--- 1/draft-ietf-roll-trickle-mcast-04.txt 2013-08-29 08:14:22.992428212 -0700 +++ 2/draft-ietf-roll-trickle-mcast-05.txt 2013-08-29 08:14:23.044429531 -0700 @@ -1,116 +1,119 @@ ROLL J. Hui Internet-Draft Cisco Intended status: Standards Track R. Kelsey -Expires: August 29, 2013 Silicon Labs - February 25, 2013 +Expires: March 02, 2014 Silicon Labs + August 29, 2013 Multicast Protocol for Low power and Lossy Networks (MPL) - draft-ietf-roll-trickle-mcast-04 + draft-ietf-roll-trickle-mcast-05 Abstract This document specifies the Multicast Protocol for Low power and Lossy Networks (MPL) that provides IPv6 multicast forwarding in constrained networks. MPL avoids the need to construct or maintain any multicast forwarding topology, disseminating messages to all MPL Forwarders in an MPL Domain. MPL uses the Trickle algorithm to manage message transmissions for both control and data-plane messages. Different Trickle parameter configurations allow MPL to 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 provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on August 29, 2013. + This Internet-Draft will expire on March 02, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 6 - 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 - 4.1. Information Base Overview . . . . . . . . . . . . . . . . 7 - 4.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 4.3. Signaling Overview . . . . . . . . . . . . . . . . . . . . 9 - 5. MPL Parameters and Constants . . . . . . . . . . . . . . . . . 10 - 5.1. MPL Multicast Addresses . . . . . . . . . . . . . . . . . 10 - 5.2. MPL Message Types . . . . . . . . . . . . . . . . . . . . 10 - 5.3. MPL Seed Identifiers . . . . . . . . . . . . . . . . . . . 10 - 5.4. MPL Forwarder Parameters . . . . . . . . . . . . . . . . . 10 - 5.5. MPL Trickle Parameters . . . . . . . . . . . . . . . . . . 11 - 6. Protocol Message Formats . . . . . . . . . . . . . . . . . . . 13 - 6.1. MPL Option . . . . . . . . . . . . . . . . . . . . . . . . 13 - 6.2. MPL Control Message . . . . . . . . . . . . . . . . . . . 14 - 6.3. MPL Seed Info . . . . . . . . . . . . . . . . . . . . . . 15 - 7. Information Base . . . . . . . . . . . . . . . . . . . . . . . 17 - 7.1. Local Interface Set . . . . . . . . . . . . . . . . . . . 17 - 7.2. Domain Set . . . . . . . . . . . . . . . . . . . . . . . . 17 - 7.3. Seed Set . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 7.4. Buffered Message Set . . . . . . . . . . . . . . . . . . . 17 - 8. MPL Domains . . . . . . . . . . . . . . . . . . . . . . . . . 19 - 9. MPL Seed Sequence Numbers . . . . . . . . . . . . . . . . . . 20 - 10. MPL Data Messages . . . . . . . . . . . . . . . . . . . . . . 21 - 10.1. MPL Data Message Generation . . . . . . . . . . . . . . . 21 - 10.2. MPL Data Message Transmission . . . . . . . . . . . . . . 21 - 10.3. MPL Data Message Processing . . . . . . . . . . . . . . . 22 - 11. MPL Control Messages . . . . . . . . . . . . . . . . . . . . . 24 - 11.1. MPL Control Message Generation . . . . . . . . . . . . . . 24 - 11.2. MPL Control Message Transmission . . . . . . . . . . . . . 24 - 11.3. MPL Control Message Processing . . . . . . . . . . . . . . 25 - 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27 - 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 - 13.1. MPL Option Type . . . . . . . . . . . . . . . . . . . . . 28 - 13.2. MPL ICMPv6 Type . . . . . . . . . . . . . . . . . . . . . 28 - 13.3. Well-known Multicast Addresses . . . . . . . . . . . . . . 28 - 14. Security Considerations . . . . . . . . . . . . . . . . . . . 29 - 15. Normative References . . . . . . . . . . . . . . . . . . . . . 30 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 + 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5 + 4.1. MPL Domains . . . . . . . . . . . . . . . . . . . . . . . 5 + 4.2. Information Base Overview . . . . . . . . . . . . . . . . 6 + 4.3. Overview . . . . . . . . . . . . . . . . . . . . . . . . 6 + 4.4. Signaling Overview . . . . . . . . . . . . . . . . . . . 8 + 5. MPL Parameters and Constants . . . . . . . . . . . . . . . . 9 + 5.1. MPL Multicast Addresses . . . . . . . . . . . . . . . . . 9 + 5.2. MPL Message Types . . . . . . . . . . . . . . . . . . . . 9 + 5.3. MPL Seed Identifiers . . . . . . . . . . . . . . . . . . 9 + 5.4. MPL Forwarder Parameters . . . . . . . . . . . . . . . . 