draft-ietf-softwire-mesh-multicast-20.txt   draft-ietf-softwire-mesh-multicast-21.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: September 25, 2018 S. Yang Expires: December 2, 2018 Tsinghua University
Tsinghua University S. Yang
Oudmon Tech
C. Metz C. Metz
Cisco Systems Cisco Systems
March 24, 2018 May 31, 2018
IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network
draft-ietf-softwire-mesh-multicast-20 draft-ietf-softwire-mesh-multicast-21
Abstract Abstract
During the transition to IPv6, there will be scenarios where a During the transition to IPv6, there will be scenarios where a
backbone network internally running one IP address family (referred backbone network internally running one IP address family (referred
to as the internal IP or I-IP family), connects client networks to as the internal IP or I-IP family), connects client networks
running another IP address family (referred to as the external IP or running another IP address family (referred to as the external IP or
E-IP family). In such cases, the I-IP backbone needs to offer both E-IP family). In such cases, the I-IP backbone needs to offer both
unicast and multicast transit services to the client E-IP networks. unicast and multicast transit services to the client E-IP networks.
skipping to change at page 1, line 44 skipping to change at page 1, line 45
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 25, 2018. This Internet-Draft will expire on December 2, 2018.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Mesh Multicast Mechanism . . . . . . . . . . . . . . . . . . 7 5. Mesh Multicast Mechanism . . . . . . . . . . . . . . . . . . 7
4.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 8 5.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 7
4.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 8 5.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 7
4.3. Source Address Mapping . . . . . . . . . . . . . . . . . 9 5.3. Source Address Mapping . . . . . . . . . . . . . . . . . 8
4.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9 5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9
5. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10 6. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10
5.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10 6.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10
5.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10 6.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10
5.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 11 6.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 10
5.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 11 6.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 10
5.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13 6.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13
5.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13 6.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13
5.7. Other PIM States Maintenance . . . . . . . . . . . . . . 13 6.7. Other PIM States Maintenance . . . . . . . . . . . . . . 13
6. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 13 7. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 13
6.1. Process and Forward Multicast Data . . . . . . . . . . . 14 7.1. Process and Forward Multicast Data . . . . . . . . . . . 13
6.2. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.2. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14 7.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14
7. Packet Format and Translation . . . . . . . . . . . . . . . . 14 8. Packet Format and Translation . . . . . . . . . . . . . . . . 14
8. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 15 9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . 16 12.1. Normative References . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . 17 12.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
During the transition to IPv6, there will be scenarios where a During the transition to IPv6, there will be scenarios where a
backbone network internally running one IP address family (referred backbone network internally running one IP address family (referred
to as the internal IP or I-IP family), connects client networks to as the internal IP or I-IP family), connects client networks
running another IP address family (referred to as the external IP or running another IP address family (referred to as the external IP or
E-IP family). E-IP family).
One solution is to leverage the multicast functions inherent in the One solution is to leverage the multicast functions inherent in the
skipping to change at page 4, line 10 skipping to change at page 4, line 10
The need for multicast aggregation at the edge (where many customer The need for multicast aggregation at the edge (where many customer
multicast trees are mapped into one or more backbone multicast trees) multicast trees are mapped into one or more backbone multicast trees)
does not exist and to date has not been identified. Thus the need does not exist and to date has not been identified. Thus the need
for alignment between the E-IP and I-IP multicast mechanisms emerges. for alignment between the E-IP and I-IP multicast mechanisms emerges.
[RFC5565] describes the "Softwire Mesh Framework". This document [RFC5565] describes the "Softwire Mesh Framework". This document
provides a more detailed description of how one-to-one mapping provides a more detailed description of how one-to-one mapping
schemes ([RFC5565], Section 11.1) for IPv4-over-IPv6 multicast can be schemes ([RFC5565], Section 11.1) for IPv4-over-IPv6 multicast can be
achieved. achieved.
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].
