1. 2001/09/26Chin-Kai Wu, CS, NTHU1 Resource Allocation and Management in DiffServ Networks for IP Telephony Maarten Büchli, Danny De Vleeschauwer, Jan Janssen, Annelies Van Moffaert, Guido H. Petit 11th International workshop on Network and Operating Systems support for digital audio and video, June 25 - 26, 2001, Port Jefferson, NY USA

2. 2001/09/26Chin-Kai Wu, CS, NTHU2 Outline Introduction Voice Traffic Model Quality of Service End-To-End Delay Analysis Mouth-to-ear delay Queuing delay Simulation Results

3. 2001/09/26Chin-Kai Wu, CS, NTHU3 Introduction In DiffServ, a scheduler is needed in order to guarantee throughput and delay to the different aggregate flows in the system. The class-based Weighted Fail Queuing (WFQ) is considered. Hence, dimensioning the bandwidth for the voice traffic is therefore of great concern. The paper shows how to set the weights of a WFQ scheduler in a DiffServ router such that a certain delay bound is met.

4. 2001/09/26Chin-Kai Wu, CS, NTHU4 Voice Traffic Model Steps Packet Size Analog Voice SampleQuantizeEncodePackitize M:voice packet size R cod :codec bit rate T pack :packetization delay S OH :header overhead

5. 2001/09/26Chin-Kai Wu, CS, NTHU5 CBR voice flows is well modeled by a Poisson process, and cannot become more bursty than it. Voice sources that use VAD (Voice Activity Detection) are much harder to characterize.

6. 2001/09/26Chin-Kai Wu, CS, NTHU6 Quality of Service

7. 2001/09/26Chin-Kai Wu, CS, NTHU7 Capacity assigned to voice traffic Queue load C voice :capacity of voice traffic φ voice :weight of voice traffic i:number of queues ρ:queue load B voice :average bit rate of voice flows

8. 2001/09/26Chin-Kai Wu, CS, NTHU8 Mouth-to-ear delay Deterministic part T pack, packetization T ser, serialization T prop, propagation T dejitter, dejittering T oth, other (encoding, decoding etc.) Stochastic part T queue, queuing delay

9. 2001/09/26Chin-Kai Wu, CS, NTHU9 Only interested in the maximum queuing delay. For this delay, a reasonable quantile can be used since this is the fraction of packets that arrive in time. The queuing delay has to be compensated for in the dejittering buffer of the receiver. Hence, the dejittering delay should be chosen equal to a quantile of the queuing delay. When perfect dejittering is used, the queuing and dejittering delay of each packet is equal to the maximum queuing delay.

10. 2001/09/26Chin-Kai Wu, CS, NTHU10 Delay distribution

11. 2001/09/26Chin-Kai Wu, CS, NTHU11 Queuing delay R:reserved rate b:max burst size M:max voice packet size N:number of hops MTU i :MTU at node i C i link :link capacity at node i R i :reserved rate at node i b i :max burst size at node i

12. 2001/09/26Chin-Kai Wu, CS, NTHU12 Simulation Scenario

13. 2001/09/26Chin-Kai Wu, CS, NTHU13 Simulation Results

14. 2001/09/26Chin-Kai Wu, CS, NTHU14

15. 2001/09/26Chin-Kai Wu, CS, NTHU15 Results

16. 2001/09/26Chin-Kai Wu, CS, NTHU16