draft-ietf-softwire-mesh-multicast-14.txt   draft-ietf-softwire-mesh-multicast-15.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 17, 2017 S. Yang Expires: July 14, 2017 S. Yang
Tsinghua University Tsinghua University
C. Metz C. Metz
G. Shepherd G. Shepherd
Cisco Systems Cisco Systems
November 13, 2016 January 10, 2017
Softwire Mesh Multicast Softwire Mesh Multicast
draft-ietf-softwire-mesh-multicast-14 draft-ietf-softwire-mesh-multicast-15
Abstract Abstract
The Internet needs to support IPv4 and IPv6 packets. Both address The Internet needs to support IPv4 and IPv6 packets. Both address
families and their related protocol suites support multicast of the families and their related protocol suites support multicast of the
single-source and any-source varieties. During IPv6 transition, single-source and any-source varieties. During IPv6 transition,
there will be scenarios where a backbone network running one IP there will be scenarios where a backbone network running one IP
address family internally (referred to as internal IP or I-IP) will address family internally (referred to as internal IP or I-IP) will
provide transit services to attached client networks running another provide transit services to attached client networks running another
IP address family (referred to as external IP or E-IP). It is IP address family (referred to as external IP or E-IP). It is
expected that the I-IP backbone will offer unicast and multicast expected that the I-IP backbone will offer unicast and multicast
transit services to the client E-IP networks. transit services to the client E-IP networks.
Softwire Mesh is a solution providing E-IP unicast and multicast Softwire Mesh is a solution providing E-IP unicast and multicast
support across an I-IP backbone. This document describes the support across an I-IP backbone. This document describes the
mechanism for supporting Internet-style multicast across a set of mechanism for supporting Internet-style multicast across a set of
E-IP and I-IP networks supporting softwire mesh. E-IP and I-IP networks supporting softwire mesh. We focus on IPv4-
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 http://datatracker.ietf.org/drafts/current/. Drafts is at http://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 July 14, 2017.
This Internet-Draft will expire on May 17, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 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
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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. Scenarios of Interest . . . . . . . . . . . . . . . . . . . . 6
3.1. IPv4-over-IPv6 . . . . . . . . . . . . . . . . . . . . . 6 4. IPv4-over-IPv6 Mechanism . . . . . . . . . . . . . . . . . . 7
3.2. IPv6-over-IPv4 . . . . . . . . . . . . . . . . . . . . . 7 4.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 8
4. IPv4-over-IPv6 Mechanism . . . . . . . . . . . . . . . . . . 9 4.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 8
4.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 9 4.3. Source Address Mapping . . . . . . . . . . . . . . . . . 9
4.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 9 4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 10
4.3. Source Address Mapping . . . . . . . . . . . . . . . . . 10 5. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 11
4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 11 5.1. E-IP (*,G) State Maintenance . . . . . . . . . . . . . . 11
5. IPv6-over-IPv4 Mechanism . . . . . . . . . . . . . . . . . . 12 5.2. E-IP (S,G) State Maintenance . . . . . . . . . . . . . . 11
5.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 12 5.3. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 11
5.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 12 5.4. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 11
5.3. Source Address Mapping . . . . . . . . . . . . . . . . . 12 5.5. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 11
5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 14 5.6. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 14
6. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 14 5.7. Other PIM Message Types . . . . . . . . . . . . . . . . . 14
6.1. E-IP (*,G) State Maintenance . . . . . . . . . . . . . . 14 5.8. Other PIM States Maintenance . . . . . . . . . . . . . . 14
6.2. E-IP (S,G) State Maintenance . . . . . . . . . . . . . . 14 6. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 14
6.3. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 15 6.1. Process and Forward Multicast Data . . . . . . . . . . . 14
6.4. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 15 6.2. Selecting a Tunneling Technology . . . . . . . . . . . . 15
6.5. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 15 6.3. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.6. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 17 6.4. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 15
6.7. Other PIM Message Types . . . . . . . . . . . . . . . . . 17 7. Packet Format and Translation . . . . . . . . . . . . . . . . 15
6.8. Other PIM States Maintenance . . . . . . . . . . . . . . 17 8. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 16
7. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 18 9. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7.1. Process and Forward Multicast Data . . . . . . . . . . . 18 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7.2. Selecting a Tunneling Technology . . . . . . . . . . . . 18 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.3. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 11.1. Normative References . . . . . . . . . . . . . . . . . . 17
7.4. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 18 11.2. Informative References . . . . . . . . . . . . . . . . . 18
8. Packet Format and Translation . . . . . . . . . . . . . . . . 18 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 18
9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
10. Security Considerations . . . . . . . . . . . . . . . . . . . 20
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
12.1. Normative References . . . . . . . . . . . . . . . . . . 20
12.2. Informative References . . . . . . . . . . . . . . . . . 21
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
The Internet needs to support IPv4 and IPv6 packets. Both address The Internet needs to support IPv4 and IPv6 packets. Both address
families and their related protocol suites support multicast of the families and their related protocol suites support multicast of the
single-source and any-source varieties. During IPv6 transition, single-source and any-source varieties. During IPv6 transition,
there will be scenarios where a backbone network running one IP there will be scenarios where a backbone network running one IP
address family internally (referred to as internal IP or I-IP) will address family internally (referred to as internal IP or I-IP) will
provide transit services to attached client networks running another provide transit services to attached client networks running another
IP address family (referred to as external IP or E-IP). IP address family (referred to as external IP or E-IP).
skipping to change at page 4, line 10 skipping to change at page 4, line 7
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
schemes ([RFC5565], Section 11.1) for IPv6 over IPv4 and IPv4 over schemes ([RFC5565], Section 11.1) for IPv4 over IPv6 can be achieved.
IPv6 can be achieved. We focus on IPv4-over-IPv6 scenario in this document, due to lack of
real-world use cases for IPv6-over-IPv4 scenario.
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 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
skipping to change at page 5, line 49 skipping to change at page 6, line 4
act as a source and/or receiver in an I-IP multicast tree. act as a source and/or receiver in an I-IP multicast tree.
o Upstream AFBR: The AFBR router that is located on the upper reaches o Upstream AFBR: The AFBR router that is located on the upper reaches
of a multicast data flow. of a multicast data flow.
o Downstream AFBR: The AFBR router that is located on the lower o Downstream AFBR: The AFBR router that is located on the lower
reaches of a multicast data flow. reaches of a 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 (or backbone) network.
An I-IPv6 core network runs IPv6 and an I-IPv4 core network runs
IPv4.
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. An E-IPv6 client network runs attached to the I-IP transit core.
IPv6 and an E-IPv4 client network runs IPv4.
o I-IP core tree: A distribution tree rooted at one or more AFBR o I-IP core tree: A distribution tree rooted at one or more AFBR
source nodes and branched out to one or more AFBR leaf nodes. An source nodes and branched out to one or more AFBR leaf nodes. An
I-IP core tree is built using standard IP or MPLS multicast signaling I-IP core tree is built using standard IP or MPLS multicast 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 uPrefix64: The /96 unicast IPv6 prefix for constructing an
IPv4-embedded IPv6 source address in IPv6-over-IPv4 scenario.
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 source address in IPv4-over-IPv6 scenario.
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 in IPv4-over-IPv6 scenario.
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. PIM messages to the upstream AFBR.
3. Scenarios of Interest 3. Scenarios of Interest
This section describes the two different scenarios that softwires This document focus on IPv4-over-IPv6 scenario, however, the
mesh multicast is appliacable to. following mechanism offers a reference for IPv6-over-IPv4 scenario if
needed.
3.1. IPv4-over-IPv6
._._._._. ._._._._. ._._._._. ._._._._.
| 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 45 skipping to change at page 7, line 46
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 accomodated.
3.2. IPv6-over-IPv4
._._._._. ._._._._.
| IPv6 | | IPv6 | --------
| Client | | Client |--|Source S|
| network | | network | --------
._._._._. ._._._._.
| |
AFBR upstream AFBR
| |
__+____________________+__
/ : : : : \
| : : : : |
| : IPv4 transit core : |
| : : : : |
| : : : : |
\_._._._._._._._._._._._._./
+ +
downstream AFBR downstream AFBR
| |
._._._._ ._._._._
-------- | IPv6 | | IPv6 | --------
|Receiver|-- | Client | | Client |--|Receiver|
-------- | network| | network| --------
._._._._ ._._._._
Figure 3: IPv6-over-IPv4 Scenario
In Figure 3, the E-IP Client Networks run IPv6 while the I-IP core
runs IPv4.
