Abstract not found

Several recent proposals for sharing congestion information across concurrent flows between end-systems overlook an important problem: two or more flows sharing congestion state may in fact not share the same bottleneck. In this paper, we categorize the origins of this false sharing into two distinct cases: (i) networks with QoS enhancements such as differentiated services, where a flow classifier segregates flows into different queues, and (ii) networks with path diversity where different flows to the same destination address are routed differently. We evaluate the impact of false sharing on flow performance and investigate how false sharing can be detected by a sender. We discuss how a sender must respond upon detecting false sharing. Our results show that persistent overload can be avoided with window-based congestion control even for extreme false sharing, but higher bandwidth flows run at a slower rate. We find that delay and reordering statistics can be used to develop robust detectors of false sharing and are superior to those based on loss patterns. We also find that it is markedly easier to detect and react to false sharing than it is to start by isolating flows and merge their congestion state afterward. 1.

Images account for a significant and growing fraction of Web downloads. The traditional approach to transporting images uses TCP, which provides a generic reliable, in-order byte-stream abstraction, but which is overly restrictive for image data. We analyze the progression of image quality at the receiver with time and show that the in-order delivery abstraction provided by a TCP-based approach prevents the receiver application from processing and rendering portions of an image when they actually arrive. The end result is that an image is rendered in bursts interspersed with long idle times rather than smoothly.

A Framework for Interactive Multicast Data Transport in the Internet by Suchitra Raman Doctor of Philosophy in Computer Science University of California at Berkeley Professor Steven R. McCanne, Chair The remarkable growth of the Internet as the a data transmission medium has in part been enabled by the simplicity and scalability of the core Internet Protocol (IP), which is used for addressing and routing unicast data packets through the network. The IP service model does not provide any packet delivery guarantees, but rather provides a "best-effort" contract, and leaves it to higher layers to provide enhanced services using this basic service. Today, the de facto transport protocol on the Internet is the Transmission Control Protocol (TCP) [109, 128]. TCP was designed primarily for applications such as telnet, a remote terminal application, and ftp, a file transfer application, which require data to be delivered reliably and in an ordered manner. While the TCP abstraction and pro...

An aggregate congestion control mechanism, namely Probe-Aided MulTCP (PA-MulTCP), is proposed in this paper. It is based on MulTCP, a proposal for enabling an aggregate to emulate the behavior of multiple concurrent TCP connections. The objective of PA-MulTCP is to ensure the fair sharing of the bottleneck bandwidth between the aggregate and other TCP or TCP-friendly flows while keeping lightweightness and responsiveness. Unlike MulTCP, there are two congestion window loops in PA-MulTCP, namely the probe window loop and the adjusting window loop. The probe window loop constantly probes the congestion situation and the adjusting window loop dynamically adjusts the congestion window size for the arriving and departing flows within the aggregate. Our simulations demonstrate that PA-MulTCP is more stable and fairer than MulTCP over a wide range of the weight N in steady conditions as well as in varying congestion conditions. PA-MulTCP is also responsive to flow arrival/departure and thus reduces the latency of short-lived transfers. Furthermore, PA-MulTCP is lightweight, since it enjoys above advantages at the cost of only an extra probe window loop, which has a marginal influence on the implementation complexity. Finally, the design of PA-MulTCP decouples the congestion management from the other functionalities in the aggregate flow management. As a result, PA-MulTCP could be potentially applied to a wider range of scenarios, e.g. wireless TCP proxies, edge-to-edge overlays, QoS provisioning and mass data transport.