draft-ietf-softwire-mesh-multicast-12.txt   draft-ietf-softwire-mesh-multicast-13.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: October 6, 2016 S. Yang Expires: November 23, 2016 S. Yang
Tsinghua University Tsinghua University
C. Metz C. Metz
G. Shepherd G. Shepherd
Cisco Systems Cisco Systems
April 4, 2016 May 22, 2016
Softwire Mesh Multicast Softwire Mesh Multicast
draft-ietf-softwire-mesh-multicast-12 draft-ietf-softwire-mesh-multicast-13
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
skipping to change at page 1, line 48 skipping to change at page 1, line 48
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 October 6, 2016. This Internet-Draft will expire on November 23, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 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
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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
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Scenarios of Interest . . . . . . . . . . . . . . . . . . . . 6 3. Scenarios of Interest . . . . . . . . . . . . . . . . . . . . 6
3.1. IPv4-over-IPv6 . . . . . . . . . . . . . . . . . . . . . 6 3.1. IPv4-over-IPv6 . . . . . . . . . . . . . . . . . . . . . 6
3.2. IPv6-over-IPv4 . . . . . . . . . . . . . . . . . . . . . 7 3.2. IPv6-over-IPv4 . . . . . . . . . . . . . . . . . . . . . 7
4. IPv4-over-IPv6 Mechanism . . . . . . . . . . . . . . . . . . 9 4. IPv4-over-IPv6 Mechanism . . . . . . . . . . . . . . . . . . 9
4.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 9 4.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 9
4.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 9 4.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 9
4.3. Source Address Mapping . . . . . . . . . . . . . . . . . 10 4.3. Source Address Mapping . . . . . . . . . . . . . . . . . 10
4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 11 4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 11
5. IPv6-over-IPv4 Mechanism . . . . . . . . . . . . . . . . . . 12 5. IPv6-over-IPv4 Mechanism . . . . . . . . . . . . . . . . . . 12
skipping to change at page 2, line 51 skipping to change at page 2, line 52
6.4. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 15 6.4. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 15
6.5. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 15 6.5. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 15
6.6. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 17 6.6. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 17
6.7. Other PIM Message Types . . . . . . . . . . . . . . . . . 17 6.7. Other PIM Message Types . . . . . . . . . . . . . . . . . 17
6.8. Other PIM States Maintenance . . . . . . . . . . . . . . 17 6.8. Other PIM States Maintenance . . . . . . . . . . . . . . 17
7. Data Plane Functions of AFBR . . . . . . . . . . . . . . . . 17 7. Data Plane Functions of AFBR . . . . . . . . . . . . . . . . 17
7.1. Process and Forward Multicast Data . . . . . . . . . . . 17 7.1. Process and Forward Multicast Data . . . . . . . . . . . 17
7.2. Selecting a Tunneling Technology . . . . . . . . . . . . 18 7.2. Selecting a Tunneling Technology . . . . . . . . . . . . 18
7.3. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7.3. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.4. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 18 7.4. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18 8. Packet Format and Translation . . . . . . . . . . . . . . . . 18
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 10. Security Considerations . . . . . . . . . . . . . . . . . . . 20
10.1. Normative References . . . . . . . . . . . . . . . . . . 19 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
10.2. Informative References . . . . . . . . . . . . . . . . . 19 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 19 12.1. Normative References . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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).
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aggregation at the edge (where many customer multicast trees are aggregation at the edge (where many customer multicast trees are
mapped into a few or one backbone multicast trees) does not exist and mapped into a few or one 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.
A framework on how to support such methods is described in [RFC5565]. A framework on how to support such methods is described in [RFC5565].
In this document, a more detailed discussion supporting the "one-to- In this document, a more detailed discussion supporting the "one-to-
one" mapping schemes for the IPv6 over IPv4 and IPv4 over IPv6 one" mapping schemes for the IPv6 over IPv4 and IPv4 over IPv6
scenarios will be discussed. scenarios will be discussed.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Terminology 2. Terminology
An example of a softwire mesh network supporting multicast is An example of a softwire mesh network supporting multicast is
illustrated in Figure 1. A multicast source S is located in one E-IP illustrated in Figure 1. 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 some multicast I-IP core. There may be several E-IP sources for some 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
skipping to change at page 5, line 16 skipping to change at page 5, line 16
| | | | -------- | | | | --------
| E-IP | | E-IP |--|Source S| | E-IP | | E-IP |--|Source S|
| network | | network | -------- | network | | network | --------
._._._._. ._._._._. ._._._._. ._._._._.
| | | |
AFBR upstream AFBR AFBR upstream AFBR
| | | |
__+____________________+__ __+____________________+__
/ : : : : \ / : : : : \
| : : : : | E-IP Multicast | : : : : | E-IP Multicast
| : I-IP transit core : | packets should | : I-IP transit core : | packets MUST
| : : : : | get across the | : : : : | get across the
| : : : : | I-IP transit core | : : : : | I-IP transit core
\_._._._._._._._._._._._._./ \_._._._._._._._._._._._._./
+ + + +
downstream AFBR downstream 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
Terminology used in this document: Terminologies used in this document:
o Address Family Border Router (AFBR) - A dual-stack router o Address Family Border Router (AFBR) - A router interconnecting two
interconnecting two or more networks using different IP address or more networks using different IP address families. In the context
families. In the context of softwire mesh multicast, the AFBR runs of softwire mesh multicast, the AFBR runs E-IP and I-IP control
E-IP and I-IP control planes to maintain E-IP and I-IP multicast planes to maintain E-IP and I-IP multicast states respectively and
states respectively and performs the appropriate encapsulation/ performs the appropriate encapsulation/decapsulation of client E-IP
decapsulation of client E-IP multicast packets for transport across multicast packets for transport across the I-IP core. An AFBR will
the I-IP core. An AFBR will act as a source and/or receiver in an act as a source and/or receiver in an I-IP multicast tree.