Figure 1 shows an example of how a softwire mesh network can support Figure 1 shows an example of how a softwire mesh network can support
multicast traffic. A multicast source S is located in one E-IP multicast traffic. A multicast source S is located in one E-IP
client network, while candidate E-IP group receivers are located in client network, while candidate E-IP group receivers are located in
the same or different E-IP client networks that all share a common the same or different E-IP client networks that all share a common
I-IP transit network. When E-IP sources and receivers are not local I-IP transit network. When E-IP sources and receivers are not local
to each other, they can only communicate with each other through the to each other, they can only communicate with each other through the
I-IP core. There may be several E-IP sources for a single multicast I-IP core. There may be several E-IP sources for a single multicast
group residing in different client E-IP networks. In the case of group residing in different client E-IP networks. In the case of
shared trees, the E-IP sources, receivers and rendezvous points (RPs) shared trees, the E-IP sources, receivers and rendezvous points (RPs)
might be located in different client E-IP networks. In the simplest might be located in different client E-IP networks. In the simplest
case, a single operator manages the resources of the I-IP core, case, a single operator manages the resources of the I-IP core,
although the inter-operator case is also possible and so not although the inter-operator case is also possible and so not
precluded. precluded.
+---------+ +---------+ +---------+ +---------+
| | | | +--------+ | | | | +--------+
| E-IP | | E-IP |--|Source S| | E-IP | | E-IP +--+Source S|
| network | | network | +--------+ | network | | network | +--------+
+---------+ +---------+ +---+-----+ +--+------+
| | | |
+----------+ +----------+ +-+--------+ +-------+--+
| | | upstream | | | | upstream |
+-| AFBR |--| AFBR |-+ +-| AFBR +--+ AFBR |-+
| +----------+ +----------+ | | +----------+ +----------+ |
| | E-IP Multicast | | E-IP Multicast
| I-IP transit core | packets are forwarded | I-IP transit core | packets are forwarded
| | across the I-IP | | across the I-IP
| +----------+ +----------+ | transit core | +----------+ +----------+ | transit core
+-|dowstream | |downstream|-+ +-|dowstream | |downstream|-+
| AFBR |--| AFBR | | AFBR |--| AFBR |
+----------+ +----------+ +--+-------+ +--------+-+
| | | |
+--------+ +--------+ +---+----+ +---+----+
+--------+ | | | | +--------+ +--------+ | | | | +--------+
|Receiver|-- | E-IP | | E-IP |--|Receiver| |Receiver+---+ E-IP | | E-IP +--+Receiver|
+--------+ |network | |network | +--------+ +--------+ |network | |network | +--------+
+--------+ +--------+ +--------+ +--------+
Figure 1: Softwire Mesh Multicast Framework Figure 1: Softwire Mesh Multicast Framework
2. Terminology 2. 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].
3. Terminology
Terminology used in this document: Terminology used in this document:
o Address Family Border Router (AFBR) - A router interconnecting two o Address Family Border Router (AFBR) - A router interconnecting two
or more networks using different IP address families. Besides, in or more networks using different IP address families. Besides, in
the context of softwire mesh multicast, the AFBR runs E-IP and I-IP the context of softwire mesh multicast, the AFBR runs E-IP and I-IP
control planes to maintain E-IP and I-IP multicast states control planes to maintain E-IP and I-IP multicast states
respectively and performs the appropriate encapsulation/decapsulation respectively and performs the appropriate encapsulation/decapsulation
of client E-IP multicast packets for transport across the I-IP core. 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 I-IP multicast An AFBR will act as a source and/or receiver in an I-IP multicast
skipping to change at page 6, line 33 skipping to change at page 6, line 13
IPv4-embedded IPv6 unicast address [RFC6052]. IPv4-embedded IPv6 unicast address [RFC6052].
o mPrefix46: The /96 multicast IPv6 prefix for constructing an o mPrefix46: The /96 multicast IPv6 prefix for constructing an
IPv4-embedded IPv6 multicast address. IPv4-embedded IPv6 multicast address.
o PIMv4, PIMv6: refer to [RFC8114]. o PIMv4, PIMv6: refer to [RFC8114].
o Inter-AFBR signaling: A mechanism used by downstream AFBRs to send o Inter-AFBR signaling: A mechanism used by downstream AFBRs to send
PIMv6 messages to the upstream AFBR. PIMv6 messages to the upstream AFBR.
