< draft-ietf-roll-trickle-mcast-03.txt   draft-ietf-roll-trickle-mcast-04.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: July 28, 2013 Silicon Labs Expires: August 29, 2013 Silicon Labs
January 24, 2013 February 25, 2013
Multicast Protocol for Low power and Lossy Networks (MPL) Multicast Protocol for Low power and Lossy Networks (MPL)
draft-ietf-roll-trickle-mcast-03 draft-ietf-roll-trickle-mcast-04
Abstract Abstract
This document specifies the Multicast Protocol for Low power and This document specifies the Multicast Protocol for Low power and
Lossy Networks (MPL) that provides IPv6 multicast forwarding in Lossy Networks (MPL) that provides IPv6 multicast forwarding in
constrained networks. MPL avoids the need to construct or maintain constrained networks. MPL avoids the need to construct or maintain
any multicast forwarding topology, disseminating messages to all MPL any multicast forwarding topology, disseminating messages to all MPL
forwarders in an MPL domain. MPL uses the Trickle algorithm to Forwarders in an MPL Domain. MPL uses the Trickle algorithm to
manage message transmissions for both control and data-plane manage message transmissions for both control and data-plane
messages. Different Trickle parameter configurations allow MPL to messages. Different Trickle parameter configurations allow MPL to
trade between dissemination latency and transmission efficiency. trade between dissemination latency and transmission efficiency.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on July 28, 2013. This Internet-Draft will expire on August 29, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 6
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Information Base Overview . . . . . . . . . . . . . . . . 6 4.1. Information Base Overview . . . . . . . . . . . . . . . . 7
4.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.3. Signaling Overview . . . . . . . . . . . . . . . . . . . . 7 4.3. Signaling Overview . . . . . . . . . . . . . . . . . . . . 9
5. MPL Constants . . . . . . . . . . . . . . . . . . . . . . . . 9 5. MPL Parameters and Constants . . . . . . . . . . . . . . . . . 10
5.1. Multicast Addresses . . . . . . . . . . . . . . . . . . . 9 5.1. MPL Multicast Addresses . . . . . . . . . . . . . . . . . 10
5.2. Message Types . . . . . . . . . . . . . . . . . . . . . . 9 5.2. MPL Message Types . . . . . . . . . . . . . . . . . . . . 10
5.3. MPL Forwarder Parameters . . . . . . . . . . . . . . . . . 9 5.3. MPL Seed Identifiers . . . . . . . . . . . . . . . . . . . 10
5.4. Trickle Parameters . . . . . . . . . . . . . . . . . . . . 9 5.4. MPL Forwarder Parameters . . . . . . . . . . . . . . . . . 10
6. Protocol Message Formats . . . . . . . . . . . . . . . . . . . 11 5.5. MPL Trickle Parameters . . . . . . . . . . . . . . . . . . 11
6.1. MPL Option . . . . . . . . . . . . . . . . . . . . . . . . 11 6. Protocol Message Formats . . . . . . . . . . . . . . . . . . . 13
6.2. MPL Control Message . . . . . . . . . . . . . . . . . . . 12 6.1. MPL Option . . . . . . . . . . . . . . . . . . . . . . . . 13
6.3. MPL Seed Info . . . . . . . . . . . . . . . . . . . . . . 13 6.2. MPL Control Message . . . . . . . . . . . . . . . . . . . 14
7. Information Base . . . . . . . . . . . . . . . . . . . . . . . 15 6.3. MPL Seed Info . . . . . . . . . . . . . . . . . . . . . . 15
7.1. Local Interface Set . . . . . . . . . . . . . . . . . . . 15 7. Information Base . . . . . . . . . . . . . . . . . . . . . . . 17
7.2. Domain Set . . . . . . . . . . . . . . . . . . . . . . . . 15 7.1. Local Interface Set . . . . . . . . . . . . . . . . . . . 17
7.3. Seed Set . . . . . . . . . . . . . . . . . . . . . . . . . 15 7.2. Domain Set . . . . . . . . . . . . . . . . . . . . . . . . 17
7.4. Buffered Message Set . . . . . . . . . . . . . . . . . . . 15 7.3. Seed Set . . . . . . . . . . . . . . . . . . . . . . . . . 17
8. MPL Domains . . . . . . . . . . . . . . . . . . . . . . . . . 17 7.4. Buffered Message Set . . . . . . . . . . . . . . . . . . . 17
9. MPL Seed Sequence Numbers . . . . . . . . . . . . . . . . . . 18 8. MPL Domains . . . . . . . . . . . . . . . . . . . . . . . . . 19
10. MPL Data Messages . . . . . . . . . . . . . . . . . . . . . . 19 9. MPL Seed Sequence Numbers . . . . . . . . . . . . . . . . . . 20
10.1. MPL Data Message Generation . . . . . . . . . . . . . . . 19 10. MPL Data Messages . . . . . . . . . . . . . . . . . . . . . . 21
10.2. MPL Data Message Transmission . . . . . . . . . . . . . . 19 10.1. MPL Data Message Generation . . . . . . . . . . . . . . . 21
10.3. MPL Data Message Processing . . . . . . . . . . . . . . . 20 10.2. MPL Data Message Transmission . . . . . . . . . . . . . . 21
11. MPL Control Messages . . . . . . . . . . . . . . . . . . . . . 22 10.3. MPL Data Message Processing . . . . . . . . . . . . . . . 22
11.1. MPL Control Message Generation . . . . . . . . . . . . . . 22 11. MPL Control Messages . . . . . . . . . . . . . . . . . . . . . 24
11.2. MPL Control Message Transmission . . . . . . . . . . . . . 22 11.1. MPL Control Message Generation . . . . . . . . . . . . . . 24
11.3. MPL Control Message Processing . . . . . . . . . . . . . . 23 11.2. MPL Control Message Transmission . . . . . . . . . . . . . 24
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25 11.3. MPL Control Message Processing . . . . . . . . . . . . . . 25
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
13.1. MPL Option Type . . . . . . . . . . . . . . . . . . . . . 26 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
13.2. MPL ICMPv6 Type . . . . . . . . . . . . . . . . . . . . . 26 13.1. MPL Option Type . . . . . . . . . . . . . . . . . . . . . 28
13.3. Well-known Multicast Addresses . . . . . . . . . . . . . . 26 13.2. MPL ICMPv6 Type . . . . . . . . . . . . . . . . . . . . . 28
14. Security Considerations . . . . . . . . . . . . . . . . . . . 27 13.3. Well-known Multicast Addresses . . . . . . . . . . . . . . 28
15. Normative References . . . . . . . . . . . . . . . . . . . . . 28 14. Security Considerations . . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29 15. Normative References . . . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction 1. Introduction
Low power and Lossy Networks typically operate with strict resource Low power and Lossy Networks typically operate with strict resource
constraints in communication, computation, memory, and energy. Such constraints in communication, computation, memory, and energy. Such
resource constraints may preclude the use of existing IPv6 multicast resource constraints may preclude the use of existing IPv6 multicast
routing and forwarding mechanisms. Traditional IP multicast delivery routing and forwarding mechanisms. Traditional IP multicast delivery
typically relies on topology maintenance mechanisms to discover and typically relies on topology maintenance mechanisms to discover and
maintain routes to all subscribers of a multicast group. However, maintain routes to all subscribers of a multicast group. However,
maintaining such topologies in LLNs is costly and may not be feasible maintaining such topologies in LLNs is costly and may not be feasible
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involve selecting a connected dominating set used to forward involve selecting a connected dominating set used to forward
multicast messages to all nodes in an administrative domain. multicast messages to all nodes in an administrative domain.
However, existing mechanisms often require two-hop topology However, existing mechanisms often require two-hop topology
information and the cost of maintaining such information grows information and the cost of maintaining such information grows
polynomially with network density. polynomially with network density.
