Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

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Author: search.filters.author.Baras, John S.Subject: search.filters.subject.TCP

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    Window Distribution of Multiple TCPs with Random Loss Queues
    (1999) Misra, Archan; Baras, John S.; Ott, Teunis; Baras, John S.; ISR; CSHCN
    In this paper, we consider the case of multiple ideal and persistent TCP flows (flows that are assumed to be performing idealized congestion avoidance) interacting with queue management algorithms that perform random drop-based buffer management. Our objective is to determine the stationary congestion window distribution of each of the TCP flows whenthe router port implements algorithms like RED (Random Early Detection)or ERD (Early Random Drop).

    We first present an analyticaltechnique to obtain the 'mean' queue occupancy and the 'mean' of the individual TCP windows. Armed with this estimate of the means, wethen derive the window distribution of each individual TCPconnection. Extensive simulation experiments indicate that, under a wide variety of operating conditions, our analytical method is quite accurate in predicting the 'mean' as well asthe distributions. The derivation of the individual distributions is based upon a numerical analysis presented which considers the case of a single TCP flow subject to variable state-dependent packet loss.

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    A Simulation Study of Enhanced TCP/IP Gateways for Broadband Internet over Satellite
    (1999) Karir, Manish; Liu, Mingyan D.; Barrett, Bradley A.; Baras, John S.; Baras, John S.; ISR; CSHCN
    The demand for Internet bandwidth has been growing rapidlyover the years and the use of high-bandwidth satellites has been proposed as one possible solution to meet the increasingdemand.

    However, there are certain performance problems withproviding Internet over satellite due to the nature of TCP/IP protocol suite and the satellite link characteristics. In this paper, we describe a simulation study of an architecture for improving the performance of TCP/IP over satellite links.

    On each end of the satellite link, there are gateways that split the TCP connection so that the satellite link is transparent to the end hosts.

    The split TCP connection over the satellite segment is then optimized.TCP congestion control is maintained on each segment of the split connection.

    We simulated such an architecture in OPNET and present results showing improved throughput over the satellite link.

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    Internet Service via Broadband Satellite Networks
    (1999) Bharadwaj, Vijay G.; Baras, John S.; Butts, Norman P.; Baras, John S.; ISR; CSHCN
    The demand for Internet bandwidth has grown rapidly in the past few years. A new generation of broadband satellite constellations promises to provide high speed Internet connectivity to areas not served by optical fiber, cable or other high speed terrestrial connections. However, using satellitelinks to supply high bandwidth has been difficult due to problems with inefficient performance of the Internet's TCP/IP protocol suite over satellite. We describe an architecture for improving the performance of TCP/IP protocols over heterogeneous network environments, especially networks containing satellite links. The end-to-end connection is split into segments, and the protocol on the satellite segment is optimized for the satellite link characteristics. TCP congestion control mechanisms are maintained on each segment, with some coupling between the segments to produce the effect of end-to-end TCP flow control. We have implemented this design and present results showing that using such gateways can improve throughput for individual connections by a large factor over paths containing a satellite link.

    The research and scientific content in this material has been published in the Proceedings of the SPIE, vol. 3528, February 1999, 169-180.