MBONED Working Group M. Boucadair, Ed.
Internet-Draft France Telecom
Intended status: Standards Track J. Qin
Expires: February 11, 2013 Cisco
Y. Lee
Comcast
S. Venaas
Cisco Systems
X. Li
CERNET Center/Tsinghua
University
M. Xu
Tsinghua University
August 10, 2012
IPv6 Multicast Address With Embedded IPv4 Multicast Address
draft-ietf-mboned-64-multicast-address-format-03
Abstract
This document reserves two IPv6 multicast prefixes to be used in the
context of IPv4-IPv6 interconnection. The document specifies an
algorithmic translation of an IPv6 multicast address to a
corresponding IPv4 multicast address, and vice versa. This
algorithmic translation can be used in both IPv4-IPv6 translation or
encapsulation schemes.
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 RFC 2119 [RFC2119].
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
Boucadair, et al. Expires February 11, 2013 [Page 1]
Internet-Draft 64 Multicast Address Format August 2012
This Internet-Draft will expire on February 11, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Boucadair, et al. Expires February 11, 2013 [Page 2]
Internet-Draft 64 Multicast Address Format August 2012
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. IPv4-Embedded IPv6 Multicast Prefix & Address . . . . . . . . 5
3.1. Reserving Dedicated Prefixes . . . . . . . . . . . . . . . 5
3.2. IPv4-Embedded IPv6 Multicast Address . . . . . . . . . . . 6
3.3. Address Translation Algorithm . . . . . . . . . . . . . . 7
3.4. Textual Representation . . . . . . . . . . . . . . . . . . 7
3.5. Source IPv4 Address in the IPv6 Realm . . . . . . . . . . 7
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Motivations . . . . . . . . . . . . . . . . . . . . . 10
A.1. Why an Address Format is Needed for Multicast
IPv4-IPv6 Interconnection? . . . . . . . . . . . . . . . . 10
A.2. Why Identifying an IPv4-Embedded IPv6 Multicast
Address is Required? . . . . . . . . . . . . . . . . . . . 10
A.3. Location of the IPv4 Address . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Boucadair, et al. Expires February 11, 2013 [Page 3]
Internet-Draft 64 Multicast Address Format August 2012
1. Introduction
Various solutions (e.g., [I-D.ietf-softwire-mesh-multicast],
[I-D.ietf-softwire-dslite-multicast]) have been proposed to allow
access to IPv4 multicast content from hosts attached to IPv6-enabled
domains. Even if these solutions have distinct applicability scopes
(translation vs. encapsulation) and target different use cases, they
all make use of specific IPv6 multicast addresses to embed an IPv4
multicast address. Particularly, the IPv4-embedded IPv6 multicast
address is used as a destination IPv6 address of multicast flows
received from an IPv4-enabled domain and injected by the IPv4-IPv6
Interconnection Function into an IPv6-enabled domain. It is also
used to build an IPv6 multicast state (*, G6) or (S6, G6)
corresponding to their (*, G4) or (S4, G4) IPv4 counter parts by the
IPv4-IPv6 Interconnection Function. [I-D.ietf-mboned-v4v6-mcast-ps]
provides more discussion about issues related to IPv4/IPv6 multicast.
This document reserves two prefixes to be used to synthesize IPv4-
embedded IPv6 multicast address. This document also defines how
IPv4-embedded IPv6 multicast addresses are constructed. Both IPv4-
IPv6 translation or encapsulation schemes can make use of these
prefixes.
Appendix A.1 enumerates the arguments in favor of reserving dedicated
prefixes Appendix A.2 discusses why identifying an IPv4-embedded IPv6
multicast address is needed.
This specification can be used in conjunction with other extensions
such as building unicast prefix-based multicast IPv6 address
[RFC3306] or embedding the rendezvous point [RFC3956]. These
techniques are important tools to simplify IPv6 multicast
deployments. Indeed, unicast prefix-based IPv6 addressing is used in
many current IPv6 multicast deployments, and has also been defined
for IPv4, and is seen as a very useful technique. Also embedded-RP
is used in existing deployments.
This document is a companion document to [RFC6052] which focuses
exclusively on IPv4-embedded IPv6 unicast addresses.
2. Terminology
This document makes use of the following terms:
o IPv4-embedded IPv6 multicast address: denotes a multicast IPv6
address which includes in 32 bits an IPv4 address.
Boucadair, et al. Expires February 11, 2013 [Page 4]
Internet-Draft 64 Multicast Address Format August 2012
o Multicast Prefix64 (or MPREFIX64 for short) refers to an IPv6
multicast prefix to be used to construct IPv4-embedded IPv6
multicast addresses. This prefix is used to build an IPv4-
embedded IPv6 multicast address as defined in Section 3.3.
