6man Working Group                                          M. Boucadair
Internet-Draft                                            France Telecom
Updates: 3306,3956,4607,4291 3306,3956,4291 (if approved)                          S. Venaas
Intended status: Standards Track                                   Cisco
Expires: November 24, 2013                                  May 23, April 21, 2014                                 October 18, 2013

         Updates to the IPv6 Multicast Addressing Architecture
             draft-ietf-6man-multicast-addr-arch-update-01
             draft-ietf-6man-multicast-addr-arch-update-02

Abstract

   This document updates the IPv6 multicast addressing architecture by
   defining the 17-20 reserved bits as generic flag bits.  The document
   provides also some clarifications related to the use of these flag
   bits.

   This document updates RFC 3956, RFC 3306, RFC 4607 3306 and RFC 4291.

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
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   This Internet-Draft will expire on November 24, 2013. April 21, 2014.

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Addressing Architecture Update  . . . . . . . . . . . . . . .   2
   3.  Clarifications  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Flag Bits . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  IANA Assigned SSM Block . . . . . . . . . . . . . . . . .   4
   4.  RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  RFC3306 .  RFC 3306  . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  RFC3956 . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.3.  RFC4607 .  RFC 3956  . . . . . . . . . . . . . . . . . . . . . . . .   8   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   9   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10   8

1.  Introduction

   This document updates the IPv6 multicast addressing architecture
   [RFC4291] by defining the 17-20 reserved bits as generic flag bits
   (Section 2).  The document provides also some clarifications related
   to the use of these flag bits (Section 3.1) and also about IANA
   assigned SSM blocks (Section 3.2). 3.1).

   This document updates [RFC3956], [RFC3306], [RFC4607] and [RFC4291].

2.  Addressing Architecture Update

   Bits 17-20 of a multicast address are defined in [RFC3956] and
   [RFC3306] as reserved bits.  This document defines these bits as
   generic flag bits so that they apply to any multicast address.
   Figure 1 and Figure 2 show the updated structure of the addressing
   architecture.  The first diagram shows the update of the base IPv6
   addressing architecture, and the second shows the update of so-called
   Embedded-RP.

    OLD:
    |   8    |  4 |  4 |                  112 bits                    |
    +--------+----+----+----------------------------------------------+
    |11111111|flgs|scop|                  group ID                    |
    +--------+----+----+----------------------------------------------+

    NEW:
    |   8    |  4 |  4 |  4 |             108 bits                    |
    +--------+----+----+----------------------------------------------+
    |11111111|flgs|scop|flgs|             group ID                    |
    +--------+----+----+----+-----------------------------------------+

         Figure 1: Updated IPv6 Multicast Addressing Architecture

    OLD (RFC3956): (RFC 3956):
    |   8    |  4 |  4 |  4 |  4 |   8    |       64       |    32    |
    +--------+----+----+----+----+--------+----------------+----------+
    |11111111|flgs|scop|rsvd|RIID|  plen  | network prefix | group ID |
    +--------+----+----+----+----+--------+----------------+----------+

    NEW:
    |   8    |  4 |  4 |  4 |  4 |   8    |       64       |    32    |
    +--------+----+----+----+----+--------+----------------+----------+
    |11111111|flgs|scop|flgs|RIID|  plen  | network prefix | group ID |
    +--------+----+----+----+----+--------+----------------+----------+

      Figure 2: Embedded-RP with Updated IPv6 Multicast Address Arch.

   Further specification documents may define a meaning for these flag
   bits.  Defining the bits 17-20 as flags for all IPv6 multicast
   addresses allows addresses to be treated in a more uniform and
   generic way, and allows for these bits to be defined in the future
   for different purposes, irrespective of the specific type of
   multicast address.

3.  Clarifications

3.1.  Flag Bits

   Some implementations and specification documents do not treat the
   flag bits as separate bits but tend to use their combined value as a
   4-bit integer.  This practice is a hurdle for assigning a meaning to
   the remaining flag bits.  Below are listed some examples for
   illustration purposes:

   o  the reading of [RFC4607] [RFC3306] may lead to conclude that ff3x::/32 is
      the only allowed SSM IPv6 prefix block.

   o  [RFC3956] states only ff70::/12 applies to Embedded-RP.
      Particularly, implementations should not treat the fff0::/12 range
      as Embedded-RP.

   To avoid such confusion and to unambiguously associate a meaning with
   the remaining flags, the following recommendation requirement is made

      Implementations MUST treat flag bits as separate bits.

3.2.  IANA Assigned SSM Block

   Another issue related to SSM is the IANA assigned SSM address block.
   Per [RFC4607], ff3x::4000:0001 through ff3x::7fff:fff is the block
   for IANA assignments (http://www.iana.org/assignments/ipv6-multicast-
   addresses/ipv6-multicast-addresses.xml).  However, IANA assignments
   are permanent addresses and should not have the transient bit set.
   Quoting from [RFC4607]:

      "T = 1 indicates a non-permanently-assigned ("transient")
      multicast address.".

