header.
Trickle Multicast Forwarder A IPv6 router that can process a Trickle
Multicast option and follows the forwarding rules
specified in this document.
Trickle Multicast Domain An administrative domain that defines the
scope of Trickle dissemination. All routers
within a Trickle Multicast Domain participate in
the same dissemination process.
Seed The router that starts the dissemination process
for a Trickle multicast message. The Seed may be
different than the node identified by the IPv6
Source address of the multicast message.
3. Overview
Trickle multicast forwarding implements a controlled, density-aware
flood to disseminate a IPv6 multicast message to all nodes within a
Trickle Multicast Domain. The basic process is similar to
traditional flooding - nodes forward newly received multicast
messages using link-layer broadcasts. Nodes maintain state of
recently received multicast messages to detect duplicates and ensure
that each node receives at most one copy of each multicast message.
Each Trickle multicast message carries a Trickle Multicast option
that includes a SeedID and Sequence value. The SeedID uniquely
identifies the Seed that initiated the message's dissemination
process within the Trickle Multicast Domain. Note that the Seed does
not have to be the same node as the message's source. It is possible
to tunnel a multicast message to a Seed node and start the
dissemination process from a different node within the Trickle
Multicast Domain.
The Sequence value establishes a total ordering of multicast messages
disseminated by SeedID. Nodes maintain a sliding window of recently
received multicast messages for each SeedID. The sliding window
establishes what messages can be received and ensure at most one copy
of each multicast message is received. Messages with sequence values
lower than the lower bound of the window MUST be ignored. Messages
with sequence values stored within the sliding window MUST be
ignored. All other messages MUST be received, advancing the sliding
window if necessary. Larger sequence values always take precedence.
The sliding window can be of variable size, trading memory
requirements for reliability of disseminating multiple messages
simultaneously.
Trickle's density-aware properties come from its suppression
mechanism. When suppression is enabled, nodes periodically advertise
a summary of recently received multicast messages. These
advertisements allow nodes to determine if they have any additional
multicasts to offer to neighboring nodes. A multicast message is
only retransmitted upon receiving positive indication that a neighbor
has not yet received that multicast message.
Nodes suppress advertisement transmissions and multicast
retransmissions after recently receiving "consistent" advertisements.
A node determines that a neighbor's advertisement is "consistent"
when neither node has new multicast messages to offer to the other.
The suppression reduces the number of redundant transmissions and is
what allows Trickle to maintain low channel utilization in dense
environments. However, suppression trades low control overhead for
longer propagation times. When using suppression, Trickle's
propagation times often have a long-tail distribution.
Trickle provides an adaptive timer, called the Trickle timer. When MPL forwarder An IPv6 router that subscribes to the MPL
receiving an "inconsistent" advertisement, nodes reset the Trickle multicast group and participates in disseminating
timer period to a small period so that dissemination happens quickly. MPL multicast packets.
The Trickle timer period doubles when the period expires and no
"inconsistent" advertisements have been received, reducing control
overhead when the network is in a consistent state.
This document does allow configurations that disable the suppression MPL multicast scope The multicast scope that MPL uses when forwarding
mechanism, reducing Trickle Multicast Forwarding to simple flooding. MPL multicast packets. In other words, the
This can be done by setting the suppression threshold for received multicast scope of the IPv6 Destination Address
"consistent" advertisements to infinity. In this mode, Trickle of an MPL multicast packet.
advertisements are not sent since consistency checks are not
performed. Instead, nodes simply retransmit multicast messages they
are trying to forward.
4. Trickle Multicast Parameters MPL domain A connected set of MPL forwarders that define the
extent of the MPL dissemination process. As a
form of flood, all MPL forwarders in an MPL
domain will receive MPL multicast packets. The
MPL domain MUST be composed of at least one MPL
multicast scope and MAY be composed of multiple
MPL multicast scopes.
All Trickle multicast forwarders within a Trickle multicast domain MPL seed A MPL forwarder that begins the dissemination
MUST be configured with two sets of configurations (one for each process for an MPL multicast packet. The MPL
value of the M flag). Each configuration has five parameters: seed may be different than the source of the
original multicast packet.
Imin The minimum Trickle timer interval as defined in MPL seed identifier An identifier that uniquely identifies an MPL
[RFC6206]. forwarder within its MPL domain.
Imax The maximum Trickle timer interval as defined in original multicast packet An IPv6 multicast packet that is
[RFC6206]. disseminated using MPL.
k The redundancy constant as defined in [RFC6206]. MPL multicast packet An IPv6 multicast packet that contains an MPL
Hop-by-Hop Option. When either source or
destinations are beyond the MPL multicast scope,
the MPL multicast packet is an IPv6-in-IPv6
packet that contains an MPL Hop-by-Hop Option in
the outer IPv6 header and encapsulates an
original multicast packet. When both source and
destinations are within the MPL multicast scope,
the MPL Hop-by-Hop Option may be included
directly within the original multicast packet.
