draft-ietf-softwire-mesh-multicast-18.txt   draft-ietf-softwire-mesh-multicast-19.txt 
Softwire WG M. Xu Softwire WG M. Xu
Internet-Draft Y. Cui Internet-Draft Y. Cui
Intended status: Standards Track J. Wu Intended status: Standards Track J. Wu
Expires: March 28, 2018 S. Yang Expires: May 19, 2018 S. Yang
Tsinghua University Tsinghua University
C. Metz C. Metz
G. Shepherd G. Shepherd
Cisco Systems Cisco Systems
September 24, 2017 November 15, 2017
Softwire Mesh Multicast IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network
draft-ietf-softwire-mesh-multicast-18 draft-ietf-softwire-mesh-multicast-19
Abstract Abstract
The Internet needs to support IPv4 and IPv6 packets. Both address During IPv6 transition, there will be scenarios where a backbone
families and their related protocol suites support multicast of the network running one IP address family internally (referred to as
single-source and any-source varieties. During IPv6 transition, internal IP or I-IP), while the attached client networks running
there will be scenarios where a backbone network running one IP another IP address family (referred to as external IP or E-IP). The
address family internally (referred to as internal IP or I-IP), while I-IP backbone should offer both unicast and multicast transit
the attached client networks running another IP address family services to the client E-IP networks.
(referred to as external IP or E-IP). The I-IP backbone should offer
both unicast and multicast transit services to the client E-IP
networks.
Softwire Mesh is a solution providing E-IP unicast and multicast This document describes the mechanism for supporting multicast across
support across an I-IP backbone. This document describes the a set of E-IP and I-IP networks supporting softwire mesh. The
mechanism for supporting Internet-style multicast across a set of document focuses on IPv4-over-IPv6 scenario, due to lack of real-
E-IP and I-IP networks supporting softwire mesh. We focus on IPv4- world use cases for IPv6-over-IPv4 scenario.
over-IPv6 scenario in this document, due to lack of real-world use
cases for IPv6-over-IPv4 scenario.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 28, 2018.
This Internet-Draft will expire on May 19, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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 26 skipping to change at page 2, line 25
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Scenarios of Interest . . . . . . . . . . . . . . . . . . . . 6 3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. IPv4-over-IPv6 Mechanism . . . . . . . . . . . . . . . . . . 7 4. Mesh Multicast Mechanism . . . . . . . . . . . . . . . . . . 7
4.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 8 4.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 8
4.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 8 4.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 8
4.3. Source Address Mapping . . . . . . . . . . . . . . . . . 9 4.3. Source Address Mapping . . . . . . . . . . . . . . . . . 9
4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 10 4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9
5. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 11 5. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10
5.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 11 5.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10
5.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 11 5.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10
5.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 11 5.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 11
5.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 11 5.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 11
5.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 14 5.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13
5.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 14 5.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13
5.7. Other PIM States Maintenance . . . . . . . . . . . . . . 14 5.7. Other PIM States Maintenance . . . . . . . . . . . . . . 13
6. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 14 6. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 13
6.1. Process and Forward Multicast Data . . . . . . . . . . . 14 6.1. Process and Forward Multicast Data . . . . . . . . . . . 14
6.2. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.2. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 15 6.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14
7. Packet Format and Translation . . . . . . . . . . . . . . . . 15 7. Packet Format and Translation . . . . . . . . . . . . . . . . 14
8. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 16 8. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . 17 11.1. Normative References . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . 18 11.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 18 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
The Internet needs to support IPv4 and IPv6 packets. Both address During IPv6 transition, there will be scenarios where a backbone
families and their related protocol suites support multicast of the network running one IP address family internally (referred to as
single-source and any-source varieties. During IPv6 transition, internal IP or I-IP) will provide transit services to attached client
there will be scenarios where a backbone network running one IP networks running another IP address family (referred to as external
address family internally (referred to as internal IP or I-IP) will IP or E-IP).
provide transit services to attached client networks running another
IP address family (referred to as external IP or E-IP).
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, which is rooted at one or more ingress inside an I-IP core tree, which is rooted at one or more ingress
Address Family Border Routers (AFBR) and branches out to one or more Address Family Border Routers (AFBRs) [RFC5565] and branches out to
egress Address Family Border Routers (AFBR). one or more egress AFBRs.
[RFC4925] outlines the requirements for the softwires mesh scenario [RFC4925] outlines the requirements for the softwires 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 client E-IP source-rooted or shared tree to traverse the I-IP
backbone network. backbone network.