Section 3.3 specifies also how to extract an IPv4 address from an
IPv4-embedded IPv6 multicast address.
o ASM_MPREFIX64: denotes a multicast Prefix64 used in Any Source
Multicast (ASM) mode.
o SSM_MPREFIX64: denotes a multicast Prefix64 used in Source
Specific Multicast (SSM) mode.
o IPv4-IPv6 Interconnection Function: refers to a function which is
enabled in a node interconnecting an IPv4-enabled domain with an
IPv6-enabled one. It can be located in various places of the
multicast network. Particularly, in terms of multicast control
messages, it can be an IGMP/MLD Interworking Function or an IPv4-
IPv6 PIM Interworking Function. An IPv4-IPv6 Interconnection
Function is configured with one or two MPREFIX64s.
3. IPv4-Embedded IPv6 Multicast Prefix & Address
3.1. Reserving Dedicated Prefixes
The following constraints should be met when reserving dedicated
prefix(es) to be used for IPv4/IPv6 multicast interconnection:
1: Belong to ff3x::/32 and be compatible with unicast-based prefix
[RFC3306] for SSM. Note that [RFC3306] suggests to set "plen" to
0 and "network-prefix" to 0. As such, any prefix in the 33-96
range can be convenient. Given [RFC4607] indicates future
specifications may allow a non-zero network prefix field, a /33
would allow for future extensions but it has the drawback of
reserving a large block. A /96 would be adequate for the use
cases already identified in [I-D.ietf-mboned-v4v6-mcast-ps]. In
the event of any concrete extension, reserving additional
prefixes may be considered.
2: Be compatible with embedded-RP [RFC3956] and unicast-based prefix
[RFC3306] for ASM. This results in a prefix length to be in the
17-20 range. A /17 has the advantage of allowing for future
extensions but it may be seen as a waste of the multicast address
space. Consequently, a /20 is preferred.
Boucadair, et al. Expires February 11, 2013 [Page 5]
Internet-Draft 64 Multicast Address Format August 2012
3: Avoid ff3x::4000:0001-ff3x::7fff:ffff which is reserved for IANA.
Meeting (1) and (2) with the same prefix is not feasible without
modifying embedded-RP and unicast-based prefix specifications; this
option is avoided.
As a consequence, two multicast prefixes are proposed to be used when
embedding IPv4 address: one prefix for ASM and another one for the
SSM. This document reserves the following multicast prefixes to be
used in the context of IPv4/IPv6 multicast interconnection:
o ff3x:0:8000::/96 SSM range to embed an IPv4 multicast address in
the last 32 bits.
o ffxx:8000::/20 ASM range to embed an IPv4 multicast address in the
last 32 bits.
3.2. IPv4-Embedded IPv6 Multicast Address
For the delivery of the IPv4-IPv6 multicast interconnection services,
a dedicated multicast prefix denoted as MPREFIX64 should be
provisioned (e.g., using NETCONF or
[I-D.ietf-softwire-multicast-prefix-option]) to any function
requiring to build an IPv4-embedded IPv6 multicast address based on
an IPv4 multicast address. MPREFIX64 can be of ASM or SSM type.
When both modes are used, two prefixes are required to be
provisioned.
The length of MPREFIX64 MUST be /96. MPREFIX64 should belong to
ffxx:8000::/20 for ASM mode and ff3x:0:8000::/96 for the SSM mode.
For the ASM mode, the format of the MPREFIX64 should follow what is
specified in [RFC3306] and [RFC3956] if corresponding mechanisms are
used. If not, bits 21-96 can be set to any value.
Figure 1 shows how to build an IPv4-embedded IPv6 multicast address
using a configured MPREFIX64 and an IPv4 multicast address. The low-
order 32 bits MUST include an IPv4 multicast address. The enclosed
IPv4 multicast address SHOULD NOT be in 232/8 range if an
ASM_PREFIX64 is configured. The enclosed IPv4 multicast address
SHOULD be in 232/8 range if an SSM_PREFIX64 is configured.
Embedding an IPv4 multicast address in the last 32 bits does not
conflict with the Group IDs assigned by IANA (i.e., 0x00000001 to
0x3FFFFFFF [RFC3307]).
When several MPREFIX64 are available, it is RECOMMENDED to use the
MPREFIX64 which preserve the scope of the IPv4 multicast address.