Tactive The duration that a multicast forwarder can 3. Overview
attempt to forward a multicast message.
Specified in units of Imax.
Tdwell The duration that a multicast forwarder must MPL delivers IPv6 multicast packets by disseminating them to all MPL
maintain sliding window state for SeedID after forwarders within an MPL domain. MPL dissemination is a form of
receiving the last multicast message from SeedID. flood. An MPL forwarder may broadcast/multicast an MPL multicast
Specified in units of Imax. packet out of the same physical interface on which it was received.
Using link-layer broadcast/multicast allows MPL to forward multicast
packets without explicitly identifying next-hop destinations. An MPL
forwarder may also broadcast/multicast MPL multicast packets out
other interfaces to disseminate the message across different links.
MPL does not build or maintain a multicast forwarding topology to
forward multicast packets.
Tactive specifies the time duration that a node may retransmit a Any MPL forwarder may initiate the dissemination process by serving
multicast message in attempt to forward it to neighboring nodes. as an MPL seed for an original multicast packet. The MPL seed may or
Larger values of Tactive increases the number of retransmissions and may not be the same device as the source of the original multicast
overall dissemination reliability. packet. When the original multicast packet's source is outside the
LLN, the MPL seed may be the ingress router. Even if an original
multicast packet source is within the LLN, the source may first
forward the multicast packet to the MPL seed using IPv6-in-IPv6
tunneling. Because MPL state requirements grows with the number of
active MPL seeds, limiting the number of MPL seeds reduces the amount
of state that MPL forwarders must maintain.
Tdwell specifies the time duration for maintaining sliding window Because MPL typically broadcasts/multicasts MPL packets out of the
state to ensure that a multicast message from SeedID is received at same interface on which they were received, MPL forwarders are likely
most once. Larger values of Tdwell decreases the likelihood that a to receive an MPL multicast packet more than once. The MPL seed tags
node will receive a multicast message more than once. each original multicast packet with an MPL seed identifier and a
sequence number. The sequence number provides a total ordering of
MPL multicast packets disseminated by the MPL seed.
The specific values are left out of scope of this document as they MPL defines a new IPv6 Hop-by-Hop Option, the MPL Option, to include
are dependent on link-specific properties. How those parameters are MPL-specific information along with the original multicast packet.
configured are also left out of scope. Each IPv6 multicast packet that MPL disseminates includes the MPL
Option. Because the original multicast packet's source and the MPL
seed may not be the same device, the MPL Option may be added to the
original multicast packet en-route. To allow Path MTU discovery to
work properly, MPL encapsulates the original multicast packet in
another IPv6 header that includes the MPL Option.
The Trickle multicast parameters allow both aggressive and Upon receiving a new MPL multicast packet for forwarding, the MPL
conservative multicast forwarding strategies. For example, an forwarder may proactively transmit the MPL multicast packet packet a
aggressive strategy may specify each multicast forwarder to limited number of times and then falls back into an optional reactive
retransmit any newly received message 3 times on a short fixed period mode. In maintenance mode, an MPL forwarder buffers recently
and maintain state for 12 retransmission periods to avoid receiving received MPL multicast packets and advertises a summary of recently
duplicate messages. This aggressive policy can be specified using a received MPL multicast packets from time to time, allowing
Trickle parameter set of Imin = Imax = 100ms, k = infinity, Tactive = neighboring MPL forwarders to determine if they have any new
3, and Tdwell = 12. Setting k to infinity disables the Trickle multicast packets to offer or receive.
suppression mechanism.
A conservative multicast forwarding strategy utilizes Trickle MPL forwarders schedule their packet (control and data) transmissions
suppression and a larger Imax value to minimize redundant using the Trickle algorithm [RFC6206]. Trickle's adaptive
transmissions. One such conservative policy is a Trickle parameter transmission interval allows MPL to quickly disseminate messages when
set of Imin = 100ms, Imax = 30min, k = 1, Tactive = 3, and Tdwell = there are new MPL multicast packets, but reduces transmission
12. overhead as the dissemination process completes. Trickle's
suppression mechanism and transmission time selection allow MPL's
communication rate to scale logarithmically with density.
5. Message Formats 4. Message Formats
5.1. Trickle Multicast Option 4.1. MPL Option
The Trickle Multicast option is carried in an IPv6 Hop-by-Hop Options The MPL Option is carried in an IPv6 Hop-by-Hop Options header,
header, immediately following the IPv6 header. The Trickle Multicast immediately following the IPv6 header. The MPL Option has the
option has the following format: 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 | Opt Data Len | | Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SeedID (optional) |M| Sequence | | S |M| rsv | sequence | seed-id (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type XX (to be confirmed by IANA). Option Type XX (to be confirmed by IANA).
Opt Data Len Length of the Option Data field in octets. MUST Opt Data Len Length of the Option Data field in octets. MUST
be set to either 2 or 4. be set to either 2 or 4.
