draft-ietf-softwire-mesh-multicast-01.txt   draft-ietf-softwire-mesh-multicast-02.txt 
Network Working Group M. Xu Network Working Group M. Xu
Internet-Draft Y. Cui Internet-Draft Y. Cui
Expires: May 1, 2012 S. Yang Expires: October 20, 2012 S. Yang
J. Wu J. Wu
Tsinghua University Tsinghua University
C. Metz C. Metz
G. Shepherd G. Shepherd
Cisco Systems Cisco Systems
October 29, 2011 April 18, 2012
Softwire Mesh Multicast Softwire Mesh Multicast
draft-ietf-softwire-mesh-multicast-01 draft-ietf-softwire-mesh-multicast-02
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 attendant protocol suites support multicast of the families and their attendant protocol suites support multicast of the
single-source and any-source varieties. As part of the transition to single-source and any-source varieties. As part of the transition to
IPv6, there will be scenarios where a backbone network running one IP IPv6, 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
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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 May 1, 2012. This Internet-Draft will expire on October 20, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2012 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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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Scenarios of Interest . . . . . . . . . . . . . . . . . . . . 7 3. Scenarios of Interest . . . . . . . . . . . . . . . . . . . . 7
3.1. IPv4-over-IPv6 . . . . . . . . . . . . . . . . . . . . . . 7 3.1. IPv4-over-IPv6 . . . . . . . . . . . . . . . . . . . . . . 7
3.2. IPv6-over-IPv4 . . . . . . . . . . . . . . . . . . . . . . 8 3.2. IPv6-over-IPv4 . . . . . . . . . . . . . . . . . . . . . . 8
4. IPv4-over-IPv6 . . . . . . . . . . . . . . . . . . . . . . . . 10 4. IPv4-over-IPv6 . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Source Address Mapping . . . . . . . . . . . . . . . . . . 10 4.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 10
4.3. Group Address Mapping . . . . . . . . . . . . . . . . . . 12 4.3. Source Address Mapping . . . . . . . . . . . . . . . . . . 11
4.4. Actions performed by AFBR . . . . . . . . . . . . . . . . 12 4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 12
4.5. Distribution of Routing Information among AFBRs . . . . . 13 4.5. Actions performed by AFBR . . . . . . . . . . . . . . . . 12
5. IPv6-over-IPv4 . . . . . . . . . . . . . . . . . . . . . . . . 14 5. IPv6-over-IPv4 . . . . . . . . . . . . . . . . . . . . . . . . 16
5.1. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . 14 5.1. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . 16
5.2. Source Address Mapping . . . . . . . . . . . . . . . . . . 14 5.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 16
5.3. Group Address Mapping . . . . . . . . . . . . . . . . . . 15 5.3. Source Address Mapping . . . . . . . . . . . . . . . . . . 16
5.4. Actions performed by AFBR . . . . . . . . . . . . . . . . 16 5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 17
5.5. Distribution of Routing Information among AFBRs . . . . . 16 5.5. Actions performed by AFBR . . . . . . . . . . . . . . . . 18
6. Other Consideration . . . . . . . . . . . . . . . . . . . . . 17 6. Other Consideration . . . . . . . . . . . . . . . . . . . . . 21
6.1. Selecting a Tunneling Technology . . . . . . . . . . . . . 17 6.1. Selecting a Tunneling Technology . . . . . . . . . . . . . 21
6.2. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 17 6.2. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 21
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 7. Security Considerations . . . . . . . . . . . . . . . . . . . 22
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . . 20 9.1. Normative References . . . . . . . . . . . . . . . . . . . 24
9.2. Informative References . . . . . . . . . . . . . . . . . . 20 9.2. Informative References . . . . . . . . . . . . . . . . . . 24
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 21 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
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 attendant protocol suites support multicast of the families and their attendant protocol suites support multicast of the
single-source and any-source varieties. As part of the transition to single-source and any-source varieties. As part of the transition to
IPv6, there will be scenarios where a backbone network running one IP IPv6, 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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\_._._._._._._._._._._._._./ \_._._._._._._._._._._._._./
+ + + +
