draft-ietf-softwire-mesh-multicast-25.txt   rfc8638.txt 
Softwire WG M. Xu Internet Engineering Task Force (IETF) M. Xu
Internet-Draft Y. Cui Request for Comments: 8638 Y. Cui
Intended status: Standards Track J. Wu Category: Standards Track J. Wu
Expires: December 10, 2019 Tsinghua University ISSN: 2070-1721 Tsinghua University
S. Yang S. Yang
Shenzhen University Shenzhen University
C. Metz C. Metz
Cisco Systems Cisco Systems
June 8, 2019 September 2019
IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Networks
draft-ietf-softwire-mesh-multicast-25
Abstract Abstract
During the transition to IPv6, there will be scenarios where a During the transition to IPv6, there are scenarios where a backbone
backbone network internally running one IP address family (referred network internally running one IP address family (referred to as the
to as the internal IP or I-IP family), connects client networks internal IP or I-IP family) connects client networks running another
running another IP address family (referred to as the external IP or IP address family (referred to as the external IP or E-IP family).
E-IP family). In such cases, the I-IP backbone needs to offer both In such cases, the I-IP backbone needs to offer both unicast and
unicast and multicast transit services to the client E-IP networks. multicast transit services to the client E-IP networks.
This document describes a mechanism for supporting multicast across This document describes a mechanism for supporting multicast across
backbone networks where the I-IP and E-IP protocol families differ. backbone networks where the I-IP and E-IP protocol families differ.
The document focuses on IPv4-over-IPv6 scenario, due to lack of real- The document focuses on the IPv4-over-IPv6 scenario, due to lack of
world use cases for IPv6-over-IPv4 scenario. real-world use cases for the IPv6-over-IPv4 scenario.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on December 10, 2019. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8638.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 27 skipping to change at page 2, line 27
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Mesh Multicast Mechanism . . . . . . . . . . . . . . . . . . 7 5. Mesh Multicast Mechanism . . . . . . . . . . . . . . . . . . 7
5.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 8 5.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 7
5.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 8 5.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 7
5.3. Source Address Mapping . . . . . . . . . . . . . . . . . 9 5.3. Source Address Mapping . . . . . . . . . . . . . . . . . 8
5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9 5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9
6. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10 6. Control-Plane Functions of AFBR . . . . . . . . . . . . . . . 10
6.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10 6.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10
6.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10 6.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10
6.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 11 6.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 10
6.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 11 6.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 10
6.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13 6.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13
6.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13 6.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13
6.7. Other PIM States Maintenance . . . . . . . . . . . . . . 13 6.7. Maintenance of Other PIM States . . . . . . . . . . . . . 13
7. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 14 7. Data-Plane Functions of the AFBR . . . . . . . . . . . . . . 13
7.1. Process and Forward Multicast Data . . . . . . . . . . . 14 7.1. Process and Forward Multicast Data . . . . . . . . . . . 13
7.2. TTL or Hop Count . . . . . . . . . . . . . . . . . . . . 14 7.2. TTL or Hop Count . . . . . . . . . . . . . . . . . . . . 14
7.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14 7.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14
8. Packet Format and Translation . . . . . . . . . . . . . . . . 14 8. Packet Format and Translation . . . . . . . . . . . . . . . . 14
9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 15 9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 16
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16 10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
12. Normative References . . . . . . . . . . . . . . . . . . . . 16 12. Normative References . . . . . . . . . . . . . . . . . . . . 16
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 18 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
During the transition to IPv6, there will be scenarios where a During the transition to IPv6, there are scenarios where a backbone
backbone network internally running one IP address family (referred network internally running one IP address family (referred to as the
to as the internal IP or I-IP family), connects client networks internal IP or I-IP family) connects client networks running another
running another IP address family (referred to as the external IP or IP address family (referred to as the external IP or E-IP family).
E-IP family).
One solution is to leverage the multicast functions inherent in the One solution is to leverage the multicast functions inherent in the
I-IP backbone to efficiently forward client E-IP multicast packets I-IP backbone to efficiently forward client E-IP multicast packets
inside an I-IP core tree. The I-IP tree is rooted at one or more inside an I-IP core tree. The I-IP tree is rooted at one or more
ingress Address Family Border Routers (AFBRs) [RFC5565] and branches ingress Address Family Border Routers (AFBRs) [RFC5565] and branches
out to one or more egress AFBRs. out to one or more egress AFBRs.
[RFC4925] outlines the requirements for the softwire mesh scenario [RFC4925] outlines the requirements for the softwire mesh scenario
and includes support for multicast traffic. It is likely that client and includes support for multicast traffic. It is likely that client
E-IP multicast sources and receivers will reside in different client E-IP multicast sources and receivers will reside in different client
E-IP networks connected to an I-IP backbone network. This requires E-IP networks connected to an I-IP backbone network. This requires
the client E-IP source-rooted or shared tree to traverse the I-IP the source-rooted or shared tree of the client E-IP to traverse the
backbone network. I-IP backbone network.
This could be accomplished by re-using the multicast VPN approach This could be accomplished by reusing the multicast VPN (MVPN)
outlined in [RFC6513]. MVPN-like schemes can support the softwire approach outlined in [RFC6513]. MVPN-like schemes can support the
mesh scenario and achieve a "many-to-one" mapping between the E-IP softwire mesh scenario and achieve a "many-to-one" mapping between
client multicast trees and the transit core multicast trees. The the E-IP client multicast trees and the transit-core multicast trees.
advantage of this approach is that the number of trees in the I-IP The advantage of this approach is that the number of trees in the
backbone network scales less than linearly with the number of E-IP I-IP backbone network scales less than linearly with the number of
client trees. Corporate enterprise networks, and by extension E-IP client trees. Corporate enterprise networks, and by extension
multicast VPNs, have been known to run applications that create too multicast VPNs, have been known to run applications that create too
many (S,G) states, which is source specific states related with a many (S,G) states, which are source-specific states related to a
specified multicast group [RFC7761][RFC7899]. Aggregation at the specified multicast group [RFC7761] [RFC7899]. Aggregation at the
edge contains the (S,G) states for customer's VPNs and these need to edge contains the (S,G) states for customers' VPNs and these need to
be maintained by the network operator. The disadvantage of this be maintained by the network operator. The disadvantage of this
approach is the possibility of inefficient bandwidth and resource approach is the possibility of inefficient bandwidth and resource
utilization when multicast packets are delivered to a receiving AFBR utilization when multicast packets are delivered to a receiving AFBR
with no attached E-IP receivers. with no attached E-IP receivers.