SeedID Uniquely identifies a Trickle multicast seed that S 2-bit unsigned integer. Identifies the length of
initiated the dissemination process. The SeedID seed-id. 0 indicates that the seed-id is 0 and
field is optional and only appears when Opt Data not included in the MPL Option. 1 indicates that
Len is set to 4. When Opt Data Len is set to 2, the seed-id is a 16-bit unsigned integer. 2
the SeedID is equivalent to the IPv6 Source indicates that the seed-id is a 64-bit unsigned
address. integer. 3 indicates that the seed-id is a 128-
bit unsigned integer.
M Mode flag. Identifies one of two Trickle M 1-bit flag. 0 indicates that the value in
parameters to use when forwarding this multicast sequence is not the greatest sequence number that
message. was received from the MPL seed.
Sequence Identifies relative ordering of multicast rsv 5-bit reserved field. MUST be set to zero and
messages from the source identified by SeedID. incoming MPL multicast packets in which they are
not zero MUST be dropped.
The Option Data of the Trickle Multicast option MUST NOT change en- sequence 8-bit unsigned integer. Identifies relative
route. Nodes that do not understand the Trickle Multicast option ordering of MPL multicast packets from the source
MUST skip over this option and continue processing the header. Thus, identified by seed-id.
seed-id Uniquely identifies the MPL seed that initiated
dissemination of the MPL multicast packet. The
size of seed-id is indicated by the S field.
The Option Data of the Trickle Multicast option MUST NOT change as
the MPL multicast packet is forwarded. Nodes that do not understand
the Trickle Multicast option MUST discard the packet. Thus,
according to [RFC2460] the three high order bits of the Option Type according to [RFC2460] the three high order bits of the Option Type
must be equal set to zero. The Option Data length is variable. must be set to '010'. The Option Data length is variable.
The SeedID uniquely identifies a Trickle multicast seed within the The seed-id uniquely identifies an MPL seed within the MPL domain.
Trickle multicast domain. The SeedID field may either be an IPv6 When seed-id is 128 bits (S=3), the MPL seed MAY use an IPv6 address
address assigned to the seed node or a managed 16-bit value. In assigned to one of its interfaces that is unique within the MPL
either case, the SeedID MUST be unique within the Trickle multicast domain. Managing MPL seed identifiers is not within scope of this
domain. Managing the SeedID namespace is left out of scope. document.
The M flag identifies one of two Trickle parameters to use when The sequence field establishes a total ordering of MPL multicast
forwarding the message. This capability allows a Trickle Multicast packets from the same MPL seed. The MPL seed MUST increment the
Domain to support two different Trickle parameter sets that make sequence field's value on each new MPL multicast packet that it
different propagation time vs. control overhead trade-offs. disseminates. Implementations MUST follow the Serial Number
Arithmetic as defined in [RFC1982] when incrementing a sequence value
or comparing two sequence values.
Sequence establishes a relative ordering of multicast messages from Future updates to this specification may define additional fields
the same SeedID. The source MUST increment the Sequence value when following the seed-id field.
sourcing a new Trickle multicast message. Implementations MUST
follow the Serial Number Arithmetic as defined in [RFC1982].
5.2. Trickle ICMPv6 Message 4.2. ICMPv6 MPL Message
The Trickle ICMP message is used to advertise metadata for recently The MPL forwarder uses ICMPv6 MPL messages to advertise information
received Trickle multicast messages. The Trickle ICMP message has about recently received MPL multicast packets. The ICMPv6 MPL
the following format: message 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. Sequence List[1..n] . . MPL Window[1..n] .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IP Fields: IP Fields:
Source Address A link-local address assigned to the sending Source Address A link-local address assigned to the sending
interface. interface.
Destination Address The link-local all-nodes (FF02::1) or link-local Destination Address The link-local all-nodes MPL forwarders multicast
all-routers (FF02::2) multicast address. address (FF02::TBD).
Hop Limit 255 Hop Limit 255
ICMP Fields: ICMPv6 Fields:
Type XX (to be confirmed by IANA). Type XX (to be confirmed by IANA).
Code 0 Code 0
Checksum The ICMP checksum. See [RFC4443]. Checksum The ICMP checksum. See [RFC4443].
Sequence List[1..n] List of zero, one, or more Sequence Lists MPL Window[1..n] List of one or more MPL Windows (defined in
(defined in Section 5.2.1). Section 4.2.1).
The Trickle ICMP message advertises sliding windows maintained by the An MPL forwarder transmits an ICMPv6 MPL message to advertise
multicast forwarder. The advertisement serves to notify neighbors of information about buffered MPL multicast packets. More explicitly,
newer messages that it can propagate or has yet to receive. Only the ICMPv6 MPL message encodes the sliding window state (described in
entries for messages where Tactive has not expired are included in Section 5.2) that the MPL forwarder maintains for each MPL seed. The
the ICMP message. The sliding windows are encoded using a Sequence advertisement serves to indicate to neighboring MPL forwarders
List, defined in Section 5.2.1. regarding newer messages that it may send or the neighboring MPL
forwarders have yet to receive.
