Quality of Service and the End to End Argument IEEE Network November/December 2007

1. Quality of Service and the End to End ArgumentIEEE Network November/December 2007 Gunnar Karlsson, School of Electrical Engineering of KTH, the Royal Institute of Technology Ignacio Mas, IPTV development at Ericsson Research Presented by Guan-Wei, Chen OPLAB_IM_NTU

2. About Authors - Gunnar Karlsson • receive his M.S. degree from Chalmers University of Technology in Gothenburg, Sweden(1983) • receive his PH.D. degree from Columbia university(1989), New York • research related to quality of service and wireless content distribution OPLAB_IM_NTU

3. About Authors - Ignacio Mas • receive his M.S. degree in electrical engineering from the Royal Institute of Technology (Stockholm, Sweden) • now he is a doctoral student at KTH • his research interests are in multimedia networking ,quality of service, and operating systems OPLAB_IM_NTU

4. Abstract • Audio-visual service are now popular in the internet • earlier base on batch downloading, now real-time interactive and streaming services grow rapidly • can benefit from QoS if it widely provided • Quality is obtained by means of probe-based admission control • then implementation on Application Layer, Transport Layer, Network Layer • Compared and discussed the possibility deployment OPLAB_IM_NTU

5. Today’s Agenda 1-Introduction About Quality of Service 2-Probe-Based Admission Control 3-Different Layer QoS Support 4-Comparison of the Proposals 5-Deployment and Operator 6-Related Work 7-Conclusion OPLAB_IM_NTU

6. Today’s Agenda 1-Introduction About Quality of Service 2-Probe-Based Admission Control 3-Different Layer QoS Support 4-Comparison of the Proposals 5-Deployment and Operator 6-Related Work 7-Conclusion OPLAB_IM_NTU

7. Introduction • multitude of quality of service, the traffic defined • Asynchronous transfer mode architecture • Integrated service architecture • Differentiated service architecture • most proposed QoS solution within one of three architecture • limited QoS offering from Internet Service Provider • lock of deployed QoS solutions OPLAB_IM_NTU

8. Introduction • little attention QoS researchers have given the culture of network operations to avoid complexity and anticipate failure • addition of QoS mechanisms would introduce new potential failure mode • it might be difficult to debug and • has to be weighed against the uncertain benefit of providing QoS support • QoS function traditionally been associated with the network (Ex: admission control ,scheduling, and policy ) OPLAB_IM_NTU

9. Introduction • provide some form of QoS without changes to the network operation or network • lifting the QoS mechanisms out of the network to higher protocol layers would have advantages: • QoS is provided from host to host • The QoS mechanisms may develop independent of the network • the management and operation of a network remains unaffected • assigning functions to the layers of a protocol architecture relied on end-to-end argument OPLAB_IM_NTU

10. Introduction • Functions places at low levels of a system may be redundant or of a little value when compared with the cost of providing them at that low level • Application Layer solution can be without standardization, but gives the least benefit (Ex: prevent setting up session when congestion) • Transport Layer solution needs standardization and provides differentiation into two traffic class • Network Layer solution can reinforce differentiation OPLAB_IM_NTU

11. Introduction-Quality of Service • QoS is the collective effect of service performances which determine the degree of satisfaction of a user of the service • QoS is often associated performance metrics are packet loss and delay, and also restricted scope • Affect user satisfaction: traffic control behavior、route changes、sensitivity to service attack and latency in fault handling…. OPLAB_IM_NTU

12. Introduction-Quality of Service • TCP attempts to share the rate of a bottleneck link fairly over all ongoing TCP sessions • Throughput variations when sessions enter or leave and when the total data rate of the sessions changes due to additive-increase multiplicative-decrease congestion control • One possible is complementary policy to block new real time session when congestion, to allow admitted sessions to remain unresponsive OPLAB_IM_NTU

13. Introduction-Quality of Service • the policy base on human perception of real time streaming interactive service with audio-visual signals • There is a trade-off between the distortion and the resulting bit rate • Lower data rate, higher the distortion • Noticeable quality variations reduce user satisfaction even average quality is high, so our interesting in limiting the throughput variations • Use probe-base admission control OPLAB_IM_NTU

14. Today’s Agenda 1-Introduction About Quality of Service 2-Probe-Based Admission Control 3-Different Layer QoS Support 4-Comparison of the Proposals 5-Deployment and Operator 6-Related Work 7-Conclusion OPLAB_IM_NTU

15. Probe-Based Admission Control • base on transmission of a probe which consists of a stream of probe packets • used to infer the state of a network path • lasts a few seconds and constitutes small addition to total session length • Probe rate (rpr) is constant, and session rate is not allowed to exceed it • the mean of the data rate of the session and distribution can’t know in advance when the rate is variable OPLAB_IM_NTU