[RFC8114] provides a solution for delivering IPv4 multicast services [RFC8114] provides a solution for delivering IPv4 multicast services
over an IPv6 network. But it mainly focuses on the DS-lite [RFC6333] over an IPv6 network, but it mainly focuses on the DS-Lite scenario
scenario, where IPv4 addresses assigned by a broadband service [RFC6333], where IPv4 addresses assigned by a broadband service
provider are shared among customers. This document describes a provider are shared among customers. This document describes a
detailed solution for the IPv4-over-IPv6 softwire mesh scenario, detailed solution for the IPv4-over-IPv6 softwire mesh scenario,
where client networks run IPv4 and the backbone network runs IPv6. where client networks run IPv4 and the backbone network runs IPv6.
Internet-style multicast is somewhat different to the [RFC8114] Internet-style multicast is somewhat different from the scenario in
scenario in that the trees are source-rooted and relatively sparse. [RFC8114] in that the trees are source-rooted and relatively sparse.
The need for multicast aggregation at the edge (where many customer The need for multicast aggregation at the edge (where many customer
multicast trees are mapped into one or more backbone multicast trees) multicast trees are mapped to one or more backbone multicast trees)
does not exist and to date has not been identified. Thus the need does not exist and to date has not been identified. Thus, the need
for alignment between the E-IP and I-IP multicast mechanisms emerges. for alignment between the E-IP and I-IP multicast mechanisms emerges.
[RFC5565] describes the "Softwire Mesh Framework". This document [RFC5565] describes the "Softwire Mesh Framework". This document
provides a more detailed description of how one-to-one mapping provides a more detailed description of how one-to-one mapping
schemes ([RFC5565], Section 11.1) for IPv4-over-IPv6 multicast can be schemes ([RFC5565], Section 11.1) for IPv4-over-IPv6 multicast can be
achieved. achieved.
Figure 1 shows an example of how a softwire mesh network can support Figure 1 shows an example of how a softwire mesh network can support
multicast traffic. A multicast source S is located in one E-IP multicast traffic. A multicast source S is located in one E-IP
client network, while candidate E-IP group receivers are located in client network, while candidate E-IP group receivers are located in
the same or different E-IP client networks that all share a common the same or different E-IP client networks that all share a common
I-IP transit network. When E-IP sources and receivers are not local I-IP transit network. When E-IP sources and receivers are not local
to each other, they can only communicate with each other through the to each other, they can only communicate with each other through the
I-IP core. There may be several E-IP sources for a single multicast I-IP core. There may be several E-IP sources for a single multicast
group residing in different client E-IP networks. In the case of group residing in different client E-IP networks. In the case of
shared trees, the E-IP sources, receivers and rendezvous points (RPs) shared trees, the E-IP sources, receivers, and rendezvous points
might be located in different client E-IP networks. In the simplest (RPs) might be located in different client E-IP networks. In the
case, a single operator manages the resources of the I-IP core, simplest case, a single operator manages the resources of the I-IP
although the inter-operator case is also possible and so not core, although the inter-operator case is also possible and so not
precluded. precluded.
+---------+ +---------+ +---------+ +---------+
| | | | +--------+ | | | | +--------+
| E-IP | | E-IP +--+Source S| | E-IP | | E-IP +--+Source S|
| network | | network | +--------+ | network | | network | +--------+
+---+-----+ +--+------+ +---+-----+ +--+------+
| | | |
+-+--------+ +-------+--+ +-+--------+ +-------+--+
| | | upstream | | | | upstream |
+-| AFBR +--+ AFBR |-+ +-| AFBR +--+ AFBR |-+
| +----------+ +----------+ | | +----------+ +----------+ |
| | E-IP Multicast | | E-IP multicast
| I-IP transit core | packets are forwarded | I-IP transit core | packets are forwarded
| | across the I-IP | | across the I-IP
| +----------+ +----------+ | transit core | +----------+ +----------+ | transit core
+-|dowstream | |downstream|-+ +-|downstream| |downstream|-+
| AFBR |--| AFBR | | AFBR |--| AFBR |
+--+-------+ +--------+-+ +--+-------+ +--------+-+
| | | |
+---+----+ +---+----+ +---+----+ +---+----+
+--------+ | | | | +--------+ +--------+ | | | | +--------+
|Receiver+---+ E-IP | | E-IP +--+Receiver| |Receiver+---+ E-IP | | E-IP +--+Receiver|
+--------+ |network | |network | +--------+ +--------+ |network | |network | +--------+
+--------+ +--------+ +--------+ +--------+
Figure 1: Softwire Mesh Multicast Framework Figure 1: Softwire Mesh Multicast Framework
2. Requirements Language 2. Requirements Language
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 BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Terminology 3. Terminology
Terminology used in this document: The following terminology is used in this document.
o Address Family Border Router (AFBR) - A router interconnecting two o Address Family Border Router (AFBR) - A router interconnecting two
or more networks using different IP address families. Additionally, or more networks using different IP address families.
in the context of softwire mesh multicast, the AFBR runs E-IP and Additionally, in the context of softwire mesh multicast, the AFBR
I-IP control planes to maintain E-IP and I-IP multicast states runs E-IP and I-IP control planes to maintain E-IP and I-IP
respectively and performs the appropriate encapsulation/decapsulation multicast states respectively and performs the appropriate
of client E-IP multicast packets for transport across the I-IP core. encapsulation/decapsulation of client E-IP multicast packets for
An AFBR will act as a source and/or receiver in an I-IP multicast transport across the I-IP core. An AFBR will act as a source and/
tree. or receiver in an I-IP multicast tree.
o Upstream AFBR: An AFBR that is closer to the source of a multicast o Upstream AFBR: An AFBR that is closer to the source of a multicast
data flow. data flow.
