An Empirical Model of HTTP Network Traffic
INFOCOM '97 Proceedings of the INFOCOM '97. Sixteenth Annual Joint Conference of the IEEE Computer and Communications Societies. Driving the Information Revolution
Link layer-based TCP optimisation for disconnecting networks
ACM SIGCOMM Computer Communication Review
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Over paths characterized by extended outage periods, a TCP connection can suffer a severe performance penalty due to its Retransmission Timeout (RTO) backoff mechanism. If outages are long enough, the RTO can grow large enough to cause unacceptably long pauses when the link is eventually restored. One proposed solution is "Link-Up Notification" (LUN), which involves an intermediate device that can detect the link state. When the link is restored, the device immediately sends a packet that causes traffic to resume, terminating the TCP timeout. We have implemented a version of LUN that we call "kickstart." A kickstart gateway buffers a packet from each connection and uses them to restart the connections when the channel is restored. Based on empirical data, we have built a mobile satellite channel emulator and demonstrated how the technique can effectively eliminate the pause in restarting a TCP flow once a blocked channel is reestablished. When conducting experiments with shorter channel outages and shorter TCP flows, a different picture emerges; in this case, while connection transfer times are not noticeably reduced by a kickstart gateway, the overall completion ratio of TCP connections is increased, as fewer connections are dropped due to exceeding the maximum number of retransmissions. Our experiments also exposed some problems in the Linux and FreeBSD end host TCP implementations that impair performance in such an environment. Correcting these problems improves success ratios still more, while having little positive effect on transfer times.