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: Terminology used in this document:
o Address Family Border Router (AFBR) - A dual-stack router o Address Family Border Router (AFBR) - A dual-stack router
interconnecting two or more networks using different IP address interconnecting two or more networks using different IP address
families. In the context of softwire mesh multicast, the AFBR runs families. In the context of softwire mesh multicast, the AFBR runs
E-IP and I-IP control planes to maintain E-IP and I-IP multicast E-IP and I-IP control planes to maintain E-IP and I-IP multicast
states respectively and performs the appropriate encapsulation/ states respectively and performs the appropriate encapsulation/
decapsulation of client E-IP multicast packets for transport across decapsulation of client E-IP multicast packets for transport across
the I-IP core. An AFBR will act as a source and/or receiver in an the I-IP core. An AFBR will act as a source and/or receiver in an
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\_._._._._._._._._._._._._./ \_._._._._._._._._._._._._./
+ + + +
downstream AFBR(C) downstream AFBR(D) downstream AFBR(C) downstream AFBR(D)
| | | |
._._._._ ._._._._ ._._._._ ._._._._
-------- | IPv4 | | IPv4 | -------- -------- | IPv4 | | IPv4 | --------
|Receiver|-- | Client | | Client |--|Receiver| |Receiver|-- | Client | | Client |--|Receiver|
-------- | network| | network| -------- -------- | network| | network| --------
._._._._ ._._._._ ._._._._ ._._._._
Figure 2: IPv4-over-IPv6 Scenario Figure 2: IPv4-over-IPv6 Scenario
In this scenario, the E-IP client networks run IPv4 and I-IP core In this scenario, the E-IP client networks run IPv4 and I-IP core
runs IPv6. This scenario is illustrated in Figure 2. runs IPv6. This scenario is illustrated in Figure 2.
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.
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\_._._._._._._._._._._._._./ \_._._._._._._._._._._._._./
+ + + +
downstream AFBR downstream AFBR downstream AFBR downstream AFBR
| | | |
._._._._ ._._._._ ._._._._ ._._._._
-------- | IPv6 | | IPv6 | -------- -------- | IPv6 | | IPv6 | --------
|Receiver|-- | Client | | Client |--|Receiver| |Receiver|-- | Client | | Client |--|Receiver|
-------- | network| | network| -------- -------- | network| | network| --------
._._._._ ._._._._ ._._._._ ._._._._
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
skipping to change at page 10, line 12 skipping to change at page 10, line 12
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.
4. IPv4-over-IPv6 4. IPv4-over-IPv6
4.1. Mechanism 4.1. Mechanism
Routers in the client E-IPv4 networks contain routes to all other Routers in the client E-IPv4 networks contain routes to all other
client E-IPv4 networks. Through the set of known and deployed client E-IPv4 networks. Through the set of known and deployed
mechanisms, E-IPv4 hosts and routers have discovered or learned of mechanisms, E-IPv4 hosts and routers have discovered or learned of
(S,G) or (*,G) IPv4 addresses. Any I-IP multicast state instantiated (S,G) or (*,G) IPv4 addresses. Any I-IPv6 multicast state
in the core is referred to as (S',G') or (*,G') and is certainly instantiated in the core is referred to as (S',G') or (*,G') and is
separated from E-IP multicast state. certainly separated from E-IP 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 should be translated back into an E-IPv4 PIM
message. The result of these actions is the construction of E-IPv4 message. The result of these actions is the construction of E-IPv4
trees and a corresponding I-IP tree in the I-IP network. trees and a 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. Source Address Mapping 4.2. Group Address Mapping
There are two kinds of multicast --- ASM and SSM. It's possible for For IPv4-over-IPv6 scenario, a simple algorithmic mapping between
I-IP network and E-IP network to support different kinds of IPv4 multicast group addresses and IPv6 group addresses is supported.
multicast, and the source address translation rules may vary a lot. [11] has already defined an applicable format. Figure 4 is the
There are four scenarios to be discussed in detail: reminder of the format:
| 8 | 4 | 4 | 16 | 4 | 60 | 32 |
+--------+----+----+-----------+----+------------------+----------+
|11111111|0011|scop|00.......00|64IX| sub-group-id |v4 address|
+--------+----+----+-----------+----+------------------+----------+
+-+-+-+-+
IPv4-IPv6 Interconnection bits (64IX): |M|r|r|r|
+-+-+-+-+
Figure 4: IPv4-Embedded IPv6 Multicast Address Format: SSM Mode
The high order bits of the I-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 IPv4 multicast address.
