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An Overview of QoS for Multi-Service IP Networks

An Overview of QoS for Multi-Service IP Networks. Peter Thompson Chief Scientist U4EA Technologies Ltd. Overview. Understand the reasons for performance variability in IP networks Examine the techniques to control this in the network core

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An Overview of QoS for Multi-Service IP Networks

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  1. An Overview of QoS for Multi-Service IP Networks Peter Thompson Chief Scientist U4EA Technologies Ltd.

  2. Overview • Understand the reasons for performance variability in IP networks • Examine the techniques to control this in the network core • See why these techniques are less useful in the access part of the network • Explore how QoS can be achieved in parts of the network where contention is likely

  3. Terminal device Customer support User Quality of Experience Network performance Application performance Application servers “Quality of Service” – one term, many meanings

  4. Network performance: the problem • Every service is carried in a stream of packets: • Flexible: easy to add services • Efficient: streams share network resources • Limited resources: • Bandwidth • Packet buffers • Packet Service Network Element • Sharing resources causes performance to vary: • Not all streams can see an empty network • Some streams’ delivery will vary drastically • Packet streams are often bursty • Bursts can overload network resources • Call this ‘contention’

  5. Avoiding contention – vanilla IP • Packets routed independently • Congestion changes routing – upsets QoS • Congestion point moves, causes route flap

  6. Avoiding contention - MPLS Label switch path • MPLS gives more control • Routing decision taken once per flow

  7. Optimising route selection Stream X: 5 Stream Y: 5 Stream Z: 6 A 10 12 8 10 B Choice 1: X via A, Y via B Choice 2: X via A, Y via A Z cannot be routed Z via B is OK

  8. Bursts where loss and/or delay become excessive Allocating bandwidth Bandwidth Time

  9. Allocating bandwidth Bursts for which loss and delay are tolerable Bandwidth Allocation above average to get acceptable performance Time

  10. Contention strikes again! • Plenty of routes and bandwidth in the core network • Less so in the network edge • Not at all in the access Core Edge Access

  11. Contention management X Use resources efficiently Differentiate performance for multiple types of service Keep average load below 30-40% Network Element • Various mechanisms: • Policing • Shaping • Queuing • Scheduling X Maintain consistent performance under saturation

  12. Effective contention management Use resources efficiently Differentiated performance for multiple service classes Network Element Deep analysis of the scheduling problem – use the degrees of freedom Guarantee worst-case performance under saturation

  13. ∆Q ∆Q ∆Q Edge-to-edge network performance Edge/access: • Effective contention management • QoS under saturation Core: • Contention avoidance • Route control • Bandwidth allocation End-to-end: • Performance is the sum of the ‘∆Q’

  14. Thank you! Any questions? Peter Thompson U4EA Technologies Limited Peter.Thompson@u4eatech.com www.u4eatech.com

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