4.  RFC Updates

4.1.  RFC3306  RFC 3306

   This document changes Section 4 of [RFC3306] as follows:

   OLD:

         |   8    |  4 |  4 |   8    |    8   |       64       |    32    |
         +--------+----+----+--------+--------+----------------+----------+
         |11111111|flgs|scop|reserved|  plen  | network prefix | group ID |
         +--------+----+----+--------+--------+----------------+----------+

                                      +-+-+-+-+
      flgs is a set of 4 flags:       |0|0|P|T|
                                      +-+-+-+-+

            o  P = 0 indicates a multicast address that is not assigned
               based on the network prefix.  This indicates a multicast
               address as defined in [ADDRARCH].

            o  P = 1 indicates a multicast address that is assigned based
               on the network prefix.

            o  If P = 1, T MUST be set to 1, otherwise the setting of the T
               bit is defined in Section 2.7 of [ADDRARCH].

      The reserved field MUST be zero.

   NEW:

         |   8    |  4 |  4 |   8    |    8   |       64       |    32    |
         +--------+----+----+--------+--------+----------------+----------+
         |11111111|flgs|scop|reserved|  plen  | network prefix | group ID |
         +--------+----+----+--------+--------+----------------+----------+

                                      +-+-+-+-+
      flgs is a set of 4 flags:       |X|Y|P|T|
                                      +-+-+-+-+

      X and Y may each be set to 0 or 1.

            o  P = 0 indicates a multicast address that is not assigned
               based on the network prefix.  This indicates a multicast
               address as defined in [ADDRARCH].

            o  P = 1 indicates a multicast address that is assigned based
               on the network prefix.

            o  If P = 1, T is MUST be set according to 1, otherwise the setting of the definition T
               bit is defined in Section 2.7 of [ADDRARCH]. Unicast-Prefix-based addresses would
               typically not be IANA assigned, so in most cases T would
               be set to 1.

   This document changes Section 6 of [RFC3306] as follows:

   OLD:

      These settings create an SSM range of FF3x::/32 (where 'x' is any
      valid scope value).  The source address field in the IPv6 header
      identifies the owner of the multicast address.

   NEW:

      T flag is set according to whether the addresses are assigned by
      IANA.

      If the flag bits are set to 0011, these settings create an SSM
      range of ff3x::/32 (where 'x' is any valid scope value).  The
      source address field in the IPv6 header identifies the owner of
      the multicast address. ff3x::/32 is not the only allowed SSM
      prefix range.  For example, ff2x::/32 example if the most significant flag bit is
      set, then we would be IANA assigned get the SSM
      addresses. range ffbx::/32.

4.2.  RFC3956  RFC 3956

   This document changes Section 2 of [RFC3956] as follows:

   OLD:

      As described in [RFC3306], the multicast address format is as
      follows:

         |   8    |  4 |  4 |   8    | 8  |       64       |    32    |
         +--------+----+----+--------+----+----------------+----------+
         |11111111|flgs|scop|reserved|plen| network prefix | group ID |
         +--------+----+----+--------+----+----------------+----------+

      Where flgs are "0011".  (The first two bits are as yet undefined,
      sent as zero and ignored on receipt.)

   NEW:

      As described in [RFC3306], the

      The multicast address format is as
      follows:

         |   8    |  4 |  4 |  4 |  4 | 8  |       64       |    32    |
         +--------+----+----+---------+----+----------------+----------+
         |11111111|flgs|scop|flgs|rsvd|plen| network prefix | group ID |
         +--------+----+----+---------+----+----------------+----------+

                                         +-+-+-+-+
         flgs is a set of four flags:    |X|R|P|T|
                                         +-+-+-+-+

         X may be set to 0 or 1.

   This document changes Section 3 of [RFC3956] as follows:

   OLD:

         |   8    |  4 |  4 |  4 |  4 | 8  |       64       |    32    |
         +--------+----+----+----+----+----+----------------+----------+
         |11111111|flgs|scop|rsvd|RIID|plen| network prefix | group ID |
         +--------+----+----+----+----+----+----------------+----------+
                                         +-+-+-+-+
         flgs is a set of four flags:    |0|R|P|T|
                                         +-+-+-+-+

      When the highest-order bit is 0, R = 1 indicates a multicast address
      that embeds the address on the RP.  Then P MUST be set to 1, and
      consequently T MUST be set to 1, as specified in [RFC3306].  In
      effect, this implies the prefix FF70::/12.  In this case, the last 4
      bits of the previously reserved field are interpreted as embedding
      the RP interface ID, as specified in this memo.

      The behavior is unspecified if P or T is not set to 1, as then the
      prefix would not be FF70::/12.  Likewise, the encoding and the
      protocol mode used when the two high-order bits in "flgs" are set to
      11 ("FFF0::/12") is intentionally unspecified until such time that
      the highest-order bit is defined.  Without further IETF
      specification, implementations SHOULD NOT treat the FFF0::/12 range
      as Embedded-RP.