16. Probe-Based Admission Control OPLAB_IM_NTU

17. Probe-base admission control • Receiver measures the loss and possibly the delay for the probe • Admission control classified in Per-hop and End-point (Probe-base ) • Need queue to save probe • Double queues • Threshold-queue • The acceptance decision given that OPLAB_IM_NTU

18. Probe-base admission control • The backoff randomizes new setup attempts if the failure was too many simultaneous probes • Probe packets contain session and control data • Control data include parameters for the configuration of the receiving application • Session data can be a greeting or ring tone • Probe packet stream can use for clock synchronization and allowing the jitter removal system to settle into steady state • Use data rate of the session for decision rather than probe rate ,the to leave group more reliable and to remain group less reliable OPLAB_IM_NTU

19. Probe-base admission control • An important of end-to-end admission control is the stability of the route for an accepted session • Route changes occur two conditions: • Load balancing scheme reducing the load of the link • topological changes application notice a disruption in the data flow OPLAB_IM_NTU

20. Today’s Agenda 1-Introduction About Quality of Service 2-Probe-Based Admission Control 3-Different Layer QoS Support 4-Comparison of the Proposals 5-Deployment and Operator 6-Related Work 7-Conclusion OPLAB_IM_NTU

21. Different Layer QoS Support(Application Layer QoS Support) • Self-Admission Control measures the packet loss ratio of the first few seconds and estimate the packet loss probability • Two-way sessions • Initiated by the first received probe packet • Carried out by the called application • Relation between the loss ratio of an initial part of the call and the loss ratio of the whole duration • Initial interval increases , the points group closer around the line Y=X OPLAB_IM_NTU

22. Different Layer QoS Support(Application Layer QoS Support) OPLAB_IM_NTU

23. Different Layer QoS Support(blocking threshold) • denote lp : the loss ratio of an initial interval lt : the loss ratio of the total call ε: a stochastic variable , is lt - lp la : pre-established loss rate Use statistics method: Strict policy : higher risk than 10% => la-2.6% Relax policy : more than 90% => la+1.81% OPLAB_IM_NTU

24. Different Layer QoS Support(Application Layer QoS Support) • Different kinds of calls based on the initial estimation and the final outcome OPLAB_IM_NTU

25. Different Layer QoS Support(Application Layer QoS Support) • Advantage: • Not be loaded by new sessions when congestion • Interactive session is not disturbed by session that risks being aborted due to poor quality • Receiver may avoid starting to listen to or view a session that is likely to be rendered useless by poor throughput • Although it is much simpler to implement than feedback congestion control, it might be desirable to provide probe-based admission control at the transport layer as a generic service to all applications that might benefit from it OPLAB_IM_NTU

26. Different Layer QoS Support(Transport Layer Service differentiation ) • Provide two generic traffic classed : Batch controlled by TCP and Streaming useprobe-based admission control • All sessions to enter the network are congestion controlled • probe-based admission control makes the aggregate of streaming sessions responsive to load variations by blocking new sessions to prevent the load from increasing OPLAB_IM_NTU

27. Different Layer QoS Support(Transport Layer Service differentiation ) • Fair sharing of bottleneck capacity between sessions of the two classed by choosing the admission criterion appropriately OPLAB_IM_NTU

28. Different Layer QoS Support(Transport Layer Service differentiation ) • acceptance decision Wmax : maximum window size RTT : the round-trip time b : the number of packets acknowledged by a received ACK T0: timeout value If rpr <= rTCP , then accept the session OPLAB_IM_NTU

29. Proof • Reference: Modeling TCP Reno Performance: A Simple Model and Its Empirical validation Yi=αi+ Wi -1 OPLAB_IM_NTU

30. Proof Windows size Other Yi calculated (E[β]=E[W] /2) OPLAB_IM_NTU

31. Proof Use above estimation combine E[X] and E[A] OPLAB_IM_NTU

32. Proof B(P)=Mi/Si OPLAB_IM_NTU

33. Proof Using L’Hopital rule, can calculate Q R is geometric distribution, so E[R] T0 (time out) is most 64T0, E(ZTO) is OPLAB_IM_NTU

34. Proof Substituting expressions for Q,E[S],E[R] ,and E[ZTO] for B(P) Where OPLAB_IM_NTU

35. Different Layer QoS Support(Transport Layer Service differentiation ) • An issue concerns the quality admitted streaming sessions • Session will be disturbed by new streaming session that probe the network for admission • The admitted sessions should be protected by forward error correction with error control codes to withstand the loss by the disturbing sessions • The loss estimate from the probing • can be used to calculate the appropriate level of redundancy necessary for insulting the session in this way OPLAB_IM_NTU

