Internet Telephony Conference and EXPO East An Overview of QoS for Multi-Service IP Networks Peter Thompson Chief Scientist U4EA Technologies Ltd.

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 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

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 “Quality of Service” – one term, many meanings User Quality of Experience Customer support Network performance Application performance Terminal device Application servers

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Network performance: the problem Network Element Limited resources: Bandwidth Packet buffers Packet Service Every service is carried in a stream of packets: Flexible: easy to add services Efficient: streams share network resources 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’

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Avoiding contention – vanilla IP Packets routed independently Congestion changes routing – upsets QoS Congestion point moves, causes route flap

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Avoiding contention - MPLS Label switch path MPLS gives more control Routing decision taken once per flow

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Optimising route selection A B Stream X: 5 Stream Y: 5 Stream Z: 6 Choice 1: X via A, Y via B Choice 2: X via A, Y via A Z cannot be routedZ via B is OK

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Allocating bandwidth Bursts where loss and/or delay become excessive Bandwidth Time

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Allocating bandwidth Bursts for which loss and delay are tolerable Bandwidth Allocation above average to get acceptable performance Time

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Contention strikes again! Plenty of routes and bandwidth in the core network Less so in the network edge Not at all in the access CoreEdgeAccess

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Contention management Network Element Use resources efficiently Maintain consistent performance under saturation Various mechanisms: Policing Shaping Queuing Scheduling Differentiate performance for multiple types of service Keep average load below 30-40%

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Effective contention management Network Element Use resources efficiently Guarantee worst- case performance under saturation Deep analysis of the scheduling problem – use the degrees of freedom Differentiated performance for multiple service classes

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 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’ ∆Q

© U4EA Technologies Internet Telephony Conference and EXPO East 2006 Thank you! Any questions? Peter Thompson U4EA Technologies Limited