IP addresses are allocated to ISPs by four Regional Internet Registries (RIRs); in turn, the ISPs further assign addresses to end users. To understand the relationship, if any, between address allocation and global routing table growth, we present a quantitative analysis of the IPv4 address allocation and the growth of the global BGP routing table over the last four-and-one-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 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% were aggregated into shorter (less specific) prefixes; and
4. Different address allocations have varying degrees of impact on routing table growth. A sample snapshot of the global routing table on April 30, 2002, shows that more than 70% of the routing table entries came from 10% of the allocated address blocks.

About the Presenter
Cathy Wittbrodt is a member of the technical staff of Packet Design. Before joining Packet Design she was with Excite@Home, where she was responsible for network routing and IP addressing. Cathy is a member of the ARIN advisory council as well as the Address Supporting Organization (ASO) address council. She has been active in the Internet for 12 years. She began at Merit Network, Inc. where she worked on the NSFNET Backbone. Also while at Merit Cathy built CICNet, a network that connected the Big 10 universities. Following Merit, Cathy designed and implemented OSI/CLNP for the Energy Sciences Network. Although OSI/CLNP was never widely deployed, the experience has given greater insight into addressing and scaling issues. Cathy also spent three years in the engineering group of the Bay Area Regional Research Network, BARRNet, which was bought by BBN Planet. Cathy is on the Board of Directors of Panzer Motorcycle Works, USA, Inc. She has a B.S. in mathematics from Northern Arizona University.