Internet Engineering Task Force H. Asaeda
Internet-Draft Keio University
Intended status: Informational M. Eubanks
Expires: August 19, 2012 AmericaFree.TV
T. Tsou
Huawei Technologies (USA)
S. Venaas
Cisco Systems
February 16, 2012
Multicast Transition Overview
draft-eubanks-mboned-transition-overview-02
Abstract
IPTV providers must serve content to their customers during the
period of transition from IPv4 to IPv6. During this period, the
content provider may support only one version of IP while the
customer supports only the other. Likewise, the network between the
provider and its customer may include segments supporting only one
version of IP or another.
This document provides an overview of the multicast transition
problem. It also provides an overview of the solution space. The
solution space is characterized by an adaptation function (AF) that
provides an interface between IPv4 and IPv6 multicast domains.
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
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 19, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. A Look At the Multicast Transition Problem Space . . . . . . . 3
3. A Look At the Solution Space For Multicast Transition . . . . . 4
3.1. AF Forwarding Plane Operation . . . . . . . . . . . . . . . 4
3.2. AF Control Plane Operation . . . . . . . . . . . . . . . . 5
3.3. Source Discovery . . . . . . . . . . . . . . . . . . . . . 5
3.4. Transitional Multicast Path Optimization . . . . . . . . . 5
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8. Informative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
IPTV providers must serve content to their customers during the
period of transition from IPv4 to IPv6. During this period, the
content provider may support only one version of IP while the
customer supports only the other. Likewise, the network between the
provider and its customer may include segments supporting only one
version of IP or another.
This document provides an overview of the multicast transition
problem. It also provides an overview of the solution space. The
solution space is characterized by an adaptation function (AF) that
provides an interface between IPv4 and IPv6 multicast domains.
Section 2 describes the problem space in detail. This section
describes an environment that includes a content provider a customer
and an intervening network. Any component of that environment may
support only one version of IP or the other. At points where IPv4-
only devices interface with IPv6-only devices, an adaptation function
is required.
Section 3 defines formal requirements for any proposed solution.
Section 4 proposes a framework for the solution.
2. A Look At the Multicast Transition Problem Space
Historically, IPTV providers have served IPv4 content to consumers
over IPv4 multicast networks. CPE has supported IPv4 only. As the
Internet transitions to IPv6, IPv6-capable equipment will be deployed
by content providers and consumers, as well as the networks that
connect them to one another. So long as all of the newly deployed
gear supports both IPv4 and IPv6, the transition to IPv6 may not
require new IETF protocol specifications. However, if some of the
newly deployed gear supports IPv6 only, incompatibilities will be
introduced.
An incompatibility occurs when two IP-adjacent devices do not support
a common version of IP (i.e., one device supports IPv4 only and the
other supports IPv6 only). For the purposes of this document, we
will call these points of incompatibility "IP version boundaries".
The communication path between provider and consumer (which includes
both endpoints) can include zero or more IP version boundaries.
IP version boundaries may be introduced at any point along the path.
These IP version boundaries may reside in the subscriber premises, at
the CPE, in the intervening network etc. In addition, the Set Top
Box (STB) and Electronic Program Guides (EPG) may have differnt IP
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versions.
In order to maintain multicast connectivity, an adaptation function
(AF) is required at each IP version boundary. The AF operates in
both the forwarding and control planes. Because it provides an
interface between the IPv4 and IPv6 domain, it must be both IPv4-
capable and IPv6-capable.
In most cases, the adaptation function will translate between IPv4
and IPv6 on both the control and forwarding planes. However, in
scenarios where the path between provider and consumer contains
multiple IP version boundaries, adaptation function instances may
tunnel traffic between one another.
3. A Look At the Solution Space For Multicast Transition
The AF operates on both the forwarding and control planes. On the
forwarding plane, the AF inserts itself into the forwarding path
translating multicast packets from one IP version to the other. On
the control plane, the AF translates routing and signaling messages
from one protocol to another.
On both the forwarding and control plane, the AF can be viewed as a
bump-in-the-wire that provides translation services. It provides no
services other than translation.
3.1. AF Forwarding Plane Operation
The AF accepts packets from one IP version, removes the IP header,
and replaces it with an IP Header of the other version. A
significant portion of that task is address translation. The address
translation strategy used by AF must be algorithmic, stateless and
reversible. This is to say that given a particular IPv4 address, any
two AF instances will translate it to the same IPv6 address.