o Downstream AFBR: An AFBR that is closer to a receiver of a o Downstream AFBR: An AFBR that is closer to a receiver of a
multicast data flow. multicast data flow.
o I-IP (Internal IP): This refers to IP address family that is o I-IP (Internal IP): This refers to the IP address family that is
supported by the core network. In this document, the I-IP is IPv6. supported by the core network. In this document, the I-IP is
IPv6.
o E-IP (External IP): This refers to the IP address family that is o E-IP (External IP): This refers to the IP address family that is
supported by the client network(s) attached to the I-IP transit core. supported by the client network(s) attached to the I-IP transit
In this document, the E-IP is IPv4. core. In this document, the E-IP is IPv4.
o I-IP core tree: A distribution tree rooted at one or more AFBR o I-IP core tree: A distribution tree rooted at one or more AFBR
source nodes and branched out to one or more AFBR leaf nodes. An source nodes and branched out to one or more AFBR leaf nodes. An
I-IP core tree is built using standard IP or MPLS multicast signaling I-IP core tree is built using standard IP or MPLS multicast
protocols (in this document, we focus on IP multicast) operating signaling protocols (in this document, we focus on IP multicast)
exclusively inside the I-IP core network. An I-IP core tree is used operating exclusively inside the I-IP core network. An I-IP core
to forward E-IP multicast packets belonging to E-IP trees across the tree is used to forward E-IP multicast packets belonging to E-IP
I-IP core. Another name for an I-IP core tree is multicast or trees across the I-IP core. Another name for an I-IP core tree is
multipoint softwire. multicast or multipoint softwire.
o E-IP client tree: A distribution tree rooted at one or more hosts o E-IP client tree: A distribution tree rooted at one or more hosts
or routers located inside a client E-IP network and branched out to or routers located inside a client E-IP network and branched out
one or more leaf nodes located in the same or different client E-IP to one or more leaf nodes located in the same or different client
networks. E-IP networks.
o uPrefix64: The /96 unicast IPv6 prefix for constructing an o uPrefix64: The /96 unicast IPv6 prefix for constructing an
IPv4-embedded IPv6 unicast address [RFC8114]. IPv4-embedded IPv6 unicast address [RFC8114].
o mPrefix64: The /96 multicast IPv6 prefix for constructing an o mPrefix64: The /96 multicast IPv6 prefix for constructing an
IPv4-embedded IPv6 multicast address [RFC8114]. IPv4-embedded IPv6 multicast address [RFC8114].
o PIMv4, PIMv6: refer to [RFC8114]. o PIMv4, PIMv6: Refer to [RFC8114].
o Inter-AFBR signaling: A mechanism used by downstream AFBRs to send o Inter-AFBR signaling: A mechanism used by downstream AFBRs to send
PIMv6 messages to the upstream AFBR. PIMv6 messages to the upstream AFBR.
4. Scope 4. Scope
This document focuses on the IPv4-over-IPv6 scenario, as shown in the This document focuses on the IPv4-over-IPv6 scenario, as shown in the
following diagram: following diagram.
+---------+ +---------+ +---------+ +---------+
| IPv4 | | IPv4 | +--------+ | IPv4 | | IPv4 | +--------+
| Client | | Client |--+Source S| | Client | | Client |--+Source S|
| Network | | Network | +--------+ | Network | | Network | +--------+
+----+----+ +----+----+ +----+----+ +----+----+
| | | |
+--+-------+ +-------+--+ +--+-------+ +-------+--+
| | | Upstream | | | | Upstream |
+-+ AFBR +--+ AFBR |-+ +-+ AFBR +--+ AFBR |-+
skipping to change at page 7, line 31 skipping to change at page 6, line 47
+--+-------+ +-------+--+ +--+-------+ +-------+--+
| | | |
+----+----+ +----+----+ +----+----+ +----+----+
+--------+ | IPv4 | | IPv4 | +--------+ +--------+ | IPv4 | | IPv4 | +--------+
|Receiver+--+ Client | | Client +--+Receiver| |Receiver+--+ Client | | Client +--+Receiver|
+--------+ | Network | | Network | +--------+ +--------+ | Network | | Network | +--------+
+---------+ +---------+ +---------+ +---------+
Figure 2: IPv4-over-IPv6 Scenario Figure 2: IPv4-over-IPv6 Scenario
In Figure 2, the E-IP client networks run IPv4 and the I-IP core runs In Figure 2, the E-IP client networks run IPv4, and the I-IP core
IPv6. runs IPv6.
Because of the much larger IPv6 group address space, the client E-IP Because of the much larger IPv6 group address space, the client E-IP
tree can be mapped to a specific I-IP core tree. This simplifies tree can be mapped to a specific I-IP core tree. This simplifies
operations on the AFBR because it becomes possible to algorithmically operations on the AFBR because it becomes possible to algorithmically
map an IPv4 group/source address to an IPv6 group/source address and map an IPv4 group/source address to an IPv6 group/source address and
vice-versa. vice versa.
The IPv4-over-IPv6 scenario is an emerging requirement as network The IPv4-over-IPv6 scenario is an emerging requirement as network
operators build out native IPv6 backbone networks. These networks operators build out native IPv6 backbone networks. These networks
support native IPv6 services and applications but in many cases, support native IPv6 services and applications, but, in many cases,
support for legacy IPv4 unicast and multicast services will also need support for legacy IPv4 unicast and multicast services will also need
to be accommodated. to be accommodated.
5. Mesh Multicast Mechanism 5. Mesh Multicast Mechanism
5.1. Mechanism Overview 5.1. Mechanism Overview
Routers in the client E-IP networks have routes to all other client Routers in the client E-IP networks have routes to all other client
E-IP networks. Through PIMv4 messages, E-IP hosts and routers have E-IP networks. Through PIMv4 messages, E-IP hosts and routers have
discovered or learnt of (S,G) or (*,G)[RFC7761] IPv4 addresses. Any discovered or learnt of IPv4 addresses that are in (S,G) or (*,G)
I-IP multicast state instantiated in the core is referred to as state [RFC7761]. Any I-IP multicast state instantiated in the core
(S',G') or (*,G') and is separated from E-IP multicast state. is referred to as (S',G') or (*,G') and is separated from E-IP
multicast state.