4.3. 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 could be very complex
to support all possible scenarios. But since SSM can be implemented
with a strict subset of the PIM-SM protocol mechanisms [5], we 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:
o E-IP network supports SSM
o E-IP network supports SSM, I-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 4 is the address that leads to the upstream AFBR. Figure 5 is the
recommended address format based on [9]: recommended address format based on [9]:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 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------------------>| |<------------------uPrefix64------------------>|
Figure 4: 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 a 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 [9]; "v4" field is the IP address is 64:ff9b, which is defined in [9]; "v4" field is the IP address
of one of upstream AFBR's E-IPv4 interface; "u" field is defined of one of upstream AFBR's E-IPv4 interfaces; "u" field is defined
in [4], and MUST be set to zero; "suffix" field is reserved for in [4], and MUST be set to zero; "suffix" field is reserved for
future extensions and SHOULD be set to zero; "source address" future extensions and SHOULD be set to zero; "source address"
field stores the original S. We call the overall /96 prefix field stores the original S. We call the overall /96 prefix
("prefix" field and "v4" field and "u" field and "suffix" field ("prefix" field and "v4" field and "u" field and "suffix" field
altogether) "uPrefix64". altogether) "uPrefix64".
To make it feasible, the /32 prefix must be known to every AFBR,
and every AFBR should not only announce the IP address of one of
its E-IPv4 interface presented in the "v4" field to other AFBRs by
MPBGP, but also announce the corresponding uPrefix64 to the I-IPv6
network. Since every IP address of upstream AFBR's E-IPv4
interface is different from each other, every uPrefix64 that AFBR
announces shoud be different either, and uniquely identifies each
AFBR. In this way, when a downstream AFBR receives a (S,G)
message, it can translate it into (S',G') by looking up 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 network, the translated message will eventually arrive at
the corresponding upstream AFBR, and the upstream AFBR can
translate the message back to (S,G).
o E-IP network supports SSM, I-IP network supports ASM o E-IP network supports ASM
Since any network that supports ASM can also support SSM, we can
construct a SSM tree in I-IP network. The operation in this
scenario is the same as that in the first scenario.
o E-IP network supports ASM, I-IP network supports SSM ASM and SSM have simalar PIM message format. The main differences
ASM and SSM have the same PIM message format. The main between ASM and SSM are RP and (*,G) messages. To make this
differences between ASM and SSM are RP and (*,G) messages. To scenario feasible, we must be able to translate (*,G) messages
make this scenario feasible, we must be able to translate (*,G) into (S',G') messages at downstream AFBRs, and translate it back
messages into (S',G') messages at downstream AFBRs, and translate at upstream AFBRs.
it back at upstream AFBRs. Assume RP' is the upstream AFBR that
locates between RP and the downstream AFBR. When a downstream
AFBR receives an E-IPv4 PIM (*,G) message, S' can be generated
according to the format specified in Figure 4, with "v4" field
setting to the IP address of one of RP's E-IPv4 interface and
"source address" field setting to *(the IPv4 address of RP). The
translated message will eventually arrive at RP'. RP' checks the
"source address" field and finds the IPv4 address of RP, so RP'
judges that this is originally a (*,G) message, then it translates
the message back to (*,G) message and forwards it to RP.
o E-IP network supports ASM, I-IP network supports ASM 4.4. Routing Mechanism
To keep it as simple as possible, we treat I-IP network as SSM and
the solution is the same as the third scenario.
4.3. Group Address Mapping In the mesh multicast scenario, routing information is required to
distribute among AFBRs to make sure that PIM messages a downstream
AFBR send reach the right upstream AFBR.
For IPv4-over-IPv6 scenario, a simple algorithmic mapping between To make it feasible, the /32 prefix in "IPv4-Embedded IPv6 Virtual
IPv4 multicast group addresses and IPv6 group addresses is supported. Source Address Format" must be known to every AFBR, and every AFBR
[11] has already defined an applicable format. Figure 5 is the should not only announce the IP address of one of its E-IPv4
reminder of the format: interfaces presented in the "v4" field to other AFBRs by MPBGP, but
also announce the corresponding uPrefix64 to the I-IPv6 network.
