RFC 1519 (rfc1519) - Page 2 of 24

Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy

RFC 1519                 CIDR Address Strategy            September 1993


   5.1  Address allocation .......................................... 15
   5.2  Routing advertisements ...................................... 17
   6.  Extending CIDR to class A addresses .......................... 18
   7.  Domain Naming Service considerations ......................... 20
   7.1 Procedural changes for class-C "supernets" ................... 20
   7.2 Procedural changes for class-A subnetting .................... 21
   8.  Transitioning to a long term solution ........................ 22
   9.  Conclusions .................................................. 22
   10.  Recommendations ............................................. 22
   11.  References .................................................. 23
   12.  Security Considerations ..................................... 23
   13.  Authors' Addresses .......................................... 24

Acknowledgements

   The authors wish to express their appreciation to the members of the
   ROAD group with whom many of the ideas contained in this document
   were inspired and developed.

1.  Problem, Goal, and Motivation

   As the Internet has evolved and grown over in recent years, it has
   become evident that it is soon to face several serious scaling
   problems. These include:

      1.   Exhaustion of the class B network address space. One
           fundamental cause of this problem is the lack of a network
           class of a size which is appropriate for mid-sized
           organization; class C, with a maximum of 254 host
           addresses, is too small, while class B, which allows up to
           65534 addresses, is too large for most organizations.

      2.   Growth of routing tables in Internet routers beyond the
           ability of current software, hardware, and people to
           effectively manage.

      3.   Eventual exhaustion of the 32-bit IP address space.

   It has become clear that the first two of these problems are likely
   to become critical within the next one to three years.  This memo
   attempts to deal with these problems by proposing a mechanism to slow
   the growth of the routing table and the need for allocating new IP
   network numbers. It does not attempt to solve the third problem,
   which is of a more long-term nature, but instead endeavors to ease
   enough of the short to mid-term difficulties to allow the Internet to
   continue to function efficiently while progress is made on a longer-
   term solution.




Fuller, Li, Yu & Varadhan