5.2.1. Sequence List 4.2.1. MPL Window
A Sequence List contains a list of Sequence values for a SeedID. An MPL Window encodes the sliding window state (described in
Each Sequence List has the following format: Section 5.2 that the MPL forwarder maintains for an MPL seed. Each
MPL Window 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|M| rsv | SeqLen | SeedID (2 or 16 octets) | | w-min | w-len | S | seed-id (0, 2 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. Sequence[1..SeqLen] . . buffered-mpl-packets (0 to 8 octets) .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S Indicates length of SeedID. When set to 0, w-min 8-bit unsigned integer. Indicates the first
SeedID is 16 octets. When set to 1, SeedID is 2 sequence number associated with the first bit in
octets. buffered-mpl-packets.
M Indicates one of two Trickle parameter sets used w-len 6-bit unsigned integer. Indicates the size of
for disseminating multicast messages. the sliding window and the number of valid bits
in buffered-mpl-packets. The sliding window's
upper bound is the sum of w-min and w-len.
SeqLen Number of 2-octet Sequence entries. S 2-bit unsigned integer. Identifies the length of
seed-id. 0 indicates that the seed-id value is 0
and not included in the MPL Option. 1 indicates
that the seed-id value is a 16-bit unsigned
integer. 2 indicates that the seed-id value is a
128-bit unsigned integer. 3 is reserved.
SeedID Copied from a recently received Trickle Multicast seed-id Indicates the MPL seed associated with this
option. sliding window.
Sequence[1..SeqLen] List of recently received Sequence values from buffered-mpl-packets Variable-length bit vector. Identifies the
SeedID. Note that the Sequence value is only 15 sequence numbers of MPL multicast packets that
bits and the highest order bit MUST be set to 0. the MPL forwarder has buffered. The sequence
number is determined by w-min + i, where i is the
offset within buffered-mpl-packets.
6. Trickle Multicast Forwarder Behavior The MPL Window does not have any octet alignment requirement.
A Trickle Multicast Forwarder implementation needs to manage sliding 5. MPL Forwarder Behavior
windows and Trickle timers. These mechanisms are used to determine
when received messages should be accepted, when ICMP messages are
transmitted, and when multicast messages are retransmitted.
6.1. Managing Sliding Windows An MPL forwarder implementation needs to manage sliding windows for
each active MPL seed. The sliding window allows the MPL forwarder to
determine what multicast packets to accept and what multicast packets
are buffered. An MPL forwarder must also manage MPL packet
transmissions.
Every Trickle multicast forwarder MUST maintain a sliding window of 5.1. Multicast Packet Dissemination
Sequence values for each SeedID that generated recently received
multicast messages.
When receiving a Trickle multicast message, if no existing sliding MPL uses the Trickle algorithm to control packet transmissions when
window exists for the SeedID, a new sliding window MUST be created disseminating MPL multicast packets [RFC6206]. MPL provides two
before accepting the message. If memory constraints are such that a propagation mechanisms for disseminating MPL multicast packets.
new sliding window cannot be created, then the message must be
ignored.
If a sliding window exists for the SeedID, the message must be 1. With proactive propagation, an MPL forwarder transmits buffered
ignored if the message's Sequence value falls below the lower bound MPL multicast packets using the Trickle algorithm. This method
of the window or appears in the list of stored Sequence values within is called proactive propagation since an MPL forwarder actively
the window. All other messages MUST be received. transmits MPL multicast packets without discovering that a
neighboring MPL forwarder has yet to receive the message.
When receiving a message, the sliding window MUST be updated with the 2. With reactive propagation, an MPL forwarder transmits ICMPv6 MPL
message's Sequence value. If the Sequence value is larger than the messages using the Trickle algorithm. An MPL forwarder only
upper bound of the window, the new message establishes the new upper transmits buffered MPL multicast packets upon discovering that
bound. neighboring devices have not yet to receive the corresponding MPL
multicast packets.
Memory constraints may limit the total number of Sequence values that When receiving a new multicast packet, an MPL forwarder first
can be stored. An entry may be reclaimed before the dwell time utilizes proactive propagation to forward the MPL multicast packet.
expires if it serves as the lower bound of the window and the window Proactive propagation reduces dissemination latency since it does not
has more than one entry. Note that entries can be reclaimed from require discovering that neighboring devices have not yet received
sliding windows for other SeedIDs. the MPL multicast packet. MPL forwarders utilize proactive
propagation for newly received MPL multicast packets since they can
assume that some neighboring MPL forwarders have yet to receive the
MPL multicast packet. After a limited number of MPL multicast packet
transmissions, the MPL forwarder may terminate proactive propagation
for the MPL multicast packet.