Since every IP address of upstream AFBR's E-IPv4 interface is
different from each other, every uPrefix64 that AFBR announces should
be different either, and uniquely identifies each AFBR. As uPrefix64
is an IPv6 prefix, the distribution of uPrefix64 is the same as the
distribution in mesh unicast scenario. But since "v4" field is an
E-IPv4 address, and BGP messages are NOT tunneled through softwires
or through any other mechanism as specified in [8], AFBRs MUST be
able to transport and encode/decode BGP messages that are carried
over I-IPv6, whose NLRI and NH are of E-IPv4 address family.
| 8 | 4 | 4 | 16 | 4 | 60 | 32 | In this way, when a downstream AFBR receives an E-IPv4 PIM (S,G)
+--------+----+----+-----------+----+------------------+----------+ message, it can translate it into (S',G') by looking up the IP
|11111111|0011|scop|00.......00|64IX| sub-group-id |v4 address| 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
+-+-+-+-+ network, the translated message will eventually arrive at the
IPv4-IPv6 Interconnection bits (64IX): |M|r|r|r| corresponding upstream AFBR, and the upstream AFBR can translate the
+-+-+-+-+ 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
in Figure 4, with "source address" field setting to *(the IPv4
address of RP). The translated message will eventually arrive at the
corresponding 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 Section 4.7 of [5]), when this upstream AFBR checks
the "source address" field of the message, it'll find the IPv4
address of RP, so this upstream AFBR judges that this is originally a
(*,G) message, then it translates the message back to the (*,G)
message and processes it.
Figure 5: IPv4-Embedded IPv6 Multicast Address Format: SSM Mode 4.5. Actions performed by AFBR
The high order bits of the I-IPv6 address range will be fixed for The following actions are performed by AFBRs:
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 IPv4 multicast address.
4.4. Actions performed by AFBR o E-IPv4 (*,G) state maintenance
The following actions are performed by AFBRs: When an AFBR wishes to propagate a (*,G) Join/Prune message to an
I-IPv6 upstream router, the AFBR MUST translate (*,G) Join/Prune
messages into (S',G') Join/Prune messages following the rules
specified above, then send the latter.
o Receive E-IPv4 PIM messages o E-IPv4 (S,G) state maintenance
When a downstream AFBR receives an E-IPv4 PIM message, it should
check the address family of the next-hop towards the destination.
If the address family is IPv4, the AFBR should forward the message
without any translation; otherwise it should take the following
operation.
o Translate E-IPv4 PIM messages into I-IPv6 PIM messages When an AFBR wishes to propagate a (S,G) Join/Prune message to an
E-IPv4 PIM message with S(or *) and G is translated into I-IPv6 I-IPv6 upstream router, the AFBR MUST translate (S,G) Join/Prune
PIM message with S' and G' following the rules specified above. messages into (S',G') Join/Prune messages following the rules
specified above, then send the latter.
o Transmit I-IPv6 PIM messages o I-IPv6 (S',G') state maintenance
The downstream AFBR sends the I-IPv6 PIM message to the upstream
AFBR. When the upstream AFBR receives this I-IPv6 PIM message, it It is possible that there runs a pure I-IPv6 PIM-SSM in the I-IPv6
checks the prefix of the source address and judges that the transit core. Since the translated souce address starts with the
message is a translated message, then translates the message back unique "Well-Known" prefix or the ISP-defined prefix that should
to E-IPv4 PIM message and sends it towards source or RP. not be used otherwise, mash multicast won't influnce pure PIM-SM
multicast at all. When one AFBR receives a I-IPv6 (S',G')
message, it should check S'. If S' starts with the unique prefix,
it means that this message is actually a translated E-IPv4 (S,G)
or (*,G) message, then the AFBR should translate this message back
to E-IPv4 PIM message and process it.
o E-IPv4 (S,G,rpt) state maintenance
When an AFBR wishes to propagate a (S,G,rpt) Join/Prune message to
an I-IPv6 upstream router, the AFBR MUST do as follows.
o Inter-AFBR signaling
(S,G,rpt) messages are not supported by I-IPv6 transit core since
I-IPv6 transit core only works in SSM. As a result, we're unable
to stop receiving data from any given S along the RP tree even if
downstream AFBR has already switched over to the SPT, which may
bring about a lot of redundancy. In order to solve this problem,
we introduce a new mechanism for downstream AFBR to inform
upstream AFBR to prune a given S from RPT, in order to reduce
redundancy.
When a downstream AFBR wishes to propagate a (S,G,rpt) message to
I-IPv6 upstream router, it should encapsulate the (S,G,rpt)
message, then unicast the encapsulated message to the
corresponding upstream AFBR, which we call it "RP'".