Boucadair, et al. Expires February 11, 2013 [Page 6]
Internet-Draft 64 Multicast Address Format August 2012
| 96 | 32 |
+------------------------------------------------------+----------+
| MPREFIX64 |v4 address|
+------------------------------------------------------+----------+
Figure 1: IPv4-Embedded IPv6 Multicast Address Format
3.3. Address Translation Algorithm
IPv4-embedded IPv6 multicast addresses are composed according to the
following algorithm:
o Concatenate the MPREFIX64 and the 32 bits of the IPv4 address to
obtain a 128-bit address.
The IPv4 multicast addresses are extracted from the IPv4-embedded
IPv6 multicast addresses according to the following algorithm:
o If the multicast address belongs to ff3x:0:8000::/96 or ffxx:
8000::/20, extract the last 32 bits of the IPv6 multicast address.
3.4. Textual Representation
The embedded IPv4 address in an IPv6 multicast address is included in
the last 32 bits; therefore dotted decimal notation can be used.
3.5. Source IPv4 Address in the IPv6 Realm
An IPv4 source is represented in the IPv6 realm with its IPv4-
converted IPv6 address [RFC6052].
4. Examples
Figure 2 provides an example of ASM IPv4-Embedded IPv6 Address while
Figure 3 provides an example of SSM IPv4-Embedded IPv6 Address.
IPv4 multicast addresses used in the examples are derived from the
IPv4 multicast block reserved for documentation in
[I-D.ietf-mboned-mcaddrdoc].
Boucadair, et al. Expires February 11, 2013 [Page 7]
Internet-Draft 64 Multicast Address Format August 2012
+---------------------+--------------+----------------------------+
| MPREFIX64 | IPv4 address | IPv4-embedded IPv6 address |
+---------------------+--------------+----------------------------+
| ffxx:8000:0:abc::/96| 233.252.0.1 |ffxx:8000:0:abc::233.252.0.1|
+---------------------+--------------+----------------------------+
Figure 2: Example of ASM IPv4-embedded IPv6 address
+---------------------+--------------+----------------------------+
| MPREFIX64 | IPv4 address | IPv4-embedded IPv6 address |
+---------------------+--------------+----------------------------+
| ff3x:0:8000::/96 | 233.252.0.5 | ff3x:0:8000::233.252.0.5 |
+---------------------+--------------+----------------------------+
Figure 3: Example of SSM IPv4-embedded IPv6 address
5. IANA Considerations
Authors of this document request to reserve:
o ff3x:0:8000::/96 SSM range to embed an IPv4 multicast address in
the last 32 bits.
o ffxx:8000::/20 ASM range to embed an IPv4 multicast address in the
last 32 bits.
6. Security Considerations
This document defines an algorithmic translation of an IPv6 multicast
address into an IPv4 multicast address, and vice versa. The security
considerations discussed in [RFC6052] are to be taken into
consideration.
7. Acknowledgements
Many thanks to R. Bonica, B. Sarikaya, P. Savola, T. Tsou and C.
Bormann for their comments and review.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Boucadair, et al. Expires February 11, 2013 [Page 8]
Internet-Draft 64 Multicast Address Format August 2012
[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses", RFC 3306, August 2002.
[RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast
Addresses", RFC 3307, August 2002.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address",
RFC 3956, November 2004.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, August 2006.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
8.2. Informative References
[I-D.ietf-behave-nat64-learn-analysis]
Korhonen, J. and T. Savolainen, "Analysis of solution
proposals for hosts to learn NAT64 prefix",
draft-ietf-behave-nat64-learn-analysis-03 (work in
progress), March 2012.
[I-D.ietf-mboned-mcaddrdoc]
Venaas, S., Parekh, R., Velde, G., Chown, T., and M.
Eubanks, "Multicast Addresses for Documentation",
draft-ietf-mboned-mcaddrdoc-04 (work in progress),
May 2012.
[I-D.ietf-mboned-v4v6-mcast-ps]
Jacquenet, C., Boucadair, M., Lee, Y., Qin, J., Tsou, T.,
and Q. Sun, "IPv4-IPv6 Multicast: Problem Statement and
Use Cases", draft-ietf-mboned-v4v6-mcast-ps-00 (work in
progress), May 2012.
[I-D.ietf-softwire-dslite-multicast]
Qin, J., Boucadair, M., Jacquenet, C., Lee, Y., and Q.
Wang, "Multicast Extensions to DS-Lite Technique in
Broadband Deployments",
draft-ietf-softwire-dslite-multicast-02 (work in
progress), May 2012.
[I-D.ietf-softwire-mesh-multicast]
Xu, M., Cui, Y., Wu, J., Yang, S., Metz, C., and G.