One method of accomplishing this is to re-use the multicast VPN One method of accomplishing this is to re-use the multicast VPN
approach outlined in [RFC6513]. MVPN-like schemes can support the approach outlined in [RFC6513]. MVPN-like schemes can support the
softwire mesh scenario and achieve a "many-to-one" mapping between softwire mesh scenario and achieve a "many-to-one" mapping between
the E-IP client multicast trees and the transit core multicast trees. the E-IP client multicast trees and the transit core multicast trees.
The advantage of this approach is that the number of trees in the The advantage of this approach is that the number of trees in the
I-IP backbone network scales less than linearly with the number of I-IP backbone network scales less than linearly with the number of
E-IP 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. Aggregation at the edge contains the (S,G) states many (S,G) states [RFC7899]. Aggregation at the edge contains the
for customer's VPNs and these need to be maintained by the network (S,G) states for customer's VPNs and these need to be maintained by
operator. The disadvantage of this approach is the possibility of the network operator. The disadvantage of this approach is the
inefficient bandwidth and resource utilization when multicast packets possibility of inefficient bandwidth and resource utilization when
are delivered to a receiving AFBR with no attached E-IP receivers. multicast packets are delivered to a receiving AFBR with no attached
E-IP receivers.
[RFC8114] provides a solution for delivering IPv4 multicast services
over an IPv6 network. But it mainly focuses on DS-lite [RFC6333]
scenario. This document describes a detailed solution for IPv4-over-
IPv6 softwire mesh scenario, where client networks run IPv4 but the
backbone network runs IPv6.
Internet-style multicast is somewhat different in that the trees are Internet-style multicast is somewhat different in that the trees are
source-rooted and relatively sparse. The need for multicast source-rooted and relatively sparse. The need for multicast
aggregation at the edge (where many customer multicast trees are aggregation at the edge (where many customer multicast trees are
mapped into one or more backbone multicast trees) does not exist and mapped into one or more backbone multicast trees) does not exist and
to date has not been identified. Thus the need for a basic or closer to date has not been identified. Thus the need for a basic or closer
alignment with E-IP and I-IP multicast procedures emerges. alignment with E-IP and I-IP multicast procedures 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
skipping to change at page 4, line 25 skipping to change at page 4, line 25
2. Terminology 2. Terminology
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 RPs might be located in shared trees, the E-IP sources, receivers and rendezvous points (RPs)
different client E-IP networks. In the simplest case, a single might be located in different client E-IP networks. In the simplest
operator manages the resources of the I-IP core, although the inter- case, a single operator manages the resources of the I-IP core,
operator case is also possible and so not precluded. although the inter-operator case is also possible and so not
precluded.
._._._._. ._._._._. ._._._._. ._._._._.
| | | | -------- | | | | --------
| E-IP | | E-IP |--|Source S| | E-IP | | E-IP |--|Source S|
| network | | network | -------- | network | | network | --------
._._._._. ._._._._. ._._._._. ._._._._.
| | | |
AFBR upstream AFBR AFBR upstream AFBR
| | | |
__+____________________+__ __+____________________+__
skipping to change at page 5, line 34 skipping to change at page 5, line 34
-------- | | | | -------- -------- | | | | --------
|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
Terminology used in this document: Terminology 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. In the context or more networks using different IP address families. It MUST
of softwire mesh multicast, the AFBR runs E-IP and I-IP control support functions specified in [RFC5565]. Besides, in the context of
planes to maintain E-IP and I-IP multicast states respectively and softwire mesh multicast, the AFBR runs E-IP and I-IP control planes
performs the appropriate encapsulation/decapsulation of client E-IP to maintain E-IP and I-IP multicast states respectively and performs
multicast packets for transport across the I-IP core. An AFBR will the appropriate encapsulation/decapsulation of client E-IP multicast
act as a source and/or receiver in an I-IP multicast tree. packets for transport across the I-IP core. An AFBR will act as a
source and/or receiver in an I-IP multicast tree.
o Upstream AFBR: An AFBR router that is located on the upper reaches o Upstream AFBR: An AFBR that is located on the upper reaches of a
of a multicast data flow. multicast data flow.
o Downstream AFBR: An AFBR router that is located on the lower o Downstream AFBR: An AFBR that is located on the lower reaches of a
reaches of a multicast data flow. multicast data flow.
o I-IP (Internal IP): This refers to IP address family (i.e., either o I-IP (Internal IP): This refers to IP address family (i.e., either
IPv4 or IPv6) that is supported by the core (or backbone) network. IPv4 or IPv6) that is supported by the core network.
o E-IP (External IP): This refers to the IP address family (i.e. o E-IP (External IP): This refers to the IP address family (i.e.
either IPv4 or IPv6) that is supported by the client network(s) either IPv4 or IPv6) that is supported by the client network(s)
attached to the I-IP transit core. attached to the I-IP transit core.