The encapsulated message will evevtually arrive at RP', but the
incoming interface of it may be different from the outcoming
interface along the RP tree to the corresponding downstream AFBR
that send this message, so RP' is unable to determine the
(S,G,rpt) state of each I-IPv6 outgoing interface. To solve this
problem, and keep the solution as simple as possible, we
conceptually treat all the I-IPv6 outgoing interfaces as equal,
and introduce a "virtual interface" as the representative of all
the I-IPv6 outgoing interfaces, which is specified in Figure 6.
+----------------------------------------+
| |
| +-----------+----------+ |
| | PIM-SSM | UDP | |
| +-----------+----------+ |
| ^ | |
| | | |
| | v |
| +----------------------+ |
| | Virtual I/F | |
| +----------------------+ |
| PIM ^ | multicast |
| messages | | data |
| | +-------------+---+ |
| +--+--|-----------+ | |
| | v | v |
| +--------- + +----------+ |
| | I-IP I/F | | I-IP I/F | |
| +----------+ +----------+ |
| ^ | ^ | |
| | | | | |
+--------|-----|----------|-----|--------+
| v | v
Figure 6: upstream AFBR virtual interface
The virtual interface has two responsibilities: On control plane,
it should process the encapsulated (S,G,rpt) messages received
from all the I-IPv6 interfaces, and work as a real interface that
has joint (*,G). Since all the I-IPv6 interfaces are treated
equal, the virtual interface only send (S,G,rpt) Prune messages to
PIM-SSM module when every received encapsulated message has a
(S,G,rpt) Prune inside, which means that no downstream AFBR want
to receive data from source S of group G along the RPT; On data
plane, upon receiving a multicast data packet, the virtual
interface should encapsulate it at first, then send to every
I-IPv6 interface a copy of the encapsulated data.In this way,
downstream AFBRS may receive some redundant data, but avoid black
holes.
NOTICE: There may exist an E-IPv4 neighbor of RP' that has joint
the RP tree, so the per-interface state machine for receiving
E-IPv4 (S,G,rpt) Join/Prune messages should still take effect.
o Process and forward multicast data o Process and forward multicast data
On receiving multicast data from upstream routers, the AFBR looks On receiving multicast data from upstream routers, the AFBR looks
up its forwarding table to check the IP address of each outgoing up its forwarding table to check the IP address of each outgoing
interface. If there exists at least one outgoing interface whose interface. If there exists at least one outgoing interface whose
IP address family is different from the incoming interface, the IP address family is different from the incoming interface, the
AFBR should encapsulate/decapsulate this packet and forward it to AFBR should encapsulate/decapsulate this packet and forward it to
the outgoing interface(s), then forward the data to other outgoing the outgoing interface(s), then forward the data to other outgoing
interfaces without encapsulation/decapsulation. interfaces without encapsulation/decapsulation.
4.5. Distribution of Routing Information among AFBRs Since all I-IP interfaces of upstream AFBR are treated equal, a
AFBR may receive encapsulated data from S along the RP tree even
if it has already switched over to SPT of S. At this time, the
AFBR should silently drop this data.
It is described in [8] that AFBRs take advantage of BGP to distribute o SPT switchover
the E-IP routing information to each other by I-IP transport. In
IPv4-over-IPv6 scenario of softwire mesh multicast in addition, every
AFBR should not only announce the IP address of one of its E-IPv4
interface presented in the "v4" field to other AFBRs, but also
announce the corresponding uPrefix64 to the I-IPv6 network to ensure
the softwire mesh multicast mechanism functions properly. This
should also be done by BGP.
As uPrefix64 is an IPv6 prefix, the distribution of uPrefix64 is the When a new AFBR expresses its interest in receiving traffic
same as the the distribution in unicast scenario. But since "v4" destined for a multicast group, it needs to receive all the data
field is an E-IPv4 address, and BGP messages are NOT tunneled through along the RP tree at first. But since downstream AFBRs in fact
softwires or through any other mechanism as specified in [8], AFBRs receive the union set of data needed by every downstream AFBR, RP'
MUST be able to transport and encode/decode BGP messages that are has to forward all the data from RP to all the downstream AFBRs.
carried over I-IPv6, whose NLRI and NH are of E-IPv4 address family. As a result, the downstream AFBRs that have already switched to
the shortest-path tree will receive two copies of the same data,
namely redundancy.
To reduce the redundancy, we recommend every AFBR's
SwitchToSptDesired(S,G) function employ the "switch on first
packet" policy. In this way, the delay of switchover to SPT is
kept as little as possible, so is the redundancy.