This document specifies the Multicast Protocol for Low power and This document specifies the Multicast Protocol for Low power and
Lossy Networks (MPL), which provides IPv6 multicast forwarding in Lossy Networks (MPL), which provides IPv6 multicast forwarding in
constrained networks. MPL avoids the need to construct or maintain constrained networks. MPL avoids the need to construct or maintain
any multicast routing topology, disseminating multicast messages to any multicast routing topology, disseminating multicast messages to
all MPL forwarders in an MPL domain. By using the Trickle algorithm all MPL Forwarders in an MPL Domain. By using the Trickle algorithm
[RFC6206], MPL requires only small, constant state for each MPL [RFC6206], MPL requires only small, constant state for each MPL
device that initiates disseminations. The Trickle algorithm also device that initiates disseminations. The Trickle algorithm also
allows MPL to be density-aware, allowing the communication rate to allows MPL to be density-aware, allowing the communication rate to
scale logarithmically with density. scale logarithmically with density.
2. Terminology 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", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
The following terms are used throughout this document: The following terms are used throughout this document:
MPL Forwarder - A router that implements this protocol. A MPL MPL Forwarder - A router that implements this protocol. An MPL
Forwarder is equipped with at least one MPL Forwarder is equipped with at least one MPL
Interface. Interface.
MPL Interface - An MPL Forwarder's attachment to a MPL Interface - An MPL Forwarder's attachment to a
communications medium, over which it transmits communications medium, over which it transmits
and receives MPL Data Messages and MPL Control and receives MPL Data Messages and MPL Control
Messages according to this specification. An MPL Messages according to this specification. An MPL
Interface is assigned one or more unicast Interface is assigned one or more unicast
addresses and is subscribed to one or more MPL addresses and is subscribed to one or more MPL
Domain Addresses. Domain Addresses.
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Messages disseminated in an MPL Domain have the Messages disseminated in an MPL Domain have the
associated MPL Domain Address as their associated MPL Domain Address as their
destination address. destination address.
MPL Domain - A scope zone, as defined in [RFC4007], in which MPL Domain - A scope zone, as defined in [RFC4007], in which
MPL Interfaces subscribe to the same MPL Domain MPL Interfaces subscribe to the same MPL Domain
Address and participate in disseminating MPL Data Address and participate in disseminating MPL Data
Messages. Messages.
MPL Data Message - A multicast message that is used to communicate MPL Data Message - A multicast message that is used to communicate
a multicast payload between MPL Forwarders and a multicast payload between MPL Forwarders within
contains an MPL Option in the IPv6 header. A MPL an MPL domain. An MPL Data Message contains an
Data Message has its destination address set to MPL Option in the IPv6 header and has as its
the MPL Domain Address. destination address the MPL Domain Address
corresponding to the MPL Domain.
MPL Control Message - A link-local multicast message that is used to MPL Control Message - A link-local multicast message that is used to
communicate information about recently received communicate information about recently received
MPL Data Messages to neighboring MPL Forwarders. MPL Data Messages to neighboring MPL Forwarders.
MPL Seed - An MPL Forwarder that generates MPL Data MPL Seed - An MPL Forwarder that generates MPL Data
Messages and serves as an entry point into an MPL Messages and serves as an entry point into an MPL
Domain. Domain.
MPL Seed Identifier - An unsigned integer that uniquely identifies an
MPL Seed within an MPL Domain.
3. Applicability Statement 3. Applicability Statement
This protocol is an IPv6 multicast forwarding protocol for Low-Power This protocol is an IPv6 multicast forwarding protocol for Low-Power
and Lossy Networks. By implementing a controlled dissemination using and Lossy Networks. By implementing a controlled dissemination using
the Trickle algorithm, this protocol is designed for networks that the Trickle algorithm, this protocol is designed for networks that
communicate using low-power and lossy links with widely varying communicate using low-power and lossy links with widely varying
topologies in both the space and time dimensions. topologies in both the space and time dimensions.
4. Protocol Overview 4. Protocol Overview
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A node records necessary protocol state in the following information A node records necessary protocol state in the following information
sets: sets:
o The Local Interface Set records the set of local MPL Interfaces o The Local Interface Set records the set of local MPL Interfaces
and the unicast addresses assigned to those MPL Interfaces. and the unicast addresses assigned to those MPL Interfaces.
o The Domain Set records the set of MPL Domain Addresses and the o The Domain Set records the set of MPL Domain Addresses and the
local MPL Interfaces that subscribe to those addresses. local MPL Interfaces that subscribe to those addresses.
o The Seed Set records information about received MPL Data Messages o A Seed Set records information about received MPL Data Messages
received from an MPL Seed. The Seed Set maintains the minimum received from an MPL Seed within an MPL Domain. Each MPL Domain
sequence number that the MPL Forwarder is willing to receive or has an associated Seed Set. A Seed Set maintains the minimum
has buffered in its Buffered Message Set. MPL uses the Seed Set sequence number for MPL Data Messages that the MPL Forwarder is
and Buffered Message Set to determine when to accept an MPL Data willing to receive or has buffered in its Buffered Message Set
Message, process its payload, and retransmit it. from an MPL Seed. MPL uses Seed Sets and Buffered Message Sets to
determine when to accept an MPL Data Message, process its payload,
and retransmit it.
o The Buffered Message Set records recently received MPL Data o A Buffered Message Set records recently received MPL Data Messages
Messages from an MPL Seed. MPL Data Messages resident in the from an MPL Seed within an MPL Domain. Each MPL Domain has an
associated Buffered Message Set. MPL Data Messages resident in a
Buffered Message Set have sequence numbers that are greater than Buffered Message Set have sequence numbers that are greater than
or equal to the minimum threshold maintained in the Seed Set. MPL or equal to the minimum threshold maintained in the corresponding
uses the Buffered Message Set to store MPL Data Messages that may Seed Set. MPL uses Buffered Message Sets to store MPL Data
be transmitted by the MPL Forwarder for forwarding. Messages that may be transmitted by the MPL Forwarder for
forwarding.
4.2. Overview 4.2. Overview
MPL achieves its goal by implementing a controlled flood that MPL achieves its goal by implementing a controlled flood that
attempts to disseminate the multicast data message to all interfaces attempts to disseminate the multicast data message to all interfaces
within an MPL Domain. MPL performs the following tasks to within an MPL Domain. MPL performs the following tasks to
disseminate a multicast message: disseminate a multicast message:
o When having a multicast message to forward into an MPL Domain, the o When having a multicast message to forward into an MPL Domain, the
MPL Seed generates an MPL Data Message that includes the MPL Seed MPL Seed generates an MPL Data Message that includes the MPL
Domain Address as the IPv6 Destination Address, the MPL Seed
Identifier, a newly generated sequence number, and the multicast Identifier, a newly generated sequence number, and the multicast
message. If the multicast destination address is not the MPL message. If the multicast destination address is not the MPL
Domain Address, IP-in-IP [RFC2473] is used to encapsulate the Domain Address, IP-in-IP [RFC2473] is used to encapsulate the
multicast message in the MPL Data Message. multicast message in an MPL Data Message, preserving the original
IPv6 Destination Address.
o Upon receiving an MPL Data Message, the MPL Forwarder extracts the o Upon receiving an MPL Data Message, the MPL Forwarder extracts the
MPL Seed and sequence number and determines whether or not the MPL MPL Seed and sequence number and determines whether or not the MPL
Data Message was previously received using the Seed Set and Data Message was previously received using the MPL Domain's Seed
Buffered Message Set. Set and Buffered Message Set.
* If the sequence number is less than the lower-bound sequence * If the sequence number is less than the lower-bound sequence
number maintained in the Seed Set or a message with the same number maintained in the Seed Set or a message with the same
sequence number exists within the Buffered Message Set, the MPL sequence number exists within the Buffered Message Set, the MPL
Forwarder marks the MPL Data Message as old. Forwarder marks the MPL Data Message as old.
* Otherwise, the MPL Forwarder marks the MPL Data Message as new. * Otherwise, the MPL Forwarder marks the MPL Data Message as new.
o For each newly received MPL Data Message, an MPL Forwarder updates o For each newly received MPL Data Message, an MPL Forwarder updates
the Seed Set, adds the MPL Data Message into the Buffered Message the Seed Set, adds the MPL Data Message into the Buffered Message
Set, processes its payload, and multicasts the MPL Data Message a Set, processes its payload, and multicasts the MPL Data Message a
number of times on all MPL Interfaces participating in the same number of times on all MPL Interfaces participating in the same
MPL Domain to forward the message. MPL Domain to forward the message.
o Each MPL Forwarder may periodically link-local multicast MPL o Each MPL Forwarder may periodically link-local multicast MPL
Control Messages on MPL Interfaces to communicate information Control Messages on MPL Interfaces to communicate information
contained in the MPL Forwarder's Seed Set and Buffered Message contained in an MPL Domain's Seed Set and Buffered Message Set.