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 signaling
protocols operating exclusively inside the I-IP core network. An protocols operating exclusively inside the I-IP core network. An
I-IP core tree is used to forward E-IP multicast packets belonging to I-IP core tree is used to forward E-IP multicast packets belonging to
E-IP trees across the I-IP core. Another name for an I-IP core tree E-IP trees across the I-IP core. Another name for an I-IP core tree
is multicast or multipoint softwire. is 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 to
one or more leaf nodes located in the same or different client E-IP one or more leaf nodes located in the same or different client E-IP
networks. networks.
o uPrefix46: The /96 unicast IPv6 prefix for constructing an o uPrefix46: The /96 unicast IPv6 prefix for constructing an
IPv4-embedded IPv6 source address in IPv4-over-IPv6 scenario. IPv4-embedded IPv6 unicast address [RFC6052].
o mPrefix46: The /96 multicast IPv6 prefix for constructing an o mPrefix46: The /96 multicast IPv6 prefix for constructing an
IPv4-embedded IPv6 multicast address in IPv4-over-IPv6 scenario. IPv4-embedded IPv6 multicast address.
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
PIM messages to the upstream AFBR. PIMv6 messages to the upstream AFBR.
3. Scenarios of Interest 3. Scope
This document focus on IPv4-over-IPv6 scenario, the following diagram This document focuses on IPv4-over-IPv6 scenario, the following
shows the scenario. diagram shows the scenario.
._._._._. ._._._._. ._._._._. ._._._._.
| IPv4 | | IPv4 | -------- | IPv4 | | IPv4 | --------
| Client | | Client |--|Source S| | Client | | Client |--|Source S|
| network | | network | -------- | network | | network | --------
._._._._. ._._._._. ._._._._. ._._._._.
| | | |
AFBR upstream AFBR AFBR upstream AFBR
| | | |
__+____________________+__ __+____________________+__
skipping to change at page 7, line 44 skipping to change at page 7, line 44
Because of the much larger IPv6 group address space, the client Because of the much larger IPv6 group address space, the client
E-IPv4 tree can be mapped to a specific I-IPv6 core tree. This E-IPv4 tree can be mapped to a specific I-IPv6 core tree. This
simplifies operations on the AFBR because it becomes possible to simplifies operations on the AFBR because it becomes possible to
algorithmically map an IPv4 group/source address to an IPv6 group/ algorithmically map an IPv4 group/source address to an IPv6 group/
source address and vice-versa. source address and 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 accomodated. to be accommodated.
4. IPv4-over-IPv6 Mechanism 4. Mesh Multicast Mechanism
4.1. Mechanism Overview 4.1. Mechanism Overview
Routers in the client E-IPv4 networks have routes to all other client Routers in the client E-IPv4 networks have routes to all other client
E-IPv4 networks. Through PIM messages, E-IPv4 hosts and routers have E-IPv4 networks. Through PIMv4 messages, E-IPv4 hosts and routers
discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any I-IPv6 have discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any
multicast state instantiated in the core is referred to as (S',G') or I-IPv6 multicast state instantiated in the core is referred to as
(*,G') and is certainly separated from E-IPv4 multicast state. (S',G') or (*,G') and is certainly separated from E-IPv4 multicast
state.
Suppose a downstream AFBR receives an E-IPv4 PIM Join/Prune message Suppose a downstream AFBR receives an E-IPv4 PIM Join/Prune message
from the E-IPv4 network for either an (S,G) tree or a (*,G) tree. from the E-IPv4 network for either an (S,G) tree or a (*,G) tree.
The AFBR can translate the E-IPv4 PIM message into an I-IPv6 PIM The AFBR translates the PIMv4 message into an PIMv6 message with the
message with the latter being directed towards the I-IP IPv6 address latter being directed towards the I-IP IPv6 address of the upstream
of the upstream AFBR. When the I-IPv6 PIM message arrives at the AFBR. When the PIMv6 message arrives at the upstream AFBR, it is
upstream AFBR, it is translated back into an E-IPv4 PIM message. The translated back into an PIMv4 message. The result of these actions
result of these actions is the construction of E-IPv4 trees and a is the construction of E-IPv4 trees and a corresponding I-IP tree in
corresponding I-IP tree in the I-IP network. An example of the the I-IP network. An example of the packet format and translation is
packet format and traslation is provided in Section 8. provided in Section 8.
