Controlling Hot Potatoes in Intradomain Traffic Engineering

The growth in Internet connectivity at the Autonomous System (AS) level and the practice of ”hot potato” routing has increased the possibility of interaction between intradomain and interdomain traffic engineering (TE). Hot potato routing occurs when a router inside an AS knows of multiple exit points out of the AS towards a destination, and selects the one that is ”closest” to it. The closeness of exit points is determined by the intradomain routing policy of the AS. In this paper, we use routing, traffic and topology data from the Sprint network to study the interaction between hot potato routing and intradomain TE based on selecting link metrics for the IS-IS (or OSPF) protocol. We find that 60% of network prefixes and 70% of traffic can be potentially affected by hot potato routing. We show that when we do not account for this problem, the results from intradomain TE can be off by 10% of link utilization. We show that considering hot potato routing explicitly when selecting link metrics improves performance by as much as 20% in terms of the maximum link load. Detailed examples are used to provide insights into this performance gain. However, this improvement comes at the cost of an increased sensitivity to changes in link metric values or link failures.