Suppose a downstream AFBR receives an E-IP PIM Join/Prune message Suppose a downstream AFBR receives an E-IP PIM Join/Prune message
from the E-IP network for either an (S,G) tree or a (*,G) tree. The from the E-IP network for either an (S,G) tree or a (*,G) tree. The
AFBR translates the PIMv4 message into an PIMv6 message with the AFBR translates the PIMv4 message into a PIMv6 message with the
latter being directed towards the I-IP IPv6 address of the upstream latter being directed towards the I-IP IPv6 address of the upstream
AFBR. When the PIMv6 message arrives at the upstream AFBR, it is AFBR. When the PIMv6 message arrives at the upstream AFBR, it is
translated back into an PIMv4 message. The result of these actions translated back into a PIMv4 message. The result of these actions is
is the construction of E-IP trees and a corresponding I-IP tree in the construction of E-IP trees and a corresponding I-IP tree in the
the I-IP network. An example of the packet format and translation is I-IP network. An example of the packet format and translation is
provided in Section 8. provided in Section 8.
In this case, it is incumbent upon the AFBRs to perform PIM message In this case, it is incumbent upon the AFBRs to perform PIM message
conversions in the control plane and IP group address conversions or conversions in the control plane and IP group address conversions or
mappings in the data plane. The AFBRs perform an algorithmic, one- mappings in the data plane. The AFBRs perform an algorithmic, one-
to-one mapping of IPv4-to-IPv6. to-one mapping of IPv4 to IPv6.
5.2. Group Address Mapping 5.2. Group Address Mapping
A simple algorithmic mapping between IPv4 multicast group addresses A simple algorithmic mapping between IPv4 multicast group addresses
and IPv6 group addresses is performed. Figure 3 is provided as a and IPv6 group addresses is performed. Figure 3 is provided as a
reminder of the format: reminder of the format:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0-------------32--40--48--56--64--72--80--88--96-----------127| | 0-------------32--40--48--56--64--72--80--88--96-----------127|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| mPrefix64 | group address | | mPrefix64 | group address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 3: IPv4-Embedded IPv6 Multicast Address Format Figure 3: IPv4-Embedded IPv6 Multicast Address Format
An IPv6 multicast prefix (mPrefix64) is provisioned on each AFBR. An IPv6 multicast prefix (mPrefix64) is provisioned on each AFBR.
AFBRs will prepend the prefix to an IPv4 multicast group address when AFBRs will prepend the prefix to an IPv4 multicast group address when
translating it to an IPv6 multicast group address. translating it to an IPv6 multicast group address.
The construction of the mPrefix64 for Source-Specific Multicast (SSM) The construction of the mPrefix64 for Source-Specific Multicast (SSM)
is the same as the construction of the mPrefix64 described in is the same as the construction of the mPrefix64 described in
Section 5 of [RFC8114]. Section 5 of [RFC8114].
With this scheme, each IPv4 multicast address can be mapped into an With this scheme, each IPv4 multicast address can be mapped to an
IPv6 multicast address (with the assigned prefix), and each IPv6 IPv6 multicast address (with the assigned prefix), and each IPv6
multicast address with the assigned prefix can be mapped into an IPv4 multicast address with the assigned prefix can be mapped to an IPv4
multicast address. The group address translation algorithm can be multicast address. The group address translation algorithm is
referred in Section 5.2 of [RFC8114]. specified in Section 5.2 of [RFC8114].
5.3. Source Address Mapping 5.3. Source Address Mapping
There are two kinds of multicast: Any-Source Multicast (ASM) and SSM. There are two kinds of multicast: Any-Source Multicast (ASM) and SSM.
Considering that the I-IP network and E-IP network may support Considering that the I-IP network and E-IP network may support
different kinds of multicast, the source address translation rules different kinds of multicast, the source address translation rules
needed to support all possible scenarios may become very complex. needed to support all possible scenarios may become very complex.
But since SSM can be implemented with a strict subset of the PIM-SM But since SSM can be implemented with a strict subset of the PIM-SM
protocol mechanisms [RFC7761], we can treat the I-IP core as SSM-only protocol mechanisms [RFC7761], we can treat the I-IP core as SSM-only
to make it as simple as possible. There then remain only two to make it as simple as possible. There then remain only two
scenarios to be discussed in detail: scenarios to be discussed in detail:
o E-IP network supports SSM o E-IP network supports SSM
One possible way to make sure that the translated PIMv6 message One possible way to make sure that the translated PIMv6 message
reaches upstream AFBR is to set S' to a virtual IPv6 address that reaches the upstream AFBR is to set S' to a virtual IPv6 address
leads to the upstream AFBR. The unicast adddress translation that leads to the upstream AFBR. The unicast address translation
should be achieved according to [RFC6052] should be achieved according to [RFC6052].
o E-IP network supports ASM o E-IP network supports ASM
The (S,G) source list entry and the (*,G) source list entry differ The (S,G) source list entry and the (*,G) source list entry differ
only in that the latter has both the WildCard (WC) and RPT bits of only in that the latter has both the WildCard (WC) and RPT bits of
the Encoded-Source-Address set, while with the former, the bits the Encoded-Source-Address set, while with the former, the bits
are cleared (See Section 4.9.5.1 of [RFC7761]). As a result, the are cleared. (See Section 4.9.5.1 of [RFC7761].) As a result,
source list entries in (*,G) messages can be translated into the source list entries in (*,G) messages can be translated into
source list entries in (S',G') messages by clearing both the WC source list entries in (S',G') messages by clearing both the WC
and RPT bits at downstream AFBRs, and vice-versa for the reverse and RPT bits at downstream AFBRs, and vice versa for the reverse
translation at upstream AFBRs. translation at upstream AFBRs.
5.4. Routing Mechanism 5.4. Routing Mechanism
With mesh multicast, PIMv6 messages originating from a downstream With mesh multicast, PIMv6 messages originating from a downstream
AFBR need to be propogated to the correct upstream AFBR, and every AFBR need to be propagated to the correct upstream AFBR, and every
AFBR needs the /96 prefix in "IPv4-Embedded IPv6 Source Address AFBR needs the /96 prefix in the IPv4-embedded IPv6 source address
Format" [RFC6052]. format [RFC6052].