Sets.
o Upon receiving an MPL Control Message, an MPL Forwarder determines o Upon receiving an MPL Control Message, an MPL Forwarder determines
whether there are any new MPL Data Messages that have yet to be whether there are any new MPL Data Messages that have yet to be
received by the MPL Control Message's source and multicasts those received by the MPL Control Message's source and multicasts those
MPL Data Messages. MPL Data Messages.
MPL's configuration parameters allow two forwarding strategies for MPL's configuration parameters allow two forwarding strategies for
disseminating MPL Data Messages. disseminating MPL Data Messages.
Proactive Forwarding - With proactive forwarding, an MPL Forwarder Proactive Forwarding - With proactive forwarding, an MPL Forwarder
schedules transmissions of MPL Data Messages using the Trickle schedules transmissions of MPL Data Messages using the Trickle
algorithm, without any prior indication that neighboring nodes algorithm, without any prior indication that neighboring nodes
have yet to receive the message. After transmitting the MPL Data have yet to receive the message. After transmitting the MPL Data
Message a limited number of times, the MPL forwarder may terminate Message a limited number of times, the MPL Forwarder may terminate
proactive forwarding for the MPL Data Message message. proactive forwarding for the MPL Data Message message.
Reactive Forwarding - With reactive forwarding, an MPL Forwarder Reactive Forwarding - With reactive forwarding, an MPL Forwarder
link-local multicasts MPL Control Messages using the Trickle link-local multicasts MPL Control Messages using the Trickle
algorithm [RFC6206]. MPL Forwarders use MPL Control Messages to algorithm [RFC6206]. MPL Forwarders use MPL Control Messages to
discover new MPL Data Messages that have not yet been received. discover new MPL Data Messages that have not yet been received.
When discovering that a neighboring MPL Forwarder has not yet When discovering that a neighboring MPL Forwarder has not yet
received a new MPL Data Message, the MPL Forwarder schedules those received an MPL Data Message, the MPL Forwarder schedules those
MPL Data Messages for transmission using the Trickle algorithm. MPL Data Messages for transmission using the Trickle algorithm.
4.3. Signaling Overview 4.3. Signaling Overview
This protocol generates and processes the following messages: This protocol generates and processes the following messages:
MPL Data Message - Generated by an MPL Seed to deliver a multicast MPL Data Message - Generated by an MPL Seed to deliver a multicast
message across an MPL Domain. The MPL Data Message's source is an message across an MPL Domain. The MPL Data Message's source is an
address in the Local Interface Set of the MPL Seed that generated address in the Local Interface Set of the MPL Seed that generated
the message and is valid within the MPL Domain. The MPL Data the message and is valid within the MPL Domain. The MPL Data
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* The Seed Identifier of the MPL Seed that generated the MPL Data * The Seed Identifier of the MPL Seed that generated the MPL Data
Message. Message.
* The sequence number of the MPL Seed that generated the MPL Data * The sequence number of the MPL Seed that generated the MPL Data
Message. Message.
* The original multicast message. * The original multicast message.
MPL Control Message - Generated by an MPL Forwarder to communicate MPL Control Message - Generated by an MPL Forwarder to communicate
information contained in the Seed Set and Buffered Message Set to information contained in an MPL Domain's Seed Set and Buffered
neighboring MPL Forwarders. An MPL Control Message contains a Message Set to neighboring MPL Forwarders. An MPL Control Message
list of tuples for each entry in the Seed Set. Each tuple contains a list of tuples for each entry in the Seed Set. Each
contains: tuple contains:
* The minimum sequence number maintained in the Seed Set for the * The minimum sequence number maintained in the Seed Set for the
MPL Seed. MPL Seed.
* A bit-vector indicating the sequence numbers of MPL Data * A bit-vector indicating the sequence numbers of MPL Data
Messages resident in the Buffered Message Set for the MPL Seed, Messages resident in the Buffered Message Set for the MPL Seed,
where the first bit represents a sequence number equal to the where the first bit represents a sequence number equal to the
minimum threshold maintained in the Seed Set. minimum threshold maintained in the Seed Set.
* The length of the bit-vector. * The length of the bit-vector.
5. MPL Constants 5. MPL Parameters and Constants
This section describes various program and networking constants used This section describes various program and networking parameters and
by MPL. constants used by MPL.
5.1. Multicast Addresses 5.1. MPL Multicast Addresses
MPL makes use of MPL Domain Addresses to identify MPL Interfaces of MPL makes use of MPL Domain Addresses to identify MPL Interfaces of
an MPL Domain. By default, MPL Forwarders subscribe to the an MPL Domain. By default, MPL Forwarders subscribe to the
ALL_MPL_FORWARDERS multicast address with a scope value of 3 (subnet- ALL_MPL_FORWARDERS multicast address with a scope value of 3 (subnet-
local). local).
For each MPL Domain Address that an MPL Interface subscribes to, the For each MPL Domain Address that an MPL Interface subscribes to, the
MPL Interface MUST also subscribe to the MPL Domain Address with a MPL Interface MUST also subscribe to the MPL Domain Address with a
scope value of 2 (link-local) when reactive forwarding is in use. scope value of 2 (link-local) when reactive forwarding is in use.
MPL Forwarders use the link-scoped MPL Domain Address to communicate MPL Forwarders use the link-scoped MPL Domain Address to communicate
MPL Control Messages to neighboring (i.e. on-link) MPL Forwarders. MPL Control Messages to neighboring (i.e. on-link) MPL Forwarders.
5.2. Message Types 5.2. MPL Message Types
MPL defines an IPv6 Option for carrying an MPL Seed Identifier and a MPL defines an IPv6 Option for carrying an MPL Seed Identifier and a
sequence number within an MPL Data Message. The IPv6 Option Type has sequence number within an MPL Data Message. The IPv6 Option Type has
value MPL_OPT_TYPE. value MPL_OPT_TYPE.
MPL defines an ICMPv6 Message (MPL Control Message) for communicating MPL defines an ICMPv6 Message (MPL Control Message) for communicating
information contained in its Seed Set and Buffered Message Set to information contained in an MPL Domain's Seed Set and Buffered
neighboring MPL Forwarders. The MPL Control Message has ICMPv6 Type Message Set to neighboring MPL Forwarders. The MPL Control Message
MPL_ICMP_TYPE. has ICMPv6 Type MPL_ICMP_TYPE.
5.3. MPL Forwarder Parameters 5.3. MPL Seed Identifiers
MPL uses MPL Seed Identifiers to uniquely identify MPL Seeds within
an MPL Domain. For each MPL Domain that the MPL Forwarder serves as
an MPL Seed, the MPL Forwarder MUST have an associated MPL Seed
Identifier. An MPL Forwarder MAY use the same MPL Seed Identifier
across multiple MPL Domains, but the MPL Seed Identifier MUST be
unique within each MPL Domain. The mechanism for assigning and
verifying uniqueness of MPL Seed Identifiers is not specified in this
document.
5.4. MPL Forwarder Parameters
PROACTIVE_FORWARDING A boolean value that indicates whether the MPL PROACTIVE_FORWARDING A boolean value that indicates whether the MPL
Forwarder should schedule MPL Data Message transmissions after Forwarder should schedule MPL Data Message transmissions after
receiving them for the first time. receiving them for the first time. PROACTIVE_FORWARDING has a
default value of TRUE.
SEED_SET_LIFETIME The minimum lifetime for an entry in the Seed Set. SEED_SET_ENTRY_LIFETIME The minimum lifetime for an entry in the
Seed Set. SEED_SET_ENTRY_LIFETIME has a default value of 30
minutes.
5.4. Trickle Parameters It is RECOMMENDED that all MPL Forwarders use the same values for the
MPL Forwarder Parameters above for a given MPL Domain. The mechanism
for setting the MPL Forwarder Parameters is not specified within this
document.