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 the form of IP (i.e., either o I-IP (Internal IP): This refers to the form of IP (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 An I-IPv6 core network runs IPv6 and an I-IPv4 core network runs
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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 o uPrefix64: The /96 unicast IPv6 prefix for constructing
IPv4-embedded IPv6 source address. IPv4-embedded IPv6 source address in IPv6-over-IPv4 scenario.
o uPrefix46: The /96 unicast IPv6 prefix for constructing
IPv4-embedded IPv6 source address in IPv4-over-IPv6 scenario.
o mPrefix46: The /96 multicast IPv6 prefix for constructing
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 where softwires This section describes the two different scenarios where softwires
mesh multicast will apply. mesh multicast will apply.
3.1. IPv4-over-IPv6 3.1. IPv4-over-IPv6
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Because of the much larger IPv6 group address space, it will not be a Because of the much larger IPv6 group address space, it will not be a
problem to map individual client E-IPv4 tree to a specific I-IPv6 problem to map individual client E-IPv4 tree to a specific I-IPv6
core tree. This simplifies operations on the AFBR because it becomes core tree. This simplifies operations on the AFBR because it becomes
possible to algorithmically map an IPv4 group/source address to an possible to algorithmically map an IPv4 group/source address to an
IPv6 group/source address and vice-versa. IPv6 group/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
naturally support native IPv6 services and applications but it is naturally support native IPv6 services and applications but it is
with near 100% certainty that legacy IPv4 networks handling unicast with near 100% certainty that legacy IPv4 networks handling unicast
and multicast should be accommodated. and multicast MUST be accommodated.
3.2. IPv6-over-IPv4 3.2. IPv6-over-IPv4
._._._._. ._._._._. ._._._._. ._._._._.
| IPv6 | | IPv6 | -------- | IPv6 | | IPv6 | --------
| Client | | Client |--|Source S| | Client | | Client |--|Source S|
| network | | network | -------- | network | | network | --------
._._._._. ._._._._. ._._._._. ._._._._.
| | | |
AFBR upstream AFBR AFBR upstream AFBR
| | | |
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Figure 3: IPv6-over-IPv4 Scenario Figure 3: IPv6-over-IPv4 Scenario
In this scenario, the E-IP Client Networks run IPv6 while the I-IP In this scenario, the E-IP Client Networks run IPv6 while the I-IP
core runs IPv4. This scenario is illustrated in Figure 3. core runs IPv4. This scenario is illustrated in Figure 3.
IPv6 multicast group addresses are longer than IPv4 multicast group IPv6 multicast group addresses are longer than IPv4 multicast group
addresses. It will not be possible to perform an algorithmic IPv6 - addresses. It will not be possible to perform an algorithmic IPv6 -
to - IPv4 address mapping without the risk of multiple IPv6 group to - IPv4 address mapping without the risk of multiple IPv6 group
addresses mapped to the same IPv4 address resulting in unnecessary addresses mapped to the same IPv4 address resulting in unnecessary
bandwidth and resource consumption. Therefore additional efforts bandwidth and resource consumption. Therefore additional efforts
will be required to ensure that client E-IPv6 multicast packets can will be REQUIRED to ensure that client E-IPv6 multicast packets can
be injected into the correct I-IPv4 multicast trees at the AFBRs. be injected into the correct I-IPv4 multicast trees at the AFBRs.
This clear mismatch in IPv6 and IPv4 group address lengths means that 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 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. and IPv4 group addresses unless the IPv6 group address is scoped.
As mentioned earlier, this scenario is common in the MVPN As mentioned earlier, this scenario is common in the MVPN
environment. As native IPv6 deployments and multicast applications environment. As native IPv6 deployments and multicast applications
emerge from the outer reaches of the greater public IPv4 Internet, it emerge from the outer reaches of the greater public IPv4 Internet, it
is envisaged that the IPv6 over IPv4 softwire mesh multicast scenario is envisaged that the IPv6 over IPv4 softwire mesh multicast scenario
will be a necessary feature supported by network operators. will be a necessary feature supported by network operators.
skipping to change at page 9, line 21 skipping to change at page 9, line 21
mechanisms, E-IPv4 hosts and routers have discovered or learnt of mechanisms, E-IPv4 hosts and routers have discovered or learnt of
(S,G) or (*,G) IPv4 addresses. Any I-IPv6 multicast state (S,G) or (*,G) IPv4 addresses. Any I-IPv6 multicast state
instantiated in the core is referred to as (S',G') or (*,G') and is instantiated in the core is referred to as (S',G') or (*,G') and is
certainly separated from E-IPv4 multicast state. certainly separated from E-IPv4 multicast state.
Suppose a downstream AFBR receives an E-IPv4 PIM Join/Prune message Suppose a downstream AFBR receives an E-IPv4 PIM Join/Prune message
from the E-IPv4 network for either an (S,G) tree or a (*,G) tree. from the E-IPv4 network for either an (S,G) tree or a (*,G) tree.