When only one entry for a sliding window remains, that entry MUST NOT An MPL forwarder may optionally use reactive propagation to continue
be reclaimed until its dwell timer expires. Maintaining the largest the dissemination process with lower communication overhead. With
sequence value received from a SeedID ensures that earlier messages reactive propagation, neighboring MPL forwarders use ICMPv6 MPL
are received at most once. messages to discover new MPL multicast messages that have not yet
been received. When discovering that a neighboring MPL forwarder has
not yet received a new MPL multicast packet, the MPL forwarder
enables proactive propagation again.
6.2. Trickle Timers 5.1.1. Trickle Parameters and Variables
A Trickle multicast forwarder maintains two Trickle timers As specified in RFC 6206 [RFC6206], a Trickle timer runs for a
parameterized on the S flag. The Trickle timer is maintained as defined interval and has three configuration parameters: the minimum
described in [RFC6206]. interval size Imin, the maximum interval size Imax, and a redundancy
constant k.
When suppression is enabled (i.e. k is finite), a Trickle MPL defines a fourth configuration parameter, TimerExpirations, which
transmission event consists of transmitting a Trickle ICMP message. indicates the number of Trickle timer expiration events that occur
before terminating the Trickle algorithm.
If an "inconsistent" advertisement was received during that period, Each MPL forwarder maintains a separate Trickle parameter set for the
multicast messages that caused the inconsistency are also proactive and reactive propagation methods. TimerExpirations MUST be
retransmitted. greater than 0 for proactive propagation. TimerExpirations MAY be
set to 0 for reactive propagation, which effectively disables
reactive propagation.
When suppression is disabled (i.e. k is infinite), a Trickle As specified in RFC 6206 [RFC6206], a Trickle timer has three
transmission event consists of transmitting multicast messages that variables: the current interval size I, a time within the current
have been received within the Tactive time window. interval t, and a counter c.
This document defines receiving a "consistent" transmission as MPL defines a fourth variable, e, which counts the number of Trickle
receiving a Trickle ICMP message that indicates neither the receiving timer expiration events since the Trickle timer was last reset.
nor transmitting node has new multicast messages to offer.
This document defines receiving an "inconsistent" transmission as 5.1.2. Proactive Propagation
receiving a Trickle ICMP message that indicates either receiving or
transmitting node has a new multicast message to offer. An
"inconsistent" transmission also includes receiving a new multicast
message.
6.3. Trickle Multicast Option Processing With proactive propagation, the MPL forwarder transmits buffered MPL
multicast packets using the Trickle algorithm. Each buffered MPL
multicast packet that is proactively being disseminated with
proactive propagation has an associated Trickle timer. Adhering to
Section 5 of RFC 6206 [RFC6206], this document defines the following:
All IPv6 datagrams containing a Trickle Multicast option MUST have a o This document defines a "consistent" transmission for proactive
multicast IPv6 Destination address. If the IPv6 Destination is not a propagation as receiving an MPL multicast packet that has the same
multicast address, the multicast forwarder MUST drop the datagram. MPL seed identifier and sequence number as a buffered MPL packet.
A multicast forwarder MUST drop the multicast message if it cannot o This document defines an "inconsistent" transmission for proactive
ensure that the message has never been received before. This occurs propagation as receiving an MPL multicast packet that has the same
when the Sequence value is below the lower bound of the sliding MPL seed identifier, the M flag set, and has a sequence number
window for SeedID or when an entry already exists for the Sequence less than the buffered MPL multicast packet's sequence number.
value.
If no sliding window state for SeedID exists, the multicast forwarder o This document does not define any external "events".
MUST allocate a new sliding window for the SeedID before accepting
the message. If a sliding window cannot be allocated, the forwarder
MUST drop the message.
Upon accepting the message, the forwarder MUST enter the sequence o This document defines both MPL multicast packets and ICMPv6 MPL
value in the sliding window and decrement the IPv6 Hop Limit. If the multicast packets as Trickle messages. These messages are defined
IPv6 Hop Limit is non-zero, the forwarder MUST buffer the message for in the sections below.
retransmission for the duration specified by Tactive.
6.4. Trickle ICMP Processing o The actions outside the Trickle algorithm that the protocol takes
involve managing sliding window state, and is specified in
Section 5.2.
Processing a Trickle ICMP message involves determining if either the 5.1.3. Reactive Propagation
receiver or transmitter has new multicast messages to offer.
The transmitter has new multicast messages to offer if any (SeedID, With reactive propagation, the MPL forwarder transmits ICMPv6 MPL
Sequence) pair falls within an existing sliding window for SeedID but messages using the Trickle algorithm. A MPL forwarder maintains a
does not have an associated entry. single Trickle timer for reactive propagation with each MPL domain.