3. Scope 4. Scope
This document focuses on the IPv4-over-IPv6 scenario, as shown in the This document focuses on the IPv4-over-IPv6 scenario, as shown in the
following diagram: following diagram:
+---------+ +---------+ +---------+ +---------+
| IPv4 | | IPv4 | +--------+ | IPv4 | | IPv4 | +--------+
| Client | | Client |--|Source S| | Client | | Client |--+Source S|
| network | | network | +--------+ | Network | | Network | +--------+
+---------+ +---------+ +----+----+ +----+----+
| | | |
+----------+ +----------+ +--+-------+ +-------+--+
| | | upstream | | | | Upstream |
+-| AFBR |--| AFBR |-+ +-+ AFBR +--+ AFBR |-+
| +----------+ +----------+ | | +----------+ +----------+ |
| | | |
| IPv6 transit core | | IPv6 transit core |
| | | |
| +----------+ +----------+ | | +----------+ +----------+ |
+-|dowstream | |downstream|-+ +-+Downstream+--+Downstream+-+
| AFBR |--| AFBR | | AFBR | | AFBR |
+----------+ +----------+ +--+-------+ +-------+--+
| | | |
+--------+ +--------+ +----+----+ +----+----+
+--------+ |IPv4 | |IPv4 | +--------+ +--------+ | IPv4 | | IPv4 | +--------+
|Receiver|-- |Client | |Client |--|Receiver| |Receiver+--+ Client | | Client +--+Receiver|
+--------+ |network | |network | +--------+ +--------+ | Network | | Network | +--------+
+--------+ +--------+ +---------+ +---------+
Figure 2: IPv4-over-IPv6 Scenario Figure 2: IPv4-over-IPv6 Scenario
In Figure 2, the E-IP client networks run IPv4 and the I-IP core runs In Figure 2, the E-IP client networks run IPv4 and the I-IP core runs
IPv6. IPv6.
Because of the much larger IPv6 group address space, the client E-IP Because of the much larger IPv6 group address space, the client E-IP
tree can be mapped to a specific I-IP core tree. This simplifies tree can be mapped to a specific I-IP core tree. This simplifies
operations on the AFBR because it becomes possible to algorithmically operations on the AFBR because it becomes possible to algorithmically
map an IPv4 group/source address to an IPv6 group/source address and map an IPv4 group/source address to an IPv6 group/source address and
vice-versa. vice-versa.
The IPv4-over-IPv6 scenario is an emerging requirement as network The IPv4-over-IPv6 scenario is an emerging requirement as network
operators build out native IPv6 backbone networks. These networks operators build out native IPv6 backbone networks. These networks
support native IPv6 services and applications but in many cases, support native IPv6 services and applications but in many cases,
support for legacy IPv4 unicast and multicast services will also need support for legacy IPv4 unicast and multicast services will also need
to be accommodated. to be accommodated.
4. Mesh Multicast Mechanism 5. Mesh Multicast Mechanism
4.1. Mechanism Overview
5.1. Mechanism Overview
Routers in the client E-IP networks have routes to all other client Routers in the client E-IP networks have routes to all other client
E-IP networks. Through PIMv4 messages, E-IP hosts and routers have E-IP networks. Through PIMv4 messages, E-IP hosts and routers have
discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any I-IP discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any I-IP
multicast state instantiated in the core is referred to as (S',G') or multicast state instantiated in the core is referred to as (S',G') or
(*,G') and is certainly separated from E-IP multicast state. (*,G') and is separated from E-IP multicast state.
Suppose a downstream AFBR receives an E-IP PIM Join/Prune message Suppose a downstream AFBR receives an E-IP PIM Join/Prune message
from the E-IP network for either an (S,G) tree or a (*,G) tree. The from the E-IP network for either an (S,G) tree or a (*,G) tree. The
AFBR translates the PIMv4 message into an PIMv6 message with the AFBR translates the PIMv4 message into an PIMv6 message with the
latter being directed towards the I-IP IPv6 address of the upstream latter being directed towards the I-IP IPv6 address of the upstream
AFBR. When the PIMv6 message arrives at the upstream AFBR, it is AFBR. When the PIMv6 message arrives at the upstream AFBR, it is
translated back into an PIMv4 message. The result of these actions translated back into an PIMv4 message. The result of these actions
is the construction of E-IP trees and a corresponding I-IP tree in is the construction of E-IP trees and a corresponding I-IP tree in
the I-IP network. An example of the packet format and translation is the I-IP network. An example of the packet format and translation is
provided in Section 8. provided in Section 8.
