Distributed Schemes for Diverse Path Computation in Multi-Domain MPLS Networks

MPLS is currently used by several JSPs to carry some high-value traffic components, such as telephony over IP trunks and VPNs. For this type of traffic, service availability is a critical QoS dimension that needs to be protected from network failures. With MPLS-TE, this can be achieved by means of path protection schemes, where active and backup LSPs are routed along diverse paths. Besides protection, path diversity can be exploited for load balancing, another common means of QoS improvement. In order to preserve other QoS requirements, the paths must meet certain constraints (e.g., bandwidth availability, low load) and/or minimize some metric (e.g., hop count). This requires the ability to establish path diversity in an optimal way. In many cases of practical interest, the QoS traffic has an interdomain scope. This is the case for ToIP and VPN traffic between different carriers, or between different ASs owned by the same carrier, as found, for example, after corporate acquisitions or mergers. Therefore, path diversity is a requirement for interdomain traffic engineering. In this work we address path diversity in a multidomain network, where individual domains are capable of connection-oriented forwarding and endowed with an MPLS-TE control plane. For administrative and/or scalability reasons intradomain routing information is not disseminated externally, so dynamic path computation must be achieved by a distributed scheme based on interdomain collaboration. We briefly describe three alternative schemes recently proposed for interdomain diverse path computation, and quantitatively assess their performance with simulations over real ISP topologies.