5.5. MPL Trickle Parameters
As specified in [RFC6206], a Trickle timer runs for a defined As specified in [RFC6206], a Trickle timer runs for a defined
interval and has three configuration parameters: the minimum interval interval and has three configuration parameters: the minimum interval
size Imin, the maximum interval size Imax, and a redundancy constant size Imin, the maximum interval size Imax, and a redundancy constant
k. k.
This specification defines a fourth Trickle configuration parameter, This specification defines a fourth Trickle configuration parameter,
TimerExpirations, which indicates the number of Trickle timer TimerExpirations, which indicates the number of Trickle timer
expiration events that occur before terminating the Trickle expiration events that occur before terminating the Trickle
algorithm. algorithm.
Each MPL forwarder maintains a separate Trickle parameter set for MPL Each MPL Forwarder uses the following Trickle parameters for MPL Data
Data Message and MPL Control Message transmissions. The Trickle Message and MPL Control Message transmissions.
parameters are listed below:
DATA_MESSAGE_IMIN The minimum Trickle timer interval, as defined in DATA_MESSAGE_IMIN The minimum Trickle timer interval, as defined in
[RFC6206], for MPL Data Message transmissions. [RFC6206], for MPL Data Message transmissions. DATA_MESSAGE_IMIN
has a default value of 10 times the worst-case link-layer latency.
DATA MESSAGE_IMAX The maximum Trickle timer interval, as defined in DATA MESSAGE_IMAX The maximum Trickle timer interval, as defined in
[RFC6206], for MPL Data Message transmissions. [RFC6206], for MPL Data Message transmissions. DATA_MESSAGE_IMAX
has a default value equal to DATA_MESSAGE_IMIN.
DATA_MESSAGE_K The redundancy constant, as defined in [RFC6206], for DATA_MESSAGE_K The redundancy constant, as defined in [RFC6206], for
MPL Data Message transmissions. MPL Data Message transmissions. DATA_MESSAGE_K has a default
value of 5.
DATA_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer DATA_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer
expirations that occur before terminating the Trickle algorithm expirations that occur before terminating the Trickle algorithm
for MPL Data Message transmissions. for MPL Data Message transmissions.
DATA_MESSAGE_TIMER_EXPIRATIONS has a default value of 3.
CONTROL_MESSAGE_IMIN The minimum Trickle timer interval, as defined CONTROL_MESSAGE_IMIN The minimum Trickle timer interval, as defined
in [RFC6206], for MPL Control Message transmissions. in [RFC6206], for MPL Control Message transmissions.
CONTROL_MESSAGE_IMIN has a default value of 10 times the worst-
case link-layer latency.
CONTROL_MESSAGE_IMAX The maximum Trickle timer interval, as defined CONTROL_MESSAGE_IMAX The maximum Trickle timer interval, as defined
in [RFC6206], for MPL Control Message transmissions. in [RFC6206], for MPL Control Message transmissions.
CONTROL_MESSAGE_IMAX has a default value of 5 minutes.
CONTROL_MESSAGE_K The redundancy constant, as defined in [RFC6206], CONTROL_MESSAGE_K The redundancy constant, as defined in [RFC6206],
for MPL Control Message transmissions. for MPL Control Message transmissions. CONTROL_MESSAGE_K has a
default value of 1.
CONTROL_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer CONTROL_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer
expirations that occur before terminating the Trickle algorithm expirations that occur before terminating the Trickle algorithm
for MPL Control Message transmissions. for MPL Control Message transmissions.
CONTROL_MESSAGE_TIMER_EXPIRATIONS has a default value of 10.
It is RECOMMENDED that all MPL Forwarder within an MPL Domain use the Following [RFC6206], it is RECOMMENDED that all MPL Forwarders use
same values for the Trickle Parameters above, as specified in the same values for the Trickle Parameters above for a given MPL
[RFC6206]. Domain. The mechanism for setting the Trickle Parameters is not
specified within this document.
6. Protocol Message Formats 6. Protocol Message Formats
The protocol messages generated and processed by an MPL Forwarder are The protocol messages generated and processed by an MPL Forwarder are
described in this section. described in this section.
6.1. MPL Option 6.1. MPL Option
The MPL Option is carried in MPL Data Messages in an IPv6 Hop-by-Hop The MPL Option is carried in MPL Data Messages in an IPv6 Hop-by-Hop
Options header, immediately following the IPv6 header. The MPL Options header, immediately following the IPv6 header. The MPL
skipping to change at page 11, line 41 skipping to change at page 13, line 41
Option. 1 indicates that the seed-id is a 16-bit Option. 1 indicates that the seed-id is a 16-bit
unsigned integer. 2 indicates that the seed-id is unsigned integer. 2 indicates that the seed-id is
a 64-bit unsigned integer. 3 indicates that the a 64-bit unsigned integer. 3 indicates that the
seed-id is a 128-bit unsigned integer. seed-id is a 128-bit unsigned integer.
M 1-bit flag. 1 indicates that the value in M 1-bit flag. 1 indicates that the value in
sequence is known to be the largest sequence sequence is known to be the largest sequence
number that was received from the MPL Seed. number that was received from the MPL Seed.
V 1-bit flag. 0 indicates that the MPL Option V 1-bit flag. 0 indicates that the MPL Option
conforms to this specification. MPL Options conforms to this specification. MPL Data
received in which this flag is 1 MUST be dropped. Messages with an MPL Option in which this flag is
1 MUST be dropped.
rsv 4-bit reserved field. MUST be set to 0 on rsv 4-bit reserved field. MUST be set to 0 on
transmission and ignored on reception. transmission and ignored on reception.
sequence 8-bit unsigned integer. Identifies relative sequence 8-bit unsigned integer. Identifies relative
ordering of MPL Data Messages from the MPL Seed ordering of MPL Data Messages from the MPL Seed
identified by seed-id. identified by seed-id.
seed-id Uniquely identifies the MPL Seed that initiated seed-id Uniquely identifies the MPL Seed that initiated
dissemination of the MPL Data Message. The size dissemination of the MPL Data Message. The size
skipping to change at page 12, line 18 skipping to change at page 14, line 18
The Option Data (in particular the M flag) of the MPL Option is The Option Data (in particular the M flag) of the MPL Option is
updated by MPL Forwarders as the MPL Data Message is forwarded. updated by MPL Forwarders as the MPL Data Message is forwarded.
Nodes that do not understand the MPL Option MUST discard the MPL Data Nodes that do not understand the MPL Option MUST discard the MPL Data
Message. Thus, according to [RFC2460] the three high order bits of Message. Thus, according to [RFC2460] the three high order bits of
the Option Type are set to '011'. The Option Data length is the Option Type are set to '011'. The Option Data length is
variable. variable.
The seed-id uniquely identifies an MPL Seed. When seed-id is 128 The seed-id uniquely identifies an MPL Seed. When seed-id is 128
bits (S=3), the MPL seed MAY use an IPv6 address assigned to one of bits (S=3), the MPL seed MAY use an IPv6 address assigned to one of
its interfaces that is unique within the MPL domain. Managing MPL its interfaces that is unique within the MPL Domain. Managing MPL
Seed Identifiers is not within scope of this document. Seed Identifiers is not within scope of this document.
The sequence field establishes a total ordering of MPL Data Messages The sequence field establishes a total ordering of MPL Data Messages
generated by an MPL Seed for an MPL Domain. The MPL Seed MUST generated by an MPL Seed for an MPL Domain. The MPL Seed MUST
increment the sequence field's value on each new MPL Data Message increment the sequence field's value on each new MPL Data Message
that it generates for an MPL Domain. Implementations MUST follow the that it generates for an MPL Domain. Implementations MUST follow the
Serial Number Arithmetic as defined in [RFC1982] when incrementing a Serial Number Arithmetic as defined in [RFC1982] when incrementing a
sequence value or comparing two sequence values. sequence value or comparing two sequence values.
Future updates to this specification may define additional fields Future updates to this specification may define additional fields
following the seed-id field. following the seed-id field.