36. Different Layer QoS Support(Transport Layer Service differentiation ) • Probe-based admission control can be used for multicast sessions • An admission policy based on estimation of RTTs • Require each receiver to estimate it ,for example, by means of pings to a rendezvous point • The solution is acceptable for a low arrival rate of new receivers • An admission policy independent of RTTs is preferable OPLAB_IM_NTU

37. Different Layer QoS Support(Transport Layer remarks ) • Batch and streaming classes can’t be argued which class is better • TCP provides a lossless service where throughput variations and retransmissions lead to uncontrolled delay • probe-based admission control allows the sender to use a fixed amount of network capacity, and thereby controls delay and loss while introducing uncontrollable blocking • Incorporated in the datagram congestion control OPLAB_IM_NTU

38. Different Layer QoS Support(network support for service differentiation) • Scheduling in the network can provide further differentiate services • allow an operator to control the blocking probability for the streaming class • control the average throughput for the batch class OPLAB_IM_NTU

39. Different Layer QoS Support(Queuing system) Denote that Cl: link capacity Cb: for elastic batch transfers Cs : for admission controlled streams OPLAB_IM_NTU

40. Different Layer QoS Support(Queuing system) • A streaming session is admitted if there is enough capacity available for its probe within link capacity • There must be a single target loss level for the admission of all hosts using the service class • no need to consider TCP fairness in the admission decision because of classes separated by scheduling OPLAB_IM_NTU

41. Different Layer QoS Support(Advantage of network support) • Ongoing streaming sessions are disturbed by neither batch transfers nor probes • The operator can control the blocking probability for streaming sessions by adjusting the capacity allocation, Cs • The delay may be reduced by configuring short buffers for streaming class • Multicast admission control OPLAB_IM_NTU

42. Today’s Agenda 1-Introduction About Quality of Service 2-Probe-Based Admission Control 3-Different Layer QoS Support 4-Comparison of the Proposals 5-Deployment and Operator 6-Related Work 7-Conclusion OPLAB_IM_NTU

43. Comparison of the Proposals • A bottleneck link with 10Mb/s capacity shared between batch and streaming • 10 batch sessions and peak rate limited to 500kb/s • Streaming sessions consist of a two-state Markov chain (on and off) with 250 kb/s in the on state ,with an average rate of 100 kb/s • Probing time is 2s at the peak rate • Corresponding to 976 probe packets of 64 bytes • Each case has been run 30 times OPLAB_IM_NTU

44. Comparison of the Proposals OPLAB_IM_NTU

45. Comparison of the Proposals(Results) • (no blocking) streaming sessions are freely admitted and experience severe packet loss • (Self) The loss in streaming sessions has been reduced at the offer expense of blocking • (TP1) bounds the loss through the formula for equivalent TCP throughput • (TP2) provides a loss target, which is met, but blocking goes up and TCP is favored • (TP+NP) network support allows the blocking to be controlled in relation to the TCP share of the link capacity OPLAB_IM_NTU

46. Comparison of the Proposals(Results) • Self-admission control is useful since the admitted streaming sessions meet the target of at most 1 percent loss • Streaming load and particular decision level can balance between streams and batch classes • Provide two generic service rather than each streaming application having its own admission control OPLAB_IM_NTU

47. Today’s Agenda 1-Introduction About Quality of Service 2-Probe-Based Admission Control 3-Different Layer QoS Support 4-Comparison of the Proposals 5-Deployment and Operator 6-Related Work 7-Conclusion OPLAB_IM_NTU

48. Deployment and OperatorApplication • End to end argument applied to QoS is the separation of roles between network operation and host function • Incognizant of the differentiation at the transport layer • Admission control at the application layer • Self-admission is incorporated into streaming and conversational application without standardization • Weakness: can’t mandate and reinforced by provider • Admission control protect user establishing session during congestion OPLAB_IM_NTU

49. Deployment and OperatorTransport • Transport layer differentiation provide two service classes: batch and streaming • Large batch is efficiently made at a fixed rate • Small batch could be inefficient because of substantial probe phase • Admission control decision policy • Datagram congestion control • Operators enforce the traffic entering networks is congestion controlled by hosts OPLAB_IM_NTU

50. Deployment and OperatorTransport • Operator’s role is further affected by QoS because of service class differentiation in the network • Operators manage the capacity allocation for the streaming class • Allocation to control the blocking probabilities of the link • If to keep blocking probability below a declared value, users need to pay charge for guarantee • Hosts manage the admission decisions of session • Decisions are time critical, fully distributed, good scaling • Network control blocking probabilities of the link, occurring less frequently than admission decision OPLAB_IM_NTU