In this case, it is incumbent upon the AFBRs to perform PIM message In this case, it is incumbent upon the AFBRs to perform PIM message
conversions in the control plane and IP group address conversions or conversions in the control plane and IP group address conversions or
mappings in the data plane. The AFBRs perform an algorithmic, one- mappings in the data plane. The AFBRs perform an algorithmic, one-
to-one mapping of IPv4-to-IPv6. to-one mapping of IPv4-to-IPv6.
4.2. Group Address Mapping 5.2. Group Address Mapping
A simple algorithmic mapping between IPv4 multicast group addresses A simple algorithmic mapping between IPv4 multicast group addresses
and IPv6 group addresses is performed. Figure 3 is provided as a and IPv6 group addresses is performed. Figure 3 is provided as a
reminder of the format: reminder of the format:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0-------------32--40--48--56--64--72--80--88--96-----------127| | 0-------------32--40--48--56--64--72--80--88--96-----------127|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| mPrefix46 |group address | | mPrefix46 | group address |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 3: IPv4-Embedded IPv6 Multicast Address Format Figure 3: IPv4-Embedded IPv6 Multicast Address Format
An IPv6 multicast prefix (mPrefix46) is provisioned on each AFBR. An IPv6 multicast prefix (mPrefix46) is provisioned on each AFBR.
AFBRs will prepend the prefix to an IPv4 multicast group address when AFBRs will prepend the prefix to an IPv4 multicast group address when
translating it to an IPv6 multicast group address. translating it to an IPv6 multicast group address.
The construction of the mPrefix46 for SSM is the same as the The construction of the mPrefix46 for SSM is the same as the
construction of the mPrefix64 described in Section 5 of [RFC8114]. construction of the mPrefix64 described in Section 5 of [RFC8114].
With this scheme, each IPv4 multicast address can be mapped into an With this scheme, each IPv4 multicast address can be mapped into an
IPv6 multicast address (with the assigned prefix), and each IPv6 IPv6 multicast address (with the assigned prefix), and each IPv6
multicast address with the assigned prefix can be mapped into an IPv4 multicast address with the assigned prefix can be mapped into an IPv4
multicast address. The group address translation algorithm can be multicast address. The group address translation algorithm can be
referred in Section 5.2 of [RFC8114]. referred in Section 5.2 of [RFC8114].
4.3. Source Address Mapping 5.3. Source Address Mapping
There are two kinds of multicast: ASM and SSM. Considering that the There are two kinds of multicast: ASM and SSM. Considering that the
I-IP network and E-IP network may support different kinds of I-IP network and E-IP network may support different kinds of
multicast, the source address translation rules needed to support all multicast, the source address translation rules needed to support all
possible scenarios may become very complex. But since SSM can be possible scenarios may become very complex. But since SSM can be
implemented with a strict subset of the PIM-SM protocol mechanisms implemented with a strict subset of the PIM-SM protocol mechanisms
[RFC7761], we can treat the I-IP core as SSM-only to make it as [RFC7761], we can treat the I-IP core as SSM-only to make it as
simple as possible. There then remain only two scenarios to be simple as possible. There then remain only two scenarios to be
discussed in detail: discussed in detail:
o E-IP network supports SSM o E-IP network supports SSM
One possible way to make sure that the translated PIMv6 message One possible way to make sure that the translated PIMv6 message
reaches upstream AFBR is to set S' to a virtual IPv6 address that reaches upstream AFBR is to set S' to a virtual IPv6 address that
leads to the upstream AFBR. The unicast adddress translation leads to the upstream AFBR. The unicast adddress translation
should be achieved according to [RFC6052] should be achieved according to [RFC6052]
o E-IP network supports ASM o E-IP network supports ASM
The (S,G) source list entry and the (*,G) source list entry only The (S,G) source list entry and the (*,G) source list entry differ
differ in that the latter has both the WildCare (WC) and RPT bits only in that the latter has both the WildCard (WC) and RPT bits of
of the Encoded-Source-Address set, while with the former, the bits the Encoded-Source-Address set, while with the former, the bits
are cleared (See Section 4.9.5.1 of [RFC7761]). So we can are cleared (See Section 4.9.5.1 of [RFC7761]). As a result, the
translate source list entries in (*,G) messages into source list source list entries in (*,G) messages can be translated into
entries in (S',G') messages by clearing both the WC and RPT bits source list entries in (S',G') messages by clearing both the WC
at downstream AFBRs, and vice-versa for the reverse translation at and RPT bits at downstream AFBRs, and vice-versa for the reverse
upstream AFBRs. translation at upstream AFBRs.
