draft-ietf-softwire-mesh-multicast-19.txt   draft-ietf-softwire-mesh-multicast-20.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: May 19, 2018 S. Yang Expires: September 25, 2018 S. Yang
Tsinghua University Tsinghua University
C. Metz C. Metz
G. Shepherd
Cisco Systems Cisco Systems
November 15, 2017 March 24, 2018
IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network
draft-ietf-softwire-mesh-multicast-19 draft-ietf-softwire-mesh-multicast-20
Abstract Abstract
During IPv6 transition, there will be scenarios where a backbone During the transition to IPv6, there will be scenarios where a
network running one IP address family internally (referred to as backbone network internally running one IP address family (referred
internal IP or I-IP), while the attached client networks running to as the internal IP or I-IP family), connects client networks
another IP address family (referred to as external IP or E-IP). The running another IP address family (referred to as the external IP or
I-IP backbone should offer both unicast and multicast transit E-IP family). In such cases, the I-IP backbone needs to offer both
services to the client E-IP networks. unicast and multicast transit services to the client E-IP networks.
This document describes the mechanism for supporting multicast across This document describes a mechanism for supporting multicast across
a set of E-IP and I-IP networks supporting softwire mesh. The backbone networks where the I-IP and E-IP protocol families differ.
document focuses on IPv4-over-IPv6 scenario, due to lack of real- The document focuses on IPv4-over-IPv6 scenario, due to lack of real-
world use cases for IPv6-over-IPv4 scenario. 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 May 19, 2018. This Internet-Draft will expire on September 25, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
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 . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Mesh Multicast 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 . . . . . . . . . . . . . . . . . . . . 9 4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9
5. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10 5. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10
5.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10 5.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10
5.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10 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
skipping to change at page 3, line 7 skipping to change at page 3, line 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . 16 11.1. Normative References . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . 17 11.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
During IPv6 transition, there will be scenarios where a backbone During the transition to IPv6, there will be scenarios where a
network running one IP address family internally (referred to as backbone network internally running one IP address family (referred
internal IP or I-IP) will provide transit services to attached client to as the internal IP or I-IP family), connects client networks
networks running another IP address family (referred to as external running another IP address family (referred to as the external IP or
IP or E-IP). 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, which is rooted at one or more ingress inside an I-IP core tree. The I-IP tree is rooted at one or more
Address Family Border Routers (AFBRs) [RFC5565] and branches out to ingress Address Family Border Routers (AFBRs) [RFC5565] and branches
one or more egress AFBRs. out to one or more egress AFBRs.
[RFC4925] outlines the requirements for the softwires 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 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 This could be accomplished by re-using the multicast VPN approach
approach outlined in [RFC6513]. MVPN-like schemes can support the outlined in [RFC6513]. MVPN-like schemes can support the softwire
softwire mesh scenario and achieve a "many-to-one" mapping between mesh scenario and achieve a "many-to-one" mapping between the E-IP
the E-IP client multicast trees and the transit core multicast trees. client multicast trees and the transit core multicast trees. The
The advantage of this approach is that the number of trees in the advantage of this approach is that the number of trees in the I-IP
I-IP backbone network scales less than linearly with the number of backbone network scales less than linearly with the number of E-IP
E-IP client trees. Corporate enterprise networks and by extension 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 [RFC7899]. Aggregation at the edge contains the many (S,G) states [RFC7899]. Aggregation at the edge contains the
(S,G) states for customer's VPNs and these need to be maintained by (S,G) states for customer's VPNs and these need to be maintained by
the network operator. The disadvantage of this approach is the the network operator. The disadvantage of this approach is the
possibility of inefficient bandwidth and resource utilization when possibility of inefficient bandwidth and resource utilization when
multicast packets are delivered to a receiving AFBR with no attached multicast packets are delivered to a receiving AFBR with no attached
E-IP receivers. 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 DS-lite [RFC6333] over an IPv6 network. But it mainly focuses on the DS-lite [RFC6333]
scenario. This document describes a detailed solution for IPv4-over- scenario. This document describes a detailed solution for the IPv4-
IPv6 softwire mesh scenario, where client networks run IPv4 but the over-IPv6 softwire mesh scenario, where client networks run IPv4 and
backbone network runs IPv6. the backbone network runs IPv6.