The AFBR can translate the E-IPv4 PIM message into an I-IPv6 PIM The AFBR can translate the E-IPv4 PIM message into an I-IPv6 PIM
message with the latter being directed towards I-IP IPv6 address of message with the latter being directed towards I-IP IPv6 address of
the upstream AFBR. When the I-IPv6 PIM message arrives at the the upstream AFBR. When the I-IPv6 PIM message arrives at the
upstream AFBR, it should be translated back into an E-IPv4 PIM upstream AFBR, it MUST be translated back into an E-IPv4 PIM message.
message. The result of these actions is the construction of E-IPv4 The result of these actions is the construction of E-IPv4 trees and a
trees and a corresponding I-IP tree in the I-IP network. corresponding I-IP tree in the I-IP network.
In this case it is incumbent upon the AFBR routers to perform PIM In this case, it is incumbent upon the AFBR routers to perform PIM
message conversions in the control plane and IP group address message conversions in the control plane and IP group address
conversions or mappings in the data plane. It becomes possible to conversions or mappings in the data plane. It becomes possible to
devise an algorithmic one-to-one IPv4-to-IPv6 address mapping at devise an algorithmic one-to-one IPv4-to-IPv6 address mapping at
AFBRs. AFBRs.
4.2. Group Address Mapping 4.2. Group Address Mapping
For IPv4-over-IPv6 scenario, a simple algorithmic mapping between For IPv4-over-IPv6 scenario, a simple algorithmic mapping between
IPv4 multicast group addresses and IPv6 group addresses is supported. IPv4 multicast group addresses and IPv6 group addresses is supported.
[RFC7371] has already defined an applicable format. Figure 4 is the [RFC7371] has already defined an applicable format. Figure 4 is 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|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| MPREFIX64 |group address | | mPrefix46 |group address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 4: IPv4-Embedded IPv6 Multicast Address Format Figure 4: IPv4-Embedded IPv6 Multicast Address Format
The MPREFIX64 for SSM mode is also defined in [RFC7371] : The mPrefix46 for SSM mode is also defined in Section 4.1 of
[RFC7371] :
o ff3x:0:8000::/96 ('x' is any valid scope) o ff3x:0:8000::/96 ('x' is any valid scope)
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 IPv4 multicast address with the assigned prefix can be mapped into IPv4
multicast address. multicast address.
4.3. Source Address Mapping 4.3. Source Address Mapping
There are two kinds of multicast --- ASM and SSM. Considering that There are two kinds of multicast --- ASM and SSM. Considering that
I-IP network and E-IP network may support different kind of I-IP network and E-IP network may support different kind of
multicast, the source address translation rules could be very complex multicast, the source address translation rules could be very complex
to support all possible scenarios. But since SSM can be implemented to support all possible scenarios. But since SSM can be implemented
with a strict subset of the PIM-SM protocol mechanisms [RFC4601], we with a strict subset of the PIM-SM protocol mechanisms [RFC7761], we
can treat I-IP core as SSM-only to make it as simple as possible, can treat I-IP core as SSM-only to make it as simple as possible,
then there remains only two scenarios to be discussed in detail: then there remains only two scenarios to be discussed in detail:
o E-IP network supports SSM o E-IP network supports SSM
One possible way to make sure that the translated I-IPv6 PIM One possible way to make sure that the translated I-IPv6 PIM
message reaches upstream AFBR is to set S' to a virtual IPv6 message reaches upstream AFBR is to set S' to a virtual IPv6
address that leads to the upstream AFBR. Figure 5 is the address that leads to the upstream AFBR. Figure 5 is the
recommended address format based on [RFC6052]: recommended address format based on [RFC6052]:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0-------------32--40--48--56--64--72--80--88--96-----------127| | 0-------------32--40--48--56--64--72--80--88--96-----------127|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| prefix |v4(32) | u | suffix |source address | | prefix |v4(32) | u | suffix |source address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|<------------------uPrefix64------------------>| |<------------------uPrefix46------------------>|
Figure 5: IPv4-Embedded IPv6 Virtual Source Address Format Figure 5: IPv4-Embedded IPv6 Virtual Source Address Format
In this address format, the "prefix" field contains a "Well-Known" In this address format, the "prefix" field contains a "Well-Known"
prefix or an ISP-defined prefix. An existing "Well-Known" prefix prefix or an ISP-defined prefix. An existing "Well-Known" prefix
is 64:ff9b, which is defined in [RFC6052]; "v4" field is the IP is 64:ff9b, which is defined in [RFC6052]; "v4" field is the IP
address of one of upstream AFBR's E-IPv4 interfaces; "u" field is address of one of upstream AFBR's E-IPv4 interfaces; "u" field is
defined in [RFC4291], and MUST be set to zero; "suffix" field is defined in [RFC4291], and MUST be set to zero; "suffix" field is
reserved for future extensions and SHOULD be set to zero; "source reserved for future extensions and SHOULD be set to zero; "source
address" field stores the original S. We call the overall /96 address" field stores the original S. We call the overall /96
prefix ("prefix" field and "v4" field and "u" field and "suffix" prefix ("prefix" field and "v4" field and "u" field and "suffix"
field altogether) "uPrefix64". field altogether) "uPrefix46".
o E-IP network supports ASM o E-IP network supports ASM
The (S,G) source list entry and the (*,G) source list entry only The (S,G) source list entry and the (*,G) source list entry only
differ in that the latter have both the WC and RPT bits of the differ in that the latter has both the WC and RPT bits of the
Encoded-Source-Address set, while the former all cleared (See Encoded-Source-Address set, while the former is all cleared (See
Section 4.9.5.1 of [RFC4601]). So we can translate source list Section 4.9.5.1 of [RFC7761]). So we can translate source list
entries in (*,G) messages into source list entries in (S'G') entries in (*,G) messages into source list entries in (S'G')
messages by applying the format specified in Figure 5 and clearing messages by applying the format specified in Figure 5 and clearing
both the WC and RPT bits at downstream AFBRs, and translate them both the WC and RPT bits at downstream AFBRs, and translate them
back at upstream AFBRs vice-versa. back at upstream AFBRs vice-versa.
