3.3.2 Growth rate projections

As of Jan '92, a default-free routing table (for example, the routing tables maintained by the routers in the NSFNET backbone) contained approximately 4700 entries. This number reflects the current size of the NSFNET routing database. Historic data shows that this number, on average, has doubled every 10 months between 1988 and 1991. Assuming that this growth rate is going to persist in the foreseeable future (and there is no reason to assume otherwise), we expect the number of entries in a default-free routing table to grow to approximately 30000 in two years time. In the following analysis, we assume that the growth of the Internet has been, and will continue to be, exponential.

It should be stressed that these projections do not consider that the current shortage of class B network numbers may increase the number of instances where many class C's are used rather than a class B. Using an assumption that new organizations which formerly obtained class B's will now obtain somewhere between 4 and 16 class C's, the rate of routing table growth can conservatively be expected to at least double and probably quadruple. This means the number of entries in a default-free routing table may well exceed 10,000 entries within six months and 20,000 entries in less than a year.

As of Dec '92, the routing table contains 8500 routes. The original growth curves would predict over 9400 routes. At this time, it is not clear if this would indicate a significant change in the rate of growth.

Under the proposed plan, growth of the routing table in a default- free router is greatly reduced since most new address assignment will come from one of the large blocks allocated to the service providers. For the sake of this analysis, we assume prompt implementation of this proposal and deployment of the revised routing protocols. We make the initial assumption that any initial block given to a provider is sufficient to satisfy its needs for two years.

Since under this plan, multi-homed networks must continue to be explicitly advertised throughout the system (according to Rule #1 described in section 4.2), the number multi-homed routes is expected to be the dominant factor in future growth of routing table size, once the supernetting plan is applied.

Presently, it is estimated that there are fewer than 100 multi-homed organizations connected to the Internet. Each such organization's network is comprised of one or more network numbers. In many cases (and in all future cases under this plan), the network numbers used by an organization are consecutive, meaning that aggregation of those networks during route advertisement may be possible. This means that the number of routes advertised within the Internet for multi-homed networks may be approximated as the total number of multi-homed organizations. Assuming that the number of multi-homed organization will double every year (which may be a over-estimation, given that every connection costs money), the number of routes for multi-homed networks would be expected to grow to approximately 800 in three years.

If we further assume that there are approximately 100 service providers, then each service provider will also need to advertise its block of addresses. However, due to aggregation, these advertisements will be reduced to only 100 additional routes. We assume that after the initial two years, new service providers combined with additional requests from existing providers will require an additional 50 routes per year. Thus, the total is 4700 + 800 + 150 = 5650. This represents an annual growth rate of approximately 6%. This is in clear contrast to the current annual growth of 130%. This analysis also assumes an immediate deployment of this plan with full compliance. Note that this analysis assumes only a single level of route aggregation in the current Internet - intelligent address allocation should significantly improve this.

Clearly, this is not a very conservative assumption in the Internet environment nor can 100% adoption of this proposal be expected. Still, with only a 90% participation in this proposal by service providers, at the end of the target three years, global routing table size will be "only" 4700 + 800 + 145 + 7500 = 13145 routes -- without any action, the routing table will grow to approximately 75000 routes during that time period.