4.4. Routing Mechanism 5.4. Routing Mechanism
With mesh multicast, PIMv6 messages originating from a downstream With mesh multicast, PIMv6 messages originating from a downstream
AFBR need to be propogated to the correct upstream AFBR, and every AFBR need to be propogated to the correct upstream AFBR, and every
AFBR needs the /96 prefix in "IPv4-Embedded IPv6 Virtual Source AFBR needs the /96 prefix in "IPv4-Embedded IPv6 Virtual Source
Address Format". Address Format".
To achieve this, every AFBR MUST announce the address of one of its To achieve this, every AFBR MUST announce the address of one of its
E-IPv4 interfaces in the "v4" field alongside the corresponding E-IPv4 interfaces in the "v4" field alongside the corresponding
uPreifx64. The announcement MUST be sent to the other AFBRs through uPreifx64. The announcement MUST be sent to the other AFBRs through
MBGP [RFC4760]. Since every IP address of upstream AFBR's E-IP MBGP [RFC4760]. Every uPrefix46 that an AFBR announces MUST be
interface is different from each other, every uPrefix46 that AFBR unique. "uPrefix46" is an IPv6 prefix, and the distribution
announces MUST be different. "uPrefix46" is an IPv6 prefix, and the mechanism is the same as the traditional mesh unicast scenario.
distribution mechanism is the same as the traditional mesh unicast
scenario. But as the "v4" field is an E-IP address, and BGP messages As the "v4" field is an E-IP address, and BGP messages are not
are not tunneled through softwires or any other mechanism specified tunneled through softwires or any other mechanism specified in
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-IP, whose NLRI and NH are of E-IP messages that are carried over the I-IP, and whose NLRI and NH are of
address family. the E-IP address family.
In this way, when a downstream AFBR receives an E-IP PIM (S,G) In this way, when a downstream AFBR receives an E-IP PIM (S,G)
message, it can translate this message into (S',G') by looking up the message, it can translate this message into (S',G') by looking up the
IP address of the corresponding AFBR's E-IP interface. Since the IP address of the corresponding AFBR's E-IP interface. Since the
uPrefix46 of S' is unique, and is known to every router in the I-IP uPrefix46 of S' is unique, and is known to every router in the I-IP
network, the translated message will be forwarded to the network, the translated message will be forwarded to the
corresponding upstream AFBR, and the upstream AFBR can translate the corresponding upstream AFBR, and the upstream AFBR can translate the
message back to (S,G). message back to (S,G).
When a downstream AFBR receives an E-IP PIM (*,G) message, S' can be When a downstream AFBR receives an E-IP PIM (*,G) message, S' can be
generated according to the format specified in Figure 3, with the generated according to the format specified in Figure 3, with the
"source address" field set to * (wildcard value). The translated "source address" field set to * (wildcard value). The translated
message will be forwarded to the corresponding upstream AFBR. Since message will be forwarded to the corresponding upstream AFBR. Since
every PIM router within a PIM domain MUST be able to map a particular 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 multicast group address to the same RP (see Section 4.7 of
[RFC7761]), when the upstream AFBR checks the "source address" field [RFC7761]), when the upstream AFBR checks the "source address" field
of the message, it finds the IPv4 address of the RP, and ascertains of the message, it finds the IPv4 address of the RP, and ascertains
that this is originally a (*,G) message. This is then translated that this is originally a (*,G) message. This is then translated
back to the (*,G) message and processed. back to the (*,G) message and processed.