IPv6 multicast group addresses are longer than IPv4 multicast group
addresses so it is not possible to perform an algorithmic IPv6 to
IPv4 address mapping without the risk of multiple IPv6 group
addresses mapped to the same IPv4 address, resulting in unnecessary
bandwidth and resource consumption.Therefore, additional efforts will
be required to ensure that client E-IPv6 multicast packets can be
injected into the correct I-IPv4 multicast trees at the AFBRs. This
clear mismatch in IPv6 and IPv4 group address lengths means that it
will not be possible to perform a one-to-one mapping between IPv6 and
IPv4 group addresses unless the IPv6 group address is scoped, such as
applying a "Well-Known" prefix or an ISP-defined prefix.
As mentioned earlier, this scenario is common in the MVPN
environment. As native IPv6 deployments and multicast applications
emerge from the outer reaches of the greater public IPv4 Internet, it
is envisaged that the IPv6 over IPv4 softwire mesh multicast scenario
will be a necessary feature supported by network operators.
4. IPv4-over-IPv6 Mechanism 4. IPv4-over-IPv6 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 PIM messages, E-IPv4 hosts and routers have
discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any I-IPv6 discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any I-IPv6
multicast state instantiated in the core is referred to as (S',G') or multicast state instantiated in the core is referred to as (S',G') or
(*,G') and is certainly separated from E-IPv4 multicast state. (*,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.
skipping to change at page 12, line 13 skipping to change at page 11, line 11
(*,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 assertains 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. IPv6-over-IPv4 Mechanism 5. Control Plane Functions of AFBR
5.1. Mechanism Overview
Routers in the client E-IPv6 networks contain routes to all other
client E-IPv6 networks. Through PIM messages, E-IPv6 hosts and
routers have discovered or learnt of (S,G) or (*,G) IPv6 addresses.
Any I-IP multicast state instantiated in the core is referred to as
(S',G') or (*,G') and is separated from E-IP multicast state.
This particular scenario introduces unique challenges. Unlike the
IPv4-over-IPv6 scenario, it is impossible to map all of the IPv6
multicast address space into the IPv4 address space to address the
one-to-one Softwire Multicast requirement. To coordinate with the
"IPv4-over-IPv6" scenario and keep the solution as simple as
possible, one possible solution to this problem is to limit the scope
of the E-IPv6 source addresses for mapping, such as applying a "Well-
Known" prefix or an ISP-defined prefix.
5.2. Group Address Mapping
To keep one-to-one group address mapping simple, the group address
range of E-IP IPv6 can be reduced in a number of ways to limit the
scope of addresses that need to be mapped into the I-IP IPv4 space.
For example, the high order bits of the E-IPv6 address range will be
fixed for mapping purposes. With this scheme, each IPv4 multicast
address can be mapped into an IPv6 multicast address (with the
assigned prefix), and each IPv6 multicast address with the assigned
prefix can be mapped into an IPv4 multicast address.
5.3. Source Address Mapping
There are two kinds of multicast --- ASM and SSM. Considering that
I-IP network and E-IP network may support different kind of
multicast, the source address translation rules needed to support all
possible scenarios may become very complex. But since SSM can be
implemented with a strict subset of the PIM-SM protocol mechanisms
[RFC7761], we can treat the I-IP core as SSM-only to make it as
simple as possible. There then remain only two scenarios to be
discussed in detail:
o E-IP network supports SSM
To make sure that the translated I-IPv4 PIM message reaches the
upstream AFBR, we need to set S' to an IPv4 address that leads to
the upstream AFBR. But due to the non-"one-to-one" mapping of
E-IPv6 to I-IPv4 unicast address, the upstream AFBR is unable to
remap the I-IPv4 source address to the original E-IPv6 source
address without any constraints.