9 + 5.5. MPL Trickle Parameters . . . . . . . . . . . . . . . . . 10 + 6. Protocol Message Formats . . . . . . . . . . . . . . . . . . 11 + 6.1. MPL Option . . . . . . . . . . . . . . . . . . . . . . . 11 + 6.2. MPL Control Message . . . . . . . . . . . . . . . . . . . 13 + 6.3. MPL Seed Info . . . . . . . . . . . . . . . . . . . . . . 14 + 7. Information Base . . . . . . . . . . . . . . . . . . . . . . 15 + 7.1. Local Interface Set . . . . . . . . . . . . . . . . . . . 15 + 7.2. Domain Set . . . . . . . . . . . . . . . . . . . . . . . 15 + 7.3. Seed Set . . . . . . . . . . . . . . . . . . . . . . . . 15 + 7.4. Buffered Message Set . . . . . . . . . . . . . . . . . . 16 + 8. MPL Seed Sequence Numbers . . . . . . . . . . . . . . . . . . 16 + 9. MPL Data Messages . . . . . . . . . . . . . . . . . . . . . . 17 + 9.1. MPL Data Message Generation . . . . . . . . . . . . . . . 17 + 9.2. MPL Data Message Transmission . . . . . . . . . . . . . . 17 + 9.3. MPL Data Message Processing . . . . . . . . . . . . . . . 18 + 10. MPL Control Messages . . . . . . . . . . . . . . . . . . . . 19 + 10.1. MPL Control Message Generation . . . . . . . . . . . . . 19 + 10.2. MPL Control Message Transmission . . . . . . . . . . . . 20 + 10.3. MPL Control Message Processing . . . . . . . . . . . . . 20 + 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 + 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 + 12.1. MPL Option Type . . . . . . . . . . . . . . . . . . . . 22 + 12.2. MPL ICMPv6 Type . . . . . . . . . . . . . . . . . . . . 22 + 12.3. Well-known Multicast Addresses . . . . . . . . . . . . . 23 + 13. Security Considerations . . . . . . . . . . . . . . . . . . . 23 + 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 + 14.1. Normative References . . . . . . . . . . . . . . . . . . 23 + 14.2. Informative References . . . . . . . . . . . . . . . . . 24 + + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 1. Introduction Low power and Lossy Networks typically operate with strict resource constraints in communication, computation, memory, and energy. Such resource constraints may preclude the use of existing IPv6 multicast routing and forwarding mechanisms. Traditional IP multicast delivery typically relies on topology maintenance mechanisms to discover and - maintain routes to all subscribers of a multicast group. However, - maintaining such topologies in LLNs is costly and may not be feasible - given the available resources. + maintain routes to all subscribers of a multicast group (e.g. + [RFC3973] [RFC4601]). However, maintaining such topologies in LLNs + is costly and may not be feasible given the available resources. Memory constraints may limit devices to maintaining links/routes to one or a few neighbors. For this reason, the Routing Protocol for LLNs (RPL) specifies both storing and non-storing modes [RFC6550]. The latter allows RPL routers to maintain only one or a few default routes towards a LLN Border Router (LBR) and use source routing to forward messages away from the LBR. For the same reasons, a LLN device may not be able to maintain a multicast routing topology when operating with limited memory. @@ -178,33 +181,75 @@ MPL Seed - An MPL Forwarder that generates MPL Data Messages and serves as an entry point into an MPL Domain. MPL Seed Identifier - An unsigned integer that uniquely identifies an MPL Seed within an MPL Domain. 3. Applicability Statement - This protocol is an IPv6 multicast forwarding protocol for Low-Power - and Lossy Networks. By implementing a controlled dissemination using - the Trickle algorithm, this protocol is designed for networks that - communicate using low-power and lossy links with widely varying - topologies in both the space and time dimensions. + This protocol is an IPv6 multicast forwarding protocol designed for + the communication characteristics and resource constraints of Low- + Power and Lossy Networks. By implementing controlled disseminations + of multicast messages using the Trickle algorithm, this protocol is + designed for networks that communicate using low-power and lossy + links with widely varying topologies in both the space and time + dimensions. + + While designed specifically for Low-Power and Lossy Networks, this + protocol is not limited to use over such networks. This protocol may + be applicable to any network