language: en

Internet Routing Instability

Craig Labovitz, G. Robert Malan, and Farnam Jahanian
University of Michigan Department of Electrical Engineering and Computer Science
1301 Beal Ave. Ann Arbor, Michigan 48109-2122
flabovit, rmalan, farnamg@eecs.umich.edu

Abstract This paper examines the network inter-domain routing information exchanged between backbone service providers at the major U.S. public Internet exchange points. Internet routing instability, or the rapid fluctuation of network reach-ability information, is an important problem currently facing the Internet engineering community. High levels of network instability can lead to packet loss, increased network latency and time to convergence. At the extreme, high levels of routing instability have lead to the loss of internal connectivity in wide-area, national networks. In this paper, we describe several unexpected trends in routing instability, and examine a number of anomalies and pathologies observed in the exchange of inter-domain routing information. The analysis in this paper is based on data collected from BGP routing messages generated by border routers at five of the Internet core's public exchange points during a nine month period. We show that the volume of these routing updates is several orders of magnitude more than expected and that the majority of this routing information is redundant, or pathological. Furthermore, our analysis reveals several unexpected trends and ill-behaved systematic properties in Internet routing. We finally posit a number of explanations for these anomalies and evaluate their potential impact on the Internet infrastructure.

1 Introduction