To achieve this, every AFBR MUST announce the address of one of its To achieve this, every AFBR MUST announce the address of one of its
E-IPv4 interfaces in the "v4" field [RFC6052] alongside the E-IPv4 interfaces in the "v4" field [RFC6052] alongside the
corresponding uPreifx46. The announcement MUST be sent to the other corresponding uPrefix46. The announcement MUST be sent to the other
AFBRs through MBGP [RFC4760]. Every uPrefix64 that an AFBR announces AFBRs through Multiprotocol BGP (MBGP) [RFC4760]. Every uPrefix64
MUST be unique. "uPrefix64" is an IPv6 prefix, and the distribution that an AFBR announces MUST be unique. "uPrefix64" is an IPv6
mechanism is the same as the traditional mesh unicast scenario. prefix, and the distribution mechanism is the same as the traditional
mesh unicast scenario.
As the "v4" field is an E-IP address, and BGP messages are not As the "v4" field is an E-IP address, and BGP messages are not
tunneled through softwires or any other mechanism specified in tunneled through softwires or any other mechanism specified in
[RFC5565], AFBRs MUST be able to transport and encode/decode BGP [RFC5565], AFBRs MUST be able to transport and encode/decode BGP
messages that are carried over the I-IP, and whose NLRI and NH are of messages that are carried over the I-IP, and whose Network Layer
the E-IP address family. Reachability Information (NLRI) and next hop (NH) are of the E-IP
address family.
In this way, when a downstream AFBR receives an E-IP PIM (S,G) In this way, when a downstream AFBR receives an E-IP PIM (S,G)
message, it can translate this message into (S',G') by looking up the message, it can translate this message into (S',G') by looking up the
IP address of the corresponding AFBR's E-IP interface. Since the IP address of the corresponding AFBR's E-IP interface. Since the
uPrefix64 of S' is unique, and is known to every router in the I-IP uPrefix64 of S' is unique and is known to every router in the I-IP
network, the translated message will be forwarded to the network, the translated message will be forwarded to the
corresponding upstream AFBR, and the upstream AFBR can translate the corresponding upstream AFBR, and the upstream AFBR can translate the
message back to (S,G). message back to (S,G).
When a downstream AFBR receives an E-IP PIM (*,G) message, S' can be When a downstream AFBR receives an E-IP PIM (*,G) message, S' can be
generated with the "source address" field set to * (wildcard value). generated with the "source address" field set to * (the wildcard
The translated message will be forwarded to the corresponding value). The translated message will be forwarded to the
upstream AFBR. Since every PIM router within a PIM domain MUST be corresponding upstream AFBR. Every PIM router within a PIM domain
able to map a particular multicast group address to the same RP when MUST be able to map a particular multicast group address to the same
the source address is set to wildcard value (see Section 4.7 of RP when the source address is set to the wildcard value. (See
[RFC7761]), when the upstream AFBR checks the "source address" field Section 4.7 of [RFC7761].) So, when the upstream AFBR checks the
of the message, it finds the IPv4 address of the RP, and ascertains "source address" field of the message, it finds the IPv4 address of
that this is originally a (*,G) message. This is then translated the RP and ascertains that this was originally a (*,G) message. This
back to the (*,G) message and processed. is then translated back to the (*,G) message and processed.
6. Control Plane Functions of AFBR 6. Control-Plane Functions of AFBR
AFBRs are responsible for the following functions: AFBRs are responsible for the functions detailed in the subsections
that follow.
6.1. E-IP (*,G) and (S,G) State Maintenance 6.1. E-IP (*,G) and (S,G) State Maintenance
E-IP (*,G) and (S,G) state maintenance for an AFBR is the same as E-IP (*,G) and (S,G) state maintenance for an AFBR is the same as
E-IP (*,G) and (S,G) state maintenance for an mAFTR described in E-IP (*,G) and (S,G) state maintenance for a multicast AFTR (mAFTR)
Section 7.2 of [RFC8114] described in Section 7.2 of [RFC8114].
6.2. I-IP (S',G') State Maintenance 6.2. I-IP (S',G') State Maintenance
It is possible that the I-IP transit core runs another, non-transit, It is possible that the I-IP transit core runs another, non-transit,
I-IP PIM-SSM instance. Since the translated source address starts I-IP PIM-SSM instance. Since the translated source address starts
with the unique "Well-Known" prefix or the ISP-defined prefix that with the unique "Well-Known" prefix or the ISP-defined prefix that
MUST NOT be used by another service provider, mesh multicast will not MUST NOT be used by another service provider, mesh multicast will not
influence non-transit PIM-SSM multicast at all. When an AFBR influence non-transit PIM-SSM multicast at all. When an AFBR
receives an I-IP (S',G') message, it MUST check S'. If S' starts receives an I-IP (S',G') message, it MUST check S'. If S' starts
with the unique prefix, then the message is actually a translated with the unique prefix, then the message is actually a translated
E-IP (S,G) or (*,G) message, and the AFBR translate this message back E-IP (S,G) or (*,G) message, and the AFBR translates this message
to a PIMv4 message and process it. back to a PIMv4 message and processes it.
6.3. E-IP (S,G,rpt) State Maintenance 6.3. E-IP (S,G,rpt) State Maintenance
When an AFBR wishes to propagate a Join/Prune(S,G,rpt)[RFC7761] When an AFBR wishes to propagate a Join/Prune(S,G,rpt) message
message to an I-IP upstream router, the AFBR MUST operate as [RFC7761] to an I-IP upstream router, the AFBR MUST operate as
specified in Section 6.5 and Section 6.6. specified in Sections 6.5 and 6.6.
