This thesis presents the studies of end-to-end quality of service (QoS) in satellite networks. The end-to-end QoS is affected by r0U:ting algorithms at the Internet Protocol (IP) networking layer and transmission control protocol/ user datagram protocol (TCPIUDP) protocols at the transport layer. In particular, this thesis investigates multi-constrained routing algorithm in low earth orbit (LEO) satellite networks and transport layer performance enhancements via reliable link layer support in satellite IP networks. Firstly, the routing algorithms/protocols for LEO satellite networks are investigated. A novel QoS routing algorithm is proposed for LEO satellite networks. A weighted graph model is used to analyse the QoS routing problem in LEO satellite networks. Based on this model, a Delay Constrained Longest lifeTime (DCLT) routing algorithm is proposed for LEO satellite networks. The novelty of this work is that the algorithm proposed tries to fmd the paths that fulfil the delay constraint of users' requests using heuristic methodology and at the same time, it tries to fmd a path that has longest lifetime to make sure the connection lasts as long as possible. This algorithm is more efficient particularly for LEO satellite networks since the re-routing attempts are reduced. Both theoretical analysis and simulation methods have been used to evaluate the performance of the algorithm. Secondly, the TCP performance with different link layer frame sizes and link layer retransmission mechanisms over geostationary earth orbit (GEO) satellite networks is investigated. TCP' performance decreases over satellite link with poor channel condition and long propagation delay. This work is mainly focused on how to eliminate the effect ofthe poor channel conditions on TCP performance. An analytical model is proposed to study the effect of different link layer frame sizes and retransmission mechanisms. Then, a link layer relay mechanism is proposed to enhance the TCP performance. From both the mathematical analysis and simulation results, it can be found that link layer frame with small sizes and link layer automatic repeat request (ARQ) can enhance TCP performance. Furthermore, with the proposed link layer relay mechanism, TCP throughput can be enhanced substantially especially under the very poor channel condition. Finally, the TCP performance with different link layer frame sizes and link layer frame retransmission mechanism is investigated over low earth orbit! medium earth orbit (LEO/MEO) multi-hop satellite networks. A LEOIMEO satellite network can be considered as a wireless multi-hop network with lower propagation delay compared with a GEO satellite network. With the analytical model proposed, the TCP performance with link layer retransmission mechanisms and different link layer frame sizes over multi-hop satellite networks is studied. In addition, a novel hop-by-hop link layer relay mechanism is proposed. From the results .. of modelling and simulation, it shows that rcp throughput can also be improved under poor channel condition. Key words: Quality of Service (QoS), QoS Routing, End-to-End QoS, rcp, Satellite IP Networks.