Internet-style multicast is somewhat different in that the trees are Internet-style multicast is somewhat different to the [RFC8114]
source-rooted and relatively sparse. The need for multicast scenario in that the trees are source-rooted and relatively sparse.
aggregation at the edge (where many customer multicast trees are The need for multicast aggregation at the edge (where many customer
mapped into one or more backbone multicast trees) does not exist and multicast trees are mapped into one or more backbone multicast trees)
to date has not been identified. Thus the need for a basic or closer does not exist and to date has not been identified. Thus the need
alignment with E-IP and I-IP multicast procedures 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 can be achieved. schemes ([RFC5565], Section 11.1) for IPv4-over-IPv6 multicast can be
achieved.
1.1. Requirements Language 1.1. 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
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 rendezvous points (RPs) shared trees, the E-IP sources, receivers and rendezvous points (RPs)
might be located in different client E-IP networks. In the simplest might be located in different client E-IP networks. In the simplest
case, a single operator manages the resources of the I-IP core, case, a single operator manages the resources of the I-IP core,
although the inter-operator case is also possible and so not 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 | +--------+
._._._._. ._._._._. +---------+ +---------+
| | | |
AFBR upstream AFBR +----------+ +----------+
| | | | | upstream |
__+____________________+__ +-| 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|-+
+ + | AFBR |--| AFBR |
downstream AFBR downstream 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. Terminology
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. It MUST or more networks using different IP address families. Besides, in
support functions specified in [RFC5565]. Besides, in the context of the context of softwire mesh multicast, the AFBR runs E-IP and I-IP
softwire mesh multicast, the AFBR runs E-IP and I-IP control planes control planes to maintain E-IP and I-IP multicast states
to maintain E-IP and I-IP multicast states respectively and performs respectively and performs the appropriate encapsulation/decapsulation
the appropriate encapsulation/decapsulation of client E-IP multicast of client E-IP multicast packets for transport across the I-IP core.
packets for transport across the I-IP core. An AFBR will act as a An AFBR will act as a source and/or receiver in an I-IP multicast
source and/or receiver in an I-IP multicast tree. tree.
o Upstream AFBR: An AFBR that is located on the upper reaches of a o Upstream AFBR: An AFBR that is located on the upper reaches of a
multicast data flow. multicast data flow.
o Downstream AFBR: An AFBR that is located on the lower reaches of a o Downstream AFBR: An AFBR that is located on the lower 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 that is
IPv4 or IPv6) that is supported by the core network. 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 (i.e. o E-IP (External IP): This refers to the IP address family that is
either IPv4 or IPv6) that is supported by the client network(s) supported by the client network(s) attached to the I-IP transit core.
attached to the I-IP transit core. In this document, the I-IP is IPv6.
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
skipping to change at page 6, line 35 skipping to change at page 6, line 35
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. IPv4-embedded IPv6 multicast address.
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.
3. Scope 3. Scope
This document focuses on IPv4-over-IPv6 scenario, the following This document focuses on the IPv4-over-IPv6 scenario, as shown in the
diagram shows the scenario. following diagram:
._._._._. ._._._._. +---------+ +---------+
| IPv4 | | IPv4 | -------- | IPv4 | | IPv4 | +--------+
| Client | | Client |--|Source S| | Client | | Client |--|Source S|
| network | | network | -------- | network | | network | +--------+
._._._._. ._._._._. +---------+ +---------+
| | | |
AFBR upstream AFBR +----------+ +----------+
| | | | | upstream |
__+____________________+__ +-| AFBR |--| AFBR |-+
/ : : : : \ | +----------+ +----------+ |
| : : : : | | |
| : IPv6 transit core : | | IPv6 transit core |
| : : : : | | |
| : : : : | | +----------+ +----------+ |
\_._._._._._._._._._._._._./ +-|dowstream | |downstream|-+
+ + | AFBR |--| AFBR |
downstream AFBR downstream AFBR +----------+ +----------+
| | | |
._._._._ ._._._._ +--------+ +--------+
-------- | 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 runs
IPv6. IPv6.
Because of the much larger IPv6 group address space, the client Because of the much larger IPv6 group address space, the client E-IP
E-IPv4 tree can be mapped to a specific I-IPv6 core tree. This tree can be mapped to a specific I-IP core tree. This simplifies
simplifies operations on the AFBR because it becomes possible to operations on the AFBR because it becomes possible to algorithmically
algorithmically map an IPv4 group/source address to an IPv6 group/ map an IPv4 group/source address to an IPv6 group/source address and
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.
