1 Multi-layer Active Queue Management and Congestion Control for Scalable Video Streaming Kang, S.-R.; Zhang, Y.; Dai, M.; Loguinov, D.; Distributed Computing Systems, Proceedings. 24th International Conference on, March 2004

2 Core components Priority Active Queue Management  mark packets of different importance and drop less important packets first Congestion Control  feedback network information from router and adjust the frame size Partitioned Enhancement Layer Streaming (PELS)  priority marking, AQM, congestion control

3 Outline Background Best-effort network is not enough AQM Congestion control Simulation Conclusion

4 Goal majority of packets across bottleneck carry useful information retransmission-free

5 MPEG-4 FGS base layer is more important than enhancement layer

6 Best-Effort Streaming assume independent Bernoulli packet loss with probability p, expected number of useful packets (consecutively received) is

7 Best-Effort Streaming

8 Optimal Preferential Streaming goal: achieve U = 1 in order to be optimal, upper layer should be dropped before lower layer enhancement layers further divide into two layers

9 Active Queue Management two types of queues: PELS queue and Internet queue Weighted round-robin (WRR)

10 Active Queue Management send low-priority packets only after all high- priority packets are sent no end-user can gain by marking all packets with highest priority

11 Selection of γ p R = px i /γx i = p/γ = p thr optimistic: p thr ~1  U~1 pessimistic: p thr ~p  γ =1  yellow layer = (1- γ)x i = 0 close-form expression for γ

12 Selection of γ when p=0.1, p thr =0.75, U>=0.96 when p=0.01, p thr =0.75, U>=0.996

13 Congestion control modified from Kelly’s control (a game- theoretic and optimization method), discrete version called Max-min Kelly Control (MKC) reduce bitrate and keep waste to minimum

14 Simulation ns2 simple bar-bell topology 1 video frame = bytes = 126 packets (21 base layer packets) 50% bottleneck for TCP cross traffic

15 Stability properties ofγ show that  γis stable in the close-form expression with dynamic loss prob;  by using found γ, loss prob of red packets kept to target threshold

16 Delay characteristic of PELS

17 Fairness of MKC congestion control

18 Conclusion preferential streaming framework (PELS) provides high level of end-user QoS independent of underneath congestion control methods