5. IPv6-over-IPv4 5. IPv6-over-IPv4
5.1. Mechanism 5.1. Mechanism
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 learned of mechanisms, E-IPv6 hosts and routers have discovered or learned 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's 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 a ISP-defined prefix. Known" prefix or an ISP-defined prefix.
5.2. Source Address Mapping 5.2. Group Address Mapping
There are two kinds of multicast --- ASM and SSM. It's possible for To keep one-to-one group address mapping simple, the group address
I-IP network and E-IP network to support different kind of multicast, range of E-IP IPv6 can be reduced in a number of ways to limit the
and the source address translation rules may vary a lot. There are scope of addresses that need to be mapped into the I-IP IPv4 space.
four scenarios to be discussed in detail:
A recommended multicast address format is defined in [11]. 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 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 could be very complex
to support all possible scenarios. But since SSM can be implemented
with a strict subset of the PIM-SM protocol mechanisms [5], we 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:
o E-IP network supports SSM
o E-IP network supports SSM, I-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.
We apply a fixed IPv6 prefix and static mapping to solve this We apply a fixed IPv6 prefix and static mapping to solve this
problem. A recommended source address format is defined in [9]. problem. A recommended source address format is defined in [9].
Figure 6 is the reminder of the format: Figure 7 is the reminder of the format:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0-------------32--40--48--56--64--72--80--88--96-----------127| | 0-------------32--40--48--56--64--72--80--88--96-----------127|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| uPrefix64 |source address | | uPrefix64 |source address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 6: IPv4-Embedded IPv6 Source Address Format Figure 7: 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 a 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 [9]; "source address" prefix is 64:ff9b/32, which is defined in [9]; "source address"
field is the corresponding I-IPv4 source address. field is the corresponding I-IPv4 source address.
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 should announce the I-IPv4 address in
"source address" field to the I-IPv4 network. 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 eventually arrive at the corresponding upstream AFBR,
and the upstream AFBR can translate the message back to (S,G) by
appending the prefix to S'.
o E-IP network supports SSM, I-IP network supports ASM o E-IP network supports ASM
Since any network that supports ASM can also support SSM, we can
construct a SSM tree in I-IP network. The operation in this
scenario is the same as that in the first scenario.
o E-IP network supports ASM, I-IP network supports SSM ASM and SSM have similar PIM message format. The main differences
ASM and SSM have the same PIM message format. The main between ASM and SSM are RP and (*,G) messages. To make this
differences between ASM and SSM are RP and (*,G) messages. To scenario feasible, we must be able to translate (*,G) messages
make this scenario feasible, we must be able to translate (*,G) into (S',G') messages at downstream AFBRs and translate it back at
messages into (S',G') messages at downstream AFBRs and translate upstream AFBRs. Here, the E-IPv6 address of RP MUST follow the
it back at upstream AFBRs. Here, the E-IPv6 address of RP MUST format specified in Figure 7. Assume RP' is the upstream AFBR
follow the format specified in Figure 6. Assume RP' is the that locates between RP and the downstream AFBR.
upstream AFBR that locates between RP and the downstream AFBR.
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 eventually arrive at RP'.
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 forward it to RP.
o E-IP network supports ASM, I-IP network supports ASM 5.4. Routing Mechanism
To keep it as simple as possible, we treat I-IP network as SSM and
the solution is the same as the third scenario.
5.3. Group Address Mapping In the mesh multicast scenario, routing information is required to
distribute among AFBRs to make sure that PIM messages a downstream
AFBR send reach the right upstream AFBR.
To keep one-to-one group address mapping simple, the group address To make it feasible, the /96 uPrefix64 must be known to every AFBR,
range of E-IP IPv6 can be reduced in a number of ways to limit the every E-IPv6 address of sources that support mesh multicast MUST
scope of addresses that need to be mapped into the I-IP IPv4 space. follow the format specified in Figure 7, and the corresponding
upstream AFBR should announce the I-IPv4 address in "source address"
field 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.
A recommended multicast address format is defined in [11]. The high The distribution of "source address" field of multicast source
order bits of the E-IPv6 address range will be fixed for mapping addresses is a pure I-IPv4 process and no more specification is
purposes. With this scheme, each IPv4 multicast address can be needed.
mapped into an IPv6 multicast address(with the assigned prefix), and
each IPv6 multicast address with the assigned prefix can be mapped
into IPv4 multicast address.
