Internet DRAFT - draft-ietf-ipngwg-uni-based-mcast

draft-ietf-ipngwg-uni-based-mcast




   IPNGWG Working Group                                        B. Haberman 
   Internet Draft                                          Nortel Networks 
   draft-ietf-ipngwg-uni-based-mcast-03.txt                      D. Thaler 
   October 2001                                                  Microsoft 
   Expires April 2002                                                      
 
 
             Unicast-Prefix-based IPv6 Multicast Addresses 
 
    
Status of this Memo 
    
   This document is an Internet-Draft and is in full conformance with 
   all provisions of Section 10 of RFC2026 [RFC 2026].  
    
   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF), its areas, and its working groups. Note that 
   other groups may also distribute working documents as Internet-
   Drafts. 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."  
    
   The list of current Internet-Drafts can be accessed at 
   http://www.ietf.org/ietf/1id-abstracts.txt. 
     
   The list of Internet-Draft Shadow Directories can be accessed at 
   http://www.ietf.org/shadow.html. 
     
     
Abstract 
    
   This specification defines an extension to the multicast addressing 
   architecture of the IP Version 6 protocol.  The extension presented 
   in this document allows for unicast-prefix-based allocation of 
   multicast addresses.  By delegating multicast addresses at the same 
   time as unicast prefixes, network operators will be able to identify 
   their multicast addresses without needing to run an inter-domain 
   allocation protocol. 
 
 
Table of Contents 
    
   Status of this Memo................................................1 
   Abstract...........................................................1 
   1. Introduction....................................................2 
   2. Motivation......................................................2 
   3. Terminology.....................................................2 
   4. Multicast Address Format........................................2 
   5. Address Lifetime................................................3 
   6. Source-Specific Multicast Addresses.............................4 
   7. Examples........................................................4 
   8. Security Considerations.........................................4 
  
Haberman, Thaler                                                     1 
 

 
Internet Draft   Unicast Prefix-based IPv6 Multicast     October 2001 
    
   9. References......................................................5 
   AuthorĘs Address...................................................6 
   Full Copyright Statement...........................................6 
    
 
1. Introduction 
    
   This document specifies an extension to the multicast portion of the 
   IPv6 addressing architecture [ADDRARCH].  The current architecture 
   does not contain any built-in support for dynamic address 
   allocation.  This proposal introduces encoded information in the 
   multicast address to allow for dynamic allocation of IPv6 multicast 
   addresses and IPv6 source-specific multicast addresses. 
    
 
2. Motivation 
    
   The current IPv4 multicast address allocation architecture [RFC 
   2908] is based on a multi-layered, multi-protocol system.  The goal 
   of this proposal is to reduce the number of protocols that need to 
   be deployed in order to get dynamic multicast address allocation. 
    
   The use of unicast prefix-based multicast address allocation will, 
   at a minimum, remove the need to run the Multicast Address 
   Allocation Protocol (AAP) [AAP WORK] and the Multicast Address-Set 
   Claim (MASC) Protocol [RFC 2909]. 
    
    
3. Terminology 
    
   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]. 
    
    
4. Multicast Address Format 
    
   Section 2.7 of [ADDRARCH] defines the following operational format 
   of IPv6 multicast addresses: 
    
     |    8   |  4 |  4 |                     112                     | 
     +--------+----+----+---------------------------------------------+ 
     |11111111|flgs|scop|                  group ID                   | 
     +--------+----+----+---------------------------------------------+ 
 
   This document introduces a new format that incorporates unicast 
   prefix information in the multicast address.  The following 
   illustrates the new format: 
    
    


  
Haberman, Thaler                                                     2 
    

 
Internet Draft   Unicast Prefix-based IPv6 Multicast     October 2001 
    
     |   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. 
    
   plen indicates the actual number of bits in the network prefix field 
   that identify the subnet when P = 1. 
    
   network prefix identifies the network prefix of the unicast subnet 
   owning the multicast address.  If P = 1, this field contains the 
   unicast network prefix assigned to the domain owning, or allocating, 
   the multicast address.  All non-significant bits of the network 
   prefix field SHOULD be zero. 
    
   It should be noted that the Interface Identifier requirements in 
   Section 2.5.1 of [ADDRARCH] effectively restricts the length of the 
   unicast prefix to 64 bits, hence the network prefix portion of the 
   multicast address will be at most 64 bits. 
    
   Group ID is set based on the guidelines outlined in [IPV6 GID]. 
    
   The scope of the unicast-prefix based multicast address MUST NOT 
   exceed the scope of the unicast prefix embedded in the multicast 
   address. 
    
