Quality of Service — IWQoS 2001

Volume 2092 of the series Lecture Notes in Computer Science pp 140-153


Granularity of QoS Routing in MPLS Networks

  • Ying-Dar LinAffiliated withDept of Computer and Info. Science, National Chiao Tung University
  • , Nai-Bin HsuAffiliated withDept of Computer and Info. Science, National Chiao Tung University
  • , Ren-Hung HwangAffiliated withDept of Computer Science and Info. Eng., National Chung Cheng University

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This study investigates how the Constraint-based routing decision granularity significantly affects 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-effort traffic. On the other hand, the finegrained granularity, such as per-flow, provides lower blocking probability for bandwidth requests, but requires a huge number of states and high computational cost.

To achieve cost-effective scalability, this study proposes using hybrid granularity schemes. The Overflowed cache of the per-pair/flow scheme adds a per-pair cache and a per-flow cache as the routing cache, and performs well in blocking probability with a reasonable overflow ratio of 10% as offered load=0.7. Per-pair/class scheme groups the flows into several paths using routing marks, thus allowing packets to be labelforwarded with a bounded cache.