Conformance deterioration in QoS networks: phenomenon, analysis and elimination

  • Authors:

  • Frank Y. Li;Norvald Stol;Bjarne E. Helvik

  • Affiliations:

  • UniK--University Graduate Center, University of Oslo, Kjeller, Norway;Department of Telematics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway;Centre for Quantifiable Quality of Service in Communication Systems, Norwegian University of Science and Technology, Trondheim, Norway

  • Venue:
  • Computer Networks: The International Journal of Computer and Telecommunications Networking - Special issue: Network modelling and simulation
  • Year:
  • 2006

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Abstract

To verify conformance consistency of a previously regulated flow in QoS networks, two token buckets with identical token rate (r) and bucket size (b) are employed at the ingress and the egress nodes as the traffic shaper and policer respectively. In the presence of variable packet length, it has been found that an originally conformant packet may become non-conformant even transmitted at a constant speed. This non-intuitive phenomenon is referred to as conformance dete-roration. After illustrating how conformance deterioration happens, the paper analyzes the probability of conformance deterioration for the single-hop case, both in general and for a special case. The analytical results are enriched by discussions and examples. To further understand the phenomenon, a set of simulations is carried out based on a generic multi-hop network model, for both individual and aggregated traffic flows. Finally, measures to eliminate conformance deterioration are also studied and compared in the paper.