4. Mesh Multicast 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-IP networks have routes to all other client
E-IPv4 networks. Through PIMv4 messages, E-IPv4 hosts and routers E-IP networks. Through PIMv4 messages, E-IP hosts and routers have
have discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any I-IP
I-IPv6 multicast state instantiated in the core is referred to as multicast state instantiated in the core is referred to as (S',G') or
(S',G') or (*,G') and is certainly separated from E-IPv4 multicast (*,G') and is certainly separated from E-IP multicast state.
state.
Suppose a downstream AFBR receives an E-IPv4 PIM Join/Prune message Suppose a downstream AFBR receives an E-IP PIM Join/Prune message
from the E-IPv4 network for either an (S,G) tree or a (*,G) tree. from the E-IP network for either an (S,G) tree or a (*,G) tree. The
The AFBR translates the PIMv4 message into an PIMv6 message with the AFBR translates the PIMv4 message into an 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 an PIMv4 message. The result of these actions
is the construction of E-IPv4 trees and a corresponding I-IP tree in is the construction of E-IP trees and a corresponding I-IP tree in
the I-IP network. An example of the packet format and translation is the 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.
4.2. Group Address Mapping 4.2. Group Address Mapping
For the IPv4-over-IPv6 scenario, a simple algorithmic mapping between A simple algorithmic mapping between IPv4 multicast group addresses
IPv4 multicast group addresses and IPv6 group addresses is performed. and IPv6 group addresses is performed. Figure 3 is provided as a
Figure 4 shows the 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|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| mPrefix46 |group address | | mPrefix46 |group address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 4: IPv4-Embedded IPv6 Multicast Address Format Figure 3: IPv4-Embedded IPv6 Multicast Address Format
An IPv6 multicast prefix (mPrefix46) is provisioned on each AFBR. An IPv6 multicast prefix (mPrefix46) 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 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
referred 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 modes: ASM and SSM. Considering There are two kinds of multicast: ASM and SSM. Considering that the
that the I-IP network and E-IP network may support different kinds of 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 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 upstream AFBR is to set S' to a virtual IPv6 address that
leads to the upstream AFBR. The unicast adddress translation leads to the upstream AFBR. The unicast adddress 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 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 WildCare (WC) and RPT bits
Encoded-Source-Address set, while the former is all cleared (See of the Encoded-Source-Address set, while with the former, the bits
Section 4.9.5.1 of [RFC7761]). So we can translate source list are cleared (See Section 4.9.5.1 of [RFC7761]). So we can
entries in (*,G) messages into source list entries in (S'G') translate source list entries in (*,G) messages into source list
messages by applying the format specified in Figure 5 and clearing entries in (S',G') messages by clearing both the WC and RPT bits
both the WildCard (WC) and RPT bits at downstream AFBRs, and vice- at downstream AFBRs, and vice-versa for the reverse translation at
versa for the reverse translation at upstream AFBRs. upstream AFBRs.
4.4. Routing Mechanism 4.4. Routing Mechanism
In the mesh multicast scenario, extra multicast routing information With mesh multicast, PIMv6 messages originating from a downstream
is REQUIRED to be distributed among AFBRs to make sure that the PIMv6 AFBR need to be propogated to the correct upstream AFBR, and every
messages that a downstream AFBR propagates reach the right upstream AFBR needs the /96 prefix in "IPv4-Embedded IPv6 Virtual Source
AFBR. Address Format".
Every AFBR MUST know the /32 prefix in "IPv4-Embedded IPv6 Virtual To achieve this, every AFBR MUST announce the address of one of its
Source Address Format". To achieve this, every AFBR should announce E-IPv4 interfaces in the "v4" field alongside the corresponding
one of its E-IPv4 interfaces in the "v4" field, and the corresponding uPreifx64. The announcement MUST be sent to the other AFBRs through
uPrefix46. The announcement SHOULD be sent to the other AFBRs MBGP [RFC4760]. Since every IP address of upstream AFBR's E-IP
through MBGP [RFC4760]. Since every IP address of upstream AFBR's interface is different from each other, every uPrefix46 that AFBR
E-IPv4 interface is different from each other, every uPrefix46 that announces MUST be different. "uPrefix46" is an IPv6 prefix, and the
AFBR announces MUST be different, and uniquely identifies each AFBR. distribution mechanism is the same as the traditional mesh unicast
"uPrefix46" is an IPv6 prefix, and the distribution mechanism is the scenario. But as the "v4" field is an E-IP address, and BGP messages
same as the traditional mesh unicast scenario. But "v4" field is an are not tunneled through softwires or any other mechanism specified
E-IPv4 address, and BGP messages are not tunneled through softwires in [RFC5565], AFBRs MUST be able to transport and encode/decode BGP
or any other mechanism specified in [RFC5565], AFBRs MUST be able to messages that are carried over I-IP, whose NLRI and NH are of E-IP
transport and encode/decode BGP messages that are carried over 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-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-IPv4 interface. Since the IP address of the corresponding AFBR's E-IP 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-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). When a downstream AFBR receives an E-IPv4 PIM message back to (S,G).