6.2. MPL Control Message 6.2. MPL Control Message
An MPL Forwarder uses ICMPv6 messages to communicate information An MPL Forwarder uses ICMPv6 messages to communicate information
contained in its Seed Set and Buffered Message Set to neighboring MPL contained in an MPL Domain's Seed Set and Buffered Message Set to
Forwarders. The MPL Control Message has the following format: neighboring MPL Forwarders. The MPL Control 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. MPL Seed Info[1..n] . . MPL Seed Info[1..n] .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IP Fields: IP Fields:
Source Address A link-local address assigned to the sending Source Address An IPv6 address in the AddressSet of the
interface. corresponding MPL Interface and MUST be valid
within the MPL Domain.
Destination Address The link-scoped MPL Domain Address corresponding Destination Address The link-scoped MPL Domain Address corresponding
to the MPL Domain. to the MPL Domain.
Hop Limit 255 Hop Limit 255
ICMPv6 Fields: ICMPv6 Fields:
Type MPL_ICMP_TYPE Type MPL_ICMP_TYPE
Code 0 Code 0
Checksum The ICMP checksum. See [RFC4443]. Checksum The ICMP checksum. See [RFC4443].
MPL Seed Info[1..n] List of one or more MPL Seed Info entries. MPL Seed Info[0..n] List of zero or more MPL Seed Info entries.
The MPL Control Message indicates the sequence numbers of MPL Data The MPL Control Message indicates the sequence numbers of MPL Data
Messages that are within the Buffered Message Set. The MPL Control Messages that are within the MPL Domain's Buffered Message Set. The
Message also indicates the sequence numbers of MPL Data Messages that MPL Control Message also indicates the sequence numbers of MPL Data
an MPL Forwarder is willing to receive. The MPL Control Message Messages that an MPL Forwarder is willing to receive. The MPL
allows neighboring MPL Forwarders to determine whether there are any Control Message allows neighboring MPL Forwarders to determine
new MPL Data Messages to exchange. whether there are any new MPL Data Messages to exchange.
6.3. MPL Seed Info 6.3. MPL Seed Info
An MPL Seed Info encodes the minimum sequence number for the MPL Seed An MPL Seed Info encodes the minimum sequence number for an MPL Seed
maintained in the Seed Set. The MPL Seed Info also indicates the maintained in the MPL Domain's Seed Set. The MPL Seed Info also
sequence numbers of MPL Data Messages generated by the MPL Seed indicates the sequence numbers of MPL Data Messages generated by the
within the Buffered Message Set. The MPL Seed Info has the following MPL Seed that are stored within the MPL Domain's Buffered Message
format: Set. The MPL Seed Info 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| min-seqno | bm-len | S | seed-id (0/2/8/16 octets) | | min-seqno | bm-len | S | seed-id (0/2/8/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. buffered-mpl-messages (variable length) . . buffered-mpl-messages (variable length) .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 14, line 25 skipping to change at page 16, line 25
is a 16-bit unsigned integer. 2 indicates that is a 16-bit unsigned integer. 2 indicates that
the seed-id value is a 64-bit unsigned integer. 3 the seed-id value is a 64-bit unsigned integer. 3
indicates that the seed-id is a 128-bit unsigned indicates that the seed-id is a 128-bit unsigned
integer. integer.
seed-id Variable-length unsigned integer. Indicates the seed-id Variable-length unsigned integer. Indicates the
MPL Seed associated with this MPL Seed Info. MPL Seed associated with this MPL Seed Info.
buffered-mpl-messages Variable-length bit vector. Identifies the buffered-mpl-messages Variable-length bit vector. Identifies the
sequence numbers of MPL Data Messages maintained sequence numbers of MPL Data Messages maintained
in the Buffered Message Set for the MPL Seed. in the corresponding Buffered Message Set for the
The sequence number is determined by min-seqno + MPL Seed. The i'th bit represents a sequence
i, where i is the bit offset within buffered-mpl- number of min-seqno + i. '0' indicates that the
messages. corresponding MPL Data Message does not exist in
the Buffered Message Set. '1' indicates that the
corresponding MPL Data Message does exist in the
Buffered Message Set.
The MPL Seed Info does not have any octet alignment requirement. The MPL Seed Info does not have any octet alignment requirement.
7. Information Base 7. Information Base
7.1. Local Interface Set 7.1. Local Interface Set
The Local Interface Set records the local MPL Interfaces of an MPL The Local Interface Set records the local MPL Interfaces of an MPL
Forwarder. The Local Interface Set consists of Local Interface Forwarder. The Local Interface Set consists of Local Interface
Tuples, one per MPL Interface: (AddressSet). Tuples, one per MPL Interface: (AddressSet).
skipping to change at page 15, line 27 skipping to change at page 17, line 27
The Domain Set records the MPL Interfaces that subscribe to each MPL The Domain Set records the MPL Interfaces that subscribe to each MPL
Domain Address. The Domain Set consists of MPL Domain Tuples, one Domain Address. The Domain Set consists of MPL Domain Tuples, one
per MPL Domain: (MPLInterfaceSet). per MPL Domain: (MPLInterfaceSet).
MPLInterfaceSet - a set of MPL Interfaces that subscribe to the MPL MPLInterfaceSet - a set of MPL Interfaces that subscribe to the MPL
Domain Address that identifies the MPL Domain. Domain Address that identifies the MPL Domain.
7.3. Seed Set 7.3. Seed Set
The Seed Set records a sliding window used to determine the sequence A Seed Set records a sliding window used to determine the sequence
numbers of MPL Data Messages that an MPL Forwarder is willing to numbers of MPL Data Messages that an MPL Forwarder is willing to
accept generated by the MPL Seed. It consists of MPL Seed Tuples: accept generated by the MPL Seed. An MPL Forwarder maintains a Seed
(SeedID, MinSequence, Lifetime). Set for each MPL Domain that it participates in. A Seed Set consists
of MPL Seed Tuples: (SeedID, MinSequence, Lifetime).
SeedID - the identifier for the MPL Seed. SeedID - the identifier for the MPL Seed.
MinSequence - a lower-bound sequence number that represents the MinSequence - a lower-bound sequence number that represents the
sequence number of the oldest MPL Data Message the MPL Forwarder sequence number of the oldest MPL Data Message the MPL Forwarder
is willing to receive or transmit. An MPL Forwarder MUST ignore is willing to receive or transmit. An MPL Forwarder MUST ignore
any MPL Data Message that has sequence value less than than any MPL Data Message that has sequence value less than than
MinSequence. MinSequence.
Lifetime - indicates the minimum lifetime of the Seed Set entry. An Lifetime - indicates the minimum remaining lifetime of the Seed Set
MPL Forwarder MUST NOT free a Seed Set entry before its expires. entry. An MPL Forwarder MUST NOT free a Seed Set entry before the
remaining lifetime expires.
7.4. Buffered Message Set 7.4. Buffered Message Set
The Buffered Message Set records recently received MPL Data Messages A Buffered Message Set records recently received MPL Data Messages
from an MPL Seed. An MPL Forwarder uses the Buffered Message Set to from an MPL Seed within an MPL Domain. An MPL Forwarder uses a
buffer MPL Data Messages while the MPL Forwarder is forwarding the Buffered Message Set to buffer MPL Data Messages while the MPL
MPL Data Messages. The Buffered Message Set consists of Buffered Forwarder is forwarding the MPL Data Messages. An MPL Forwarder
Message Tuples: (SeedID, SequenceNumber, DataMessage). maintains a Buffered Message Set for each MPL Domain that it
participates in. A Buffered Message Set consists of Buffered Message
Tuples: (SeedID, SequenceNumber, DataMessage).
SeedID - the identifier for the MPL Seed that generated the MPL Data SeedID - the identifier for the MPL Seed that generated the MPL Data
Message. Message.
SequenceNumber - the sequence number for the MPL Data Message. SequenceNumber - the sequence number for the MPL Data Message.
DataMessage - the MPL Data Message. DataMessage - the MPL Data Message.