5. Control Plane Functions of AFBR 6. Control Plane Functions of AFBR
AFBRs are responsible for the following functions: AFBRs are responsible for the following functions:
5.1. E-IP (*,G) and (S,G) State Maintenance 6.1. E-IP (*,G) and (S,G) State Maintenance
E-IP (*,G) and (S,G) state maintenance for an AFBR is the same as E-IP (*,G) and (S,G) state maintenance for an AFBR is the same as
E-IP (*,G) and (S,G) state maintenance for an mAFTR described in E-IP (*,G) and (S,G) state maintenance for an mAFTR described in
Section 7.2 of [RFC8114] Section 7.2 of [RFC8114]
5.2. I-IP (S',G') State Maintenance 6.2. I-IP (S',G') State Maintenance
It is possible that the I-IP transit core runs another non-transit It is possible that the I-IP transit core runs another, non-transit,
I-IP PIM-SSM instance. Since the translated source address starts I-IP PIM-SSM instance. Since the translated source address starts
with the unique "Well-Known" prefix or the ISP-defined prefix that with the unique "Well-Known" prefix or the ISP-defined prefix that
SHOULD NOT be used by other service provider, mesh multicast will not MUST NOT be used by another service provider, mesh multicast will not
influence non-transit PIM-SSM multicast at all. When an AFBR influence non-transit PIM-SSM multicast at all. When an AFBR
receives an I-IP (S',G') message, it MUST check S'. If S' starts receives an I-IP (S',G') message, it MUST check S'. If S' starts
with the unique prefix, then the message is actually a translated with the unique prefix, then the message is actually a translated
E-IP (S,G) or (*,G) message, and the AFBR MUST translate this message E-IP (S,G) or (*,G) message, and the AFBR translate this message back
back to PIMv4 message and process it. to a PIMv4 message and process it.
5.3. E-IP (S,G,rpt) State Maintenance 6.3. E-IP (S,G,rpt) State Maintenance
When an AFBR wishes to propagate a Join/Prune(S,G,rpt) message to an When an AFBR wishes to propagate a Join/Prune(S,G,rpt) message to an
I-IP upstream router, the AFBR MUST operate as specified in I-IP upstream router, the AFBR MUST operate as specified in
Section 6.5 and Section 6.6. Section 6.5 and Section 6.6.
5.4. Inter-AFBR Signaling 6.4. Inter-AFBR Signaling
Assume that one downstream AFBR has joined a RPT of (*,G) and a SPT Assume that one downstream AFBR has joined a RPT of (*,G) and a SPT
of (S,G), and decided to perform an SPT switchover. According to of (S,G), and decided to perform an SPT switchover. According to
[RFC7761], it SHOULD propagate a Prune(S,G,rpt) message along with [RFC7761], it SHOULD propagate a Prune(S,G,rpt) message along with
the periodical Join(*,G) message upstream towards the RP. However, the periodical Join(*,G) message upstream towards the RP. However,
routers in the I-IP transit core do not process (S,G,rpt) messages routers in the I-IP transit core do not process (S,G,rpt) messages
since the I-IP transit core is treated as SSM-only. As a result, the since the I-IP transit core is treated as SSM-only. As a result, the
downstream AFBR is unable to prune S from this RPT, so it will downstream AFBR is unable to prune S from this RPT, so it will
receive two copies of the same data for (S,G). In order to solve receive two copies of the same data for (S,G). In order to solve
this problem, we introduce a new mechanism for downstream AFBRs to this problem, we introduce a new mechanism for downstream AFBRs to
skipping to change at page 13, line 15 skipping to change at page 13, line 9
SHOULD send a Join (S,G,rpt) to the PIM-SM module immediately. SHOULD send a Join (S,G,rpt) to the PIM-SM module immediately.
In the data plane, upon receiving a multicast data packet, the In the data plane, upon receiving a multicast data packet, the
interface agent SHOULD encapsulate it at first, then propagate the interface agent SHOULD encapsulate it at first, then propagate the
encapsulated packet from every I-IP interface. encapsulated packet from every I-IP interface.
NOTICE: It is possible that an E-IP neighbor of RP' has joined the NOTICE: It is possible that an E-IP neighbor of RP' 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 be preserved. Prune (S,G,rpt) messages SHOULD be preserved.
5.5. SPT Switchover 6.5. SPT Switchover
After a new AFBR requests the receipt of traffic destined for a After a new AFBR requests the receipt of traffic destined for a
multicast group, it will receive all the data from the RPT at first. multicast group, it will receive all the data from the RPT at first.
At this time, every downstream AFBR will receive multicast data from At this time, every downstream AFBR will receive multicast data from
any source from this RPT, in spite of whether they have switched over any source from this RPT, in spite of whether they have switched over
to an SPT or not. to an SPT or not.