5.4. Actions performed by AFBR 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 eventually arrive at 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
eventually arrive at 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 [5]), 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.
The following actions are performed by AFBRs 5.5. Actions performed by AFBR
o Receive E-IPv6 PIM messages The following actions are performed by AFBRs:
When a downstream AFBR receives an E-IPv6 PIM message, it should
check the address family of the upstream router. If the address
family is IPv6, the AFBR should not translate this message;
otherwise it should take the following operation.
o Translate E-IPv6 PIM messages into I-IPv4 PIM messages o E-IPv6 (*,G) state maintenance
E-IPv6 PIM message with S(or *) and G is translated into I-IPv4
PIM message with S' and G' following the rules specified above.
o Transmit I-IPv4 PIM messages When an AFBR wishes to propagate a (*,G) Join/Prune message to an
The downstream AFBR sends the I-IPv4 PIM message to the upstream I-IPv4 upstream router, the AFBR MUST translate (*,G) Join/Prune
AFBR. When the upstream AFBR receives this I-IPv4 PIM message, it messages into (S',G') Join/Prune messages following the rules
checks the source address and judges that the message is a specified above, then send the latter.
translated message, then translates the message back to E-IPv6 PIM
message and sends it towards source or RP. o E-IPv6 (S,G) state maintenance
When an AFBR wishes to propagate a (S,G) Join/Prune message to an
I-IPv4 upstream router, the AFBR MUST translate (S,G) Join/Prune
messages into (S',G') Join/Prune messages following the rules
specified above, then send the latter.
o I-IPv4 (S',G') state maintenance
It is possible that there runs a pure I-IPv4 PIM-SSM in the I-IPv4
transit core. Since the translated souce address is known to the
corresponding upstream AFBR, mash multicast won't influnce pure
PIM-SM multicast at all. When one AFBR receives a (S',G') message
whose S' is the "source address" field of an E-IPv6 source, which
means that this message is actually a translated E-IPv6 (S,G) or
(*,G) message, it should translate this message back to E-IPv6 PIM
message and process it.
o E-IPv6 (S,G,rpt) state maintenance
When an AFBR wishes to propagate a (S,G,rpt) Join/Prune message to
an I-IPv4 upstream router, the AFBR MUST do as follows.
o Inter-AFBR signaling
(S,G,rpt) messages are not supported by I-IPv4 transit core since
I-IPv4 transit core only works in SSM. As a result, we're unable
to stop receiving data from any given S along the RP tree even if
downstream AFBR has already switched over to the SPT, which may
bring about a lot of redundancy. In order to solve this problem,
we introduce a new mechanism for downstream AFBR to inform
upstream AFBR to prune a given S from RPT, in order to reduce
redundancy.
When a downstream AFBR wishes to propagate a (S,G,rpt) message to
I-IPv4 upstream router, it should encapsulate the (S,G,rpt)
message, then unicast the encapsulated message to the
corresponding upstream AFBR, which we call it "RP'".
The encapsulated message will evevtually arrive at RP', but the
incoming interface of it may be different from the outcoming
interface along the RP tree to the corresponding downstream AFBR
that send this message, so RP' is unable to determine the
(S,G,rpt) state of each I-IPv4 outgoing interface. To solve this
problem, and keep the solution as simple as possible, we
conceptually treat all the I-IPv4 outgoing interfaces as equal,
and introduce a "virtual interface" as the representative of all
the I-IPv4 outgoing interfaces, which is specified in Figure 6.
The virtual interface has two responsibilities: On control plane,
it should process the encapsulated (S,G,rpt) messages received
from all the I-IPv4 interfaces, and work as a real interface that
has joint (*,G). Since all the I-IPv4 interfaces are treated
equal, the virtual interface only send (S,G,rpt) Prune messages to
PIM-SSM module when every received encapsulated message has a
(S,G,rpt) Prune inside, which means that no downstream AFBR want
to receive data from source S of group G along the RPT; On data
plane, upon receiving a multicast data packet, the virtual
interface should encapsulate it at first, then send to every
I-IPv4 interface a copy of the encapsulated data.In this way,
downstream AFBRS may receive some redundant data, but avoid black
holes.