4.4. Routing Mechanism 4.4. Routing Mechanism
In the mesh multicast scenario, routing information is required to be In the mesh multicast scenario, routing information is REQUIRED to be
distributed among AFBRs to make sure that PIM messages that a distributed among AFBRs to make sure that PIM messages that a
downstream AFBR propagates reach the right upstream AFBR. downstream AFBR propagates reach the right upstream AFBR.
To make it feasible, the /32 prefix in "IPv4-Embedded IPv6 Virtual To make it feasible, the /32 prefix in "IPv4-Embedded IPv6 Virtual
Source Address Format" must be known to every AFBR, and every AFBR Source Address Format" MUST be known to every AFBR, and every AFBR
should not only announce the IP address of one of its E-IPv4 should not only announce the IP address of one of its E-IPv4
interfaces presented in the "v4" field to other AFBRs by MPBGP, but interfaces presented in the "v4" field to other AFBRs by MPBGP, but
also announce the corresponding uPrefix64 to the I-IPv6 network. also announce the corresponding uPrefix46 to the I-IPv6 network.
Since every IP address of upstream AFBR's E-IPv4 interface is Since every IP address of upstream AFBR's E-IPv4 interface is
different from each other, every uPrefix64 that AFBR announces should different from each other, every uPrefix46 that AFBR announces MUST
be different either, and uniquely identifies each AFBR. "uPrefix64" be different, and uniquely identifies each AFBR. "uPrefix46" is an
is an IPv6 prefix, and the distribution of it is the same as the IPv6 prefix, and the distribution of it is the same as the
distribution in the traditional mesh unicast scenario. But since distribution in the traditional mesh unicast scenario. But since
"v4" field is an E-IPv4 address, and BGP messages are NOT tunneled "v4" field is an E-IPv4 address, and BGP messages are NOT tunneled
through softwires or through any other mechanism as specified in through softwires or through any other mechanism as specified in
[RFC5565], AFBRs MUST be able to transport and encode/decode BGP [RFC5565], AFBRs MUST be able to transport and encode/decode BGP
messages that are carried over I-IPv6, whose NLRI and NH are of messages that are carried over I-IPv6, whose NLRI and NH are of
E-IPv4 address family. E-IPv4 address family.
In this way, when a downstream AFBR receives an E-IPv4 PIM (S,G) In this way, when a downstream AFBR receives an E-IPv4 PIM (S,G)
message, it can translate this message into (S',G') by looking up the message, it can translate this message into (S',G') by looking up the
IP address of the corresponding AFBR's E-IPv4 interface. Since the IP address of the corresponding AFBR's E-IPv4 interface. Since the
uPrefix64 of S' is unique, and is known to every router in the I-IPv6 uPrefix46 of S' is unique, and is known to every router in the I-IPv6
network, the translated message will eventually arrive at the network, the translated message will eventually arrive at the
corresponding upstream AFBR, and the upstream AFBR can translate the corresponding upstream AFBR, and the upstream AFBR can translate the
message back to (S,G). When a downstream AFBR receives an E-IPv4 PIM message back to (S,G). When a downstream AFBR receives an E-IPv4 PIM
(*,G) message, S' can be generated according to the format specified (*,G) message, S' can be generated according to the format specified
in Figure 4, with "source address" field set to *(the IPv4 address of in Figure 4, with "source address" field set to *(the IPv4 address of
RP). The translated message will eventually arrive at the RP). The translated message will eventually arrive at the
corresponding upstream AFBR. Since every PIM router within a PIM corresponding upstream AFBR. Since every PIM router within a PIM
domain must be able to map a particular multicast group address to domain MUST be able to map a particular multicast group address to
the same RP (see Section 4.7 of [RFC4601]), when this upstream AFBR the same RP (see Section 4.7 of [RFC7761]), when this upstream AFBR
checks the "source address" field of the message, it'll find the IPv4 checks the "source address" field of the message, it will find the
address of RP, so this upstream AFBR judges that this is originally a IPv4 address of RP, so this upstream AFBR judges that this is
(*,G) message, then it translates the message back to the (*,G) originally a (*,G) message, then it translates the message back to
message and processes it. the (*,G) message and processes it.
5. IPv6-over-IPv4 Mechanism 5. IPv6-over-IPv4 Mechanism
5.1. Mechanism Overview 5.1. Mechanism Overview
Routers in the client E-IPv6 networks contain routes to all other Routers in the client E-IPv6 networks contain routes to all other
client E-IPv6 networks. Through the set of known and deployed client E-IPv6 networks. Through the set of known and deployed
mechanisms, E-IPv6 hosts and routers have discovered or learnt of mechanisms, E-IPv6 hosts and routers have discovered or learnt of
(S,G) or (*,G) IPv6 addresses. Any I-IP multicast state instantiated (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 certainly in the core is referred to as (S',G') or (*,G') and is certainly
separated from E-IP multicast state. separated from E-IP multicast state.