To minimize this redundancy, it is recommended that every AFBR's To minimize this redundancy, it is recommended that every AFBR's
SwitchToSptDesired(S,G) function employs the "switch on first packet" SwitchToSptDesired(S,G) function employs the "switch on first packet"
policy. In this way, the delay in switchover to SPT is kept as small policy. In this way, the delay in switchover to SPT is kept as small
as possible, and after the moment that every AFBR has performed the as possible, and after the moment that every AFBR has performed the
SPT switchover for every S of group G, no data will be forwarded in SPT switchover for every S of group G, no data will be forwarded in
the RPT of G, thus no more unnecessary duplication will be produced. the RPT of G, thus no more unnecessary duplication will be produced.
5.6. Other PIM Message Types 6.6. Other PIM Message Types
In addition to Join or Prune, other message types exist, including In addition to Join or Prune, other message types exist, including
Register, Register-Stop, Hello and Assert. Register and Register- Register, Register-Stop, Hello and Assert. Register and Register-
Stop messages are sent by unicast, while Hello and Assert messages Stop messages are sent by unicast, while Hello and Assert messages
are only used between directly linked routers to negotiate with each are only used between directly linked routers to negotiate with each
other. It is not necessary to translate these for forwarding, thus other. It is not necessary to translate these for forwarding, thus
the processing of these messages is out of scope for this document. the processing of these messages is out of scope for this document.
5.7. Other PIM States Maintenance 6.7. Other PIM States Maintenance
In addition to states mentioned above, other states exist, including In addition to states mentioned above, other states exist, including
(*,*,RP) and I-IP (*,G') state. Since we treat the I-IP core as SSM- (*,*,RP) and I-IP (*,G') state. Since we treat the I-IP core as SSM-
only, the maintenance of these states is out of scope for this only, the maintenance of these states is out of scope for this
document. document.
6. Data Plane Functions of the AFBR 7. Data Plane Functions of the AFBR
6.1. Process and Forward Multicast Data
7.1. Process and Forward Multicast Data
Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing
interface whose IP address family is different from the incoming interface whose IP address family is different from the incoming
interface, the AFBR MUST encapsulate this packet with interface, the AFBR MUST encapsulate this packet with
mPrefix46-derived and uPrefix46-derived IPv6 address to form an IPv6 mPrefix46-derived and uPrefix46-derived IPv6 address to form an IPv6
multicast packet. multicast packet.
6.2. TTL 7.2. TTL
Processing of TTL information in protocol headers depends on the Processing of TTL information in protocol headers depends on the
tunneling technology, and it is out of scope of this document. tunneling technology, and it is out of scope of this document.
6.3. Fragmentation 7.3. Fragmentation
The encapsulation performed by an upstream AFBR will increase the The encapsulation performed by an upstream AFBR will increase the
size of packets. As a result, the outgoing I-IP link MTU may not size of packets. As a result, the outgoing I-IP link MTU may not
accommodate the larger packet size. As it is not always possible for accommodate the larger packet size. As it is not always possible for
core operators to increase the MTU of every link. Fragmentation core operators to increase the MTU of every link. Fragmentation
after encapsulation and reassembling of encapsulated packets MUST be after encapsulation and reassembling of encapsulated packets MUST be
supported by AFBRs [RFC5565]. supported by AFBRs [RFC5565].
7. Packet Format and Translation 8. Packet Format and Translation
Because the PIM-SM Specification is independent of the underlying Because the PIM-SM Specification is independent of the underlying
unicast routing protocol, the packet format in Section 4.9 of unicast routing protocol, the packet format in Section 4.9 of
[RFC7761] remains the same, except that the group address and source [RFC7761] remains the same, except that the group address and source
address MUST be translated when traversing an AFBR. address MUST be translated when traversing an AFBR.
For example, Figure 5 shows the register-stop message format in the For example, Figure 5 shows the register-stop message format in the
IPv4 and IPv6 address families. IPv4 and IPv6 address families.
0 1 2 3 0 1 2 3
skipping to change at page 15, line 44 skipping to change at page 15, line 44
IPv4 Source Address (Encoded-Group format): The encoded-unicast IPv4 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv4 source address described in Section 4.3. format of the IPv4 source address described in Section 4.3.