Furthermore, because the algorithm is reversible, both AF instances
can translate the IPv6 address back into the original IPv4 address.
[RFC6052] provides an algorithm for translating unicast addresses
between IPv4 and IPv6. Likewise [I-D.mboned-64-mcast-addr-fmt]
provides an algorithm for multicast address conversion between IPv4
and IPv6.
Other issues associated with IP version translation may arise (e.g.,
fragmentation). The scope of these issues is wider than that of
multicast transition. As such issues are identified, they will be
resolved in conjunction with appropriate IETF working groups.
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3.2. AF Control Plane Operation
On the control plane, the AF performs the following translations:
o IGMPv3 [RFC3376] to MLDv2 [RFC3810];
o PIM [RFC4601] to PIM;
o IGMPv3 to PIM;
o MLD to PIM;
The IGMP-to-MLD translation may be configured to use only IGMPv2
features. It is defined in [draft to come].
The PIM-to-PIM translation translates a PIM message populated with
addresses of one IP version to a similar PIM message populated with
addresses of the other version. This translation is defined in
[draft to come].
3.3. Source Discovery
Multicast requires a mechanism through which a receiver can associate
a multicast stream with a multicast group address. The Session
Announcement Protocol (SAP, [RFC2974]) is such a mechanism which is
still in use in academic environments. AF translation rules for this
protocol are also described in [draft to come]. For commercial
purposes, different standards development organizations have
specified protocols for transmission of electronic program guides.
[ID.tsou-multrans-addr-acquisition] specifies the operation of the AF
in such an environment [... in a future version of the draft which
comes to a conclusion on the best way forward].
3.4. Transitional Multicast Path Optimization
A mechanism to optimize the path to the multicast source for a
combination of IPv4 and IPv6 networks is not immediately required,
but is a topic for future work.
4. Requirements
From the description above, we can distill the following
requirements:
REQ 1: It must be possible for the receiver to acquire the
multicast group address and, where applicable, the unicast source
address of the target stream in the IP version that the receiver
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supports.
REQ 2: It must be possible for the receiver to join the multicast
distribution tree for the target stream even if the IP version
used in the interior of the network to which the receiver is
attached is different from the version supported by the receiver.
REQ 3: Where local policy permits, it must be possible to extend
the multicast distribution tree for a given stream across a
network boundary where different IP versions are supported in the
two networks separated by that boundary.
REQ 4: When the multicast distribution tree for a given stream is
extended across multiple network boundaries across one or more of
which the IP version changes, it must be possible to avoid
multicast routing loops.
REQ 5: It must be possible to pass packets belonging to a given
multicast stream to all joined receivers, regardless of changes in
IP version encountered along the way.
REQ 6: Both ASM and SSM technology must be supported.
REQ 7: The solution(s) should allow operators to minimize the
total incremental cost (investment plus operations during the
transitional period)) due to multicast transition.
REQ 8: The solution(s) should provide a clear evolutionary path to
all-IPv6 operation.
5. Acknowledgements
Ron Bonica inspired the writing of this memo and shaped its content.
Michael McBride provided useful comments on an intermediate version
of this document.
6. IANA Considerations
This memo includes no request to IANA.
7. Security Considerations
To come.
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8. Informative References
[I-D.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)", February 2012.
[ID.tsou-multrans-addr-acquisition]
Tsou, T., "Address Acquisition For Multicast Content When
Source and Receiver Support Differing IP Versions (Work in
Progress)", December 2011.
[RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session
Announcement Protocol", RFC 2974, October 2000.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, October 2002.
[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
Authors' Addresses
Hitoshi Asaeda
Keio University
Graduate School of Media and Governance
5322 Endo
Fujisawa, Kanagawa 252-0882
Japan
Email: asaeda@wide.ad.jp
URI: http://www.sfc.wide.ad.jp/~asaeda/
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Marshall Eubanks
AmericaFree.TV
P.O. Box 141
Clifton, VA 20124
USA
Phone:
Email: marshall.eubanks@gmail.com
Tina Tsou
Huawei Technologies (USA)
2330 Central Expressway
Santa Clara, CA 95050
USA
Phone: +1 408 330 4424
Email: Tina.Tsou.Zouting@huawei.com
Stig Venaas
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA
Phone:
Email: stig@cisco.com
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