This particular scenario introduces unique challenges. Unlike the This particular scenario introduces unique challenges. Unlike the
IPv4-over-IPv6 scenario, it's impossible to map all of the IPv6 IPv4-over-IPv6 scenario, it is impossible to map all of the IPv6
multicast address space into the IPv4 address space to address the multicast address space into the IPv4 address space to address the
one-to-one Softwire Multicast requirement. To coordinate with the one-to-one Softwire Multicast requirement. To coordinate with the
"IPv4-over-IPv6" scenario and keep the solution as simple as "IPv4-over-IPv6" scenario and keep the solution as simple as
possible, one possible solution to this problem is to limit the scope 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- of the E-IPv6 source addresses for mapping, such as applying a "Well-
Known" prefix or an ISP-defined prefix. Known" prefix or an ISP-defined prefix.
5.2. Group Address Mapping 5.2. Group Address Mapping
To keep one-to-one group address mapping simple, the group address 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 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. scope of addresses that need to be mapped into the I-IP IPv4 space.
A recommended multicast address format is defined in [RFC7371]. The A recommended multicast address format is defined in [RFC7371]. The
high order bits of the E-IPv6 address range will be fixed for mapping high order bits of the E-IPv6 address range will be fixed for mapping
purposes. With this scheme, each IPv4 multicast address can be purposes. With this scheme, each IPv4 multicast address can be
mapped into an IPv6 multicast address(with the assigned prefix), and mapped into an IPv6 multicast address (with the assigned prefix), and
each IPv6 multicast address with the assigned prefix can be mapped each IPv6 multicast address with the assigned prefix can be mapped
into IPv4 multicast address. into IPv4 multicast address.
5.3. Source Address Mapping 5.3. Source Address Mapping
There are two kinds of multicast --- ASM and SSM. Considering that There are two kinds of multicast --- ASM and SSM. Considering that
I-IP network and E-IP network may support different kind of I-IP network and E-IP network may support different kind of
multicast, the source address translation rules could be very complex multicast, the source address translation rules could be very complex
to support all possible scenarios. But since SSM can be implemented to support all possible scenarios. But since SSM can be implemented
with a strict subset of the PIM-SM protocol mechanisms [RFC4601], we with a strict subset of the PIM-SM protocol mechanisms [RFC7761], we
can treat I-IP core as SSM-only to make it as simple as possible, can treat I-IP core as SSM-only to make it as simple as possible,
then there remains only two scenarios to be discussed in detail: then there remains only two scenarios to be discussed in detail:
o E-IP network supports SSM o E-IP network supports SSM
To make sure that the translated I-IPv4 PIM message reaches the 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 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 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 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 remap the I-IPv4 source address to the original E-IPv6 source
address without any constraints. address without any constraints.
skipping to change at page 13, line 31 skipping to change at page 13, line 31
Figure 6: IPv4-Embedded IPv6 Source Address Format Figure 6: IPv4-Embedded IPv6 Source Address Format
In this address format, the "uPrefix64" field starts with a "Well- In this address format, the "uPrefix64" field starts with a "Well-
Known" prefix or an ISP-defined prefix. An existing "Well-Known" Known" prefix or an ISP-defined prefix. An existing "Well-Known"
prefix is 64:ff9b/32, which is defined in [RFC6052]; "source prefix is 64:ff9b/32, which is defined in [RFC6052]; "source
address" field is the corresponding I-IPv4 source address. address" field is the corresponding I-IPv4 source address.
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 have both the WC and RPT bits of the differ in that the latter has both the WC and RPT bits of the
Encoded-Source-Address set, while the former all cleared (See Encoded-Source-Address set, while the former is all cleared (See
Section 4.9.5.1 of [RFC4601]). So we can translate source list Section 4.9.5.1 of [RFC7761]). So we can translate source list
entries in (*,G) messages into source list entries in (S',G') entries in (*,G) messages into source list entries in (S',G')
messages by applying the format specified in Figure 5 and setting messages by applying the format specified in Figure 5 and setting
both the WC and RPT bits at downstream AFBRs, and translate them both the WC and RPT bits at downstream AFBRs, and translate them
back at upstream AFBRs vice-versa. Here, the E-IPv6 address of RP back at upstream AFBRs vice-versa. Here, the E-IPv6 address of RP
MUST follow the format specified in Figure 6. RP' is the upstream MUST follow the format specified in Figure 6. RP' is the upstream
AFBR that locates between RP and the downstream AFBR. AFBR that locates between RP and the downstream AFBR.
5.4. Routing Mechanism 5.4. Routing Mechanism
In the mesh multicast scenario, routing information is required to be In the mesh multicast scenario, routing information is REQUIRED to be
distributed among AFBRs to make sure that PIM messages that a distributed among AFBRs to make sure that PIM messages that a
downstream AFBR propagates reach the right upstream AFBR. downstream AFBR propagates reach the right upstream AFBR.
