A simulation study of reordering-resilient TCP enhancements

Abstract

TCP traffic makes up a large portion of the Internet's load. The throughput TCP connections are able to obtain depends heavily on the underlying network providing in-order packet delivery. IP networks do not guarantee in-order delivery, but the design of hardware, networks, protocols have been influenced by TCP's in-order requirement. Despite this the Internet today does reorder packets on some links. More importantly, more throughput could be achieved if techniques such as multipath routing could be used. Unfortunately, the parallelism in these schemes results in packet reordering and a resulting TCP performance loss. This work examines methods for allowing TCP connections to obtain high throughput in the presence of packet reordering. We review the existing proposals, describe a new, receiver based proposal, and provide a detailed simulation-based evaluation. In this thesis we present results which show that our modified receiver with an unmodified Reno sender was able to perform as well or better than any of the other proposed solutions. In addition, Eifel is able to consistently out perform DSACK despite using much less packet overhead and internal state.