where no multicast routing state is + desired. This protocol may also be used in environments where only a + subset of links are considered Low-Power and Lossy links. + + Operationally, the scope of this protocol is administratively + determined. In other words, the scope of dissemination is determined + by routers configured to disallow transmission or reception of MPL + messages on a subset of interfaces. + + A host need not be aware that their multicast is supported by MPL as + long as its attachment router forwards multicast messages between the + MPL Domain and the host. However, a host may choose to implement MPL + so that it can take advantage of the broadcast medium inherent in + many Low-Power and Lossy Networks and receive multicast messages + carried by MPL directly. 4. Protocol Overview The goal of MPL is to deliver multicast messages to all interfaces that subscribe to the multicast messages' destination address within an MPL Domain. -4.1. Information Base Overview +4.1. MPL Domains + + An MPL Domain is a scope zone, as defined in [RFC4007], in which MPL + Interfaces subscribe to the same MPL Domain Address and participate + in disseminating MPL Data Messages. + + By default, an MPL Forwarder SHOULD participate in an MPL Domain + identified by the ALL_MPL_FORWARDERS multicast address with a scope + value of 3 (Realm-Local) [I-D.droms-6man-multicast-scopes]. When + used with MPL, Realm-Local scope is administratively defined and used + to define the boundaries of multicast message dissemination by MPL. + + An MPL Forwarder MAY participate in additional MPL Domains identified + by other multicast addresses. An MPL Interface MUST subscribe to the + MPL Domain Addresses for the MPL Domains that it participates in. + The assignment of other multicast addresses is out of scope. + + For each MPL Domain Address that an MPL Interface subscribes to, the + 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 + (i.e. when communicating MPL Control Messages). + +4.2. Information Base Overview A node records necessary protocol state in the following information sets: o The Local Interface Set records the set of local MPL Interfaces and the unicast addresses assigned to those MPL Interfaces. o The Domain Set records the set of MPL Domain Addresses and the local MPL Interfaces that subscribe to those addresses. @@ -219,21 +264,21 @@ o A Buffered Message Set records recently received MPL Data Messages 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 or equal to the minimum threshold maintained in the corresponding Seed Set. MPL uses Buffered Message Sets to store MPL Data Messages that may be transmitted by the MPL Forwarder for forwarding. -4.2. Overview +4.3. Overview MPL achieves its goal by implementing a controlled flood that attempts to disseminate the multicast data message to all interfaces within an MPL Domain. MPL performs the following tasks to disseminate a multicast message: o When having a multicast message to forward into an MPL Domain, the 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 @@ -280,21 +325,29 @@ proactive forwarding for the MPL Data Message message. Reactive Forwarding - With reactive forwarding, an MPL Forwarder link-local multicasts MPL Control Messages using the Trickle algorithm [RFC6206]. MPL Forwarders use MPL Control Messages to discover new MPL Data Messages that have not yet been received. When discovering that a neighboring MPL Forwarder has not yet received an MPL Data Message, the MPL Forwarder schedules those MPL Data Messages for transmission using the Trickle algorithm. -4.3. Signaling Overview + Note that the use of proactive and reactive forwarding strategies + within the same MPL Domain are not mutually exclusive and may be used + simultaneously. For example, upon receiving a new MPL Data messages + when both proactive and reactive forwarding techniques are enabled, + an MPL Forwarder will proactively retransmit the MPL Data Message a + limited number of times and schedule further transmissions upon + receiving MPL Control Messages. + +4.4. Signaling Overview This protocol generates and processes the following messages: 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 address in the Local Interface Set of the MPL Seed that generated the message and is valid within the MPL Domain. The MPL Data Message's