Challenges In Using Simulation to Explain Global Routing Instabilities

The global Internet is comprised of a large number of autonomous networks that agree to cooperate. Each such network---called an Autonomous System, or AS---is entirely responsible for management and routing of all internet traffic within its own domain. The global Internet works though because ASes enter into business agreements to route traffic from one to another if traffic sources and destinations are in distinct ASes. At the level of AS, socalled border routers forward Internet traffic from one AS to another. agree to route traffic between themselves. When a border router processes a received packet, it looks at the addressing information on the packet, infers which AS the packet is ultimately destined for, looks up in a table the outgoing port it is presently using to redirect traffic for that AS, and sends the packet out that way. This action is called forwarding, and the data structures used to direct the forwarding are called forwarding tables. A packet may be forwarded through multiple routers on the way from the source to the destination AS, the sequence of routers visited is called its path. Two routers that are directly connected (at least logically) so that one may forward traffic directly to another are called peers. A distributed algorithm called the Border Gateway Protocol (BGP) is used among routers to construct the forwarding tables.