Performance analysis of transmitting H.263 over DCCP Recent years have seen a large increase in applications using user datagram protocol (UDP) for long-lived flows, and most of these applications have been reluctant to use congestion control. This poses a potential threat to the security of the Internet. Datagram congestion control protocol (DCCP) is proposed by IETF to transmit real-time traffic as a substitute for UDP. In this paper the basic principle of DCCP, as well as its congestion control mechanisms, is introduced. An overview of H.263 video codingis also provided. Then based on network simulator 2(NS2) simulation, follows the study of performance of transmitting H.263 over DCCP. Finally, a conclusion that DCCP is suitable to transmit real-time applications is presented.