destination is the MPL Domain Address corresponding to the MPL Domain. An MPL Data Message contains: @@ -324,22 +377,22 @@ 5. MPL Parameters and Constants This section describes various program and networking parameters and constants used by MPL. 5.1. MPL Multicast Addresses MPL makes use of MPL Domain Addresses to identify MPL Interfaces of an MPL Domain. By default, MPL Forwarders subscribe to the - ALL_MPL_FORWARDERS multicast address with a scope value of 3 (subnet- - local). + ALL_MPL_FORWARDERS multicast address with a scope value of 3 + [I-D.droms-6man-multicast-scopes]. For each MPL Domain Address that an MPL Interface subscribes to, the MPL Interface MUST also subscribe to the MPL Domain Address with a scope value of 2 (link-local) when reactive forwarding is in use. MPL Forwarders use the link-scoped MPL Domain Address to communicate MPL Control Messages to neighboring (i.e. on-link) MPL Forwarders. 5.2. MPL Message Types MPL defines an IPv6 Option for carrying an MPL Seed Identifier and a @@ -380,41 +433,41 @@ 5.5. MPL Trickle Parameters As specified in [RFC6206], a Trickle timer runs for a defined interval and has three configuration parameters: the minimum interval size Imin, the maximum interval size Imax, and a redundancy constant k. This specification defines a fourth Trickle configuration parameter, TimerExpirations, which indicates the number of Trickle timer - expiration events that occur before terminating the Trickle - algorithm. + expiration events that occur before terminating the Trickle algorithm + for a given MPL Data Message or MPL Control Message. Each MPL Forwarder uses the following Trickle parameters for MPL Data Message and MPL Control Message transmissions. DATA_MESSAGE_IMIN The minimum Trickle timer interval, as defined in [RFC6206], for MPL Data Message transmissions. DATA_MESSAGE_IMIN - has a default value of 10 times the worst-case link-layer latency. + has a default value of 10 times the expected link-layer latency. DATA MESSAGE_IMAX The maximum Trickle timer interval, as defined in [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 MPL Data Message transmissions. DATA_MESSAGE_K has a default - value of 5. + value of 1. DATA_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer - expirations that occur before terminating the Trickle algorithm - for MPL Data Message transmissions. + expirations that occur before terminating the Trickle algorithm's + retransmission of a given MPL Data Message. DATA_MESSAGE_TIMER_EXPIRATIONS has a default value of 3. CONTROL_MESSAGE_IMIN The minimum Trickle timer interval, as defined 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 in [RFC6206], for MPL Control Message transmissions. CONTROL_MESSAGE_IMAX has a default value of 5 minutes. @@ -426,20 +479,31 @@ CONTROL_MESSAGE_TIMER_EXPIRATIONS The number of Trickle timer expirations that occur before terminating the Trickle algorithm for MPL Control Message transmissions. CONTROL_MESSAGE_TIMER_EXPIRATIONS has a default value of 10. Following [RFC6206], it is RECOMMENDED that all MPL Forwarders use the same values for the Trickle Parameters above for a given MPL Domain. The mechanism for setting the Trickle Parameters is not specified within this document. + The default Trickle parameter values above combined with the default + MPL Forwarder parameters in the prior section specify a forwarding + strategy that utilizes both proactive and reactive techniques. Using + these default values, an MPL Forwarder proactively transmits any new + MPL Data Messages it receives then uses MPL Control Messages to + trigger additional MPL Data Message retransmissions where message + drops are detected. Setting DATA_MESSAGE_IMAX to the same as + DATA_MESSAGE_IMIN in this case is acceptable since subsequent MPL + Data Message retransmissions are triggered by MPL Control Messages, + where CONTROL_MESSAGE_IMAX is greater than CONTROL_MESSAGE_IMIN. + 6. Protocol Message Formats The protocol messages generated and processed by an MPL Forwarder are described in this section. 