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.Barrett, Bradley A.

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    Traffic Models for Hybrid Satellite-Terrestrial Networks
    (2000) Barrett, Bradley A.; Baras, John S.; ISR; CSHCN
    While Hybrid Satellite-Terrestrial Networks (HSTNs) have become a popular method of providing Internet connectivity, network dimensioning and performance prediction problems in these networkss in their terrestrial counterpartsave remain largely unsolved. A key hindrance to the resolution of these issues has been accurate, tractable traffic models. While a number of rather complex models have been proposed for terrestrial network traffic, these have not been evaluated against HSTN traffic. And further, recent studies have questioned whether these more complex models, while statistically better fits, really provide significantly better performance prediction.

    We examine the question of how to model HSTN traffic for network dimensioning and performance prediction, and in particular, how far ahead into the future a traffic model can be expected to accurately function. We investigate these issues by directly comparing four of the most likely candidate statistical distributionshe exponential, log-normal, Weibull and Pareto. These distributions are fit to two key traffic parameters from real HSTN traffic traces (connection interarrival times and downloaded bytes), and their relative fits are compared using statistical techniques. We further compare traffic models built using these distributions in a simulated environment; comparing performance predictions (over a number of metrics) obtained from these models to the actual results from our real-world traffic traces.

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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.