Robust connection-less service over a packet satellite link
The intention of the study presented in this thesis is to obtain an understanding of the issues involved in using connection-less services over a non-reliable satellite link and to suggest suitable solutions to enhance packet communication services. Particular attention is paid to using VSAT systems for interconnecting LANs through satellite links. A detailed study of Connection-Less Services (CLNS) and end to end transport protocols that use the CLNS over a satellite link with different propagation conditions is presented. Since most existing link, network and transport protocols were originally designed to work with terrestrial networks, they do not necessarily perform well over a satellite link. The main weaknesses in the link protocols are the insufficiency of connection-less data link services, the interaction between error recovery procedures implemented by transport layer and link layer and the interaction between different conversations due to link layer error recovery procedures. The inefficiency in the segmentation and reassembling service is the main weakness in the network protocol. The weaknesses in the transport protocols are the interaction between error recovery procedures and congestion control procedures, the significant delay in receiving feed-back from the remote receiver, the oscillating behaviour of the congestion control algorithms and the inaccuracy of round trip time estimation. Two approaches were used to improve the connection-less service over a satellite link. First, new data link protocols were developed to transparently improve the network service. The second approach was to modify transport protocols (which provide end to end transport service) to suit the characteristics of the satellite network.