6.1. MPL Option The MPL Option is carried in MPL Data Messages in an IPv6 Hop-by-Hop Options header, immediately following the IPv6 header. The MPL Option has the following format: @@ -450,26 +514,26 @@ | Option Type | Opt Data Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | S |M|V| rsv | sequence | seed-id (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option Type MPL_OPT_TYPE Opt Data Len Length of the Option Data field in octets. S 2-bit unsigned integer. Identifies the length of - seed-id. 0 indicates that the seed-id is the IPv6 - Source Address and not included in the MPL + seed-id. 0 indicates that the seed-id is the + IPv6 Source Address and not included in the MPL Option. 1 indicates that the seed-id is a 16-bit - unsigned integer. 2 indicates that the seed-id is - a 64-bit unsigned integer. 3 indicates that the - seed-id is a 128-bit unsigned integer. + unsigned integer. 2 indicates that the seed-id + is a 64-bit unsigned integer. 3 indicates that + the seed-id is a 128-bit unsigned integer. M 1-bit flag. 1 indicates that the value in sequence is known to be the largest sequence number that was received from the MPL Seed. V 1-bit flag. 0 indicates that the MPL Option conforms to this specification. MPL Data Messages with an MPL Option in which this flag is 1 MUST be dropped. @@ -512,21 +576,21 @@ contained in an MPL Domain's Seed Set and Buffered Message Set to neighboring MPL Forwarders. The MPL Control Message has the following format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | - . MPL Seed Info[1..n] . + . MPL Seed Info[0..n] . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IP Fields: Source Address An IPv6 address in the AddressSet of the corresponding MPL Interface and MUST be valid within the MPL Domain. Destination Address The link-scoped MPL Domain Address corresponding @@ -571,25 +634,25 @@ min-seqno 8-bit unsigned integer. The lower-bound sequence number for the MPL Seed. bm-len 6-bit unsigned integer. The size of buffered- mpl-messages in octets. S 2-bit unsigned integer. Identifies the length of seed-id. 0 indicates that the seed-id value is the IPv6 Source Address and not included in the - MPL Seed Info. 1 indicates that the seed-id value - is a 16-bit unsigned integer. 2 indicates that - the seed-id value is a 64-bit unsigned integer. 3 - indicates that the seed-id is a 128-bit unsigned - integer. + MPL Seed Info. 1 indicates that the seed-id + value is a 16-bit unsigned integer. 2 indicates + that the seed-id value is a 64-bit unsigned + integer. 3 indicates that the seed-id is a + 128-bit unsigned integer. seed-id Variable-length unsigned integer. Indicates the MPL Seed associated with this MPL Seed Info. buffered-mpl-messages Variable-length bit vector. Identifies the sequence numbers of MPL Data Messages maintained in the corresponding Buffered Message Set for the MPL Seed. The i'th bit represents a sequence number of min-seqno + i. '0' indicates that the corresponding MPL Data Message does not exist in @@ -656,86 +719,66 @@ DataMessage - the MPL Data Message. All MPL Data Messages within a Buffered Message Set MUST have a sequence number greater than or equal to MinSequence for the corresponding SeedID. When increasing MinSequence for an MPL Seed, the MPL Forwarder MUST delete any MPL Data Messages from the corresponding Buffered Message Set that have sequence numbers less than MinSequence. -8. MPL Domains - - An MPL Domain is a scope zone, as defined in [RFC4007], in which MPL - Interfaces subscribe to the same MPL Domain Address and participate - in disseminating MPL Data Messages. - - By default, an MPL Forwarder SHOULD participate in an MPL Domain - identified by the ALL_MPL_FORWARDERS multicast address with a scope - value of 3 (subnet-local). - - An MPL Forwarder MAY participate in additional MPL Domains identified - by other multicast addresses. An MPL Interface MUST subscribe to the - MPL Domain Addresses for the MPL Domains that it participates in. - The assignment of other multicast addresses is out of scope. - - For each MPL Domain Address that an MPL Interface subscribes to, the - 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 - (i.e. when communicating MPL Control Messages). - -9. MPL Seed Sequence Numbers +8. MPL Seed Sequence Numbers Each MPL Seed maintains a sequence number for each MPL Domain that it serves. The sequence numbers are included in MPL Data Messages generated by the MPL Seed. The MPL Seed MUST increment the sequence number for each MPL Data Message that it generates for an MPL Domain. Implementations MUST follow the Serial Number Arithmetic as defined in [RFC1982] when incrementing a sequence value or comparing two sequence values. This sequence number is used to establish a total ordering of MPL Data Messages generated by an MPL Seed for an MPL Domain. -10. MPL Data Messages +9. MPL Data Messages -10.1. MPL Data Message Generation +9.1. MPL Data Message Generation MPL Data Messages are generated by MPL Seeds when these messages 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 corresponding MPL Interface and MUST be valid within the MPL Domain. o The IPv6 Destination Address MUST be set to the MPL Domain Address corresponding to the MPL Domain. 