BGP-aware IGP Link Weight Optimization in Presence of Route Reflectors

Abstract

The first generation of IGP Link Weight Optimizers (LWOs) was based on presumably invariant intra-domain traffic matrices only, ignoring the fact that updating link weights had a side effect on these traffic matrices due to hot-potato routing, thus result- ing in suboptimal link weight settings, and sometimes to very bad performance. The second generation of IGP LWOs, referred to as BGP-aware LWOs, has been able to optimize link weights while taking hot-potato effects into account. However, these tools relied on the complete visibility assumption fulfilled by e.g. a full-mesh iBGP configu- ration. This paper proposes a third generation LWO, still BGP-aware, but also able to work with iBGP con- figurations based on route reflectors, which usually hide some reachability information from routers. This partial visibility may cause various problems, including path deflections (i.e., the actual egress router is not the expected one), which may in turn create forwarding loops. Our LWO embeds a BGP routing solver which can always predict the actual egress router, even when route reflectors are used. It can also forbid solutions leading to path deflection. Its efficiency is evaluated on a real dataset, and compared to other LWOs. Index Terms—Traffic Engineering, Hot-potato Rout- ing, BGP, IGP, OSPF, Path Deflection