To make it feasible, the /96 uPrefix64 must be known to every 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 every E-IPv6 address of sources that support mesh multicast MUST
follow the format specified in Figure 6, and the corresponding follow the format specified in Figure 6, and the corresponding
upstream AFBR of this source should announce the I-IPv4 address in 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 "source address" field of this source's IPv6 address to the I-IPv4
network. Since uPrefix64 is static and unique in IPv6-over-IPv4 network. Since uPrefix64 is static and unique in IPv6-over-IPv4
scenario, there is no need to distribute it using BGP. The scenario, there is no need to distribute it using BGP. The
distribution of "source address" field of multicast source addresses distribution of "source address" field of multicast source addresses
is a pure I-IPv4 process and no more specification is needed. 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 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 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 S. Since S' is known to every router in I-IPv4 network, the
translated message will eventually arrive at the corresponding translated message will eventually arrive at the corresponding
upstream AFBR, and the upstream AFBR can translate the message back upstream AFBR, and the upstream AFBR can translate the message back
to (S,G) by appending the prefix to S'. When a downstream AFBR 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 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 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 known to every router in I-IPv4 network, the translated message will
eventually arrive at RP'. And since every PIM router within a PIM eventually arrive at RP'. And since every PIM router within a PIM
domain must be able to map a particular multicast group address to domain MUST be able to map a particular multicast group address to
the same RP (see Section 4.7 of [RFC4601]), RP' knows that S' is the 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 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. to (*,G) by appending the prefix to S' and propagate it towards RP.
6. Control Plane Functions of AFBR 6. Control Plane Functions of AFBR
The AFBRs are responsible for the following functions: The AFBRs are responsible for the following functions:
6.1. E-IP (*,G) State Maintenance 6.1. 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
skipping to change at page 14, line 50 skipping to change at page 14, line 50
6.2. E-IP (S,G) State Maintenance 6.2. 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 6.3. I-IP (S',G') State Maintenance
It is possible that there runs a non-transit I-IP PIM-SSM in the I-IP It is possible that I-IP transit core runs other non-transit I-IP
transit core. Since the translated source address starts with the PIM-SSM instance. Since the translated source address starts with
unique "Well-Known" prefix or the ISP-defined prefix that should not the unique "Well-Known" prefix or the ISP-defined prefix that SHOULD
be used otherwise, mesh multicast won't influence non-transit PIM-SM NOT be used otherwise, mesh multicast will not influence non-transit
multicast at all. When one AFBR receives an I-IP (S',G') message, it PIM-SSM multicast at all. When one AFBR receives an I-IP (S',G')
should check S'. If S' starts with the unique prefix, it means that message, it MUST check S'. If S' starts with the unique prefix, it
this message is actually a translated E-IP (S,G) or (*,G) message, means that this message is actually a translated E-IP (S,G) or (*,G)
then the AFBR should translate this message back to E-IP PIM message message, then the AFBR MUST translate this message back to E-IP PIM
and process it. message and process it.
6.4. E-IP (S,G,rpt) State Maintenance 6.4. 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 do as specified in Section 6.5 I-IP upstream router, the AFBR MUST do as specified in Section 6.5
and Section 6.6. and Section 6.6.
6.5. Inter-AFBR Signaling 6.5. 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
[RFC4601], 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. Unfortunately, the periodical Join(*,G) message upstream towards RP. Unfortunately,
routers in I-IP transit core are not supposed to understand (S,G,rpt) routers in I-IP transit core are not supposed to understand (S,G,rpt)
messages since I-IP transit core is treated as SSM-only. As a messages since I-IP transit core is treated as SSM-only. As a
result, this downstream AFBR is unable to prune S from this RPT, then result, this downstream AFBR is unable to prune S from this RPT, then
it will receive two copies of the same data of (S,G). In order to it will receive two copies of the same data of (S,G). In order to
solve this problem, we introduce a new mechanism for downstream AFBRs solve this problem, we introduce a new mechanism for downstream AFBRs
to inform upstream AFBRs of pruning any given S from RPT. to inform upstream AFBRs of pruning any given S from RPT.
When a downstream AFBR wishes to propagate a (S,G,rpt) message When a downstream AFBR wishes to propagate a (S,G,rpt) message
upstream, it should encapsulate the (S,G,rpt) message, then unicast upstream, it SHOULD encapsulate the (S,G,rpt) message, then send the
the encapsulated message to the corresponding upstream AFBR, which we encapsulated unicast message to the corresponding upstream AFBR,
call "RP'". which we call "RP'".
When RP' receives this encapsulated message, it should decapsulate When RP' receives this encapsulated message, it SHOULD decapsulate
this message as what it does in the unicast scenario, and get the this message as what it does in the unicast scenario, and get the
original (S,G,rpt) message. The incoming interface of this message original (S,G,rpt) message. The incoming interface of this message
may be different from the outgoing interface which propagates may be different from the outgoing interface which propagates
multicast data to the corresponding downstream AFBR, and there may be multicast data to the corresponding downstream AFBR, and there may be
other downstream AFBRs that need to receive multicast data of (S,G) other downstream AFBRs that need to receive multicast data of (S,G)
from this incoming interface, so RP' should not simply process this from this incoming interface, so RP' SHOULD NOT simply process this
message as specified in [RFC4601] on the incoming interface. message as specified in [RFC7761] on the incoming interface.
