OPTIC: An Efficient BGP Protection Technique For Optimal Intra-domain Convergence (Master's Thesis)

Interactions between the intra- and inter-domain routing protocols received little attention despite playing an important role in forwarding external traffic. More precisely, by default, IGP distances are taken into account in the BGP decision process to select the closest exit gateway for the transit traffic, i.e., to enforce hot-potato routing. Upon an IGP update, the new best gateway may change and should be updated through the (full) re-convergence of BGP, causing superfluous BGP processing and updates in many cases. With our novel scheme, OPTIC (Optimal Protection Technique for Inter-intra domain Convergence), we propose an efficient way to reassemble the two protocols without losing the hot-potato property. OPTIC pre-computes sets of gateways, i.e., BGP next-hops, shared by groups of prefixes. Such sets are guaranteed to contain the post-convergence gateway after any single IGP event. The new optimal exits can be found through a single walk-through of each set, allowing the transit traffic to benefit from optimal BGP routes almost as soon as the IGP converges. Compared to vanilla BGP, OPTIC's structures allow it to consider a reduced number of entries: compared to the full set of single BGP prefixes, this number can be reduced by 99\% for stub networks. The update of OPTIC's structures, which is not required as long as border routers remain at least bi-connected, scales linearly in time with its number of groups