All MPL Data Messages within the Buffered Message Set MUST have a All MPL Data Messages within a Buffered Message Set MUST have a
sequence number greater than or equal to MinSequence for the sequence number greater than or equal to MinSequence for the
corresponding SeedID. When increasing MinSequence for an MPL Seed, corresponding SeedID. When increasing MinSequence for an MPL Seed,
the MPL Forwarder MUST delete any MPL Data Messages from the Buffered the MPL Forwarder MUST delete any MPL Data Messages from the
Message Set that have sequence numbers less than MinSequence. corresponding Buffered Message Set that have sequence numbers less
than MinSequence.
8. MPL Domains 8. MPL Domains
An MPL Domain is a scope zone, as defined in [RFC4007], in which MPL An MPL Domain is a scope zone, as defined in [RFC4007], in which MPL
Interfaces subscribe to the same MPL Domain Address and participate Interfaces subscribe to the same MPL Domain Address and participate
in disseminating MPL Data Messages. in disseminating MPL Data Messages.
By default, an MPL Forwarder MUST participate in an MPL Domain By default, an MPL Forwarder SHOULD participate in an MPL Domain
identified by the ALL_MPL_FORWARDERS multicast address with a scope identified by the ALL_MPL_FORWARDERS multicast address with a scope
value of 3 (subnet-local). value of 3 (subnet-local).
An MPL Forwarder MAY participate in additional MPL Domains identified An MPL Forwarder MAY participate in additional MPL Domains identified
by other multicast addresses. An MPL Interface MUST subscribe to the by other multicast addresses. An MPL Interface MUST subscribe to the
MPL Domain Addresses for the MPL Domains that it participates in. MPL Domain Addresses for the MPL Domains that it participates in.
The allocation of other multicast addresses is out of scope. The assignment of other multicast addresses is out of scope.
For each MPL Domain Address that an MPL Interface subscribes to, the For each MPL Domain Address that an MPL Interface subscribes to, the
MPL Interface MUST also subscribe to the same MPL Domain Address with MPL Interface MUST also subscribe to the same MPL Domain Address with
a scope value of 2 (link-local) when reactive forwarding is in use a scope value of 2 (link-local) when reactive forwarding is in use
(i.e. when communicating MPL Control Messages). (i.e. when communicating MPL Control Messages).
9. MPL Seed Sequence Numbers 9. MPL Seed Sequence Numbers
Each MPL Seed maintains a sequence number for each MPL Domain that it Each MPL Seed maintains a sequence number for each MPL Domain that it
serves. The sequence numbers are included in MPL Data Messages serves. The sequence numbers are included in MPL Data Messages
skipping to change at page 19, line 9 skipping to change at page 21, line 9
Implementations MUST follow the Serial Number Arithmetic as defined Implementations MUST follow the Serial Number Arithmetic as defined
in [RFC1982] when incrementing a sequence value or comparing two in [RFC1982] when incrementing a sequence value or comparing two
sequence values. This sequence number is used to establish a total sequence values. This sequence number is used to establish a total
ordering of MPL Data Messages generated by an MPL Seed for an MPL ordering of MPL Data Messages generated by an MPL Seed for an MPL
Domain. Domain.
10. MPL Data Messages 10. MPL Data Messages
10.1. MPL Data Message Generation 10.1. MPL Data Message Generation
MPL Data Messages are generated by MPL Seeds when they enter the MPL MPL Data Messages are generated by MPL Seeds when these messages
Domain. All MPL Data messages have the following properties: enter the MPL Domain. All MPL Data messages have the following
properties:
o The IPv6 Source Address MUST be an address in the AddressSet of a o The IPv6 Source Address MUST be an address in the AddressSet of a
corresponding MPL Interface and MUST be valid within the MPL corresponding MPL Interface and MUST be valid within the MPL
Domain. Domain.
o The IPv6 Destination Address MUST be set to the MPL Domain Address o The IPv6 Destination Address MUST be set to the MPL Domain Address
corresponding to the MPL Domain. corresponding to the MPL Domain.
o A MPL Data Message MUST contain an MPL Option in its IPv6 Header o An MPL Data Message MUST contain an MPL Option in its IPv6 Header
to identify the MPL Seed that generated the message and the to identify the MPL Seed that generated the message and the
ordering relative to other MPL Data Messages generated by the MPL ordering relative to other MPL Data Messages generated by the MPL
Seed. Seed.
When the source address is in the AddressList of an MPL Interface When the source address is in the AddressList of an MPL Interface
corresponding to the MPL Domain Address and the destination address corresponding to the MPL Domain Address and the destination address
is the MPL Domain Address, the application message and the MPL Data is the MPL Domain Address, the application message and the MPL Data
Message MAY be identical. In other words, the MPL Data Message may Message MAY be identical. In other words, the MPL Data Message may
contain a single IPv6 header that includes the MPL Option. contain a single IPv6 header that includes the MPL Option.
Otherwise, IPv6-in-IPv6 encapsulation MUST be used to satisfy the MPL Otherwise, IPv6-in-IPv6 encapsulation MUST be used to satisfy the MPL
Data Message requirements listed above [RFC2473]. The complete IPv6- Data Message requirements listed above [RFC2473]. The complete IPv6-
in-IPv6 message forms an MPL Data Message. The outer IPv6 header in-IPv6 message forms an MPL Data Message. The outer IPv6 header
conforms to the MPL Data Message requirements listed above. The conforms to the MPL Data Message requirements listed above. The
encapsulated IPv6 datagram encodes the multicast data message that is encapsulated IPv6 datagram encodes the multicast data message that is
communicated beyond the MPL Domain. communicated beyond the MPL Domain.
10.2. MPL Data Message Transmission 10.2. MPL Data Message Transmission
An MPL Forwarder manages transmission of MPL Data Messages in the An MPL Forwarder manages transmission of MPL Data Messages in its
Buffered Message set using the Trickle algorithm [RFC6206]. An MPL Buffered Message Sets using the Trickle algorithm [RFC6206]. An MPL
Forwarder MUST use a separate Trickle timer for each MPL Data Message Forwarder MUST use a separate Trickle timer for each MPL Data Message
that it is actively forwarding. In accordance with Section 5 of RFC that it is actively forwarding. In accordance with Section 5 of RFC
6206 [RFC6206], this document defines the following: 6206 [RFC6206], this document defines the following:
o This document defines a "consistent" transmission as receiving an o This document defines a "consistent" transmission as receiving an
MPL Data Message that has the same seed-id and sequence value as MPL Data Message that has the same MPL Domain Address, seed-id,
the MPL Data Message managed by the Trickle timer. and sequence value as the MPL Data Message managed by the Trickle
timer.
o This document defines an "inconsistent" transmission as receiving o This document defines an "inconsistent" transmission as receiving
an MPL Data Message that has the same seed-id value and the M flag an MPL Data Message that has the same MPL Domain Address, seed-id
set, but has a sequence value less than MPL Data Message managed value, and the M flag set, but has a sequence value less than MPL
by the Trickle timer. Data Message managed by the Trickle timer.
o This document does not define any external "events". o This document does not define any external "events".
o This document defines MPL Data Messages as Trickle messages. o This document defines MPL Data Messages as Trickle messages.
o The actions outside the Trickle algorithm that the protocol takes o The actions outside the Trickle algorithm that the protocol takes
involve managing Seed Set and Buffered Message Set involve managing the MPL Domain's Seed Set and Buffered Message
Set.
As specified in [RFC6206], a Trickle timer has three variables: the As specified in [RFC6206], a Trickle timer has three variables: the
current interval size I, a time within the current interval t, and a current interval size I, a time within the current interval t, and a
counter c. MPL defines a fourth variable, e, which counts the number counter c. MPL defines a fourth variable, e, which counts the number
of Trickle timer expiration events since the Trickle timer was last of Trickle timer expiration events since the Trickle timer was last
reset. reset.
After DATA_MESSAGE_TIMER_EXPIRATIONS Trickle timer events, the MPL After DATA_MESSAGE_TIMER_EXPIRATIONS Trickle timer events, the MPL
Forwarder MUST disable the Trickle timer. When a buffered MPL Data Forwarder MUST disable the Trickle timer. When a buffered MPL Data
Message does not have an associated Trickle timer, the MPL Forwarder Message does not have an associated Trickle timer, the MPL Forwarder
skipping to change at page 20, line 40 skipping to change at page 22, line 43
10.3. MPL Data Message Processing 10.3. MPL Data Message Processing
Upon receiving an MPL Data Message, the MPL Forwarder first processes Upon receiving an MPL Data Message, the MPL Forwarder first processes
the MPL Option and updates the Trickle timer associated with the MPL the MPL Option and updates the Trickle timer associated with the MPL
Data Message if one exists. Data Message if one exists.
