On optimizing high-latency asymmetric satellite TCP/IP

Coetzee, Charl (1999-10)

Thesis (MScIng) -- University of Stellenbosch, 1999.

Thesis

ENGLISH ABSTRACT: The Transmission Control Protocol (TCP), part of the TCP/IP Internet Protocol Suite, is responsible for the reliable unicast delivery of popular Internet services such as web browsing, e-mail, and file transfer. Since satellite communication offers high-bandwidth links to geographically diverse areas, it becomes attractive to use satellite transmission (together with e.g. a remote dial-up modem as return path), to establish Internet services to a remote location. An asymmetric network is thus created. For satellite transmission to be viable in this context, it must be able to deliver data much more quickly than would be possible via the dial-up modem. Unfortunately, it has been found in practice that TCP performs suboptimally in such environments, and that a single TCP sessions can only fill a fraction of the bandwidth available to it. In fact, a single standard TCP connection will only be able to obtain around 53 kB/s throughput via satellite (roughly 8 times faster than dial-up modem), even if it has a satellite bandwidth of 54 Mbps all to itself. Other problems also exist, such as apparent unresponsiveness of connections. This thesis studies these problems, and their possible solutions. It concentrates on examining various TCP enhancements in a network emulator, and shows how TCP can be used more efficiently over the asymmetric satellite channel.

AFRIKAANSE OPSOMMING: Die 'Transmission Control Protocol' (TCP) uit die TCP/IP Internet Protokol Suite is verantwoordelik vir betroubare enkelbestemming data-aflewering. Dit word gebruik vir verskeie populere Internet dienste, insluitend web snuffeling, e~pos en leeroordrag. Aangesien satelliet-telekornrnunikasie breeband skakels na geografies diverse areas bied, word dit aanloklik om sulke kornrnunikasie (te same met byvoorbeeld 'n modem as terugpad), te gebruik om Internet dienste aan afgelee areas te voorsien. Sodoende kom 'n asirnrnetriese netwerk tot stand. Die satellietkanaal moet egter dan die data heelwat vinniger kan lewer as wat via modem moontlik sou wees, andersins is so 'n stelsel nie lewensvatbaar nie. Ongelukkig wys die praktyk dat TCP suboptimaal funksioneer in sulke omgewings, en dat 'n enkele TCP verbinding net 'n fraksie van die beskikbare bandwydte kan vul. am die waarheid te se, 'n enkele standaard TCP verbinding kan alleenlik ongeveer 53 kB/s via satelliet behaal (ongeveer 8 keer vinniger as per modem), selfs al sou die verbinding alleenreg tot 'n satellietskakel van 54 Mbps he. Ander probleme kom ook voor, byvoorbeeld die stadige reaksie van TCP satelliet-sessies. Die tesis bestudeer hierdie probleme, en moontlike oplossings word voorgestel. Daar word gekonsentreer op die ondersoek van verskeie TCP verbeteringe in 'n netwerk emuleerder, en gewys hoe TCP meer effektief oor die asimmetriese satellietkanaal gebruik kan word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/51373
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