RFC 1517 (rfc1517) - Page 2 of 4

Applicability Statement for the Implementation of Classless Inter-Domain Routing (CIDR)

RFC 1517              CIDR Applicability Statement        September 1993


   explosion problem [1].

2. Components of the Architecture

   The CIDR architecture is described in the following documents:

      - "An Architecture for IP Address Allocation with CIDR" [2]

      - "Classless Inter-Domain Routing (CIDR):  An Address Assignment
        and Aggregation Strategy" [3]

   The first of these documents presents the overall architecture of
   CIDR; the second describes the specific address allocation scheme to
   be used.

   In addition to these two documents, "Guidelines for Management of IP
   Address Space" [4] provides specific recommendations for assigning IP
   addresses that are consistent with [2] and [3], and "Status of CIDR
   Deployment in the Internet" [5] describes the timetable for deploying
   [4] in the Internet.  Both [4] and [5] should be viewed as
   supporting, rather than defining, documents.

   In addition to the documents mentioned above, CIDR requires that
   inter-domain routing protocols be capable of handling reachability
   information that is expressed solely in terms of IP address prefixes.
   While several inter-domain routing protocols are capable of
   supporting such functionality, this Applicability Statement does not
   mandate the use of a particular one.

   Although Internet routing domains are not required to use routing
   protocols capable of propagating CIDR routes, the topology such
   routing domains can support will be somewhat limited.  In particular,
   the non-CIDR-capable parts of the Internet will need to default
   towards the CIDR-capable parts of the Internet for routes which have
   been aggregated to non-network boundaries.

3. Applicability of CIDR

   The CIDR architecture is applicable to any group of connected domains
   that supports IP version 4 [6] [7].  CIDR does not require all of the
   domains in the Internet to be converted to use CIDR. It assumes that
   some of the existing domains in the Internet will never be able to
   convert.  Despite this, CIDR will still provide connectivity to such
   places, although the optimality of routes to these places may be
   impacted.

   This Applicability Statement requires Internet domains providing
   backbone and/or transit service to fully implement CIDR in order to



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