IPv4 Address Allocation and the Evolution of the BGP routing table

IP addresses are allocated to Internet service providers (ISPs) by four Regional Internet Registries (RIRs), in turn the ISPs further assign addresses to end users. To understand the relationship, if any exists, between the address allocation and the global routing table growth, we present a quantitative analysis of the IPv4 address allocation and growth of the global BGP routing table over the last four and half years. Our findings show that (1) the distribution of the first-advertisement-delay, which is defined as the time period between the allocation of an IP prefix and its first BGP announcement has a heavy-tail distribution, and a small percentage of the allocated address prefixes have never been used; (2) although up to 50% of the prefixes allocated between Jan.1, 1998 and April 30, 2002 are advertised in the global routing table with the same prefix length as allocated, most of the rest of the prefixes are advertised as longer (more specific) prefixes; (3) the IP prefix set in the global routing table has been evolving over time. More than half of the prefixes existed in the BGP routing table In January 1998 disappeared by January 2002, while 87,941 new prefixes were added. Among the prefixes that disappeared, 77% of them were aggregated into shorter (less specific) prefixes; (4) the impact on routing table size is highly uneven among the allocations. If we take a snapshot of the global routing table dated on April 30, 2002, more than 70% of the routing table prefixes came from 10% of the allocated address blocks.