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 ordering relative to other MPL Data Messages generated by the MPL Seed. - When the source address is in the AddressList of an MPL Interface - corresponding to the MPL Domain Address and the destination address - is the MPL Domain Address, the application message and the MPL Data + When the destination address is an MPL Domain Address and the source + address is in the AddressLIst of an MPL Interface that belongs to + that MPL Domain Address, the application message and the MPL Data Message MAY be identical. In other words, the MPL Data Message may contain a single IPv6 header that includes the MPL Option. Otherwise, IPv6-in-IPv6 encapsulation MUST be used to satisfy the MPL - Data Message requirements listed above [RFC2473]. The complete IPv6- - in-IPv6 message forms an MPL Data Message. The outer IPv6 header + Data Message requirements listed above [RFC2473]. The complete IPv6 + -in-IPv6 message forms an MPL Data Message. The outer IPv6 header conforms to the MPL Data Message requirements listed above. The encapsulated IPv6 datagram encodes the multicast data message that is communicated beyond the MPL Domain. -10.2. MPL Data Message Transmission +9.2. MPL Data Message Transmission An MPL Forwarder manages transmission of MPL Data Messages in its Buffered Message Sets using the Trickle algorithm [RFC6206]. An MPL Forwarder MUST use a separate Trickle timer for each MPL Data Message that it is actively forwarding. In accordance with Section 5 of RFC 6206 [RFC6206], this document defines the following: o This document defines a "consistent" transmission as receiving an MPL Data Message that has the same MPL Domain Address, seed-id, and sequence value as the MPL Data Message managed by the Trickle @@ -766,21 +809,21 @@ MAY delete the message from the Buffered Message Set by advancing MinSequence of the corresponding MPL Seed in the Seed Set. When the MPL Forwarder no longer buffers any messages for an MPL Seed, the MPL Forwarder MUST NOT increment MinSequence for that MPL Seed. When transmitting an MPL Data Message, the MPL Forwarder MUST either set the M flag to zero or set it to a level that indicates whether or not the message's sequence number is the largest value that has been received from the MPL Seed. -10.3. MPL Data Message Processing +9.3. MPL Data Message Processing Upon receiving an MPL Data Message, the MPL Forwarder first processes the MPL Option and updates the Trickle timer associated with the MPL Data Message if one exists. Upon receiving an MPL Data Message, an MPL Forwarder MUST perform one of the following actions: o Accept the message and enter the MPL Data Message in the MPL Domain's Buffered Message Set. @@ -819,23 +862,23 @@ 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 CONTROL_MESSAGE_TIMER_EXPIRATIONS is non-zero, the MPL Forwarder MUST initialize and start the MPL Control Message Trickle timer. o If the MPL Control Message Trickle timer is running, the MPL Forwarder MUST reset the MPL Control Message Trickle timer. -11. MPL Control Messages +10. MPL Control Messages -11.1. MPL Control Message Generation +10.1. MPL Control Message Generation An MPL Forwarder generates MPL Control Messages to communicate an MPL Domain's Seed Set and Buffered Message Set to neighboring MPL Forwarders. Each MPL Control Message is generated according to Section 6.2, with an MPL Seed Info for each entry in the MPL Domain's 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 min-seqno set to MinSequence of the MPL Seed. @@ -845,52 +888,54 @@ o seed-id set to the MPL seed identifier. o buffered-mpl-messages with each bit representing whether or not an MPL Data Message with the corresponding sequence number exists in the Buffered