6.4. Inter-AFBR Signaling 6.4. Inter-AFBR Signaling
Assume that one downstream AFBR has joined an RPT of (*,G) and an SPT Assume that one downstream AFBR has joined an RPT of (*,G) and a
of (S,G), and decided to perform an SPT switchover (see Section 4.2.1 shortest path tree (SPT) of (S,G) and decided to perform an SPT
of [RFC7761]). According to [RFC7761], it should propagate a switchover. (See Section 4.2.1 of [RFC7761].) According to
Prune(S,G,rpt) message along with the periodical Join(*,G) message [RFC7761], it should propagate a Prune(S,G,rpt) message along with
upstream towards the RP. However, routers in the I-IP transit core the periodic Join(*,G) message upstream towards the RP. However,
do not process (S,G,rpt) messages since the I-IP transit core is routers in the I-IP transit core do not process (S,G,rpt) messages
treated as SSM-only. As a result, the downstream AFBR is unable to since the I-IP transit core is treated as SSM only. As a result, the
prune S from this RPT, so it will receive two copies of the same data downstream AFBR is unable to prune S from this RPT, so it will
for (S,G). In order to solve this problem, we introduce a new receive two copies of the same data for (S,G). In order to solve
mechanism for downstream AFBRs to inform upstream AFBRs of pruning this problem, we introduce a new mechanism for downstream AFBRs to
any given S from an RPT. inform upstream AFBRs of pruning any given S from an RPT.
When a downstream AFBR wishes to propagate an (S,G,rpt) message When a downstream AFBR wishes to propagate an (S,G,rpt) message
upstream, it SHOULD encapsulate the (S,G,rpt) message, then send the upstream, it SHOULD encapsulate the (S,G,rpt) message, then send the
encapsulated unicast message to the corresponding upstream AFBR, encapsulated unicast message to the corresponding upstream AFBR,
which we call "RP'". which we call "RP'".
When RP' receives this encapsulated message, it MUST decapsulate the When RP' receives this encapsulated message, it MUST decapsulate the
message as in the unicast scenario, and retrieve the original message as in the unicast scenario and retrieve the original
(S,G,rpt) message. The incoming interface of this message may be (S,G,rpt) message. The incoming interface of this message may be
different to the outgoing interface which propagates multicast data different from the outgoing interface that propagates multicast data
to the corresponding downstream AFBR, and there may be other to the corresponding downstream AFBR, and there may be other
downstream AFBRs that need to receive multicast data of (S,G) from downstream AFBRs that need to receive multicast data for (S,G) from
this incoming interface, so RP' should not simply process this this incoming interface, so RP' should not simply process this
message as specified in [RFC7761] on the incoming interface. message as specified in [RFC7761] on the incoming interface.
To solve this problem, we introduce an "interface agent" to process To solve this problem, we introduce an "interface agent" to process
all the encapsulated (S,G,rpt) messages the upstream AFBR receives. all the encapsulated (S,G,rpt) messages the upstream AFBR receives.
The interface agent's RP' should prune S from the RPT of group G when The interface agent's RP' should prune S from the RPT of group G when
no downstream AFBR is subscribed to receive multicast data of (S,G) no downstream AFBR is subscribed to receive multicast data for (S,G)
along the RPT. along the RPT.
In this way, we ensure that downstream AFBRs will not miss any In this way, we ensure that downstream AFBRs will not miss any
multicast data that they need. The cost of this is that multicast multicast data that they need. The cost of this is that multicast
data for (S,G) will be duplicated along the RPT received by AFBRs data for (S,G) will be duplicated along the RPT received by AFBRs
affected by the SPT switch over, if at least one downstream AFBR affected by the SPT switchover, if at least one downstream AFBR
exists that has not yet sent Prune(S,G,rpt) messages to the upstream exists that has not yet sent Prune(S,G,rpt) messages to the upstream
AFBR. AFBR.
In certain deployment scenarios (e.g. if there is only a single In certain deployment scenarios (e.g., if there is only a single
downstream router), the interface agent function is not required. downstream router), the interface agent function is not required.
The mechanism used to achieve this is left to the implementation. The mechanism used to achieve this is left to the implementation.
The following diagram provides one possible solution for an The following diagram provides one possible solution for an
"interface agent" implementation: "interface agent" implementation:
+----------------------------------------+ +----------------------------------------+
| | | |
| +-----------+----------+ | | +-----------+----------+ |
| | PIM-SM | UDP | | | | PIM-SM | UDP | |
skipping to change at page 12, line 43 skipping to change at page 12, line 38
| ^ | ^ | | | ^ | ^ | |
| | | | | | | | | | | |
+--------|-----|----------|-----|--------+ +--------|-----|----------|-----|--------+
| v | v | v | v
Figure 4: Interface Agent Implementation Example Figure 4: Interface Agent Implementation Example
Figure 4 shows an example of an interface agent implementation using Figure 4 shows an example of an interface agent implementation using
UDP encapsulation. The interface agent has two responsibilities: In UDP encapsulation. The interface agent has two responsibilities: In
the control plane, it should work as a real interface that has joined the control plane, it should work as a real interface that has joined
(*,G), representing of all the I-IP interfaces which are outgoing (*,G), representing all the I-IP interfaces that are outgoing
interfaces of the (*,G) state machine, and process the (S,G,rpt) interfaces of the (*,G) state machine, and it should process the
messages received from all the I-IP interfaces. (S,G,rpt) messages received from all the I-IP interfaces.
The interface agent maintains downstream (S,G,rpt) state machines for The interface agent maintains downstream (S,G,rpt) state machines for
every downstream AFBR, and submits Prune (S,G,rpt) messages to the every downstream AFBR, and it submits Prune(S,G,rpt) messages to the
PIM-SM module only when every (S,G,rpt) state machine is in the PIM-SM module only when every (S,G,rpt) state machine is in the
Prune(P) or PruneTmp(P') state, which means that no downstream AFBR Prune(P) or PruneTmp(P') state, which means that no downstream AFBR
is subscribed to receive multicast data for (S,G) along the RPT of G. is subscribed to receive multicast data for (S,G) along the RPT of G.
Once a (S,G,rpt) state machine changes to NoInfo(NI) state, which Once a (S,G,rpt) state machine changes to NoInfo (NI) state, which
means that the corresponding downstream AFBR has switched to receive means that the corresponding downstream AFBR has switched to receive
multicast data of (S,G) along the RPT again, the interface agent MUST multicast data for (S,G) along the RPT again, the interface agent
send a Join (S,G,rpt) to the PIM-SM module immediately. MUST send a Join(S,G,rpt) to the PIM-SM module immediately.
