Due to the rapidly growing demands of multimedia communications with guaranteed quality of service (QoS), traditional Internet communications based on best-effort are not suitable any more, and the topic of end-to-end QoS management for multimedia communications over IP has received great attention in the past few years. It is a very challenging task to study end-to-end QoS management because of the unexpected packet loss, the bandwidth and delay fluctuation, and the heterogeneous property of networks. The objective of this research is to study, design and implement end-to-end QoS management schemes, particularly on congestion control and error control in the transportation layer, for multimedia communications over IP. In my two-year study, we focus on two theoretical problems, i.e., wireless link modeling and optimal retransmission timeout (RTO) selection, we also develop a practical RTP-based transportation system for multimedia streaming over IP with end-to-end QoS management. In particular, we propose to model the wireless link layer by converting the widely used Gilbert-Elliott channel (GEC) at different levels. We develop an analytical procedure to derive the parameters of a desired symbol-level GEC model, from the parameters of a given bit-level GEC. It can be applied to any problem of converting GEC from a level of shorter data segment to a level of longer data segment as long as the longer data segment is a multiple of the shorter data segment. We also study the problem of optimal retransmission timeout (RTO) selection for end-to-end delay-constrained multimedia communications. Based on a statistical delay model of IP network, we propose a novel algorithm for optimal RTO selection in delayconstrained multimedia communications. By appropriately choosing the RTO, we are able to adjust packet delay and transmission rate, and then achieve the optimal tradeoff between the error probability and the rate cost. iii ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library Moreover, we develop a RTP-based transportation system based on Darwin Streaming Server and MPEG4IP player. We have incorporated TCP friendly rate control (TFRC) into the system for congestion control, and two error control schemes to combat with packet loss, the class-based fast retransmission and unequal erasure protection (UXP). A simple interface is defined for the application and the transportation system to exchange information for QoS management. Experimental results show that the developed system is able to provide end-to-end QoS management appropriately.