(*,G) message, S' can be generated according to the format specified
in Figure 4, with "source address" field set to *(the IPv4 address of When a downstream AFBR receives an E-IP PIM (*,G) message, S' can be
RP). The translated message will be forwarded to the corresponding generated according to the format specified in Figure 3, with the
upstream AFBR. Since every PIM router within a PIM domain MUST be "source address" field set to * (wildcard value). The translated
able to map a particular multicast group address to the same RP (see message will be forwarded to the corresponding upstream AFBR. Since
Section 4.7 of [RFC7761]), when the upstream AFBR checks the "source every PIM router within a PIM domain MUST be able to map a particular
address" field of the message, it finds the IPv4 address of the RP, multicast group address to the same RP (see Section 4.7 of
and ascertains that this is originally a (*,G) message. This is then [RFC7761]), when the upstream AFBR checks the "source address" field
translated back to the (*,G) message and processed. of the message, it finds the IPv4 address of the RP, and ascertains
that this is originally a (*,G) message. This is then 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 for an AFBR is the same as
(*,G) and (S,G) state maintenance on mAFTR described in Section 7.2 E-IP (*,G) and (S,G) state maintenance for an mAFTR described in
of [RFC8114] Section 7.2 of [RFC8114]
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
skipping to change at page 11, line 14 skipping to change at page 11, line 14
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
of (S,G), and decide to perform an SPT switchover. According to of (S,G), and decided to perform an SPT switchover. According to
[RFC7761], it SHOULD propagate a Prune(S,G,rpt) message along with [RFC7761], it SHOULD propagate a Prune(S,G,rpt) message along with
the periodical Join(*,G) message upstream towards RP. However, the periodical Join(*,G) message upstream towards the RP. However,
routers in the I-IP transit core do not process (S,G,rpt) messages routers in the I-IP transit core do not process (S,G,rpt) messages
since the I-IP transit core is treated as SSM-only. As a result, the since the I-IP transit core is treated as SSM-only. As a result, the
downstream AFBR is unable to prune S from this RPT, so it will downstream AFBR is unable to prune S from this RPT, so it will
receive two copies of the same data of (S,G). In order to solve this receive two copies of the same data for (S,G). In order to solve
problem, we introduce a new mechanism for downstream AFBRs to inform this problem, we introduce a new mechanism for downstream AFBRs to
upstream AFBRs of pruning any given S from an RPT. inform upstream AFBRs of pruning any given S from an RPT.
When a downstream AFBR wishes to propagate a (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 SHOULD decapsulate When RP' receives this encapsulated message, it SHOULD decapsulate
the message as in the unicast scenario, and retrieve the original the 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 to the outgoing interface which 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 of (S,G) from
skipping to change at page 11, line 46 skipping to change at page 11, line 46
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 of (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 of (S,G) will be duplicated along the RPT received by SPT- data for (S,G) will be duplicated along the RPT received by AFBRs
switched-over downstream AFBRs, if at least one downstream AFBR affected by the SPT switch over, 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:
skipping to change at page 12, line 33 skipping to change at page 12, line 33
| +--+--|-----------+ | | | +--+--|-----------+ | |
| | v | v | | | v | v |
| +--------- + +----------+ | | +--------- + +----------+ |
| | I-IP I/F | | I-IP I/F | | | | I-IP I/F | | I-IP I/F | |
| +----------+ +----------+ | | +----------+ +----------+ |
| ^ | ^ | | | ^ | ^ | |
| | | | | | | | | | | |
+--------|-----|----------|-----|--------+ +--------|-----|----------|-----|--------+
| v | v | v | v
Figure 7: Interface Agent Implementation Example Figure 4: Interface Agent Implementation Example
Figure 7 shows an example of interface agent implementation using UDP Figure 4 shows an example of an interface agent implementation using
encapsulation. The interface agent has two responsibilities: In the UDP encapsulation. The interface agent has two responsibilities: In
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 of all the I-IP interfaces which are outgoing
interfaces of the (*,G) state machine, and process the (S,G,rpt) interfaces of the (*,G) state machine, and process the (S,G,rpt)
messages received from all the I-IP interfaces. messages received from all the I-IP interfaces.
