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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Item Asymmetric Internet Access over Satellite-Terrestrial Networks(1996) Arora, Vivek; Suphasindhu, N.; Baras, John S.; Dillon, Douglas; ISR; CSHCNDirecPCtm's Turbo Internet is a low-cost hybrid (satellite- terrestrial) high-speed digital transmission system developed as a collaborative effort between the Center for Satellite and Hybrid Communication Networks and Hughes Network Systems. The system uses receive-only satellite links for downstream data delivery and public telephone networks at the modem speeds to provide the upstream communications path. One of the services provided is high speed Internet access based on an asymmetric TCP/IP protocol. Our principle object is to lower cost and efficiently provide high bandwidth access to Internet services such as file transfer, the World Wide Web, and the MBONE. In the initial protocol implementation, we achieved four times higher throughput than that of Today's high-speed modems (28.8 Kbps) alone2. This throughput can be further enhanced. The mismatch in bandwidth and delay in this hybrid network prevents the full use of the satellite link bandwidth (1 Mbps). This paper presents two techniques, TCP spoofing and selective acknowledgement dropping, which significantly increase the overall throughput of the hybrid network. Our approach does not require any modification to the TCP/IP protocol stacks on the end hosts. The solutions proposed in this paper could be used to improve TCP/IP performance of other hybrid networks which have the disadvantage of high bandwidth-delay products and/or low bandwidth return paths. Furthermore, we are investigating how to extend IP multicast services to such hybrid networks. The broadcast nature of Satellite communication makes it an efficient way for high- bandwidth multicast transmission.- A revised version of this technical report has been published in
Proceedings of the AIAA: 16th International Communications Satellite Systems Conference and Exhibit, Part 1, pp. 476-482, Washington, D.C., February 25-29, 1996.Item Effective Extensions of Internet in Hybrid Satellite-Terrestrial Networks(1996) Arora, Vivek; Suphasindhu, N.; Baras, John S.; Dillon, Douglas; ISR; CSHCNDirect PCTM's Turbo Internet is a low-cost hybrid (satellite- terrestrial) high-speed digital transmission system developed as a collaborative effort between the Center for Satellite and Hybrid Communication Networks and Hughes Network Systems. The system uses receive-only VSAT satellite links for downstream data delivery and public telephone networks at modem speeds to provide the upstream communications path. One of the services provided is high speed Internet access based on an asymmetric TCP/IP protocol. In the initial protocol implementation, we achieved four times higher throughput than that of today high-speed modems (28.8 Kbps) alone (Falk 1995). This throughput can be further enhanced. The mismatch in bandwidth and delay in this hybrid network prevents the full use of the satellite link bandwidth (1 Mbps). This paper presents two techniques. TCP spoofing and selective acknowledgement dropping, which significantly increase the overall throughput of the hybrid network. Our approach does not require any modification to the TCP/IP protocol stacks on the end hosts. The solutions proposed in this paper could be used to improve TCP/IP performance of other hybrid networks which have the disadvantage of high bandwidth-delay products and/or low bandwidth return paths.- A revised version of this report has been published in
Proceedings of the 1st Conference of Commercial Development of Space, Part One, pp. 339-344, Albuquerque, New Mexico, January 7-11, 1996.Item Hybrid Internet Access(1995) Arora, Vivek; Baras, John S.; Dillon, Douglas; Falk, Aaron D.; Suphasindhu, Narin; ISR; CSHCNAccess to the Internet is either too slow (dial-up SLIP) or too expensive (switched 56 kbps, frame relay) for the home user or small enterprise. The Center for Satellite and Hybrid Communication Networks and Hughes Network Systems have collaborated using systems integration principles to develop a prototype of a low-cost hybrid (dialup and satellite) network terminal which can deliver data from the Internet to the user at rates up to 160 kbps. An asymmetric TCP/IP connection is used breaking the network link into two physical channels: a terrestrial dial-up for carrying data from the terminal into the Internet and a receive-only satellite link carrying IP packets from the Internet to the user. With a goal of supporting bandwidth hungry Internet applications such as Mosaic Gopher, and FTP, this system has been designed to support an Intel 80386/486 PC, any commercial TCP/IP package, any unmodified host on the Internet, and any of the routers, etc., within the Internet.. The design exploits the following three observations: 1) satellites are able to offer high bandwidth connections to large geographical area, 2) a receiver-only VSAT is cheap to manufacture and easier to install than one which can also transmit, and 3) most computer users, especially those in a home environment, will want to consume much more information than they generate. IP encapsulation, or tunneling, issued to manipulate the TCP/IP protocols to route packets asymmetrically.