We apply a fixed IPv6 prefix and static mapping to solve this
problem. A recommended source address format is defined in
[RFC6052]. Figure 6 is the reminder of the format:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0-------------32--40--48--56--64--72--80--88--96-----------127|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| uPrefix64 |source address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 6: IPv4-Embedded IPv6 Source Address Format
In this address format, the "uPrefix64" field starts with a "Well-
Known" prefix or an ISP-defined prefix. An existing "Well-Known"
prefix is 64:ff9b/32, which is defined in [RFC6052]; The "source
address" field is the corresponding I-IPv4 source address.
o The E-IP network supports ASM
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
Encoded-Source-Address set, while the former is all cleared (See
Section 4.9.5.1 of [RFC7761]). So we can translate source list
entries in (*,G) messages into source list entries in (S',G')
messages by applying the format specified in Figure 5 and setting
both the WC and RPT bits at downstream AFBRs, and vice-versa for
the reverse translation at upstream AFBRs. Here, the E-IPv6
address of RP MUST follow the format specified in Figure 6. RP'
is the upstream AFBR that locates between RP and the downstream
AFBR.
5.4. Routing Mechanism
In the mesh multicast scenario, routing information is REQUIRED to be
distributed among AFBRs to make sure that PIM messages that a
downstream AFBR propagates reach the right upstream AFBR.
To make it feasible, the /96 uPrefix64 MUST be known to every AFBR,
every E-IPv6 address of sources that support mesh multicast MUST
follow the format specified in Figure 6, and the corresponding
upstream AFBR of this source MUST announce the I-IPv4 address in
"source address" field of this source's IPv6 address to the I-IPv4
network. Since uPrefix64 is static and unique in IPv6-over-IPv4
scenario, there is no need to distribute it using BGP. The
distribution of "source address" field of multicast source addresses
is a pure I-IPv4 process and no more specification is needed.
In this way, when a downstream AFBR receives a (S,G) message, it can
translate the message into (S',G') by simply taking off the prefix in
S. Since S' is known to every router in I-IPv4 network, the
translated message will be forwarded to the corresponding upstream
AFBR, and the upstream AFBR can translate the message back to (S,G)
by appending the prefix to S'. When a downstream AFBR receives a
(*,G) message, it can translate it into (S',G') by simply taking off
the prefix in *(the E-IPv6 address of RP). Since S' is known to
every router in I-IPv4 network, the translated message will be
forwarded to RP'. And since every PIM router within a PIM domain
MUST be able to map a particular multicast group address to the same
RP (see Section 4.7 of [RFC7761]), RP' knows that S' is the mapped
I-IPv4 address of RP, so RP' will translate the message back to (*,G)
by appending the prefix to S' and propagate it towards RP.
6. Control Plane Functions of AFBR
AFBRs are responsible for the following functions: AFBRs are responsible for the following functions:
6.1. E-IP (*,G) State Maintenance 5.1. E-IP (*,G) State Maintenance
When an AFBR wishes to propagate a Join/Prune(*,G) message to an I-IP When an AFBR wishes to propagate a Join/Prune(*,G) message to an I-IP
upstream router, the AFBR MUST translate Join/Prune(*,G) messages upstream router, the AFBR MUST translate Join/Prune(*,G) messages
into Join/Prune(S',G') messages following the rules specified above, into Join/Prune(S',G') messages following the rules specified above,
then send the latter. then send the latter.
6.2. E-IP (S,G) State Maintenance 5.2. E-IP (S,G) State Maintenance
When an AFBR wishes to propagate a Join/Prune(S,G) message to an I-IP When an AFBR wishes to propagate a Join/Prune(S,G) message to an I-IP
upstream router, the AFBR MUST translate Join/Prune(S,G) messages upstream router, the AFBR MUST translate Join/Prune(S,G) messages
into Join/Prune(S',G') messages following the rules specified above, into Join/Prune(S',G') messages following the rules specified above,
then send the latter. then send the latter.
6.3. I-IP (S',G') State Maintenance 5.3. 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 E-IP PIM message and process it.
