RFC 3180 (rfc3180) - Page 2 of 5

GLOP Addressing in 233/8

RFC 3180                GLOP Addressing in 233/8          September 2001


   The MALLOC working group has created a specific strategy for global
   multicast address allocation [RFC 2730, RFC 2909].  However, this
   approach has not been widely implemented or deployed.  This document
   proposes a solution for a subset of the problem, namely, those cases
   not covered by Source Specific Multicast.

3. Address Space

   The IANA has allocated 223/8 as per RFC 2770 [RFC 2770].  RFC 2770
   describes the administration of the middle two octets of 233/8 in a
   manner similar to that described in RFC 1797:

       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      233      |           16 bits AS          |  local bits   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.1. Example

   Consider, for example, AS 5662.  Written in binary, left padded with
   0s, we get 0001011000011110.  Mapping the high order octet to the
   second octet of the address, and the low order octet to the third
   octet, we get 233.22.30/24.

4. Allocation

   As mentioned above, the allocation proposed here follows the RFC 1797
   (case 1) allocation scheme, modified as follows: the high-order octet
   has the value 233, and the next 16 bits are a previously assigned
   Autonomous System number (AS), as registered by a network registry
   and listed in the RWhois database system.  This allows a single /24
   per AS.

   As was the case with RFC 1797, using the AS number in this way allows
   automatic assignment of a single /24 to each service provider and
   does not require an additional registration step.

4.1. Private AS Space

   The part of 233/8 that is mapped to the private AS space [RFC 1930] is
   assigned to the IRRs [RFC 3138].

5. Large AS Numbers

   It is important to note that this approach will work only for two
   octet AS numbers.  In particular, it does not work for any AS number
   extension scheme.




Meyer & Lothberg         Best Current Practice