In this case, it is incumbent upon the AFBR routers to perform PIM In this case, it is incumbent upon the AFBRs to perform PIM message
message conversions in the control plane and IP group address conversions in the control plane and IP group address conversions or
conversions or mappings in the data plane. The AFBRs perform an mappings in the data plane. The AFBRs perform an algorithmic, one-
algorithmic, one-to-one mapping of IPv4-to-IPv6. to-one mapping of IPv4-to-IPv6.
4.2. Group Address Mapping 4.2. Group Address Mapping
For the IPv4-over-IPv6 scenario, a simple algorithmic mapping between For the IPv4-over-IPv6 scenario, a simple algorithmic mapping between
IPv4 multicast group addresses and IPv6 group addresses is performed. IPv4 multicast group addresses and IPv6 group addresses is performed.
Figure 4 shows the reminder of the format: Figure 4 shows the 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|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| mPrefix46 |group address | | mPrefix46 |group address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 4: IPv4-Embedded IPv6 Multicast Address Format Figure 4: IPv4-Embedded IPv6 Multicast Address Format
An IPv6 multicast prefix (mPrefix46) is assigned to each AFBR. AFBRs An IPv6 multicast prefix (mPrefix46) is provisioned on each AFBR.
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 mPrefix46 for SSM is the same as the The construction of the mPrefix46 for SSM is the same as the
construction of the mPrefix64 described in Section 5 of [RFC8114]. construction of the mPrefix64 described in 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 into 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 into an IPv4
multicast address. The group address translation algorithm can be multicast address. The group address translation algorithm can be
reffered in Section 5.2 of [RFC8114]. referred in Section 5.2 of [RFC8114].
4.3. Source Address Mapping 4.3. Source Address Mapping
There are two kinds of multicast: ASM and SSM. Considering that the There are two kinds of multicast modes: ASM and SSM. Considering
I-IP network and E-IP network may support different kinds of that the I-IP network and E-IP network may support different kinds of
multicast, the source address translation rules needed to support all multicast, the source address translation rules needed to support all
possible scenarios may become very complex. But since SSM can be possible scenarios may become very complex. But since SSM can be
implemented with a strict subset of the PIM-SM protocol mechanisms implemented with a strict subset of the PIM-SM protocol mechanisms
[RFC7761], we can treat the I-IP core as SSM-only to make it as [RFC7761], we can treat the I-IP core as SSM-only to make it as
simple as possible. There then remain only two scenarios to be simple as possible. There then remain only two scenarios to be
discussed in detail: discussed in detail:
o E-IP network supports SSM o E-IP network supports SSM
One possible way to make sure that the translated I-IPv6 PIM One possible way to make sure that the translated PIMv6 message
message reaches upstream AFBR is to set S' to a virtual IPv6 reaches upstream AFBR is to set S' to a virtual IPv6 address that
address that leads to the upstream AFBR. Figure 5 is the leads to the upstream AFBR. The unicast adddress translation
recommended address format based on [RFC6052]: should be achieved according to [RFC6052]
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0-------------32--40--48--56--64--72--80--88--96-----------127|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| prefix |v4(32) | u | suffix |source address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|<------------------uPrefix46------------------>|
Figure 5: IPv4-Embedded IPv6 Virtual Source Address Format
In this address format,
* The "prefix" field contains a "Well-Known" prefix or an ISP-
defined prefix. An existing "Well-Known" prefix is 64:ff9b,
which is defined in [RFC6052];
* The "v4" field is the IP address of one of upstream AFBR's
E-IPv4 interfaces;
* The "u" field is defined in [RFC4291], and MUST be set to zero;
* The "suffix" field is reserved for future extensions and SHOULD
be set to zero;
* The "source address" field stores the original source address.
