A traffic engineering-aware shortest-path routing algorithm in IP networks

Single shortest-path routing is known to perform poorly for Internet traffic engineering (TE) where the typical optimization objective is to minimize the maximum link load. Splitting traffic uniformly over equal-cost multiple shortest paths in OSPF and IS-IS does not always minimize the maximum link load when multiple paths are not carefully selected for the global traffic demand matrix. However, a TE-aware shortest path among all the equal-cost multiple shortest paths between each ingress-egress pair can be selected such that the maximum link load is significantly reduced. IP routers can use the TE-aware shortest path without any change to existing routing protocols and without any serious configuration overhead. While calculating TE-aware shortest paths, the destination-based forwarding constraint at a node should be satisfied, because an IP router will forward a packet to the next-hop towards the destination by looking up the destination prefix. In this paper, we present a mathematical problem formulation for finding a set of TE-aware shortest paths for the given network as an integer linear program (ILP), and we propose a simple heuristic for solving large instances of the problem. The proposed algorithm is evaluated through simulations in IP networks.