Granularity of QoS Routing in MPLS Networks

This study investigates how the Constraint-based routing decision granularity signi cantly a ects the scalability and blocking performance of QoS routing in MPLS network. The coarse-grained granularity, such as per-destination, has lower storage and computational overheads but is only suitable for best-e ort traÆc. On the other hand, the negrained granularity, such as perow, provides lower blocking probability for bandwidth requests, but requires a huge number of states and high computational cost. To achieve cost-e ective scalability, this study proposes using hybrid granularity schemes. The Over owed cache of the per-pair/ ow scheme adds a per-pair cache and a perow cache as the routing cache, and performs well in blocking probability with a reasonable over ow ratio of 10% as o ered load=0.7. Per-pair/class scheme groups the ows into several paths using routing marks, thus allowing packets to be labelforwarded with a bounded cache.