We examine the validity of TCP-friendliness and the utility of equation-based congestion control as a mean for the media streaming service in 802.11 multi-hop networks. Our investigation is motivated by the recent findings of the bandwidth-delay product of 802.11 multi-hop networks via intensive computer simulations. We show that TCP behavior in 802.11 multi-hop networks is generally inefficient and unstable because the standard TCP is too aggressive considering the low bandwidth-delay product of 802.11 networks. We introduce the concept of the `fractional window' mechanism (which resembles the stop-and-go protocol) for TCP, and show that the modified TCP is more stable and efficient while outperforming the legacy TCP in 802.11-based ad hoc networks. Finally, we show that many of the typical problems of TCP protocol (performance, network fairness, and TCP-friendliness) in 802.11 networks can be solved simply by increasing the bandwidth-delay product of 802.11 networks without any TCP modification. Based on this observation, we conclude that the assumption of the ideal steady-state TCP behavior is generally invalid in 802.11 multi-hop networking environment, and that congestion control based on TCP-friendly equation can hardly provide TCP-fair throughput and smoothness in 802.11 multi-hop networking environment.
In this work, we investigate the congestion control problem for layered video multicast in IP networks of active
queue management (AQM) using a simple random early detection (RED) queue model. AQM support from networks improves the visual quality of video streaming but makes network adaptation more di±cult for existing layered video multicast proticols that use the event-driven timer-based approach. We perform a simplified analysis on the response of the RED algorithm to burst traffic. The analysis shows that the primary problem lies in the weak correlation between the network feedback and the actual network congestion status when the RED queue is driven by burst traffic. Finally, a design guideline of the layered multicast protocol is proposed to overcome this problem.
KEYWORDS: Video, Receivers, Signal attenuation, Systems modeling, Electrical engineering, Lithium, System integration, Internet, Multimedia, Composites
A layered video multicast framework for differentiated service (DS) networks, which provides various levels of QoS guarantee for heterogeneous users with improved performance in network congestion adaptation, is examined in this research. The proposed system consists of three key components: extended active queue management, hierarchical priority marking, and receiver-driven layered multicast with ECN (RLME). Particularly, we introduce RLME protocol that effectively utilizes advanced features of active queues such as random early drop (RED) and early congestion notification (ECN) in DS networks. The RLME protocol quantitatively estimates the network congestion level via ECN and packet loss to improve adaptation capability to network congestion, and utilizes the priority service from DS networks to minimize the packet loss effect on reconstructed video quality. The simulation shows that the proposed system successfully achieves stable and controllable video QoS guarantee for heterogeneous video clients over DS networks.
An enhanced network service model for layered video multicast applications is presented for differentiated service (Diffserv) networks in this work, which consists of enhanced active queue management (AQM) and hierarchial priority marking. It is found from experiments that a straightforward application of the receiver-driven layer multicast (RLM) model to the Diffserv network may perform poorer than to the best-effort Internet, since RLM applications could behave like unresponsive flows and conflict with Diffserv active queues. To fix this problem, we present three sets of extended RED/RIO parameters as the enhanced AQM model, which is designed to be generally applicable to service protection as well as to support RLM traffic in Diffserv networks. Furthermore, to take advantage of the priority service in Diffserv networks, we present a priority marking model of RLM video layers that conform to the priority marking architecture of Dffserv networks. It is shown by simulation experiments that the proposed network service enhancement model improves the stability of the join experiment and reduces the packet loss rate to support RLM traffic in Diffserv networks.
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