Internet DRAFT - draft-tsou-softwire-6rd-multicast
draft-tsou-softwire-6rd-multicast
Internet Engineering Task Force T. Tsou
Internet-Draft Huawei Technologies (USA)
Intended status: Informational T. Taylor
Expires: March 8, 2013 C. Zhou
Huawei Technologies
H. Ji
China Telecom
September 4, 2012
IPv6 Multicast Using Native IPv4 Capabilities in a 6rd Deployment
draft-tsou-softwire-6rd-multicast-02
Abstract
This document describes how IPv6 multicast can be extended across an
IPv4 network to an IPv6 host, using the native multicast capabilities
of the IPv4 network.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on March 8, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Description of the Solution . . . . . . . . . . . . . . . . . . 3
2.1. Assumed Architecture . . . . . . . . . . . . . . . . . . . 3
2.2. Components of the Proposed Solution . . . . . . . . . . . . 4
2.2.1. Address Mapping . . . . . . . . . . . . . . . . . . . . 4
2.2.2. Multicast Routing . . . . . . . . . . . . . . . . . . . 5
2.2.3. Translation From MLD To IGMP . . . . . . . . . . . . . 5
2.2.4. Interworking Between PIM With IPv4 and PIM with
IPv6 At the 6rd BR . . . . . . . . . . . . . . . . . . 5
2.2.5. Transport of Multicast Data Packets and Unicast
RTCP Feedback . . . . . . . . . . . . . . . . . . . . . 5
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
6rd ([RFC5569], [RFC5969]) provides a means to connect IPv6 hosts to
the IPv6 Internet across an IPv4 provider network. Unicast traffic
is carried through IPv6-in-IPv4 tunnels. It is possible to carry
multicast traffic from the IPv6 network through the IPv4 network in
the same way, but if multiple customers wish access to the same
multicast channels, the failure to use the native multicast
capabilities of the IPv4 network wastes resources in that network.
This document describes a solution using the native multicast
capabilities of the IPv4 network to acquire and forward multicast
traffic from the IPv6 Internet to an IPv6 host attached to the IPv4
network. Typically this solution will operate in combination with
6rd for unicast traffic. However, no IPv6-in-IPv4 tunneling is
required for signalling, only the ability to interwork between IPv4
and IPv6 at the 6rd Customer Equipment (6rd CE) and the 6rd Border
Relay (6rd BR).
1.1. Terminology
The term "address pair" is used to denote the combination of unicast
source address and multicast group address corresponding to a given
multicast stream at a given point along the path between the source
and receiver.
2. Description of the Solution
A number of problems have to be solved to allow an IPv6 host attached
to an IPv4 network to request and receive a multicast stream
originating in a neighbouring IPv6 network and passing through the
IPv4 network using the native multicast facilities of that network.
These problems are described in detail in the course of presenting
proposed solutions to them.
It is assumed that the IPv6 host wishing to receive a multicast
stream acquires the corresponding IPv6 address pair by means out of
scope of this document. See [ID.mboned-multrans-addr-acq].
2.1. Assumed Architecture
This document assumes an architecture similar to that of 6rd
[RFC5569], [RFC5969], with additional capabilities for the 6rd
Customer Edge (CE) and the 6rd Border Relay (6rd BR). See Figure 1.
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+----+ +----+ Access +--------+ +------+
|IPv6| LAN | 6rd| Link |Provider| IPv4 |Border| IPv6
|Host|--------| CE |--------|IP Edge |-- network --|Relay |--- network
+----+ +----+ +--------+ +------+
Figure 1: IPv6 Multicast Across an IPv4 Domain Using a Translator
Function
In addition to its 6rd responsibilities, the 6rd CE is responsible
for:
o mapping between the IPv6 address pair presented by the IPv6 Host
and an IPv4 address pair designating the same multicast stream in
the provider's IPv4 network;
o accepting MLD [RFC3810] on the IPv6 Host side and emitting IGMP
[RFC3376] toward the provider's IPv4 network;
o using the reverse mapping from IPv6 to IPv4 address pairs to
translate incoming IPv4 multicast streams to IPv6 before
forwarding them to the IPv6 Host. Alternatively, decapsulating
IPv6 multicast data packets from incoming IPv4 packets.
The Provider IP Edge has the normal function of interworking between
IGMP [RFC3376] and PIM [RFC4601] multicast signalling.
The Border Relay has the usual 6rd responsibilities. In addition, it
is responsible for:
o mapping between IPv4 address pairs received in PIM messages from
the IPv4 network and IPv6 address pairs denoting the same
multicast streams in the neighbouring IPv6 network;
o translating addresses in PIM between the IPv4 and IPv6 networks;
o using the reverse mapping from IPv6 to IPv4 address pairs to
translate and forward multicast data packets coming from the IPv6
network. Alternatively, using the reverse mapping to generate
encapsulating IPv4 headers for the IPv6 packets before forwarding
them as multicast IPv4 data.