To solve this problem, and keep the solution as simple as possible, To solve this problem and keep the solution as simple as possible, we
we introduce an "interface agent" to process all the encapsulated introduce an "interface agent" to process all the encapsulated
(S,G,rpt) messages the upstream AFBR receives, and prune S from the (S,G,rpt) messages the upstream AFBR receives, and prune S from the
RPT of group G when no downstream AFBR wants to receive multicast RPT of group G when no downstream AFBR wants to receive multicast
data of (S,G) along the RPT. In this way, we do insure that data of (S,G) along the RPT. In this way, we do insure that
downstream AFBRs won't miss any multicast data that they needs, at downstream AFBRs will not miss any multicast data that they need, at
the cost of duplicated multicast data of (S,G) along the RPT received the cost of duplicated multicast data of (S,G) along the RPT received
by SPT-switched-over downstream AFBRs, if there exists at least one by SPT-switched-over downstream AFBRs, if there exists at least one
downstream AFBR that hasn't yet sent Prune(S,G,rpt) messages to the downstream AFBR that has not yet sent Prune(S,G,rpt) messages to the
upstream AFBR. The following diagram shows an example of how an upstream AFBR. The following diagram shows an example of how an
"interface agent" may be implemented: "interface agent" MAY be implemented:
+----------------------------------------+ +----------------------------------------+
| | | |
| +-----------+----------+ | | +-----------+----------+ |
| | PIM-SM | UDP | | | | PIM-SM | UDP | |
| +-----------+----------+ | | +-----------+----------+ |
| ^ | | | ^ | |
| | | | | | | |
| | v | | | v |
| +----------------------+ | | +----------------------+ |
| | I/F Agent | | | | I/F Agent | |
| +----------------------+ | | +----------------------+ |
| PIM ^ | multicast | | PIM ^ | multicast |
| messages | | data | | messages | | data |
| | +-------------+---+ | | | +-------------+---+ |
skipping to change at page 16, line 34 skipping to change at page 16, line 34
| +--------- + +----------+ | | +--------- + +----------+ |
| | 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 7: Interface Agent Implementation Example
In this example, the interface agent has two responsibilities: In the Figure 7 shows an example of interface agent implementation where we
control plane, it should work as a real interface that has joined choose UDP encapsulation. The interface agent has two
(*,G) in representative of all the I-IP interfaces who should have responsibilities: In the control plane, it SHOULD work as a real
been outgoing interfaces of (*,G) state machine, and process the interface that has joined (*,G) in representative of all the I-IP
(S,G,rpt) messages received from all the I-IP interfaces. The interfaces which are outgoing interfaces of (*,G) state machine, and
interface agent maintains downstream (S,G,rpt) state machines of process the (S,G,rpt) messages received from all the I-IP interfaces.
The interface agent maintains downstream (S,G,rpt) state machines of
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 at Prune(P)
or PruneTmp(P') state, which means that no downstream AFBR wants to or PruneTmp(P') state, which means that no downstream AFBR wants to
receive multicast data of (S,G) along the RPT of G. Once a (S,G,rpt) receive multicast data of (S,G) along the RPT of G. Once a (S,G,rpt)
state machine changes to NoInfo(NI) state, which means that the state machine changes to NoInfo(NI) state, which means that the
corresponding downstream AFBR has changed it mind to receive corresponding downstream AFBR has changed its mind 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 PIM-SM module immediately; In the data SHOULD send a Join(S,G,rpt) to PIM-SM module immediately; In the data
plane, upon receiving a multicast data packet, the interface agent plane, upon receiving a multicast data packet, the interface agent
should encapsulate it at first, then propagate the encapsulated SHOULD encapsulate it at first, then propagate the encapsulated
packet onto every I-IP interface. packet onto every I-IP interface.
NOTICE: There may exist an E-IP neighbor of RP' that has joined the NOTICE: There may exist an E-IP neighbor of RP' that has joined the
RPT of G, so the per-interface state machine for receiving E-IP Join/ RPT of G, so the per-interface state machine for receiving E-IP Join/
Prune(S,G,rpt) messages should still take effect. Prune(S,G,rpt) messages SHOULD still take effect.
6.6. SPT Switchover 6.6. 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 spit of whether they have data from any source from this RPT, in spite of whether they have
switched over to SPT of some source(s) or not. switched over to SPT of some source(s) or not.
To minimize this redundancy, it's 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 of switchover to SPT is kept as policy. In this way, the delay of switchover to SPT is kept as
little as possible, and after the moment that every AFBR has little as possible, and after the moment that every AFBR has
performed the SPT switchover for every S of group G, no data will be performed the 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. forwarded in the RPT of G, thus no more redundancy will be produced.
6.7. Other PIM Message Types 6.7. Other PIM Message Types
Apart from Join or Prune, there exists other message types including Apart from Join or Prune, there exists other message types 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 dierctly linked routers to negotiate with each are only used between directly linked routers to negotiate with each
other. It's not necessary to translate them for forwarding, thus the other. It is not necessary to translate them for forwarding, thus
process of these messages is out of scope for this document. the process of these messages is out of scope for this document.
6.8. Other PIM States Maintenance 6.8. Other PIM States Maintenance
Apart from states mentioned above, there exists other states Apart from states mentioned above, there exists other states
including (*,*,RP) and I-IP (*,G') state. Since we treat I-IP core including (*,*,RP) and I-IP (*,G') state. Since we treat I-IP core
as SSM-only, the maintenance of these states is out of scope for this as SSM-only, the maintenance of these states is out of scope for this
document. document.
7. Data Plane Functions of AFBR 7. Data Plane Functions of AFBR
7.1. Process and Forward Multicast Data 7.1. Process and Forward Multicast Data
On receiving multicast data from upstream routers, the AFBR looks up On receiving multicast data from upstream routers, the AFBR looks up
its forwarding table to check the IP address of each outgoing its forwarding table to check the IP address of each outgoing
interface. If there exists at least one outgoing interface whose IP interface. If there exists 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
should encapsulate/decapsulate this packet and forward it to such MUST encapsulate/decapsulate this packet and forward it to such
outgoing interface(s), then forward the data to other outgoing outgoing interface(s), then forward the data to other outgoing
interfaces without encapsulation/decapsulation. interfaces without encapsulation/decapsulation.