6.4. E-IP (S,G,rpt) State Maintenance 5.4. 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.
6.5. Inter-AFBR Signaling 5.5. 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 a SPT switchover. According to of (S,G), and decide to perform a 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 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 of (S,G). In order to solve this
problem, we introduce a new mechanism for downstream AFBRs to inform problem, we introduce a new mechanism for downstream AFBRs to inform
skipping to change at page 17, line 18 skipping to change at page 14, line 9
of (S,G) along the RPT again, the interface agent SHOULD send a Join of (S,G) along the RPT again, the interface agent SHOULD send a Join
(S,G,rpt) to the PIM-SM module immediately; In the data plane, upon (S,G,rpt) to the PIM-SM module immediately; In the data plane, upon
receiving a multicast data packet, the interface agent SHOULD receiving a multicast data packet, the interface agent SHOULD
encapsulate it at first, then propagate the encapsulated packet from encapsulate it at first, then propagate the encapsulated packet from
every I-IP interface. 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' that has joined
the RPT of G, so the per-interface state machine for receiving E-IP the RPT of G, so the per-interface state machine for receiving E-IP
Join/Prune (S,G,rpt) messages SHOULD keep alive. Join/Prune (S,G,rpt) messages SHOULD keep alive.
6.6. SPT Switchover 5.6. SPT Switchover
After a new AFBR expresses its interest in receiving traffic destined After a new AFBR expresses its interest in receiving traffic destined
for a multicast group, it will receive all the data from the RPT at for a multicast group, it will receive all the data from the RPT at
first. At this time, every downstream AFBR will receive multicast first. At this time, every downstream AFBR will receive multicast
data from any source from this RPT, in spite of whether they have data from any source from this RPT, in spite of whether they have
switched over to an SPT of some source(s) or not. switched over to an SPT of some source(s) 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 redundancy will be produced. the RPT of G, thus no more redundancy will be produced.
6.7. Other PIM Message Types 5.7. Other PIM Message Types
Apart from Join or Prune, other message types exist, including Apart from Join or Prune, other message types exist, including
Register, Register-Stop, Hello and Assert. Register and Register- Register, Register-Stop, Hello and Assert. Register and Register-
Stop messages are sent by unicast, while Hello and Assert messages Stop messages are sent by unicast, while Hello and Assert messages
are only used between directly linked routers to negotiate with each are only used between directly linked routers to negotiate with each
other. It is not necessary to translate these for forwarding, thus other. It is not necessary to translate these for forwarding, thus
the processing of these messages is out of scope for this document. the processing of these messages is out of scope for this document.
6.8. Other PIM States Maintenance 5.8. Other PIM States Maintenance
Apart from states mentioned above, other states exist, including Apart from states mentioned above, other states exist, including
(*,*,RP) and I-IP (*,G') state. Since we treat the I-IP core as SSM- (*,*,RP) and I-IP (*,G') state. Since we treat the I-IP core as SSM-
only, the maintenance of these states is out of scope for this only, the maintenance of these states is out of scope for this
document. document.
7. Data Plane Functions of the AFBR 6. Data Plane Functions of the AFBR
7.1. Process and Forward Multicast Data 6.1. Process and Forward Multicast Data
On receiving multicast data from upstream routers, the AFBR checks On receiving multicast data from upstream routers, the AFBR checks
its forwarding table to find the IP address of each outgoing its forwarding table to find the IP address of each outgoing
interface. If there is at least one outgoing interface whose IP interface. If there is at least one outgoing interface whose IP
address family is different from the incoming interface, the AFBR address family is different from the incoming interface, the AFBR
MUST encapsulate/decapsulate this packet and forward it via the MUST encapsulate/decapsulate this packet and forward it via the
outgoing interface(s), then forward the data via other outgoing outgoing interface(s), then forward the data via other outgoing
interfaces without encapsulation/decapsulation. interfaces without encapsulation/decapsulation.
When a downstream AFBR that has already switched over to the SPT of S When a downstream AFBR that has already switched over to the SPT of S
receives an encapsulated multicast data packet of (S,G) along the receives an encapsulated multicast data packet of (S,G) along the
RPT, it SHOULD silently drop this packet. RPT, it SHOULD silently drop this packet.
7.2. Selecting a Tunneling Technology 6.2. Selecting a Tunneling Technology
Choosing tunneling technology depends on the policies configured on Choosing tunneling technology depends on the policies configured on
AFBRs. It is REQUIRED that all AFBRs use the same technology, AFBRs. It is REQUIRED that all AFBRs use the same technology,
otherwise some AFBRs SHALL not be able to decapsulate encapsulated otherwise some AFBRs SHALL not be able to decapsulate encapsulated
packets from other AFBRs that use a different tunneling technology. packets from other AFBRs that use a different tunneling technology.