Message Set. The i'th bit represents a sequence number of min-seqno + i. '0' indicates that the 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. -11.2. MPL Control Message Transmission +10.2. MPL Control Message Transmission An MPL Forwarder transmits MPL Control Messages using the Trickle algorithm. An MPL Forwarder maintains a single Trickle timer for each MPL Domain. When CONTROL_MESSAGE_TIMER_EXPIRATIONS is 0, the MPL Forwarder does not execute the Trickle algorithm and does not transmit MPL Control Messages. In accordance with Section 5 of RFC 6206 [RFC6206], this document defines the following: o This document defines a "consistent" transmission as receiving an - MPL Control Message that indicates neither the receiving nor - transmitting node has any new MPL Data Messages to offer. + MPL Control Message that results in a determination that neither + the receiving nor transmitting node has any new MPL Data Messages + to offer. o This document defines an "inconsistent" transmission as receiving - an MPL Control Message that indicates either the receiving or - transmitting node has at least one new MPL Data Message to offer. + an MPL Control Message that results in a determination that either + the receiving or transmitting node has at least one new MPL Data + Message to offer. - o This document defines an "event" as increasing MinSequence of any - entry in the corresponding Seed Set or adding a message to the + o The Trickle timer is reset in response to external "events." This + document defines an "event" as increasing MinSequence of any entry + in the corresponding Seed Set or adding a message to the corresponding Buffered Message Set. o This document defines an MPL Control Message as a Trickle message. As specified in [RFC6206], a Trickle timer has three variables: the 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 of Trickle timer expiration events since the Trickle timer was last reset. After CONTROL_MESSAGE_TIMER_EXPIRATIONS Trickle timer events, the MPL Forwarder MUST disable the Trickle timer. -11.3. MPL Control Message Processing - +10.3. MPL Control Message Processing 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. An MPL Forwarder determines if a new MPL Data Message has not been received from a neighboring node if any of the following conditions hold true: o The MPL Control Message includes an MPL Seed that does not exist in the MPL Domain's Seed Set. @@ -922,121 +967,128 @@ When an MPL Forwarder determines that it has at least one MPL Data Message in its corresponding Buffered Message Set that has not yet been received by a neighbor, the MPL Forwarder MUST reset the MPL Control Message Trickle timer. Additionally, for each of those entries in the Buffered Message Set, the MPL Forwarder MUST reset the Trickle timer and reset e to 0. If a Trickle timer is not associated with the MPL Data Message, the MPL Forwarder MUST initialize and start a new Trickle timer. -12. Acknowledgements - +11. Acknowledgements The authors would like to acknowledge the helpful comments of Robert - Cragie, Esko Dijk, Ralph Droms, Paul Duffy, Ulrich Herberg, Owen - Kirby, Joseph Reddy, Don Sturek, Dario Tedeschi, and Peter van der - Stok, which greatly improved the document. + Cragie, Esko Dijk, Ralph Droms, Paul Duffy, Adrian Farrel, Ulrich + Herberg, Owen Kirby, Kerry Lynn, Joseph Reddy, Michael Richardson, + Don Sturek, Dario Tedeschi, and Peter van der Stok, which greatly + improved the document. -13. IANA Considerations +12. IANA Considerations This document defines one IPv6 Option, a type that must be allocated from the IPv6 "Destination Options and Hop-by-Hop Options" registry of [RFC2780]. This document defines one ICMPv6 Message, a type that must be allocated from the "ICMPv6 "type" Numbers" registry of [RFC4443]. This document registers two well-known multicast addresses from the IPv6 multicast address space. -13.1. MPL Option Type +12.1. MPL Option Type IANA is requested to allocate an IPv6 Option Type from the IPv6 "Destination Options and Hop-by-Hop Options" registry of [RFC2780], as specified in Table 1 below: - +--------------+-----+-----+--------------+-------------+-----------+ + +--------------+-------+-----+------------+-------------+-----------+ | Mnemonic | act | chg | rest | Description | Reference | - +--------------+-----+-----+--------------+-------------+-----------+ + +--------------+-------+-----+------------+-------------+-----------+ | MPL_OPT_TYPE | 01 | 1 | TBD | MPL Option | This | | | | | (suggested | | Document | - | | | | value 01101) | | | - +--------------+-----+-----+--------------+-------------+-----------+ + | | | | value | | | + | | | | 01101) | | | + +--------------+-------+-----+------------+-------------+-----------+ Table 1: IPv6 Option Type Allocation -13.2. MPL ICMPv6 Type +12.2. MPL ICMPv6 Type IANA is requested to allocate an ICMPv6 Type from the "ICMPv6 "type" Numbers" registry of [RFC4443], as specified in Table 2 below: +---------------+------+---------------------+---------------+ | Mnemonic | Type | Name | Reference | +---------------+------+---------------------+---------------+ | MPL_ICMP_TYPE | TBD | MPL Control Message | This Document | +---------------+------+---------------------+---------------+ Table 2: IPv6 Option Type Allocation -13.3. Well-known Multicast Addresses +12.3. Well-known Multicast Addresses 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" sub-registry of the "INTERNET PROTOCOL VERSION 6 MULTICAST ADDRESSES" registry. -14. Security Considerations +13. Security Considerations MPL uses sequence numbers to maintain a total ordering of MPL Data 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 sufficiently large sequence number to: (i) flush messages from the Buffered Message List and (ii) increase the MinSequence value for an - MPL Seed in the corresponding Seed Set. The former side effect allows - an attacker to halt the forwarding process of any MPL Data Messages - being disseminated. The latter side effect allows an attacker to - prevent MPL Forwarders from accepting new MPL Data Messages that an - MPL Seed generates while the sequence number is less than - MinSequence. + MPL Seed in the corresponding Seed Set. The former side effect + allows an attacker to halt the forwarding process of any MPL Data + Messages being disseminated. The latter side effect allows an + attacker to prevent MPL Forwarders from accepting new MPL Data + Messages that an MPL Seed generates while the sequence number is less + than MinSequence. More generally, the basic ability to inject messages into a Low-power and Lossy Network can be used as a denial-of-service attack regardless of what forwarding protocol is used. For these reasons, Low-power and Lossy Networks typically employ link-layer security mechanisms to disable an attacker's ability to inject messages. To prevent attackers from injecting packets through an MPL Forwarder, the MPL Forwarder MUST NOT accept or forward MPL Data Messages from a communication interface that does not subscribe to the MPL Domain Address identified in message's destination address. MPL uses the Trickle algorithm to manage message transmissions and the security considerations described in [RFC6206] apply. -15. Normative References +14. References + +14.1. Normative References + + [I-D.droms-6man-multicast-scopes] + Droms, R., "IPv6 Multicast Address Scopes", draft-droms- + 6man-multicast-scopes-02 (work in progress), July 2013. [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, August 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, December 1998. [RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For - Values In the Internet Protocol and Related Headers", - BCP 37, RFC 2780, March 2000. + Values In the Internet Protocol and Related Headers", BCP + 37, RFC 2780, March 2000. [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, March 2005. [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", RFC 4443, March 2006. [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, @@ -1044,20 +1096,30 @@ [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., 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. +14.2. Informative References + + [RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol + Independent Multicast - Dense Mode (PIM-DM): Protocol + Specification (Revised)", RFC 3973, January 2005. + + [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, + "Protocol Independent Multicast - Sparse Mode (PIM-SM): + Protocol Specification (Revised)", RFC 4601, August 2006. + Authors' Addresses Jonathan W. Hui Cisco 170 West Tasman Drive San Jose, California 95134 USA Phone: +408 424 1547 Email: jonhui@cisco.com