In the data plane, upon receiving a multicast data packet, the In the data plane, upon receiving a multicast data packet, the
interface agent MUST encapsulate it at first, then propagate the interface agent MUST encapsulate it at first, then propagate the
encapsulated packet from every I-IP interface. encapsulated packet from every I-IP interface.
NOTICE: It is possible that an E-IP neighbor of RP' has joined the NOTICE: It is possible that an E-IP neighbor of RP' has joined the
RPT of G, so the per-interface state machine for receiving E-IP Join/ RPT of G, so the per-interface state machine for receiving E-IP Join/
Prune (S,G,rpt) messages should be preserved. Prune(S,G,rpt) messages should be preserved.
6.5. SPT Switchover 6.5. SPT Switchover
After a new AFBR requests the receipt of traffic destined for a After a new AFBR requests the receipt of traffic destined for a
multicast group, it will receive all the data from the RPT at first. multicast group, it will receive all the data from the RPT at first.
At this time, every downstream AFBR will receive multicast data from At this time, every downstream AFBR will receive multicast data from
any source from this RPT, in spite of whether they have switched over any source from this RPT, in spite of whether they have switched over
to an SPT or not. to an SPT or not.
To minimize this redundancy, it is recommended that every AFBR's To minimize this redundancy, it is recommended that every AFBR's
skipping to change at page 13, line 47 skipping to change at page 13, line 37
6.6. Other PIM Message Types 6.6. Other PIM Message Types
In addition to Join or Prune, other message types exist, including In addition to Join or Prune, other message types exist, including
Register, Register-Stop, Hello and Assert. Register and Register- Register, Register-Stop, Hello and Assert. Register and Register-
Stop messages are sent by unicast, while Hello and Assert messages Stop messages are sent by unicast, while Hello and Assert messages
are only used between directly linked routers to negotiate with each are only used between directly linked routers to negotiate with each
other. It is not necessary to translate these for forwarding, thus other. It is not necessary to translate these for forwarding, thus
the processing of these messages is out of scope for this document. the processing of these messages is out of scope for this document.
6.7. Other PIM States Maintenance 6.7. Maintenance of Other PIM States
In addition to states mentioned above, other states exist, including In addition to states mentioned above, other states exist, including
(*,*,RP) and I-IP (*,G') state. Since we treat the I-IP core as SSM- (*,*,RP) and I-IP (*,G') state. Since we treat the I-IP core as SSM
only, the maintenance of these states is out of scope for this only, the maintenance of these states is out of scope for this
document. document.
7. Data Plane Functions of the AFBR 7. Data-Plane Functions of the AFBR
7.1. Process and Forward Multicast Data 7.1. Process and Forward Multicast Data
Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing
interface whose IP address family is different from the incoming interface whose IP address family is different from the incoming
interface, the AFBR MUST encapsulate this packet with interface, the AFBR MUST encapsulate this packet with
mPrefix64-derived and uPrefix64-derived IPv6 address to form an IPv6 mPrefix64-derived and uPrefix64-derived IPv6 addresses to form an
multicast packet. IPv6 multicast packet.
7.2. TTL or Hop Count 7.2. TTL or Hop Count
Upon encapsulation, the TTL and hop account in the outer header Upon encapsulation, the TTL and hop count in the outer header SHOULD
SHOULD be set by policy. Upon decapsulation, the TTL and hop count be set by policy. Upon decapsulation, the TTL and hop count in the
in the inner header SHOULD be modified by policy, it MUST NOT be inner header SHOULD be modified by policy; it MUST NOT be incremented
incremented and it MAY be decremented to reflect the cost of tunnel and it MAY be decremented to reflect the cost of tunnel forwarding.
forwarding. Besides, processing of TTL and hop count information in Besides, processing of TTL and hop count information in protocol
protocol headers depends on the tunneling technology, which is out of headers depends on the tunneling technology, which is out of scope of
scope of this document. this document.
7.3. Fragmentation 7.3. Fragmentation
The encapsulation performed by an upstream AFBR will increase the The encapsulation performed by an upstream AFBR will increase the
size of packets. As a result, the outgoing I-IP link MTU may not size of packets. As a result, the outgoing I-IP link MTU may not
accommodate the larger packet size. It is not always possible for accommodate the larger packet size. It is not always possible for
core operators to increase the MTU of every link, thus source core operators to increase the MTU of every link, thus source
fragmentation after encapsulation and reassembling of encapsulated fragmentation after encapsulation and reassembling of encapsulated
packets MUST be supported by AFBRs [RFC5565]. PMTUD [RFC8201] SHOULD packets MUST be supported by AFBRs [RFC5565]. Path MTU Discovery
be enabled and ICMPv6 packets MUST NOT be filtered in the I-IP (PMTUD) [RFC8201] SHOULD be enabled, and ICMPv6 packets MUST NOT be
network. Fragmentation and tunnel configuration considerations are filtered in the I-IP network. Fragmentation and tunnel configuration
provided in Section 8 of [RFC5565]. The detailed procedure can be considerations are provided in Section 8 of [RFC5565]. The detailed
referred in Section 7.2 of [RFC2473]. procedure can be referred in Section 7.2 of [RFC2473].
8. Packet Format and Translation 8. Packet Format and Translation
Because the PIM-SM Specification is independent of the underlying Because the PIM-SM specification is independent of the underlying
unicast routing protocol, the packet format in Section 4.9 of unicast routing protocol, the packet format in Section 4.9 of
[RFC7761] remains the same, except that the group address and source [RFC7761] remains the same, except that the group address and source
address MUST be translated when traversing an AFBR. address MUST be translated when traversing an AFBR.
