One document matched: draft-ietf-ipngwg-uni-based-mcast-00.txt

   IPNGWG Working Group                                         B. Haberman
   Internet Draft                                           Nortel Networks
   draft-ietf-ipngwg-uni-based-mcast-00.txt                       D. Thaler
   August 2000                                                    Microsoft
   Expires February 2001 
 
 
             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. 
    
    
1. Introduction 
    
   This document specifies an extension to the multicast portion of the 
   IPv6 addressing architecture [RFC 2373].  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, network prefix-based 
   allocation of IPv6 multicast addresses, as well as allocation of 
   source-specific multicast addresses. 
    
 
2. Multicast Address Format 
    
   Section 2.7.2 of RFC 2373 defines the following operational format 
   of IPv6 multicast addresses: 
  
Haberman, Thaler                                                     1 
 
 
Internet Draft   Unicast Prefix-based IPv6 Multicast       August 2000 
    
    
     |    8   |  4 |  4 |               80               |     32     | 
     +--------+----+----+--------------------------------+------------+ 
     |11111111|flgs|scop|     reserved must be zero      | group ID   | 
     +--------+----+----+--------------------------------+------------+ 
    
    
   This document introduces a new format that incorporates unicast 
   prefix information in the multicast address.  The following 
   illustrates the new format: 
    
    
     |   8    |  4 |  4 |   8  |      plen      |72 - plen |    32    | 
     +--------+----+----+------+----------------+----------+----------+ 
     |11111111|flgs|scop| plen | network prefix | reserved | 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. 
           o  P = 1 indicates a multicast address that is assigned 
              based on the network prefix. 
           o  The setting of the T bit is defined in Section 2.7 of RFC 
              2373 
    
   plen indicates the length of the network prefix portion of the 
   address when P = 1.  This field is required in order to determine 
   the number of bits to include as part of the unicast prefix. 
    
   network prefix identifies the network prefix of the unicast subnet 
   owning the multicast address.  If P = 1, this field contains the 
   unicast network prefix defined in [RFC 2374] and assigned to the 
   domain owning the multicast address. 
    
   The reserved field MUST be zero. 
    
   While this limits the number of unicast prefix-based IPv6 multicast 
   groups to 2^32 per prefix, this is unlikely to be a limitation in 
   the future.  If it becomes necessary to exceed this limit in the 
   future, multicast will still work but the processing will be 
   slightly slower. 
    
   With the network prefix-based architecture and the current unicast 
   address architecture [RFC 2374], the network prefix portion of the 
   multicast address will be at most 64 bits.  This allows for the 
   group ID field to be at least 40 bits. 
    
  
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Internet Draft   Unicast Prefix-based IPv6 Multicast       August 2000 
    
    
3. Source-Specific Multicast Addresses 
    
   The network prefix-based IPv6 multicast address format supports 
   Source-specific multicast addresses, as defined by [IANA].  This is 
   accomplished by: 
    
           o  Setting P = 1 
           o  Setting plen = 0 
           o  Setting network prefix = 0 
    
    
4. Security Considerations 
    
   Using unicast network-prefix based multicast addresses can sometimes 
   aid in identifying the allocation domain of a given multicast 
   address, although no guarantee is provided. 
    
   Using source-specific multicast addresses can sometimes aid in the 
   prevention of denial-of-service attacks by arbitrary sources, 
   although no guarantee is provided. 
    
 
5. 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. 
     
    
   [RFC 2373] R. Hinden and S. Deering, "IP Version 6 Addressing 
              Architecture", RFC 2373, July 1998. 
    
   [RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate     
              Requirement Levels", RFC 2119, BCP14, March 1999. 
    
   [RFC 2374] R. Hinden, M. O'Dell, and S. Deering, "An IPv6 
              Aggregatable Global Unicast Address Format", RFC 2374, 
              July 1998. 
    
   [RFC 2464] M. Crawford, "Transmission of IPv6 Packets over Ethernet 
              Networks", RFC 2464, December 1998. 
    
   [RFC 2470] M. Crawford, T. Narten, and S. Thomas, "Transmission of  
              IPv6 Packets over Token Ring Networks", RFC 2470, 
              December 1998. 
    
   [RFC 2375] R. Hinden and S. Deering, "IPv6 Multicast Address 
              Assignments", RFC 2375, July 1998. 
    
  
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Internet Draft   Unicast Prefix-based IPv6 Multicast       August 2000 
    
   [RFC 2365] D. Meyer, "Administratively Scoped IP Multicast", 
              BCP 23, RFC 2365, July 1998. 
    
   [IANA]     D. Cheriton, "Single-source IP Multicast Address Range", 
              http://www.isi.edu/in-notes/iana/assignments/single- 
              source-multicast, October 1998. 
    
 
    











































  
Haberman, Thaler                                                     4 
    


 
Author's Address 
    
   Brian Haberman 
   Nortel Networks 
   4309 Emperor Blvd. 
   Suite 200 
   Durham, NC  27703 
   1-919-992-4439 
   Email : haberman@nortelnetworks.com 
    
   Dave Thaler 
   Microsoft Corporation 
   One Microsoft Way 
   Redmond, WA  48105-6399 
   1-425-703-8835 
   Email: dthaler@microsoft.com 
    
    


































  
Haberman, Thaler                                                     5