Upon receiving an MPL Data Message, an MPL Forwarder MUST perform one Upon receiving an MPL Data Message, an MPL Forwarder MUST perform one
of the following actions: of the following actions:
o Accept the message and enter the MPL Data Message in the Buffered o Accept the message and enter the MPL Data Message in the MPL
Message Set. Domain's Buffered Message Set.
o Accept the message and update the corresponding MinSequence in the o Accept the message and update the corresponding MinSequence in the
Seed Set to 1 greater than the message's sequence number. MPL Domain's Seed Set to 1 greater than the message's sequence
number.
o Discard the message without any change to the MPL Information o Discard the message without any change to the MPL Information
Base. Base.
If a Seed Set entry exists for the MPL Seed, the MPL Forwarder MUST If a Seed Set entry exists for the MPL Seed, the MPL Forwarder MUST
discard the MPL Data Message if its sequence number is less than discard the MPL Data Message if its sequence number is less than
MinSequence or exists in the Buffered Message Set. MinSequence or exists in the Buffered Message Set.
If a Seed Set entry does not exist for the MPL Seed, the MPL If a Seed Set entry does not exist for the MPL Seed, the MPL
Forwarder MUST create a new entry for the MPL Seed before accepting Forwarder MUST create a new entry for the MPL Seed before accepting
the MPL Data Message. the MPL Data Message.
If memory is limited, an MPL Forwarder SHOULD reclaim memory If memory is limited, an MPL Forwarder SHOULD reclaim memory
resources by: resources by:
o Incrementing MinSequence entries in the Seed Set and deleting MPL o Incrementing MinSequence entries in a Seed Set and deleting MPL
Data Messages in the Buffered Message Set that fall below the Data Messages in the corresponding Buffered Message Set that fall
corresponding MinSequence value. below the MinSequence value.
o Deleting other Seed Set entries that have expired and the o Deleting other Seed Set entries that have expired and the
corresponding MPL Data Messages in the Buffered Message Set. corresponding MPL Data Messages in the Buffered Message Set.
If the MPL Forwarder accepts the MPL Data Message, the MPL Forwarder If the MPL Forwarder accepts the MPL Data Message, the MPL Forwarder
MUST perform the following actions: MUST perform the following actions:
o If PROACTIVE_PROPAGATION is true, the MPL Forwarder MUST o Reset the Lifetime of the corresponding Seed Set entry to
initialize and start a Trickle timer for the MPL Data Message. SEED_SET_ENTRY_LIFETIME.
o If PROACTIVE_FORWARDING is true, the MPL Forwarder MUST initialize
and start a Trickle timer for the MPL Data Message.
o If the MPL Control Message Trickle timer is not running and o If the MPL Control Message Trickle timer is not running and
CONTROL_MESSAGE_TIMER_EXPIRATIONS is non-zero, the MPL Forwarder CONTROL_MESSAGE_TIMER_EXPIRATIONS is non-zero, the MPL Forwarder
MUST initialize and start the MPL Control Message Trickle timer. MUST initialize and start the MPL Control Message Trickle timer.
o If the MPL Control Message Trickle timer is running, the MPL o If the MPL Control Message Trickle timer is running, the MPL
Forwarder MUST reset the MPL Control Message Trickle timer. Forwarder MUST reset the MPL Control Message Trickle timer.
11. MPL Control Messages 11. MPL Control Messages
11.1. MPL Control Message Generation 11.1. MPL Control Message Generation
An MPL Forwarder generates MPL Control Messages to communicate its An MPL Forwarder generates MPL Control Messages to communicate an MPL
Seed Set and Buffered Message Set to neighboring MPL Forwarders. Domain's Seed Set and Buffered Message Set to neighboring MPL
Each MPL Control Message is generated according to Section 6.2, with Forwarders. Each MPL Control Message is generated according to
an MPL Seed Info for each entry in Seed Set. Each MPL Seed Info entry Section 6.2, with an MPL Seed Info for each entry in the MPL Domain's
has the following content: Seed Set. Each MPL Seed Info entry has the following content:
o S set to the size of the seed-id field in the MPL Seed Info entry. o S set to the size of the seed-id field in the MPL Seed Info entry.
o min-seqno set to MinSequence of the MPL Seed. o min-seqno set to MinSequence of the MPL Seed.
o bm-len set to the size of buffered-mpl-messages in octets. o bm-len set to the size of buffered-mpl-messages in octets.
o seed-id set to the MPL seed identifier. o seed-id set to the MPL seed identifier.
o buffered-mpl-messages with each bit representing whether or not an o buffered-mpl-messages with each bit representing whether or not an
MPL Data Message with the corresponding sequence number exists in MPL Data Message with the corresponding sequence number exists in
the Buffered Message Set. The i'th bit represents a sequence the Buffered Message Set. The i'th bit represents a sequence
number of min-seqno + i. '0' indicates that the corresponding MPL number of min-seqno + i. '0' indicates that the corresponding MPL
Data Message does not exist in the Buffered Message Set. '1' Data Message does not exist in the Buffered Message Set. '1'
indicates that the corresponding MPL Data Message does exist in indicates that the corresponding MPL Data Message does exist in
the Buffered Message Set. the Buffered Message Set.
11.2. MPL Control Message Transmission 11.2. MPL Control Message Transmission
An MPL Forwarder transmits MPL Control Messages using the Trickle An MPL Forwarder transmits MPL Control Messages using the Trickle
algorithm. A MPL forwarder maintains a single Trickle timer for each algorithm. An MPL Forwarder maintains a single Trickle timer for
MPL Domain. When CONTROL_MESSAGE_TIMER_EXPIRATIONS is 0, the MPL each MPL Domain. When CONTROL_MESSAGE_TIMER_EXPIRATIONS is 0, the
Forwarder does not execute the Trickle algorithm and does not MPL Forwarder does not execute the Trickle algorithm and does not
transmit MPL Control Messages. In accordance with Section 5 of RFC transmit MPL Control Messages. In accordance with Section 5 of RFC
6206 [RFC6206], this document defines the following: 6206 [RFC6206], this document defines the following:
o This document defines a "consistent" transmission as receiving an o This document defines a "consistent" transmission as receiving an
MPL Control Message that indicates neither the receiving nor MPL Control Message that indicates neither the receiving nor
transmitting node has new MPL Data Message. transmitting node has any new MPL Data Messages to offer.
o This document defines an "inconsistent" transmission as receiving o This document defines an "inconsistent" transmission as receiving
an MPL Control Message that indicates either the receiving or an MPL Control Message that indicates either the receiving or
transmitting node has at least one new MPL Data Message to offer. transmitting node has at least one new MPL Data Message to offer.
o This document defines an "event" as increasing MinSequence of any o This document defines an "event" as increasing MinSequence of any
entry in the Seed Set or adding a message to the Buffered Message entry in the corresponding Seed Set or adding a message to the
Set. corresponding Buffered Message Set.
o This document defines an MPL Control Message as a Trickle message. o This document defines an MPL Control Message as a Trickle message.
As specified in [RFC6206], a Trickle timer has three variables: the As specified in [RFC6206], a Trickle timer has three variables: the
current interval size I, a time within the current interval t, and a current interval size I, a time within the current interval t, and a
counter c. MPL defines a fourth variable, e, which counts the number counter c. MPL defines a fourth variable, e, which counts the number
of Trickle timer expiration events since the Trickle timer was last of Trickle timer expiration events since the Trickle timer was last
reset. After CONTROL_MESSAGE_TIMER_EXPIRATIONS Trickle timer events, reset. After CONTROL_MESSAGE_TIMER_EXPIRATIONS Trickle timer events,
the MPL Forwarder MUST disable the Trickle timer. the MPL Forwarder MUST disable the Trickle timer.