7.3. TTL 6.3. TTL
Processing of TTL depends on the tunneling technology, and it is out Processing of TTL depends on the tunneling technology, and it is out
of scope of this document. of scope of this document.
7.4. Fragmentation 6.4. Fragmentation
The encapsulation performed by an upstream AFBR will increase the The encapsulation performed by an upstream AFBR will increase the
size of packets. As a result, the outgoing I-IP link MTU may not size of packets. As a result, the outgoing I-IP link MTU may not
accommodate the larger packet size. 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].
8. 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 AFBR.
For example, Figure 8 shows the register-stop message format in IPv4 For example, Figure 8 shows the register-stop message format in IPv4
and IPv6 address family. and IPv6 address family.
0 1 2 3 0 1 2 3
skipping to change at page 19, line 33 skipping to change at page 16, line 33
| 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 8: Register-Stop Message Format
In Figure 8, the semantics of fields "PIM Ver", "Type", "Reserved", In Figure 8, the semantics of fields "PIM Ver", "Type", "Reserved",
and "Checksum" remain the same. and "Checksum" remain the same.
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 and 5.2. 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 and 5.3. 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 and 5.2. of the IPv6 group address described in Section 4.2.
IPv6 Source Address (Encoded-Group format): The encoded-unicast IPv6 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv6 source address described in Section 4.3 and 5.3. format of the IPv6 source address described in Section 4.3.
9. Softwire Mesh Multicast Encapsulation 8. Softwire Mesh Multicast Encapsulation
Softwire mesh multicast encapsulation does not require the use of any Softwire mesh multicast encapsulation does not require the use of any
one particular encapsulation mechanism. Rather, it must accommodate one particular encapsulation mechanism. Rather, it MUST accommodate
a variety of different encapsulation mechanisms, and allow the use of a variety of different encapsulation mechanisms, and allow the use of
encapsulation mechanisms mentioned in [RFC4925]. Additionally, all encapsulation mechanisms mentioned in [RFC4925]. Additionally, all
of the AFBRs attached to the I-IP network MUST implement the same of the AFBRs attached to the I-IP network MUST implement the same
encapsulation mechanism. encapsulation mechanism.
10. Security Considerations 9. Security Considerations
The security concerns raised in [RFC4925] and [RFC7761] are The security concerns raised in [RFC4925] and [RFC7761] are
applicable here. In addition, the additional workload associated applicable here. In addition, the additional workload associated
with some schemes could be exploited by an attacker to perform a out with some schemes could be exploited by an attacker to perform a out
DDoS attack. Compared with [RFC4925], the security concerns SHOULD DDoS attack. Compared with [RFC4925], the security concerns SHOULD
be considered more carefully: an attacker could potentially set up be considered more carefully: an attacker could potentially set up
many multicast trees in the edge networks, causing too many multicast many multicast trees in the edge networks, causing too many multicast
states in the core network. states in the core network.
11. IANA Considerations 10. IANA Considerations
This document includes no request to IANA. This document includes no request to IANA.
12. References 11. References
12.1. Normative References 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>. 2006, <http://www.rfc-editor.org/info/rfc4291>.
skipping to change at page 21, line 11 skipping to change at page 18, line 11
[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, <http://www.rfc-editor.org/info/rfc6513>. 2012, <http://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, <http://www.rfc-editor.org/info/rfc7761>. 2016, <http://www.rfc-editor.org/info/rfc7761>.
12.2. 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,
DOI 10.17487/RFC7371, September 2014, DOI 10.17487/RFC7371, September 2014,
<http://www.rfc-editor.org/info/rfc7371>. <http://www.rfc-editor.org/info/rfc7371>.
Appendix A. Acknowledgements Appendix A. Acknowledgements
Wenlong Chen, Xuan Chen, Alain Durand, Yiu Lee, Jacni Qin and Stig Wenlong Chen, Xuan Chen, Alain Durand, Yiu Lee, Jacni Qin and Stig
Venaas provided useful input into this document. Venaas provided useful input into this document.
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