SZEROKOPASMOWE SATELITARNE SIECI DANYCH W KONTEKŚCIE DOSTĘPNYCH PROTOKOŁÓW I PLATFORM CYFROWYCH

Satellites are the transmission medium for providing connectivity and building global, continental, or regional networks around the world (satellite operators effectively use satellites to support Internet traffic), and point-to-point connections are also possible. In practical use, there are combinations of VSAT networks with terrestrial wireless extensions, allowing end users to increase the capabilities offered via satellite. This paper provides selected information on broadband satellite networks using VSAT technology, including available protocols and transmission platforms. The aim of the article is also to present the chosen technical aspects of satellite networks working with the usage of VSAT technology.Satelity stanowią medium transmisyjne dla zapewnienia łączności i budowy sieci globalnych, kontynentalnych czy regionalnych na całym świecie (operatorzy satelitarni efektywnie wykorzystują satelity do obsługi ruchu internetowego), przy czym możliwe są także połączenia typu punkt-punkt. W praktycznym użyciu są kombinacje sieci VSAT z bezprzewodowymi rozszerzeniami naziemnymi, co pozwala zwiększyć użytkownikom końcowym możliwości oferowane za pośrednictwem satelity. W artykule zamieszczono wybrane informacje na temat szerokopasmowych sieci satelitarnych z wykorzystaniem technologii VSAT, z uwzględnieniem dostępnych protokołów i platform transmisyjnych. Celem artykułu jest także przedstawienie wybranych aspektów technicznych sieci satelitarnych pracujących z wykorzystaniem technologii VSAT

Analyze TCP Protocol Performance in Satellite Communications

This research is mainly about the influence of protocols on the performance of Satellite Communication. It is widely recognized that satellite communications are affected by some peculiar problems, which penalize heavily the performance and efficiency of the Transmission Control Protocol (TCP). In fact, wireless satellite channels are usually characterized by link-asymmetry and higher Round Trip Time and Bit Error Rate in comparison to wired links. It means that TCP, which was developed for wired channels, exhibits often poor performance in a satellite scenario (unfair bandwidth allocation, low throughput and long file-transfer delay).We have studied and compared many TCP variants recently proposed. In particular we have compared TCP-Reno standard implementation with TCP-SACK, TCP-Westwood, TCP-Vegas and TCP-Tibet. We tested the different protocols on a simulated satellite scenario, with the support of NS2, a well-know network simulator platform, annotating the advantages and drawbacks of various protocols in order to improve the transmission of IP data packets over satellite channels. Keywords: Satellite link, Performance analysis, TCP behaviors

Performance Evaluation of TCP Extensions on ATM over High Bandwidth Delay Product Networks

Practical experiments in a satellite network environment assist in the design and understanding of future global networks. This paper describes the practical experiences gained from TCP/IP on ATM networks over a high speed satellite link and presents performance comparison studies of such networks with the same host/traffic configurations over local area (LAN) and wide area (WAN) networks. These comparison studies on the LAN, WAN, and satellite environments increase our understanding of the behavior of high bandwidth networks. NASA's Advanced Communications Technology Satellite (ACTS), with its special characteristics and high data rate satellite channels, and the ACTS ATM Internetwork (AAI) were used in these experiments to deliver broadband traffic. Network performance tests were carried out using application-level software (Netspec) on SONET OC-3 (155.52 Mbps) satellite links. Finally, in this paper we study the performance, efficiency, fairness, and aggressiveness of TCP Reno, TCP ..