Recent research efforts to design better Internet transport protocols combined with scalable Active Queue Management (AQM) have led to significant advances in congestion control. One of the hottest topics in this area is the design of discrete congestion control algorithms that are asymptotically stable under heterogeneous feedback delay and whose control equations do not explicitly depend on the RTTs of end-flows. In this paper, we show that max-min fair congestion control methods with a stable symmetric Jacobian remain stable under arbitrary feedback delay (including heterogeneous directional delays) and that the stability condition of such methods does not involve any of the delays. To demonstrate the practicality of the obtained result, we change the original controller in Kelly's work [14] to become robust under random feedback delay and fixed constants of the control equation. We call the resulting framework Maxmin Kelly Control ( M K C ) and show that it offers smooth sending rate, exponential convergence to efficiency, and fast convergence to fairness, all of which make it appealing for future high-speed networks.

Recent research efforts to design better Internet transport protocols combined with scalable Active Queue Management (AQM) have led to significant advances in congestion control. One of the hottest topics in this area is the design of discrete congestion control algorithms that are asymptotically stable under heterogeneous feedback delay and whose control equations do not explicitly depend on the RTTs of end-flows. In this paper, we first prove that single-link congestion control methods with a stable radial Jacobian remain stable under arbitrary feedback delay (including heterogeneous directional delays) and that the stability condition of such methods does not involve any of the delays. We then extend this result to generic networks with fixed consistent bottleneck assignments and max-min network feedback. To demonstratethe practicality of the obtained result, we change the original controller in Kelly et al.'s work ["Rate Control for communication networks: Shadow prices, proportional fairness and stability," Journal of the Operational Research Society, vol. 49, no. 3, pp. 237-252, March 1998] to become robust under random feedback delay and fixed constants of the control equation. We call the resulting framework Max-min Kelly Control (MKC) and show that it offers smooth sending rate, exponential convergence to efficiency, and fast convergence to fairness, all of which make it appealing for future high-speed networks.

Abstract-Video applications that transport delay-sensitive multimedia over best-effort networks usually require special mechanisms that can overcome packet loss without using retransmission. In response to this demand, forward-error correction (FEC) is often used in streaming applications to protect video and audio data in lossy network paths; however, studies in the literature report conflicting results on the benefits of FEC over best-effort streaming. To address this uncertainty, we start with a baseline case that examines the impact of packet loss on scalable (FGS-like) video in best-effort networks and derive a closed-form expression for the loss penalty imposed on embedded coding schemes under several simple loss models. Through this analysis, we find that the utility (i.e., usefulness to the user) of unprotected video converges to zero as streaming rates become high. We then study FEC-protected video streaming, re-derive the same utility metric, and show that for all values of loss rate inclusion of FEC overhead substantially improves the utility of video compared to the best-effort case. We finish the paper by constructing a dynamic controller on the amount of FEC that maximizes the utility of scalable video and show that the resulting system achieves a significantly better PSNR quality than alternative fixed-overhead methods.Index Terms-FEC rate control, Markov-chain loss, MPEG-4 FGS, utility of video, video streaming.

Abstract. Many paths in PlanetLab cannot be measured by Pathload. One of the main reasons for this is timing irregularities caused by interrupt moderation of network hardware, which delays generation of interrupts for a certain period of time to reduce per-packet CPU overhead. Motivated by this problem, we study Pathload in detail under various end-host interrupt delays and find that its trend detection mechanism becomes susceptible to non-negligible interrupt delays, making it unable to measure network paths under such conditions. To overcome this, we propose a new method called IMR-Pathload (Interrupt Moderation Resilient Pathload ), which incorporates robust trend detection algorithms based on signal de-noising techniques and reliably estimates available bandwidth of network paths under a wide range of interrupt delays. Through experiments in Emulab and Internet, we find that IMR-Pathload substantially improves Pathload's measurement reliability and produces accurate bandwidth estimates under a variety of real-life conditions. Key words: Bandwidth estimation, network measurement, interrupt moderation, and interrupt delays IntroductionBandwidth of Internet paths is an important metric for applications. Extensive research has been conducted over the years and the vast majority of work in this area focuses on end-to-end measurement. Although several techniques [4], [13], [11], [12], [14] attempt to measure capacity of the narrow link (i.e., the slowest link in a path) or both capacity and available bandwidth of the tight link (i.e., link with the smallest available bandwidth over a path), many measurement techniques and public tools (such as [6], [9], [16]) have been developed to estimate available bandwidth of the tight link. These methods mainly focus on fast estimation with high accuracy under a various traffic conditions. However, since the ultimate goal of bandwidth estimators is to measure diverse Internet paths, before being a full-blown measurement tool, it is highly desirable that tools are resilient to timing irregularities caused by various OS scheduling delay jitter or hardware interrupt moderation in real networks.Note that to accurately measure bandwidth, all existing methods heavily rely on high-precision delay measurement of probe packets at end-hosts. However, irregular timing due to interrupt moderation at network interface cards (NICs) has been identified as the major problem of existing bandwidth estimation tools in practice [15]. To reduce the effect of interrupt moderation, recent tools such as Pathchirp [16] and Pathload described in [15] incorporate mechanisms that aim to "weed out" packets affected by interrupt delays. However, Pathchirp requires manual modification to force it to send (often substantially) more probing packets to obtain an accurate estimate, prolonging measurement undesirably. On the other hand, Pathload attempts to filter out affected packets without increasing the number of probing packets, which unfortunately has a limited effect when interrupt delays become non-t...

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