TeXCP: Responsive Yet Stable Traffic Engineering

Intra-domain Traffic Engineering (TE) aims to route around failures and congestion, and balance load in an ISP’s network. Current TE relies on offline methods which use long term average traffic demands. It cannot react to traffic changes caused by BGP reroutes, diurnal traffic variations, attacks, or flash crowds. Further, current TE deals with network failures by pre-computing alternate routings for a limited set of failures. It may fail to prevent congestion when unanticipated or combination failures occur even though the network may have enough capacity to handle those failures. Since ISPs must ensure that each path in the network can cope with the peak load both during normal operation and under failures, current TE requires extensive over-provisioning. This paper presents TeXCP, an online distributed TE protocol that balances load in real-time, responding to actual traffic demands and failures. TeXCP uses multiple paths to deliver demands from an ingress to an egress router, adaptively moving traffic from overutilized to under-utilized paths. These adaptations are carefully designed such that, though done independently by each edge router based on local information, they balance load in the whole network without oscillations. We prove TeXCP is stable and show it is easy to implement. Our extensive simulations show that, for the same traffic demands, a network that uses TeXCP can support the same utilization and failure resilience as a network that uses traditional offline TE, but with a half or a third of the capacity.