    
5. Address Lifetime 
    
   The lifetime of a unicast prefix-based multicast addresses SHOULD 
   NOT exceed the Valid Lifetime field in the Prefix Information 
   option, corresponding to the unicast prefix being used, contained in 
   the Neighbor Discovery Router Advertisement message [RFC 2461].  The 
   lifetime of the multicast address is needed to support the Abstract 
   API for Multicast Address Allocation [RFC 2771]. 
    
   It should be noted that the unicast prefix's Valid Lifetime in the 
   Router Advertisement message does not indicate that the prefix will 
  
Haberman, Thaler                                                     3 
    

 
Internet Draft   Unicast Prefix-based IPv6 Multicast     October 2001 
    
   become invalid at the end of the lifetime.  Rather, that value is 
   typically a constant until a renumbering event is scheduled after 
   which, the prefix does become invalid. 
    
   The use of unicast prefix-based multicast addresses after the 
   unicast prefix has become invalid may lead to operational problems.  
   For example, routers that perform policy checks comparing the 
   multicast prefix against the unicast prefix assigned to an AS may 
   discard the packet. 
 
    
6. Source-Specific Multicast Addresses 
    
   The unicast prefix-based IPv6 multicast address format supports 
   Source-specific multicast addresses, as defined by [SSM ARCH].  To 
   accomplish is, a node MUST: 
    
           o Set P = 1. 
           o Set plen = 0. 
           o Set network prefix = 0. 
    
   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. 
    
    
7. Examples 
    
   The following are a few examples of the structure of unicast prefix-
   based multicast addresses. 
    
           - Global prefixes - A network with a unicast prefix of 
              3FFE:FFFF:1::/48 would also have a unicast prefix-based 
              multicast prefix of FF3x:0030:3FFE:FFFF:0001::/96 (where 
              'x' is any valid scope). 
           - Link-local prefix - A network segment (e.g. a 10baseT 
              Ethernet) using the link-local prefix would also be able 
              to use the multicast prefix FF32:000A:FE80::/96. 
           - SSM - All IPv6 SSM multicast addresses will have the 
              format FF3x::/96. 
    
    
8. Security Considerations 
    
   It is possible that the embedded unicast prefix can aid in 
   identifying the allocation domain of a given multicast address, 
   though an allocation domain choosing to avoid being traced has no 
   obstacles currently to creating addresses using a prefix not 
   assigned to it, or using a smaller scope embedded prefix. 
    
   Using source-specific multicast addresses can sometimes aid in the 
   prevention of denial-of-service attacks by arbitrary sources, 
  
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Internet Draft   Unicast Prefix-based IPv6 Multicast     October 2001 
    
   although no guarantee is provided.  A more in-depth discussion of 
   the security considerations for SSM can be found in [SSM ARCH]. 
 
 
9. References 
    
   [RFC 2026] S. Bradner, "The Internet Standards Process -- 
              Revision 3", BCP 9, RFC 2026, October 1996. 
    
   [RFC 2460] S. Deering and R. Hinden, "Internet Protocol, Version 6 
              (IPv6) Specification", RFC 2460, December 1998. 
     
   [ADDRARCH] R. Hinden and S. Deering, "IP Version 6 Addressing 
              Architecture", Work In Progress, July 2001. 
    
   [RFC 2908] Thaler, D., Handley, M., and Estrin, D., "The Internet 
              Multicast Address Allocation Architecture", RFC 2908, 
              September 2000. 
    
   [AAP WORK] M. Handley and S. Hanna, "Multicast Address Allocation 
              Protocol (AAP)", Work In Progress. 
    
   [RFC 2909] P. Radoslavov, et al, " The Multicast Address-Set Claim 
              (MASC) Protocol", RFC 2909, September 2000. 
    
   [RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate     
              Requirement Levels", RFC 2119, BCP14, March 1999. 
    
   [IPV6 GID] B. Haberman, "Dynamic Allocation Guidelines for IPv6 
              Multicast Addresses", Work In Progress, September 2001. 
    
   [RFC 2461] Narten, T., Nordmark, E., Simpson, W., "Neighbor 
              Discovery for IP Version 6 (IPv6)", RFC 2461, December 
              1998. 
    
   [RFC 2771] R. Finlayson, " An Abstract API for Multicast Address 
              Allocation", RFC 2771, February 2000. 
    
   [SSM ARCH] H. Holbrook and B. Cain, "Source-Specific Multicast 
              for IP", Work In Progress, March 2001. 












  
Haberman, Thaler                                                     5 
    


 
 
AuthorĘs Address 
    
   Brian Haberman 
   Nortel Networks 
   300 Perimeter Park 
   Morrisville, NC  27560 
   1-919-905-7484 
   haberman@nortelnetworks.com 
    
   Dave Thaler 
   Microsoft Corporation 
   One Microsoft Way 
   Redmond, WA  48105-6399 
   1-425-703-8835 
   dthaler@microsoft.com 
    
    
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Haberman, Thaler                                                     6