For example, Figure 5 shows the register-stop message format in the For example, Figure 5 shows the register-stop message format in the
IPv4 and IPv6 address families. IPv4 and IPv6 address families.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type | Reserved | Checksum | |PIM Ver| Type | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Group Address (Encoded-Group format) | | IPv4 Group Address (Encoded-Group format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Source Address (Encoded-Unicast format) | | IPv4 Source Address (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1). IPv4 Register-Stop Message Format
(a) IPv4 Register-Stop Message 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type | Reserved | Checksum | |PIM Ver| Type | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Group Address (Encoded-Group format) | | IPv6 Group Address (Encoded-Group format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Source Address (Encoded-Unicast format) | | IPv6 Source Address (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2). IPv6 Register-Stop Message Format
(b) IPv6 Register-Stop Message Format
Figure 5: Register-Stop Message Format Figure 5: Register-Stop Message Format
In Figure 5, the semantics of fields "PIM Ver", "Type", "Reserved", In Figure 5, the semantics of fields "PIM Ver", "Type", "Reserved",
and "Checksum" can be referred in Section 4.9 of [RFC7761]. and "Checksum" are specified in Section 4.9 of [RFC7761].
IPv4 Group Address (Encoded-Group format): The encoded-group format IPv4 Group Address (Encoded-Group format): The encoded-group format
of the IPv4 group address described in Section 4.9.1 of [RFC7761] of the IPv4 group address described in Section 4.9.1 of [RFC7761].
IPv4 Source Address (Encoded-Group format): The encoded-unicast IPv4 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv4 source address described in Section 4.9.1 of format of the IPv4 source address described in Section 4.9.1 of
[RFC7761] [RFC7761].
IPv6 Group Address (Encoded-Group format): The encoded-group format IPv6 Group Address (Encoded-Group format): The encoded-group format
of the IPv6 group address described in Section 5.2. of the IPv6 group address described in Section 5.2.
IPv6 Source Address (Encoded-Group format): The encoded-unicast IPv6 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv6 source address described in Section 5.3. format of the IPv6 source address described in Section 5.3.
9. Softwire Mesh Multicast Encapsulation 9. Softwire Mesh Multicast Encapsulation
Softwire mesh multicast encapsulation does not require the use of any Softwire mesh multicast encapsulation does not require the use of any
one particular encapsulation mechanism. Rather, it MUST accommodate one particular encapsulation mechanism. Rather, it MUST accommodate
a variety of different encapsulation mechanisms, and allow the use of a variety of different encapsulation mechanisms and allow the use of
encapsulation mechanisms mentioned in [RFC4925]. Additionally, all encapsulation mechanisms mentioned in [RFC4925]. Additionally, all
of the AFBRs attached to the I-IP network MUST implement the same of the AFBRs attached to the I-IP network MUST implement the same
encapsulation mechanism, and follow the requirements mentioned in encapsulation mechanism and follow the requirements mentioned in
Section 8 of [RFC5565]. Section 8 of [RFC5565].
10. Security Considerations 10. Security Considerations
The security concerns raised in [RFC4925] and [RFC7761] are The security concerns raised in [RFC4925] and [RFC7761] are
applicable here. applicable here.
The additional workload associated with some schemes, such as The additional workload associated with some schemes, such as
interface agents, could be exploited by an attacker to perform a DDoS interface agents, could be exploited by an attacker to perform a DDoS
attack. attack.
Compared with [RFC4925], the security concerns should be considered Compared with [RFC4925], the security concerns should be considered
more carefully: an attacker could potentially set up many multicast more carefully: An attacker could potentially set up many multicast
trees in the edge networks, causing too many multicast states in the trees in the edge networks, causing too many multicast states in the
core network. To defend against these attacks, BGP policies SHOULD core network. To defend against these attacks, BGP policies SHOULD
be carefully configured, e.g., AFBRs only accept Well-Known prefix be carefully configured, e.g., AFBRs only accept Well-Known prefix
advertisements from trusted peers. Besides, cryptographic methods advertisements from trusted peers. Besides, cryptographic methods
for authenticating BGP sessions [RFC7454] could be used. for authenticating BGP sessions [RFC7454] could be used.
11. IANA Considerations 11. IANA Considerations
This document includes no request to IANA. This document has no IANA actions.
12. Normative References 12. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473, IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
skipping to change at page 18, line 5 skipping to change at page 18, line 10
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201, "Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017, DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/info/rfc8201>. <https://www.rfc-editor.org/info/rfc8201>.
Appendix A. Acknowledgements Acknowledgements
Wenlong Chen, Xuan Chen, Alain Durand, Yiu Lee, Jacni Qin and Stig Wenlong Chen, Xuan Chen, Alain Durand, Yiu Lee, Jacni Qin, and Stig
Venaas provided useful input into this document. Venaas provided useful input to this document.
Authors' Addresses Authors' Addresses
Mingwei Xu Mingwei Xu
Tsinghua University Tsinghua University
Department of Computer Science, Tsinghua University Department of Computer Science
Beijing 100084 Beijing 100084
P.R. China China
Phone: +86-10-6278-5822 Phone: +86-10-6278-5822
Email: xumw@tsinghua.edu.cn Email: xumw@tsinghua.edu.cn
Yong Cui Yong Cui
Tsinghua University Tsinghua University
Department of Computer Science, Tsinghua University Department of Computer Science
Beijing 100084 Beijing 100084
P.R. China China
Phone: +86-10-6278-5822 Phone: +86-10-6278-5822
Email: cuiyong@tsinghua.edu.cn Email: cuiyong@tsinghua.edu.cn
Jianping Wu Jianping Wu
Tsinghua University Tsinghua University
Department of Computer Science, Tsinghua University Department of Computer Science
Beijing 100084 Beijing 100084
P.R. China China
Phone: +86-10-6278-5983 Phone: +86-10-6278-5983
Email: jianping@cernet.edu.cn Email: jianping@cernet.edu.cn
Shu Yang Shu Yang
Shenzhen University Shenzhen University
South Campus, Shenzhen University South Campus
Shenzhen 518060 Shenzhen 518060
P.R. China China
Phone: +86-755-2653-4078 Phone: +86-755-2653-4078
Email: yang.shu@szu.edu.cn Email: yang.shu@szu.edu.cn
Chris Metz Chris Metz
Cisco Systems Cisco Systems
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA United States of America
Phone: +1-408-525-3275 Phone: +1-408-525-3275
Email: chmetz@cisco.com Email: chmetz@cisco.com
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