2.2. Components of the Proposed Solution
2.2.1. Address Mapping
Both the 6rd CE and the 6rd BR need to map between IPv6 and IPv4
addresses, in both directions. The IPv6 address pairs do not have to
be the same at the two nodes, so long as the IPv6 address pair used
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by the host designates the same multicast stream as the IPv6 address
pair generated at the 6rd BR or received from the source IPv6
network.
Because the source network uses IPv6, mapping between the addresses
used in that network and the IPv4 addresses used in the provider
network is in general a difficult problem. The most general solution
is to configure static mappings between the IPv6 and corresponding
IPv4 address pairs at the 6rd BR. Mapping at the 6rd CE can use
IPv4-embedded IPv6 addresses as defined in [RFC6052] for the unicast
source addresses, and [ID.mboned-64-mcast-addr-fmt] for the multicast
group addresses. This assumes that the IPv6 host has been provided
with such addresses in the first place. It also assumes that the
IPv4 network provider can configure suitable prefixes at the 6rd CE
for the purpose of such mapping.
With restrictions on the IPv6 addresses used for multicast source and
group addresses in the IPv6 network, it may be possible to use
algorithmic instead of static mapping at the 6rd BR. This generally
requires coordination between the IPv4 and IPv6 network operators.
2.2.2. Multicast Routing
For each IPv4 address to which an IPv6 source address is mapped, the
routing tables that PIM uses must result in a path that passes
through a multicast-enabled 6rd BR. At the routing level, this means
that the 6rd BR must advertise reachability to the mapped IPv4 source
addresses it knows about into the IPv4 domain. Its distance metrics
to those addresses must reflect the routing information it receives
on the IPv6 side for their IPv6 counterparts.
2.2.3. Translation From MLD To IGMP
See [ID.perreault-igmp-mld-translation].
2.2.4. Interworking Between PIM With IPv4 and PIM with IPv6 At the 6rd
BR
See [ID.taylor-pim-v4v6-translation].
2.2.5. Transport of Multicast Data Packets and Unicast RTCP Feedback
The documents cited in the previous two sections describe the process
of header translation for multicast data packets. The address
mapping aspect of that translation was discussed in Section 2.2.1.
If the 6rd BR and 6rd CE are configured to use encapsulation/
decapsulation of multicast data packets instead, the encapsulating
IPv4 header uses the IPv4 address pair mapped from the original IPv6
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address pair as source and destination. However, this requires that
the IPv6 host uses the same IPv6 addresses as the source IPv6 network
for each multicast stream it receives. That may force the 6rd CE to
use static rather than algorithmic mapping for address pairs for its
MLD/IGMP translation.
When the IPv6 Host sends unicast RTCP [RFC3550] feedback toward the
source, the packets are treated by the 6rd CE and 6rd BR like any
other unicast packets. That is, they are encapsulated at the 6rd CE,
transported across the IPv4 network as IPv6-in-IPv4, and decapsulated
at the 6rd BR before forwarding into the IPv6 network.
3. Acknowledgements
Awaiting comments.
4. IANA Considerations
This memo currently includes no request to IANA.
5. Security Considerations
To come.
6. References
6.1. Normative References
[ID.mboned-64-mcast-addr-fmt]
Boucadair, M., Qin, J., Lee, Y., Venaas, S., Li, X., and
M. Xu, "IPv4-Embedded IPv6 Multicast Address Format (Work
in progress)", August 2012.
[ID.perreault-igmp-mld-translation]
Perrault, S. and T. Tsou, "Internet Group Management
Protocol (IGMP) / Multicast Listener Discovery (MLD)-Based
Multicast Translation ("IGMP/MLD Translation") (Work in
progress)", April 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
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3", RFC 3376, October 2002.
[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.
[RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol
Independent Multicast - Dense Mode (PIM-DM): Protocol
Specification (Revised)", RFC 3973, January 2005.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification",
RFC 5969, August 2010.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
6.2. Informative References
[ID.mboned-multrans-addr-acq]
Tsou, T., Clauberg, A., Boucadair, M., Venaas, S., and Q.
Sun, "Address Acquisition For Multicast Content When
Source and Receiver Support Differing IP Versions (Work in
progress)", March 2012.
[ID.taylor-pim-v4v6-translation]
Taylor, T. and C. Zhou, "Operation of a Dual-Stack
Multicast Router With Address Translation (Work in
progress)", July 2012.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC5569] Despres, R., "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd)", RFC 5569, January 2010.
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Authors' Addresses
Tina Tsou
Huawei Technologies (USA)
2330 Central Expressway
Santa Clara, CA 95050
USA
Phone: +1 408 330 4424
Email: Tina.Tsou.Zouting@huawei.com
URI: http://tinatsou.weebly.com/contact.html
Tom Taylor
Huawei Technologies
Ottawa, Ontario
Canada
Phone:
Email: tom.taylor.stds@gmail.com
Cathy Zhou
Huawei Technologies
Bantian, Longgang District
Shenzhen 518129
P.R. China
Phone:
Email: cathy.zhou@huawei.com
Hui Ji
China Telecom
NO19.North Street
Beijing, Chaoyangmen,Dongcheng District
P.R. China
Phone:
Email: jihui@chinatelecom.com.cn
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