When REACTIVE_TIMER_EXPIRATIONS is 0, the MPL forwarder does not
execute the Trickle algorithm for reactive propagation and reactive
propagation is disabled. Adhering to Section 5 of RFC 6206
[RFC6206], this document defines the following:
The transmitter has new multicast messages to offer if the (SeedID, o This document defines a "consistent" transmission for reactive
Sequence) pair is great than the upper bound of an existing sliding propagation as receiving an ICMPv6 MPL message that indicates
window for SeedID. neither the receiving nor transmitting node has new MPL multicast
packets to offer.
The receiver has new multicast messages to offer if any buffered o This document defines an "inconsistent" transmission for reactive
messages are not listed in the Trickle ICMP message and the Trickle propagation as receiving an ICMPv6 MPL message that indicates
ICMP message contains a (SeedID, Sequence) pair for a prior multicast either the receiving or transmitting node has at least one new MPL
message. multicast packet to offer.
The receiver has a new multicast message to offer if any buffered o This document defines an "event" for reactive propagation as
messages does not have an associated SeedID entry in the Trickle ICMP updating any sliding window (i.e. changing the value of WindowMin,
message. WindowMax, or the set of buffered MPL multicast packets) in
response to receiving an MPL multicast packet.
If neither receiver nor transmitter has new multicast messages to o This document defines both MPL multicast packets and ICMPv6 MPL
offer, the multicast forwarder logs a consistent event by multicast packets as Trickle messages. These messages are defined
incrementing c, as described in [RFC6206]. in the sections below.
If either receiver or transmitter has new multicast messages to o The actions outside the Trickle algorithm that the protocol takes
offer, the multicast forwarder logs an inconsistent event by involve managing sliding window state, and is specified in
resetting Trickle timer T[M], as described in [RFC6206]. All new Section 5.2.
messages that the receiver can offer MUST be scheduled for
transmission at the next transmission event. Note that these 5.2. Sliding Windows
transmissions may be suppressed if the transmission event is
suppressed. Every MPL forwarder MUST maintain a sliding window of sequence
numbers for each MPL seed of recently received MPL packets. The
sliding window performs two functions:
1. Indicate what MPL multicast packets the MPL forwarder should
accept.
2. Indicate what MPL multicast packets are buffered and may be
transmitted to neighboring MPL forwarders.
Each sliding window logically consists of:
1. A lower-bound sequence number, WindowMin, that represents the
sequence number of the oldest MPL multicast packet the MPL
forwarder is willing to receive or has buffered. An MPL
forwarder MUST ignore any MPL multicast packet that has sequence
value less than than WindowMin.
2. An upper-bound sequence value, WindowMax, that represents the
sequence number of the next MPL multicast packet that the MPL
forwarder expects to receive. An MPL forwarder MUST accept any
MPL multicast packet that has sequence number greater than or
equal to WindowMax.
3. A list of MPL multicast packets, BufferedPackets, buffered by the
MPL forwarder. Each entry in BufferedPackets MUST have a
sequence number in the range [WindowMin, WindowMax).
4. A timer, HoldTimer, that indicates the minimum lifetime of the
sliding window. The MPL forwarder MUST NOT free a sliding window
before HoldTimer expires.
When receiving an MPL multicast packet, if no existing sliding window
exists for the MPL seed, the MPL forwarder MUST create a new sliding
window before accepting the MPL multicast packet. The MPL forwarder
may reclaim memory resources by freeing a sliding window for another
MPL seed if its HoldTimer has expired. If, for any reason, the MPL
forwarder cannot create a new sliding window, it MUST discard the
packet.
If a sliding window exists for the MPL seed, the MPL forwarder MUST
ignore the MPL multicast packet if the packet's sequence number is
less than WindowMin or appears in BufferedPackets. Otherwise, the
MPL forwarder MUST accept the packet and determine whether or not to
forward the packet and/or pass the packet to the next higher layer.
When accepting an MPL multicast packet, the MPL forwarder MUST update
the sliding window based on the packet's sequence number. If the
sequence number is not less than WindowMax, the MPL forwarder MUST
set WindowMax to 1 greater than the packet's sequence number. If
WindowMax - WindowMin > MPL_MAX_WINDOW_SIZE, the MPL forwarder MUST
increment WindowMin such that WindowMax - WindowMin <=
MPL_MAX_WINDOW_SIZE. At the same time, the MPL forwarder MUST free
any entries in BufferedPackets that have a sequence number less than
WindowMin.
If the MPL forwarder has available memory resources, it MUST buffer
the MPL multicast packet for proactive propagation. If not enough
memory resources are available to buffer the packet, the MPL
forwarder MUST increment WindowMin and free entries in
BufferedPackets that have a sequence number less than WindowMin until
enough memory resources are available. Incrementing WindowMin will
ensure that the MPL forwarder does not accept previously received
packets.
An MPL forwarder MAY reclaim memory resources from sliding windows
for other MPL seeds. If a sliding window for another MPL seed is
actively disseminating messages and has more than one entry in its
BufferedPackets, the MPL forwarder may free entries for that MPL seed
by incrementing WindowMin as described above.
