Analysis of the MED Oscillation Problem in BGP

The Multi Exit Discriminator (MED) attribute of the Border Gateway Protocol (BGP) is widely used to implement “cold potato routing” between autonomous systems. However, the use of MED in practice has led to BGP persistent oscillation. The MED oscillation problem has been described with example configurations and complicated, step-by-step evaluation of dynamic route computations performed at multiple routers. Our work presents the first rigorous analysis of the MED oscillation problem. We employ the Stable Paths Problem (SPP) formalism that allows a static analysis of the interaction of routing policies. We give a formal definition of MED Induced Routing Anomalies (MIRA) and show that, in general, they can span multiple autonomous systems. However, if we assume that the BGP configurations between ASes follows a common model based on customer/provider and peer/peer relationships, then we show that the scope of any MIRA is always contained within a single autonomous system. Contr...

• Type: Conference
• Year: 2002
• Where: ICNP
• Authors: Timothy Griffin, Gordon T. Wilfong
• Keywords: Autonomous System, Computer Networks, ICNP 2002, Multi Exit Discriminator, Oscillation Problem