When a downstream AFBR that has already switched over to SPT of S When a downstream AFBR that has already switched over to 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 7.2. Selecting a Tunneling Technology
Choosing tunneling technology depends on the policies configured at Choosing tunneling technology depends on the policies configured at
AFBRs. It's recommended that all AFBRs use the same technology, AFBRs. It is recommended that all AFBRs use the same technology,
otherwise some AFBRs may not be able to decapsulate encapsulated otherwise some AFBRs may 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 7.3. TTL
Processing of TTL depends on the tunneling technology, and is out of Processing of TTL depends on the tunneling technology, and it is out
scope of this document. of scope of this document.
7.4. Fragmentation 7.4. Fragmentation
The encapsulation performed by upstream AFBR will increase the size The encapsulation performed by upstream AFBR will increase the size
of packets. As a result, the outgoing I-IP link MTU may not of packets. As a result, the outgoing I-IP link MTU may not
accommodate the extra size. As it's not always possible for core accommodate the extra size. As it is not always possible for core
operators to increase the MTU of every link. Fragmentation and operators to increase the MTU of every link. Fragmentation and
reassembling of encapsulated packets MUST be supported by AFBRs. reassembling of encapsulated packets MUST be supported by AFBRs.
8. Security Considerations 8. Packet Format and Translation
Some schemes will cause heavy burden on routers, which can be used by Because PIM-SM Specification is independent of the underlying unicast
routing protocol, the packet format in Section 4.9 of [RFC7761]
remains the same, except that the group address and source address
MUST be translated when traversing AFBR.
For example, Figure 8 shows the register-stop message format in IPv4
and IPv6 address family.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Group Address (Encoded-Group format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Source Address (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1). IPv4 Register-Stop Message Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PIM Ver| Type | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Group Address (Encoded-Group format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Source Address (Encoded-Unicast format) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2). IPv6 Register-Stop Message Format
Figure 8: Register-Stop Message Format
In Figure 8, the semantics of fields "PIM Ver", "Type", "Reserved",
"Checksum" remain the same.
IPv4 Group Address (Encoded-Group format): The encoded-group format
of the IPv4 group address mentioned in Section 4.2 and 5.2.
IPv4 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv4 source address mentioned in Section 4.3 and 5.3.
IPv6 Group Address (Encoded-Group format): The encoded-group format
of the IPv6 group address mentioned in Section 4.2 and 5.2.
IPv6 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv6 source address mentioned in Section 4.3 and 5.3.
9. Softwire Mesh Multicast Encapsulation
Softwire mesh multicast encapsulation does not require the use of any
one particular encapsulation mechanism. Rather, it MUST accommodate
a variety of different encapsulation mechanisms, and MUST allow the
use of encapsulation mechanisms mentioned in [RFC4925].
10. Security Considerations
Some schemes will place heavy burden on routers, which can be used by
attackers as a tool when they carry out DDoS attack. Compared with attackers as a tool when they carry out DDoS attack. Compared with
[RFC4925] , the security concerns should be more carefully [RFC4925], the security concerns SHOULD be considered more carefully.
considered. The attackers can set up many multicast trees in the The attackers can set up many multicast trees in the edge networks,
edge networks, causing too many multicast states in the core network. causing too many multicast states in the core network.
Besides, this document does not introduce any new security concern in Besides, this document does not introduce any new security concern in
addition to what is discussed in [RFC4925] and [RFC4601]. addition to what is discussed in [RFC4925] and [RFC7761].
9. IANA Considerations 11. IANA Considerations
When AFBRs perform address mapping, they should follow some When AFBRs perform address mapping, they follow some predefined
predefined rules, especially the IPv6 prefix for source address rules, especially the IPv6 prefix for source address mapping should
mapping should be predefined, such that ingress AFBRs and egress be predefined, such that ingress AFBRs and egress AFBRs can complete
AFBRs can complete the mapping procedure correctly. The IPv6 prefix the mapping procedure correctly. The IPv6 prefix for translation can
for translation can be unified within only the transit core, or be unified within only the transit core, or within global area. In
within global area. In the later condition, the prefix should be the later condition, the prefix MUST be assigned by IANA.
assigned by IANA.
10. References 12. References
10.1. Normative References 12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<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>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>. December 2005, <http://www.rfc-editor.org/info/rfc4301>.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601,
DOI 10.17487/RFC4601, August 2006,
<http://www.rfc-editor.org/info/rfc4601>.
[RFC4925] Li, X., Ed., Dawkins, S., Ed., Ward, D., Ed., and A. [RFC4925] Li, X., Ed., Dawkins, S., Ed., Ward, D., Ed., and A.
Durand, Ed., "Softwire Problem Statement", RFC 4925, Durand, Ed., "Softwire Problem Statement", RFC 4925,
DOI 10.17487/RFC4925, July 2007, DOI 10.17487/RFC4925, July 2007,
<http://www.rfc-editor.org/info/rfc4925>. <http://www.rfc-editor.org/info/rfc4925>.
[RFC5565] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh [RFC5565] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009, Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009,
<http://www.rfc-editor.org/info/rfc5565>. <http://www.rfc-editor.org/info/rfc5565>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010, DOI 10.17487/RFC6052, October 2010,
<http://www.rfc-editor.org/info/rfc6052>. <http://www.rfc-editor.org/info/rfc6052>.
[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>.
10.2. Informative References [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <http://www.rfc-editor.org/info/rfc7761>.
12.2. 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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