IPv6 Group Address (Encoded-Group format): The encoded-group format IPv6 Group Address (Encoded-Group format): The encoded-group format
of the IPv6 group address described in Section 4.2. of the IPv6 group address described in Section 4.2.
IPv6 Source Address (Encoded-Group format): The encoded-unicast IPv6 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv6 source address described in Section 4.3. format of the IPv6 source address described in Section 4.3.
8. Softwire Mesh Multicast Encapsulation 9. Softwire Mesh Multicast Encapsulation
Softwire mesh multicast encapsulation does not require the use of any Softwire mesh multicast encapsulation does not require the use of any
one particular encapsulation mechanism. Rather, it MUST accommodate one particular encapsulation mechanism. Rather, it MUST accommodate
a variety of different encapsulation mechanisms, and allow the use of a variety of different encapsulation mechanisms, and allow the use of
encapsulation mechanisms mentioned in [RFC4925]. Additionally, all encapsulation mechanisms mentioned in [RFC4925]. Additionally, all
of the AFBRs attached to the I-IP network MUST implement the same of the AFBRs attached to the I-IP network MUST implement the same
encapsulation mechanism. encapsulation mechanism.
9. Security Considerations 10. Security Considerations
The security concerns raised in [RFC4925] and [RFC7761] are The security concerns raised in [RFC4925] and [RFC7761] are
applicable here. In addition, the additional workload associated applicable here.
with some schemes could be exploited by an attacker to perform a out
DDoS attack. Compared with [RFC4925], the security concerns SHOULD
be considered more carefully: an attacker could potentially set up
many multicast trees in the edge networks, causing too many multicast
states in the core network.
10. IANA Considerations The additional workload associated with some schemes could be
exploited by an attacker to perform a DDoS attack.
Compared with [RFC4925], the security concerns SHOULD be considered
more carefully: an attacker could potentially set up many multicast
trees in the edge networks, causing too many multicast states in the
core network. To defend against these attacks, BGP policies SHOULD
be carefully configured, e.g., AFBRs only accept Well-Known prefix
advertisements from trusted peers.
11. IANA Considerations
This document includes no request to IANA. This document includes no request to IANA.
11. References 12. References
11.1. Normative References 12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://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, <https://www.rfc-editor.org/info/rfc4291>. 2006, <https://www.rfc-editor.org/info/rfc4291>.
skipping to change at page 17, line 36 skipping to change at page 17, line 40
Kebler, R., and J. Haas, "Multicast VPN State Damping", Kebler, R., and J. Haas, "Multicast VPN State Damping",
RFC 7899, DOI 10.17487/RFC7899, June 2016, RFC 7899, DOI 10.17487/RFC7899, June 2016,
<https://www.rfc-editor.org/info/rfc7899>. <https://www.rfc-editor.org/info/rfc7899>.
[RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q. [RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q.
Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
over an IPv6 Multicast Network", RFC 8114, over an IPv6 Multicast Network", RFC 8114,
DOI 10.17487/RFC8114, March 2017, DOI 10.17487/RFC8114, March 2017,
<https://www.rfc-editor.org/info/rfc8114>. <https://www.rfc-editor.org/info/rfc8114>.
11.2. Informative References 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,
<https://www.rfc-editor.org/info/rfc7371>. <https://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.
skipping to change at page 18, line 32 skipping to change at page 18, line 35
Jianping Wu Jianping Wu
Tsinghua University Tsinghua University
Department of Computer Science, Tsinghua University Department of Computer Science, Tsinghua University
Beijing 100084 Beijing 100084
P.R. China P.R. China
Phone: +86-10-6278-5983 Phone: +86-10-6278-5983
Email: jianping@cernet.edu.cn Email: jianping@cernet.edu.cn
Shu Yang Shu Yang
Tsinghua University Oudmon Tech
Graduate School at Shenzhen OUDMON Technology Co.,ltd
Shenzhen 518055 Shenzhen 518057
P.R. China P.R. China
Phone: +86-10-6278-5822 Phone: +86-755-2601-3697
Email: yangshu@csnet1.cs.tsinghua.edu.cn Email: yangshu@oudmon.com
Chris Metz Chris Metz
Cisco Systems Cisco Systems
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Phone: +1-408-525-3275 Phone: +1-408-525-3275
Email: chmetz@cisco.com Email: chmetz@cisco.com
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