NOTICE: There may exist an E-IPv6 neighbor of RP' that has joint
the RP tree, so the per-interface state machine for receiving
E-IPv6 (S,G,rpt) Join/Prune messages should still take effect.
o Process and forward multicast data o Process and forward multicast data
On receiving multicast data from upstream routers, the AFBR looks On receiving multicast data from upstream routers, the AFBR looks
up its forwarding table to check the IP address of each outgoing up its forwarding table to check the IP address of each outgoing
interface. If there exists at least one outgoing interface whose interface. If there exists at least one outgoing interface whose
IP address family is different from the incoming interface, the IP address family is different from the incoming interface, the
AFBR should encapsulate/decapsulate this packet and forward it to AFBR should encapsulate/decapsulate this packet and forward it to
the outgoing interface(s), and then forward the data to the other the outgoing interface(s), then forward the data to other outgoing
outgoing interfaces without encapsulation/decapsulation. interfaces without encapsulation/decapsulation.
5.5. Distribution of Routing Information among AFBRs Since all I-IP interfaces of upstream AFBR are treated equal, a
AFBR may receive encapsulated data from S along the RP tree even
if it has already switched over to SPT of S. At this time, the
AFBR should silently drop this data.
Since uPrefix64 is static and unique in IPv6-over-IPv4 scenario, o SPT switchover
there is no need to distribute it using BGP. The distribution of
"source address" field of multicast source addresses is a pure I-IPv4 When a new AFBR expresses its interest in receiving traffic
process and no more specification is needed. destined for a multicast group, it needs to receive all the data
along the RP tree at first. But since downstream AFBRs in fact
receive the union set of data needed by every downstream AFBR, RP'
has to forward all the data from RP to all the downstream AFBRs.
As a result, the downstream AFBRs that have already switched to
the shortest-path tree will receive two copies of the same data,
namely redundancy.
To reduce the redundancy, we recommend every AFBR's
SwitchToSptDesired(S,G) function employ the "switch on first
packet" policy. In this way, the delay of switchover to SPT is
kept as little as possible, so is the redundancy.
6. Other Consideration 6. Other Consideration
6.1. Selecting a Tunneling Technology 6.1. Selecting a Tunneling Technology
The choice of tunneling technology is a matter of policy configured The choice of tunneling technology is a matter of policy configured
at AFBRs. at AFBRs.
In most cases, the policy of choosing tunneling technologies will be In most cases, the policy of choosing tunneling technologies will be
very simple, such as all AFBRs use the same technology. But it's very simple, such as all AFBRs use the same technology. But it's
possible that there doesn't exist one technique that all AFBRs possible that there doesn't exist one technique that all AFBRs
support. A recommanded solution is described in [8], which divides support. A recommended solution is described in [8], which divides
AFBRs into one or more classes, and each of these classes is assigned AFBRs into one or more classes, and each of these classes is assigned
a technology that every AFBR in this class supports. In this way, a technology that every AFBR in this class supports. In this way,
all the AFBRs in the same class can choose the right technology to all the AFBRs in the same class can choose the right technology to
communicate with each other. communicate with each other.
6.2. Fragmentation 6.2. 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's not always possible for core
skipping to change at page 20, line 40 skipping to change at page 24, line 40
[8] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh [8] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
Framework", RFC 5565, June 2009. Framework", RFC 5565, June 2009.
[9] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. Li, [9] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. Li,
"IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010. October 2010.
9.2. Informative References 9.2. Informative References
[10] Aggarwal, R., Bandi, S., Cai, Y., Morin, T., Rekhter, Y., [10] Aggarwal, R. and E. Rosen, "Multicast in MPLS/BGP IP VPNs",
Rosen, E., Wijnands, I., and S. Yasukawa, "Multicast in MPLS/ draft-ietf-l3vpn-2547bis-mcast-10 (work in progress),
BGP IP VPNs", draft-ietf-l3vpn-2547bis-mcast-10 (work in January 2010.
progress), January 2010.
[11] Boucadair, M., Qin, J., Lee, Y., Venaas, S., Li, X., and M. Xu, [11] Boucadair, M., Qin, J., Lee, Y., Venaas, S., Li, X., and M. Xu,
"IPv4-Embedded IPv6 Multicast Address Format", "IPv4-Embedded IPv6 Multicast Address Format",
draft-boucadair-behave-64-multicast-address-format-02 (work in draft-ietf-mboned-64-multicast-address-format-01 (work in
progress), June 2011. progress), February 2012.
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.
Authors' Addresses Authors' Addresses
Mingwei Xu Mingwei Xu
Tsinghua University Tsinghua University
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