Shepherd, "Softwire Mesh Multicast",
draft-ietf-softwire-mesh-multicast-03 (work in progress),
Boucadair, et al. Expires February 11, 2013 [Page 9]
Internet-Draft 64 Multicast Address Format August 2012
July 2012.
[I-D.ietf-softwire-multicast-prefix-option]
Boucadair, M., Qin, J., Tsou, T., and X. Deng, "DHCPv6
Option for IPv4-Embedded Multicast and Unicast IPv6
Prefixes", draft-ietf-softwire-multicast-prefix-option-01
(work in progress), August 2012.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
Appendix A. Motivations
A.1. Why an Address Format is Needed for Multicast IPv4-IPv6
Interconnection?
Arguments why an IPv6 address format is needed to embed multicast
IPv4 address are quite similar to those of [RFC6052]. Concretely,
the definition of a multicast address format embedding a multicast
IPv4 address allows:
o Stateless IPv4-IPv6 header translation of multicast flows;
o Stateless IPv4-IPv6 PIM interworking function;
o Stateless IGMP-MLD interworking function (e.g., required for an
IPv4 receiver to access to IPv4 multicast content via an IPv6
network);
o Stateless (local) synthesis of IPv6 address when IPv4 multicast
address are embedded in application payload (e.g., SDP [RFC4566]);
o Except the provisioning of the same MPREFIX64, no coordination is
required between IPv4-IPv6 PIM interworking function, IGMP-MLD
interworking function, IPv4-IPv6 Interconnection Function and any
ALG (Application Level Gateway) in the path;
o Minimal operational constraints on the multicast address
management: IPv6 multicast addresses can be constructed using what
has been deployed for IPv4 delivery mode.
A.2. Why Identifying an IPv4-Embedded IPv6 Multicast Address is
Required?
Reserving a dedicated multicast prefix for IPv4-IPv6 interconnection
purposes is a means to guide the address selection process at the
receiver side; in particular it assists the receiver to select the
Boucadair, et al. Expires February 11, 2013 [Page 10]
Internet-Draft 64 Multicast Address Format August 2012
appropriate IP multicast address while avoiding to involve an IPv4-
IPv6 interconnection function in the path.
Two use cases to illustrate this behavior are provided below:
1. An ALG is required to help an IPv6 receiver to select the
appropriate IP address when only the IPv4 address is advertised
(e.g., using SDP); otherwise the access to the IPv4 multicast
content can not be offered to the IPv6 receiver. The ALG may be
located downstream the receiver. As such, the ALG does not know
in advance whether the receiver is dual-stack or IPv6-only. The
ALG may be tuned to insert both the original IPv4 address and
corresponding IPv6 multicast address. If a dedicated prefix is
not used, a dual-stack receiver may prefer to use the IPv6
address to receive the multicast content. This address selection
would require multicast flows to cross an IPv4-IPv6
interconnection function.
2. In order to avoid involving an ALG in the path, an IPv4-only
source can advertise both its IPv4 address and IPv4-embedded IPv6
multicast address. If a dedicated prefix is not reserved, a
dual-stack receiver may prefer to use the IPv6 address to receive
the multicast content. This address selection would require
multicast flows to cross an IPv4-IPv6 interconnection function.
Reserving dedicated IPv6 multicast prefixes for IPv4-IPv6
interconnection purposes mitigates the issues discussed in
[I-D.ietf-behave-nat64-learn-analysis] in a multicast context.
A.3. Location of the IPv4 Address
There is no strong argument to allow for flexible options to encode
the IPv4 address inside the multicast IPv6 address. The option
retained by the authors is to encode the multicast IPv4 address in
the low-order 32 bits of the IPv6 address.
This choice is also motivated by the need to be compliant with
[RFC3306] and [RFC3956].
Boucadair, et al. Expires February 11, 2013 [Page 11]
Internet-Draft 64 Multicast Address Format August 2012
Authors' Addresses
Mohamed Boucadair (editor)
France Telecom
Rennes, 35000
France
Email: mohamed.boucadair@orange.com
Jacni Qin
Cisco
China
Email: jacni@jacni.com
Yiu L. Lee
Comcast
U.S.A
Email: yiu_lee@cable.comcast.com
Stig Venaas
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA
Email: stig@cisco.com
Xing Li
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing, 100084
P.R. China
Phone: +86 10-62785983
Email: xing@cernet.edu.cn
Boucadair, et al. Expires February 11, 2013 [Page 12]
Internet-Draft 64 Multicast Address Format August 2012
Mingwei Xu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing, 100084
P.R.China
Phone: +86-10-6278-5822
Email: xmw@cernet.edu.cn
Boucadair, et al. Expires February 11, 2013 [Page 13]