We call the overall /96 prefix ("prefix" field and "v4" field and
"u" field and "suffix" field altogether) "uPrefix46".
o E-IP network supports ASM o E-IP network supports ASM
The (S,G) source list entry and the (*,G) source list entry only The (S,G) source list entry and the (*,G) source list entry only
differ in that the latter has both the WC and RPT bits of the differ in that the latter has both the WC and RPT bits of the
Encoded-Source-Address set, while the former is all cleared (See Encoded-Source-Address set, while the former is all cleared (See
Section 4.9.5.1 of [RFC7761]). So we can translate source list Section 4.9.5.1 of [RFC7761]). So we can translate source list
entries in (*,G) messages into source list entries in (S'G') entries in (*,G) messages into source list entries in (S'G')
messages by applying the format specified in Figure 5 and clearing messages by applying the format specified in Figure 5 and clearing
both the WC and RPT bits at downstream AFBRs, and vice-versa for both the WildCard (WC) and RPT bits at downstream AFBRs, and vice-
the reverse translation at upstream AFBRs. versa for the reverse translation at upstream AFBRs.
4.4. Routing Mechanism 4.4. Routing Mechanism
In the mesh multicast scenario, routing information is REQUIRED to be In the mesh multicast scenario, extra multicast routing information
distributed among AFBRs to make sure that the PIM messages that a is REQUIRED to be distributed among AFBRs to make sure that the PIMv6
downstream AFBR propagates reach the right upstream AFBR. messages that a downstream AFBR propagates reach the right upstream
AFBR.
Every AFBR MUST know the /32 prefix in "IPv4-Embedded IPv6 Virtual Every AFBR MUST know the /32 prefix in "IPv4-Embedded IPv6 Virtual
Source Address Format". To achieve this, every AFBR should announce Source Address Format". To achieve this, every AFBR should announce
one of its E-IPv4 interfaces in the "v4" field, and the corresponding one of its E-IPv4 interfaces in the "v4" field, and the corresponding
uPrefix46. The announcement SHOULD be sent to the other AFBRs uPrefix46. The announcement SHOULD be sent to the other AFBRs
through MBGP [RFC4760]. Since every IP address of upstream AFBR's through MBGP [RFC4760]. Since every IP address of upstream AFBR's
E-IPv4 interface is different from each other, every uPrefix46 that E-IPv4 interface is different from each other, every uPrefix46 that
AFBR announces MUST be different, and uniquely identifies each AFBR. AFBR announces MUST be different, and uniquely identifies each AFBR.
"uPrefix46" is an IPv6 prefix, and the distribution mechanism is the "uPrefix46" is an IPv6 prefix, and the distribution mechanism is the
same as the traditional mesh unicast scenario. But "v4" field is an same as the traditional mesh unicast scenario. But "v4" field is an
E-IPv4 address, and BGP messages are NOT tunneled through softwires E-IPv4 address, and BGP messages are not tunneled through softwires
or any other mechanism specified in [RFC5565], AFBRs MUST be able to or any other mechanism specified in [RFC5565], AFBRs MUST be able to
transport and encode/decode BGP messages that are carried over transport and encode/decode BGP messages that are carried over
I-IPv6, whose NLRI and NH are of E-IPv4 address family. I-IPv6, whose NLRI and NH are of E-IPv4 address family.
In this way, when a downstream AFBR receives an E-IPv4 PIM (S,G) In this way, when a downstream AFBR receives an E-IPv4 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-IPv4 interface. Since the IP address of the corresponding AFBR's E-IPv4 interface. Since the
uPrefix46 of S' is unique, and is known to every router in the I-IPv6 uPrefix46 of S' is unique, and is known to every router in the I-IPv6
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). When a downstream AFBR receives an E-IPv4 PIM message back to (S,G). When a downstream AFBR receives an E-IPv4 PIM
(*,G) message, S' can be generated according to the format specified (*,G) message, S' can be generated according to the format specified
in Figure 4, with "source address" field set to *(the IPv4 address of in Figure 4, with "source address" field set to *(the IPv4 address of
RP). The translated message will be forwarded to the corresponding RP). The translated message will be forwarded to the corresponding
upstream AFBR. Since every PIM router within a PIM domain MUST be upstream AFBR. Since every PIM router within a PIM domain MUST be
able to map a particular multicast group address to the same RP (see able to map a particular multicast group address to the same RP (see
Section 4.7 of [RFC7761]), when the upstream AFBR checks the "source Section 4.7 of [RFC7761]), when the upstream AFBR checks the "source
address" field of the message, it finds the IPv4 address of the RP, address" field of the message, it finds the IPv4 address of the RP,
and assertains that this is originally a (*,G) message. This is then and ascertains that this is originally a (*,G) message. This is then
translated back to the (*,G) message and processed. translated back to the (*,G) message and processed.