The interface agent maintains downstream (S,G,rpt) state machines of 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 submits Prune (S,G,rpt) messages to the
PIM-SM module only when every (S,G,rpt) state machine is at Prune(P) PIM-SM module only when every (S,G,rpt) state machine is in the
or PruneTmp(P') state, which means that no downstream AFBR is Prune(P) or PruneTmp(P') state, which means that no downstream AFBR
subscribed to receive multicast data of (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 multicast data of (S,G) along the RPT again, the interface agent
SHOULD send a Join (S,G,rpt) to the PIM-SM module immediately. SHOULD 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 SHOULD encapsulate it at first, then propagate the interface agent SHOULD 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' that has joined NOTICE: It is possible that an E-IP neighbor of RP' has joined the
the RPT of G, so the per-interface state machine for receiving E-IP RPT of G, so the per-interface state machine for receiving E-IP Join/
Join/Prune (S,G,rpt) messages SHOULD be preserved. Prune (S,G,rpt) messages SHOULD be preserved.
5.5. SPT Switchover 5.5. 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 of some source(s) 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
SwitchToSptDesired(S,G) function employs the "switch on first packet" SwitchToSptDesired(S,G) function employs the "switch on first packet"
policy. In this way, the delay in switchover to SPT is kept as small policy. In this way, the delay in switchover to SPT is kept as small
as possible, and after the moment that every AFBR has performed the as possible, and after the moment that every AFBR has performed the
SPT switchover for every S of group G, no data will be forwarded in SPT switchover for every S of group G, no data will be forwarded in
the RPT of G, thus no more unnecessary duplication will be produced. the RPT of G, thus no more unnecessary duplication will be produced.
5.6. Other PIM Message Types 5.6. Other PIM Message Types
skipping to change at page 14, line 31 skipping to change at page 14, line 31
accommodate the larger packet size. As it is not always possible for accommodate the larger packet size. As it is not always possible for
core operators to increase the MTU of every link. Fragmentation core operators to increase the MTU of every link. Fragmentation
after encapsulation and reassembling of encapsulated packets MUST be after encapsulation and reassembling of encapsulated packets MUST be
supported by AFBRs [RFC5565]. supported by AFBRs [RFC5565].
7. Packet Format and Translation 7. 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 AFBR. address MUST be translated when traversing an AFBR.
For example, Figure 8 shows the register-stop message format in IPv4 For example, Figure 5 shows the register-stop message format in the
and IPv6 address family. 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 15, line 27 skipping to change at page 15, line 27
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 (2). IPv6 Register-Stop Message Format
Figure 8: Register-Stop Message Format Figure 5: Register-Stop Message Format
In Figure 8, the semantics of fields "PIM Ver", "Type", "Reserved", In Figure 5, the semantics of fields "PIM Ver", "Type", "Reserved",
and "Checksum" remain the same. and "Checksum" can be referred 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 4.2. of the IPv4 group address described in Section 4.2.
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 4.3. format of the IPv4 source address described in Section 4.3.
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 4.2. of the IPv6 group address described in Section 4.2.
skipping to change at page 19, line 4 skipping to change at line 779
Email: yangshu@csnet1.cs.tsinghua.edu.cn Email: yangshu@csnet1.cs.tsinghua.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 USA
Phone: +1-408-525-3275 Phone: +1-408-525-3275
Email: chmetz@cisco.com Email: chmetz@cisco.com
Greg Shepherd
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Phone: +1-541-912-9758
Email: shep@cisco.com
 End of changes. 57 change blocks. 
191 lines changed or deleted 191 lines changed or added

This html diff was produced by rfcdiff 1.46. The latest version is available from http://tools.ietf.org/tools/rfcdiff/