11.3. MPL Control Message Processing 11.3. MPL Control Message Processing
An MPL Forwarder processes each MPL Control Message that it receives An MPL Forwarder processes each MPL Control Message that it receives
to determine if it has any new MPL Data Messages to receive or offer. to determine if it has any new MPL Data Messages to receive or offer.
An MPL Forwarder determines if a new MPL Data Message has not been An MPL Forwarder determines if a new MPL Data Message has not been
received from a neighboring node if any of the following conditions received from a neighboring node if any of the following conditions
hold true: hold true:
o The MPL Control Message includes an MPL Seed that does not exist o The MPL Control Message includes an MPL Seed that does not exist
in the Seed Set. in the MPL Domain's Seed Set.
o The MPL Control Message indicates that the neighbor has an MPL o The MPL Control Message indicates that the neighbor has an MPL
Data Message in its Buffered Message Set with sequence number Data Message in its Buffered Message Set with sequence number
greater than MinSequence (i.e. the i-th bit is set to 1 and min- greater than MinSequence (i.e. the i-th bit is set to 1 and min-
seqno + i > MinSequence) and is not included in the MPL seqno + i > MinSequence) and is not included in the MPL Domain's
Forwarder's Buffered Message Set. Buffered Message Set.
When an MPL Forwarder determines that it has not yet received an MPL When an MPL Forwarder determines that it has not yet received an MPL
Data Message buffered by a neighboring device, the MPL Forwarder MUST Data Message buffered by a neighboring device, the MPL Forwarder MUST
reset its Trickle timer associated with MPL Control Message reset its Trickle timer associated with MPL Control Message
transmissions. If an MPL Control Message Trickle timer is not transmissions. If an MPL Control Message Trickle timer is not
running, the MPL Forwarder MUST initialize and start a new Trickle running, the MPL Forwarder MUST initialize and start a new Trickle
timer. timer.
An MPL Forwarder determines if an MPL Data Message in the Buffered An MPL Forwarder determines if an MPL Data Message in the Buffered
Message Set has not yet been received by a neighboring MPL Forwarder Message Set has not yet been received by a neighboring MPL Forwarder
if any of the following conditions hold true: if any of the following conditions hold true:
o The MPL Control Message does not include an MPL Seed for the MPL o The MPL Control Message does not include an MPL Seed for the MPL
Data Message. Data Message.
o The MPL Data Message's sequence number is greater than or equal to o The MPL Data Message's sequence number is greater than or equal to
min-seqno and not included in the neighbor's Buffered Message Set min-seqno and not included in the neighbor's corresponding
(i.e. the MPL Data Message's sequence number does not have a Buffered Message Set (i.e. the MPL Data Message's sequence number
corresponding bit in buffered-mpl-messages set to 1). does not have a corresponding bit in buffered-mpl-messages set to
1).
When an MPL Forwarder determines that it has at least one MPL Data When an MPL Forwarder determines that it has at least one MPL Data
Message in its Buffered Message Set that has not yet been received by Message in its corresponding Buffered Message Set that has not yet
a neighbor, the MPL Forwarder MUST reset the MPL Control Message been received by a neighbor, the MPL Forwarder MUST reset the MPL
Trickle timer. Additionally, for each of those entries in the Control Message Trickle timer. Additionally, for each of those
Buffered Message Set, the MPL Forwarder MUST reset the Trickle timer entries in the Buffered Message Set, the MPL Forwarder MUST reset the
and reset e to 0. If a Trickle timer is not associated with the MPL Trickle timer and reset e to 0. If a Trickle timer is not associated
Data Message, the MPL Forwarder MUST initialize and start a new with the MPL Data Message, the MPL Forwarder MUST initialize and
Trickle timer. start a new Trickle timer.
12. Acknowledgements 12. Acknowledgements
The authors would like to acknowledge the helpful comments of Robert The authors would like to acknowledge the helpful comments of Robert
Cragie, Esko Dijk, Ralph Droms, Paul Duffy, Ulrich Herberg, Owen Cragie, Esko Dijk, Ralph Droms, Paul Duffy, Ulrich Herberg, Owen
Kirby, Joseph Reddy, Don Sturek, Dario Tedeschi, and Peter van der Kirby, Joseph Reddy, Don Sturek, Dario Tedeschi, and Peter van der
Stok, which greatly improved the document. Stok, which greatly improved the document.
13. IANA Considerations 13. IANA Considerations
skipping to change at page 26, line 48 skipping to change at page 28, line 48
+---------------+------+---------------------+---------------+ +---------------+------+---------------------+---------------+
| Mnemonic | Type | Name | Reference | | Mnemonic | Type | Name | Reference |
+---------------+------+---------------------+---------------+ +---------------+------+---------------------+---------------+
| MPL_ICMP_TYPE | TBD | MPL Control Message | This Document | | MPL_ICMP_TYPE | TBD | MPL Control Message | This Document |
+---------------+------+---------------------+---------------+ +---------------+------+---------------------+---------------+
Table 2: IPv6 Option Type Allocation Table 2: IPv6 Option Type Allocation
13.3. Well-known Multicast Addresses 13.3. Well-known Multicast Addresses
IANA is requested to allocate an IPv6 multicast address IANA is requested to allocate an IPv6 multicast address, with Group
ID in the range [0x01,0xFF] for 6LoWPAN compression [RFC6282],
"ALL_MPL_FORWARDERS" from the "Variable Scope Multicast Addresses" "ALL_MPL_FORWARDERS" from the "Variable Scope Multicast Addresses"
sub-registry of the "INTERNET PROTOCOL VERSION 6 MULTICAST ADDRESSES" sub-registry of the "INTERNET PROTOCOL VERSION 6 MULTICAST ADDRESSES"
registry. registry.
14. Security Considerations 14. Security Considerations
MPL uses sequence numbers to maintain a total ordering of MPL Data MPL uses sequence numbers to maintain a total ordering of MPL Data
Messages from an MPL Seed. The use of sequence numbers allows a Messages from an MPL Seed. The use of sequence numbers allows a
denial-of-service attack where an attacker can spoof a message with a denial-of-service attack where an attacker can spoof a message with a
sufficiently large sequence number to: (i) flush messages from the sufficiently large sequence number to: (i) flush messages from the
Buffered Message List and (ii) increase the MinSequence value for an Buffered Message List and (ii) increase the MinSequence value for an
MPL Seed in the Seed Set. The former side effect allows an attacker MPL Seed in the corresponding Seed Set. The former side effect allows
to halt the forwarding process of any MPL Data Messages being an attacker to halt the forwarding process of any MPL Data Messages
disseminated. The latter side effect allows an attacker to prevent being disseminated. The latter side effect allows an attacker to
MPL Forwarders from accepting new MPL Data Messages that an MPL Seed prevent MPL Forwarders from accepting new MPL Data Messages that an
generates while the sequence number is less than MinSequence. MPL Seed generates while the sequence number is less than
MinSequence.
More generally, the basic ability to inject messages into a Low-power More generally, the basic ability to inject messages into a Low-power
and Lossy Network can be used as a denial-of-service attack and Lossy Network can be used as a denial-of-service attack
regardless of what forwarding protocol is used. For these reasons, regardless of what forwarding protocol is used. For these reasons,
Low-power and Lossy Networks typically employ link-layer security Low-power and Lossy Networks typically employ link-layer security
mechanisms to disable an attacker's ability to inject messages. mechanisms to disable an attacker's ability to inject messages.
To prevent attackers from injecting packets through an MPL Forwarder, To prevent attackers from injecting packets through an MPL Forwarder,
the MPL Forwarder MUST NOT accept or forward MPL Data Messages from a the MPL Forwarder MUST NOT accept or forward MPL Data Messages from a
communication interface that does not subscribe to the MPL Domain communication interface that does not subscribe to the MPL Domain
skipping to change at page 28, line 34 skipping to change at page 30, line 34
B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
March 2005. March 2005.
[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.
[RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
September 2011.
[RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R., [RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
Alexander, "RPL: IPv6 Routing Protocol for Low-Power and Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
Lossy Networks", RFC 6550, March 2012. Lossy Networks", RFC 6550, March 2012.
Authors' Addresses Authors' Addresses
Jonathan W. Hui Jonathan W. Hui
Cisco Cisco
170 West Tasman Drive 170 West Tasman Drive
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