P-AQM: Low-Delay Max-Min Fairness Streaming of Scalable Real-Time CBR and VBR Media

A. Lie (Norway)


Congestion Control, Video rate adaptation, Active Queue Management, Control Theory, Max-min fairness.


The increase in Internet streaming media deployment and consumption has created a network stability challenge. The reason is that in overload situations, such sources continue submitting packets at an unmodified rate. The elastic appli cations using the TCP protocol will back-off and receive a throughput below their fair rate. The DCCP/TFRC conges tion control mechanism is one possible remedy. However, due to its steady packet rate requirement, the end-to-end delay constraints of conversational real-time media like VoIP and videoconferencing can be ruined by the TFRC transmit buffer and router queue backlog. In this paper the P-AQM alternative is presented. P AQM routers provide more accurate media traffic load in formation than RED routers, to ensure high link utilization yet low queue backlog. The paper gives the theoretical sta bility criteria of P-AQM with explicit congestion feedback (ECF) and explicit rate feedback (ERF). Elaborative ns-2 simulations compare scenarios with a mix of MPEG-4 VBR video and TCP traffic, demonstrating P-AQM robust ness and performance. The ECF and ERF max-min fairness is explained and compared to TFRC using both CBR and VBR traffic in a GFC-2 network scenario.

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