Long-term transport support mechanisms for next generation geo satellite access networks
Support for IP-based services, efficient resource management and broadband connectivity distinguish next generation of satellite systems from their narrowband predecessors. Two types of satellite access systems are studied: Hybrid and Bandwidth-on-Demand (BoD). The capacity asymmetry in these types of networks interacts with TCP resulting in reduction of forward path performance due to the characteristics of die return path. This thesis presents an ACK Modification scheme combining ACK Filtering with uplink Fair Queuing to improve the fair sharing and forward diroughput in the presence of bi-directional and competing traffic. DVB-RCS is a standard that describes an example of two-way BoD satellite access network technology. BoD is a dynamic resource allocation mechanism to optimise resource management. While increasing transmission efficiency, BoD schemes may introduce large delay, delay variations and capacity variations that impact die performance of TCP. This thesis identifies BoD characteristics that impacts TCP and present a set of rules for designing BoD to support TCP. An implementation of different QoS classes using BoD techniques to provide loose delay guarantees for TCP traffic is also studied. This thesis compares a range of enhancement techniques described in the literature to overcome the effect of large path delay and show mat the requirement for split TCP solutions in satellite networks could be eliminated by combining the connection caching techniques adopted by the Congestion Manager and HTTP1.1 with Applications layer middle boxes (e.g. web proxies). A GEO BoD system may also impact the protocol behaviour. The Current TCP timer algorithm fails to operate correctly when initial network path delay exceeds 3 seconds. This thesis presents an alternative mechanism to choose initial RTO value for TCP data transfer and define the congestion control behaviour during TCP start-up.