5. Control Plane Functions of AFBR 5. Control Plane Functions of AFBR
AFBRs are responsible for the following functions: AFBRs are responsible for the following functions:
5.1. E-IP (*,G) and (S,G) State Maintenance 5.1. E-IP (*,G) and (S,G) State Maintenance
E-IP (*,G) and (S,G) state maintenance on AFBR is the same as E-IP E-IP (*,G) and (S,G) state maintenance on AFBR is the same as E-IP
(*,G) and (S,G) state maintenance on mAFTR described in Section 7.2 (*,G) and (S,G) state maintenance on mAFTR described in Section 7.2
skipping to change at page 11, line 33 skipping to change at page 10, line 51
5.2. I-IP (S',G') State Maintenance 5.2. 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
SHOULD NOT be used by other service provider, mesh multicast will not SHOULD NOT be used by other 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 MUST translate this message E-IP (S,G) or (*,G) message, and the AFBR MUST translate this message
back to E-IP PIM message and process it. back to PIMv4 message and process it.
5.3. E-IP (S,G,rpt) State Maintenance 5.3. E-IP (S,G,rpt) State Maintenance
When an AFBR wishes to propagate a Join/Prune(S,G,rpt) message to an When an AFBR wishes to propagate a Join/Prune(S,G,rpt) message to an
I-IP upstream router, the AFBR MUST operate as specified in I-IP upstream router, the AFBR MUST operate as specified in
Section 6.5 and Section 6.6. Section 6.5 and Section 6.6.
5.4. Inter-AFBR Signaling 5.4. Inter-AFBR Signaling
Assume that one downstream AFBR has joined a RPT of (*,G) and a SPT Assume that one downstream AFBR has joined a RPT of (*,G) and a SPT
skipping to change at page 14, line 41 skipping to change at page 14, line 4
the processing of these messages is out of scope for this document. the processing of these messages is out of scope for this document.
5.7. Other PIM States Maintenance 5.7. Other PIM States Maintenance
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.
6. Data Plane Functions of the AFBR 6. Data Plane Functions of the AFBR
6.1. Process and Forward Multicast Data 6.1. Process and Forward Multicast Data
The data plane behavior on AFBR is similar with the data plane Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing
behavior on mAFTR described in Section 7.4 of [RFC8114]. If there is interface whose IP address family is different from the incoming
at least one outgoing interface whose IP address family is different interface, the AFBR MUST encapsulate this packet with
from the incoming interface, the AFBR MUST encapsulate this packet mPrefix46-derived and uPrefix46-derived IPv6 address to form an IPv6
with mPrefix46-derived and uPrefix46-derived IPv6 address to form an multicast packet.
IPv6 multicast packet.
6.2. TTL 6.2. TTL
Processing of TTL information in protocol headers depends on the Processing of TTL information in protocol headers depends on the
tunneling technology, and it is out of scope of this document. tunneling technology, and it is out of scope of this document.
6.3. Fragmentation 6.3. 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
skipping to change at page 18, line 10 skipping to change at page 17, line 10
[RFC5565] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh [RFC5565] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009, Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009,
<https://www.rfc-editor.org/info/rfc5565>. <https://www.rfc-editor.org/info/rfc5565>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010, DOI 10.17487/RFC6052, October 2010,
<https://www.rfc-editor.org/info/rfc6052>. <https://www.rfc-editor.org/info/rfc6052>.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
<https://www.rfc-editor.org/info/rfc6333>.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>. 2012, <https://www.rfc-editor.org/info/rfc6513>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>. 2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC7899] Morin, T., Ed., Litkowski, S., Patel, K., Zhang, Z.,
Kebler, R., and J. Haas, "Multicast VPN State Damping",
RFC 7899, DOI 10.17487/RFC7899, June 2016,
<https://www.rfc-editor.org/info/rfc7899>.
[RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q. [RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q.
Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
over an IPv6 Multicast Network", RFC 8114, over an IPv6 Multicast Network", RFC 8114,
DOI 10.17487/RFC8114, March 2017, DOI 10.17487/RFC8114, March 2017,
<https://www.rfc-editor.org/info/rfc8114>. <https://www.rfc-editor.org/info/rfc8114>.
11.2. Informative References 11.2. Informative References
[RFC7371] Boucadair, M. and S. Venaas, "Updates to the IPv6 [RFC7371] Boucadair, M. and S. Venaas, "Updates to the IPv6
Multicast Addressing Architecture", RFC 7371, Multicast Addressing Architecture", RFC 7371,
 End of changes. 41 change blocks. 
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