WebTP: A User-Centric Receiver-Driven Web Transport Protocol

The use of TCP for the Web has caused a variety of performance problems because the interactive request/response nature of Web tra c is incongruent with the sequenced, bi-directional, continuous, byte-stream model of TCP. We believe that these problems can be overcome by abandoning the constraints imposed by TCP and designing a new receiver-oriented transport protocol for the Web that leverages the concept of Application Level Framing (ALF). In this report, we present a receiveroriented, request/response protocol for the Web that is amenable to ALF and compatible with the dynamics of TCP's congestion control algorithm. The resulting protocol | WebTP | optimizes the transport of a document from the sender to the receiver by taking into account a number of di erent factors like the contents of the page, the state of the network, the available hardware at the client and even the preferences of the user. We set up schemes to represent all of the above information, and design a system to implement the optimization structure. The computationally feasible methodology adopted at the receiver allows it to determine an optimal order of transport for the objects contained in the document. The resulting transfer is optimized with respect to suitable utility functions and yields maximum satisfaction to the user. Such a framework for optimization demands a transport layer that is aware of the application and is controlled at the receiver end. Our protocol is designed to be completely receiver-based in terms of transport initiation, ow-control and congestion-control. In support of our receiver-driven design, we developed a novel retransmission scheme that is robust to delay variations and can operate without an explicit \ack clock". The resulting ows achieve e cient network utilization and are qualitatively fair in their interaction amongst themselves and even with competing TCP ows. The report also provides detailed simulation results to support the protocol design.