RFC 2073 (rfc2073) - Page 2 of 7

An IPv6 Provider-Based Unicast Address Format

RFC 2073       IPv6 Provider-Based Unicast Address Format   January 1997


   The specific type of an IPv6 address is indicated by the leading bits
   in the address.  The variable-length field comprising these leading
   bits is called the Format Prefix (FP).

   This document defines an address format for the 010 (binary) Format
   Prefix for Provider-Based Unicast addresses. The same address format
   could be used for other Format Prefixes, as long as these Format
   Prefixes also identify IPv6 unicast addresses.  Only the "010" Format
   Prefix is defined here.

3.0 IPv6 Provider-Based Unicast Address Format

   This document defines an address format for the IPv6 provider-based
   unicast address assignment.  It is expected that this address format
   will be widely used for IPv6 nodes connected to the Internet.

   The address format defined in this document conforms to the
   "Architecture for IPv6 Unicast Address Allocation" [ALLOC].
   Specifically, the format is designed to support aggregation of
   network layer reachability information at multiple levels of routing
   hierarchy.

   For addresses of the format described in this document the address
   administration is organized into a three level hierarchy -- registry,
   provider, and subscriber.  The address format defined here allows
   flexible address allocation at each level of the address
   administration hierarchy in such a way as to support a wide spectrum
   of demands for address allocation.

   This document assumes that the Internet routing system doesn't make
   any assumptions about the specific structure and semantics of an IPv6
   address, except for the structure and semantics of the Format Prefix
   part of the address, and the use of the "longest prefix match"
   algorithm (on arbitrary bit boundaries) for making a forwarding
   decision.

   The address format defined in this document is intended to facilitate
   scalable Internet-wide routing that does not impose any constraints
   on connectivity among the providers, as well as among the providers
   and subscribers.











Rekhter, et. al.            Standards Track