If the MPL forwarder cannot free enough memory resources to buffer
the MPL multicast packet, the MPL forwarder MUST set WindowMin to 1
greater than the packet's sequence number.
When memory resources are available, an MPL forwarder SHOULD buffer a
MPL multicast packet until the proactive propagation completes (i.e.
the Trickle algorithm stops execution) and MAY buffer for longer.
After proactive propagation completes, the MPL forwarder may advance
WindowMin to the packet's sequence number to reclaim memory
resources. When the MPL forwarder no longer buffers any packets, it
MAY set WindowMin equal to WindowMax. When setting WindowMin equal
to WindowMax, the MPL forwarder MUST initialize HoldTimer to
WINDOW_HOLD_TIME and start HoldTimer. After HoldTimer expires, the
MPL forwarder MAY free the sliding window to reclaim memory
resources.
5.3. Transmission of MPL Multicast Packets
The MPL forwarder manages buffered MPL multicast packet transmissions
using the Trickle algorithm. When adding a packet to
BufferedPackets, the MPL forwarder MUST create a Trickle timer for
the packet and start execution of the Trickle algorithm.
After PROACTIVE_TIMER_EXPIRATIONS Trickle timer events, the MPL
forwarder MUST stop executing the Trickle algorithm. When a buffered
MPL multicast packet does not have an active Trickle timer, the MPL
forwarder MAY free the buffered packet by advancing WindowMin to 1
greater than the packet's sequence number.
Each interface that supports MPL is configured with exactly one MPL
multicast scope. The MPL multicast scope MUST be site-local or
smaller and defaults to link-local. A scope larger than link-local
MAY be used only when that scope corresponds exactly to the MPL
domain.
An MPL domain may therefore be composed of one or more MPL multicast
scopes. For example, the MPL domain may be composed of a single MPL
multicast scope when using a site-local scope. Alternatively, the
MPL domain may be composed of multiple MPL multicast scopes when
using a link-local scope.
IPv6-in-IPv6 encapsulation MUST be used when using MPL to forward an
original multicast packet whose source or destination address is
outside the MPL multicast scope. IPv6-in-IPv6 encapsulation is
necessary to support Path MTU discovery when the MPL forwarder is not
the source of the original multicast packet. IPv6-in-IPv6
encapsulation also allows an MPL forwarder to remove the MPL Option
when forwarding the original multicast packet over a link that does
not support MPL. The destination address scope for the outer IPv6
header MUST be the MPL multicast scope.
When an MPL domain is composed of multiple MPL multicast scopes (e.g.
when the MPL multicast scope is link-local), an MPL forwarder MUST
decapsulate and encapsulate the original multicast packet when
crossing between different MPL multicast scopes. In doing so, the
MPL forwarder MUST duplicate the MPL Option, unmodified, in the new
outer IPv6 header.
The IPv6 destination address of the MPL multicast packet is the all-
MPL-forwarders multicast address (TBD). The scope of the IPv6
destination address is set to the MPL multicast scope.
5.4. Reception of MPL Multicast Packets
Upon receiving an MPL multicast packet, the MPL forwarder first
determines whether or not to accept and buffer the MPL multicast
packet based on its MPL seed and sequence value, as specified in
Section 5.2.
If the MPL forwarder accepts the MPL multicast packet, the MPL
forwarder determines whether or not to deliver the original multicast
packet to the next higher layer. For example, if the MPL multicast
packet uses IPv6-in-IPv6 encapsulation, the MPL forwarder removes the
outer IPv6 header, which also removes MPL Option.
5.5. Transmission of ICMPv6 MPL Messages
The MPL forwarder generates and transmits a new ICMPv6 MPL message
whenever Trickle requests a transmission. The MPL forwarder includes
an encoding of each sliding window in the ICMPv6 MPL message.
Each sliding window is encoded using an MPL Window entry, defined in
Section 5.2. The MPL forwarder sets the MPL Window fields as
follows:
S If the MPL seed identifier is 0, set S to 0. If the MPL seed
identifier is within the range [1, 65535], set S to 2. Otherwise,
set S to 3.
w-min Set to the lower bound of the sliding window (i.e.
WindowMin).
w-len Set to the length of the window (i.e. WindowMax - WindowMin).
seed-id If S is non-zero, set to the MPL seed identifier.
buffered-mpl-packets Set each bit that represents a sequence number
of a packet in BufferedPackets to 1. Set all other bits to 0.
The i'th bit in buffered-mpl-packets represents a sequence number
of w-min + i.
5.6. Reception of ICMPv6 MPL Messages
An MPL forwarder processes each ICMPv6 MPL message that it receives
to determine if it has any new MPL multicast packets to receive or
offer.
An MPL forwarder determines if a new MPL multicast packet has not
been received from a neighboring node if any of the following
conditions hold true:
1. The ICMPv6 MPL message includes an MPL Window for an MPL seed
that does not have a corresponding sliding window entry on the
MPL forwarder.
