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Versions: (draft-boucadair-6man-multicast-addr-arch-update) 00 01 02 03 04 05 06 07 08 RFC 7371

6man Working Group                                          M. Boucadair
Internet-Draft                                            France Telecom
Updates: 3306,3956,4291 (if approved)                          S. Venaas
Intended status: Standards Track                                   Cisco
Expires: September 13, 2014                               March 12, 2014


         Updates to the IPv6 Multicast Addressing Architecture
             draft-ietf-6man-multicast-addr-arch-update-04

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 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
   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."

   This Internet-Draft will expire on September 13, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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
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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Addressing Architecture Update  . . . . . . . . . . . . . . .   2
   3.  Flag Bits: A Recommendation . . . . . . . . . . . . . . . . .   3
   4.  RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  RFC 3306  . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  RFC 3956  . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

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).

   This document updates [RFC3956], [RFC3306], and [RFC4291].  These
   updates are logical consequences of the recommendation on the flag
   bits (Section 3).

   Textual representation of IPv6 addresses included in the RFC updates
   follows the recommendation in [RFC5952].

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.




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

   NEW:
   |   8    |  4 |  4 |  4 |             108 bits                    |
   +--------+----+----+----------------------------------------------+
   |11111111|ff1 |scop|ff2 |             group ID                    |
   +--------+----+----+----+-----------------------------------------+

        * ff1 refers to "flag field 1"
        * ff2 refers to "flag field 2"
        * flag bits denote both ff1 and ff2.


         Figure 1: Updated IPv6 Multicast Addressing Architecture

   OLD (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|ff1 |scop|ff2 |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.  Flag Bits: A Recommendation

   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:




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   o  the reading of [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 requirement is made

      Implementations MUST treat flag bits as separate bits.

4.  RFC Updates

4.1.  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:









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      |   8    |  4 |  4 |  4 |  4 |    8   |       64       |    32    |
      +--------+----+----+----+----+--------+----------------+----------+
      |11111111|ff1 |scop|ff2 |rsvd|  plen  | network prefix | group ID |
      +--------+----+----+----+----+--------+----------------+----------+

                                                  +-+-+-+-+
   ff1 (flag field 1) 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 [RFC4291].

         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 [RFC4291].

                                                  +-+-+-+-+
   ff2 (flag field 2) is a set of 4 flags:        |r|r|r|r|
                                                  +-+-+-+-+

   where "rrrr" are for future assignment as additional flag bits.

   Flag bits denote both ff1 and ff2.

   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:

      If the flag bits in ff1 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 if the most significant flag bit in ff1
      is set, then we would get the SSM range ffbx::/32.






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4.2.  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:

      The multicast address format is as
      follows:

         |   8    |  4 |  4 |  4 |  4 | 8  |       64       |    32    |
         +--------+----+----+----+----+----+----------------+----------+
         |11111111|ff1 |scop|ff2 |rsvd|plen| network prefix | group ID |
         +--------+----+----+----+----+----+----------------+----------+

                                                        +-+-+-+-+
         ff1 (flag field 1) is a set of four flags:     |X|R|P|T|
                                                        +-+-+-+-+
         X may be set to 0 or 1.

                                                        +-+-+-+-+
         ff2 (flag field 2) is a set of 4 flags:        |r|r|r|r|
                                                        +-+-+-+-+
         where "rrrr" are for future assignment as additional flag bits.

         Flag bits denote both ff1 and ff2.

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

   OLD:









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       |   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|ff1 |scop|ff2 |RIID|plen| network prefix | group ID |
      +--------+----+----+----+----+----+----------------+----------+
                                      +-+-+-+-+
      ff1 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, 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.  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 field that were reserved in [RFC3306] are interpreted as
   embedding the RP interface ID, as specified in this memo.


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

   OLD:




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      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.

5.  IANA Considerations

   This document does not require any action from IANA.

6.  Security Considerations

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

7.  Acknowledgements

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

   Many thanks to J. Korhonen and T. Jinmei their comments.

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.




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   [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.

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952, August 2010.

Authors' Addresses

   Mohamed Boucadair
   France Telecom
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com


   Stig Venaas
   Cisco
   USA

   Email: stig@cisco.com


























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