   NEW:

         |   8    |  4 |  4 |  4 |  4 | 8  |       64       |    32    |
         +--------+----+----+----+----+----+----------------+----------+
         |11111111|flgs|scop|flgs|RIID|plen| network prefix | group ID |
         +--------+----+----+----+----+----+----------------+----------+
                                         +-+-+-+-+
         flgs is a set of four flags:    |X|R|P|T|
                                         +-+-+-+-+
         X may be set to 0 or 1.

      R = 1 indicates a multicast address that embeds the address of the RP.
      P MUST be set to 1 1, and consequently T MUST be set to 1, according
      to [RFC3306], as this is a special case of
      unicast-prefix based addresses. This implies that for instance prefixes
      ff70::/12 and fff0::/12 are embedded RP prefixes, but all multicast
      addresses with the R-bit set to 1 MUST be treated as Embedded RP
      addresses. The behavior is unspecified if P or T is not set to 1. When the
      R-bit is set, the last 4 bits of the previously reserved field are
      interpreted as embedding the RP interface ID, as specified in this memo.

   This document changes Section 4 of [RFC3956] as follows:

   OLD:

      It MUST be a multicast address with "flgs" set to 0111, that is,
      to be of the prefix FF70::/12,

   NEW:

      It MUST be a multicast address with R-bit set to 1.

      It MUST have P-bit and T-bit both set to 1 when using the
      embedding in this document as it is a prefix-based address.

   This document changes Section 7.1 of [RFC3956] as follows:

   OLD:

      To avoid loops and inconsistencies, for addresses in the range
      FF70::/12, the Embedded-RP mapping MUST be considered the longest
      possible match and higher priority than any other mechanism.

   NEW:

      To avoid loops and inconsistencies, for addresses with R-bit set
      to 1, the Embedded-RP mapping MUST be considered the longest
      possible match and higher priority than any other mechanism.

4.3.  RFC4607

   This document changes the abstract of [RFC4607] as follows:

   OLD:

      IP version 4 (IPv4) addresses in the 232/8 (232.0.0.0 to
      232.255.255.255) range are designated as source-specific multicast
      (SSM) destination addresses and are reserved for use by source-
      specific applications and protocols.  For IP version 6 (IPv6), the
      address prefix FF3x::/32 is currently reserved for source-specific
      multicast use but others may be reserved in the future.  This
      document defines an extension to the Internet network service that
      applies to datagrams sent to SSM addresses and defines the host
      and router requirements to support this extension.

   NEW:

      IP version 4 (IPv4) addresses in the 232/8 (232.0.0.0 to
      232.255.255.255) range are designated as source-specific multicast
      (SSM) destination addresses and are reserved for use by source-
      specific applications and protocols.  For IP version 6 (IPv6), the
      address prefix ff3x::/32 is currently reserved for source-specific
      multicast use but others may be reserved in the future.  This
      document defines an extension to the Internet network service that
      applies to datagrams sent to SSM addresses and defines the host
      and router requirements to support this extension.

   This document changes Section 1 of [RFC4607] as follows:

   OLD:

      For IPv6, the address prefix FF3x::/32 is reserved for source-
      specific multicast use, where 'x' is any valid scope identifier,
      by [IPv6-UBM].  Using the terminology of [IPv6-UBM], all SSM
      addresses must have P=1, T=1, and plen=0.  [IPv6-MALLOC] mandates
      that the network prefix field of an SSM address also be set to
      zero, hence all SSM addresses fall in the FF3x::/96 range.  Future
      documents may allow a non-zero network prefix field if, for
      instance, a new IP- address-to-MAC-address mapping is defined.
      Thus, address allocation should occur within the FF3x::/96 range,
      but a system should treat all of FF3x::/32 as SSM addresses, to
      allow for compatibility with possible future uses of the network
      prefix field.

   NEW:

      For IPv6, all SSM addresses must have P=1 and plen=0 while T-bit
      is set according to whether the addresses are assigned by IANA
      [I-D.ietf-6man-multicast-addr-arch-update].  In particular, a
      system should treat all of ff3x::/32 and ff2x::/32 as SSM
      addresses, to allow for compatibility with possible future uses of
      the network prefix field.  Other SSM prefixes can be defined in
      the future.

5.  IANA Considerations
   This document may require IANA updates.  However, at this point it is
   not clear exactly what these updates may be.

6.  Security Considerations

   Security considerations discussed in [RFC3956], [RFC3306], [RFC4607] [RFC3306] and
   [RFC4291] MUST be taken into account.

7.  Acknowledgements

   Many thanks to B. Haberman for the discussions prior to the
   publication of this document.

8.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3306]  Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
              Multicast Addresses", RFC 3306, August 2002.

   [RFC3956]  Savola, P. and B. Haberman, "Embedding the Rendezvous
              Point (RP) Address in an IPv6 Multicast Address", RFC
              3956, November 2004.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4607]  Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", RFC 4607, August 2006.

Authors' Addresses

   Mohamed Boucadair
   France Telecom
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com

   Stig Venaas
   Cisco
   USA

   Email: stig@cisco.com