2. The neighbor has a packet in its BufferedPackets that has
sequence value greater than or equal to WindowMax (i.e. w-min +
w-len >= WindowMax).
3. The neighbor has a packet in its BufferedPackets that has
sequence number within range of the sliding window but is not
included in BufferedPackets (i.e. the i'th bit in buffered-mpl-
packets is set to 1, where the sequence number is w-min + i).
When an MPL forwarder determines that it has not yet received a new
MPL multicast packet buffered by a neighboring device, the MPL
forwarder resets the Trickle timer associated with reactive
propagation.
An MPL forwarder determines if an entry in BufferedPackets has not
been received by a neighboring MPL forwarder if any of the following
conditions hold true:
1. The ICMPv6 MPL message does not include an MPL Window for the
packet's MPL seed.
2. The packet's sequence number is greater than or equal to the
neighbor's WindowMax value (i.e. the packet's sequence number is
greater than or equal to w-min + w-len).
3. The packet's sequence number is within the range of the
neighbor's sliding window [WindowMin, WindowMax), but not
included in the neighbor's BufferedPacket (i.e. the packet's
sequence number is greater than or equal to w-min, strictly less
than w-min + w-len, and the corresponding bit in buffered-mpl-
packets is set to 0.
When an MPL forwarder determines that it has at least one buffered
MPL multicast packet that has not yet been received by a neighbor,
the MPL forwarder resets the Trickle timer associated with reactive
propagation. Additionally, for each buffered MPL multicast packet
that should be transferred, the MPL forwarder MUST reset the Trickle
timer and reset e to 0 for proactive propagation. If the Trickle
timer for proactive propagation has already stopped execution, the
MPL forwarder MUST initialize a new Trickle timer and start execution
of the Trickle algorithm.
6. MPL Parameters
An MPL forwarder maintains two sets of Trickle parameters for the
proactive and reactive methods. The Trickle parameters are listed
below:
PROACTIVE_IMIN The minimum Trickle timer interval, as defined in
[RFC6206] for proactive propagation.
PROACTIVE_IMAX The maximum Trickle timer interval, as defined in
[RFC6206] for proactive propagation.
PROACTIVE_K The redundancy constant, as defined in [RFC6206] for
proactive propagation.
PROACTIVE_TIMER_EXPIRATIONS The number of Trickle timer expirations
that occur before terminating the Trickle algorithm. MUST be set
to a value greater than 0.
REACTIVE_IMIN The minimum Trickle timer interval, as defined in
[RFC6206] for reactive propagation.
REACTIVE_IMAX The maximum Trickle timer interval, as defined in
[RFC6206] for reactive propagation.
REACTIVE_K The redundancy constant, as defined in [RFC6206] for
reactive propagation.
REACTIVE_TIMER_EXPIRATIONS The number of Trickle timer expirations
that occur before terminating the Trickle algorithm. MAY be set
to 0, which disables reactive propagation.
WINDOW_HOLD_TIME The minimum lifetime for sliding window state.
7. Acknowledgements 7. Acknowledgements
TODO. The authors would like to acknowledge the helpful comments of Robert
Cragie, Esko Dijk, Ralph Droms, Paul Duffy, Owen Kirby, Joseph Reddy,
Dario Tedeschi, and Peter van der Stok, which greatly improved the
document.
8. IANA Considerations 8. IANA Considerations
The Trickle Multicast option requires an IPv6 Option Number. The Trickle Multicast option requires an IPv6 Option Number.
HEX act chg rest HEX act chg rest
--- --- --- ----- --- --- --- -----
C 00 0 01100 C 01 0 TBD
The first two bits indicate that the IPv6 node may skip over this The first two bits indicate that the IPv6 node MUST discard the
option and continue processing the header if it doesn't recognize the packet if it doesn't recognize the option type, and the third bit
option type, and the third bit indicates that the Option Data MUST indicates that the Option Data MUST NOT change en-route.
NOT change en-route.
9. Security Considerations 9. Security Considerations
TODO. TODO.
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
skipping to change at page 18, line 30 skipping to change at page 23, line 30
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998. IPv6 Specification", RFC 2473, December 1998.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006. Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, March 2011. "The Trickle Algorithm", RFC 6206, March 2011.
[RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
Lossy Networks", RFC 6550, March 2012.
10.2. Informative References 10.2. Informative References
[I-D.ietf-roll-terminology] [I-D.ietf-roll-terminology]
Vasseur, J., "Terminology in Low power And Lossy Vasseur, J., "Terminology in Low power And Lossy
Networks", draft-ietf-roll-terminology-06 (work in Networks", draft-ietf-roll-terminology-06 (work in
progress), September 2011. progress), September 2011.
Authors' Addresses Authors' Addresses
Jonathan W. Hui Jonathan W. Hui
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