Sender-driven bandwidth differentiation for transmitting multimedia flows over TCP

Abstract

Over the years the Internet has shown extraordinary scalability and robustness in spite of the explosive growth in geographical reach, user population size, as well as network traffic volume. This scalability and robustness is, in no small part, supported by the Internet's transport protocols, the Transmission Control Protocol (TCP) in particular. Nevertheless, with the rapid growth of multimedia-rich contents in the Internet, such as audio and video, the many strengths of TCP in data delivery are slowly imposing bottlenecks in multimedia data delivery where different media data flows often have different needs for bandwidth. As TCP's congestion control algorithm enforces fair bandwidth sharing among traffic flows sharing the same network bottleneck, different media data flows will receive the same bandwidth irrespective of the actual needs of the multimedia data being delivered. This work addresses this limitation by proposing a new algorithm to achieve non-uniform bandwidth allocation among TCP flows originating from the same sender passing through the same network bottleneck to multiple receivers. The proposed algorithm, called Virtual Packet Substitution (VPS), has four desirable features: (a) it allows the allocation of bottleneck bandwidth between a group of TCP flows; (b) the resultant traffic flows as a whole, maintain the same fair bandwidth sharing property with other competing TCP flows; (c) it can be implemented entirely in the sender's TCP protocol stack; and (d) it is compatible with and does not require modification to existing TCP protocol stack at the clients. Simulation results show that the proposed VPS algorithm can achieve accurate bandwidth allocation while still maintaining fair bandwidth sharing with competing TCP flows.