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.

The proposed solution is to topologically allocate future IP address assignment, by allocating segments of the IP address space to the transit routing domains.

This plan for allocating IP addresses should be undertaken as soon as possible. We believe that this will suffice as a short term strategy, to fill the gap between now and the time when a viable long term plan can be put into place and deployed effectively. This plan should be viable for at least three (3) years, after which time, deployment of a suitable long term solution is expected to occur.

This plan is primarily directed at the first two problems listed above. We believe that the judicious use of variable-length subnetting techniques should help defer the onset of the last problem problem, the exhaustion of the 32-bit address space. Note also that improved tools for performing address allocation in a "supernetted" and variably-subnetted world would greatly help the user community in accepting these sometimes confusing techniques. Efforts to create some simple tools for this purpose should be encouraged by the Internet community.

Note that this plan neither requires nor assumes that already assigned addresses will be reassigned, though if doing so were possible, it would further reduce routing table sizes. It is assumed that routing technology will be capable of dealing with the current routing table size and with some reasonably small rate of growth. The emphasis of this plan is on significantly slowing the rate of this growth.

Note that this plan does not require domains to renumber if they change their attached transit routing domain. Domains are encouraged to renumber so that their individual address allocations do not need to be advertised.

This plan will not affect the deployment of any specific long term plan, and therefore, this document will not discuss any long term plans for routing and address architectures.