Reliable routing with QoS guarantees for multi-domain IP/MPLS networks

We present a distributed routing algorithm for finding two disjoint (primary and backup) QoS paths that run across multiple domains. Our work is inspired by the recent interest in establishing communication paths with QoS constrains spanning multiple IP/MPLS domains. In such settings, the routing decisions in each domain are made by the Path Computation Element (PCE). We assume that the PCEs run a joint distributed routing protocol, decoupled from the BGP, which enables them to establish efficient paths across multiple domains. This study makes the following contributions. First, we present an aggregated representation of a multi-domain network that is small enough to minimize the link-state overhead, and, at the same time, is sufficiently accurate, so that the PCEs can find optimal disjoint QoS paths across multiple domains. Second, we present a distributed routing algorithm that uses the proposed representation to find disjoint paths in an efficient manner. Finally, we consider the problem of finding two disjoint paths subject to the export policy limitations, imposed by customer-provider and peer relationships between routing domains. We show that this problem can be efficiently solved by employing the concept of line graphs. To the best of our knowledge, this is the first scheme fully decoupled from BGP that enables to establish disjoint QoS IP/MPLS paths in a multi-domain environment with provable performance guarantees.