A well-known approach to intradomain traffic engineering consists in finding the set of link weights that minimizes a network-wide objective function for a given intradomain traffic matrix. This approach is inadequate because it ignores a potential impact on interdomain routing. Indeed, the resulting set of link weights may trigger BGP to change the BGP next hop for some destination prefixes, to enforce hot-potato routing policies. In turn, this results in changes in the intradomain traffic matrix that have not been anticipated by the link weights optimizer, possibly leading to degraded network performance. We propose a BGP-aware link weights optimization method that takes these effects into account, and even turns them into an advantage. This method uses the interdomain traffic matrix and other available BGP data, to extend the intradomain topology with external virtual nodes and links, on which all the well-tuned heuristics of a classical link weights optimizer can be applied. A key innovative asset of our method is its ability to also optimize the traffic on the interdomain peering links. We show, using an operational network as a case study, that our approach does so efficiently at almost no extra computational cost.
A system of techniques is presented for optimizing open shortest path first (OSPF) or intermediate system-intermediate system (IS-IS) weights for intradomain routing in a changing world, the goal being to avoid overloaded links. We address predicted periodic changes in traffic as well as problems arising from link failures and emerging hot spots.  Intra-domain routing in IP backbone networks relies on link-state protocols such as IS-IS or OSPF. These protocols associate a weight (or cost) with each network link, and compute traffic routes based on these weight. However, proposed methods for selecting link weights largely ignore the issue of failures which arise as part of everyday network operations (maintenance, accidental, etc.). Changing link weights during a short-lived failure is impractical. However such failures are frequent enough to impact network performance. We propose a Tabu-search heuristic for choosing link weights which allow a network to function almost optimally during short link failures. The heuristic takes into account possible link failure scearios when choosing weights, thereby mitigating the effect of such failures. We find that the weights chosen by the heuristic can reduce link overload during transient link failures by as much as 40 at the cost of a small performance degradation in the absence of failures (10 ). In this paper, we adapt the heuristic of Fortz and Thorup for optimizing the weights of Shortest Path First protocols suchas Open Shortest Path First (OSPF) or Intermediate System-Intermediate System (IS-IS), in order to take into account failurescenarios.More precisely, we want to find a set of weights that is robust to all single link failures. A direct application of the originalheuristic, evaluating all the link failures, is too time consuming for realistic networks, so we developed a method based on acritical set of scenarios aimed to be representative of the whole set of scenarios. This allows us to make the problem manageableand achieve very robust solutions.