User-Perceived Quality-Aware Adaptation of Streamed Multimedia over Best-effort IP Networks

There are many transport protocols that can be used for streaming multimedia over best-effort networks. These protocols are designed are designed to enhance the services of the underlying transport protocol (i.e. TCP/IP or UDP/IP). The Real-time Transport Protocol (RTP) is used for facilitating the streaming of multimedia data packets whilst the Real-time Transport Control Protocol (RTCP) is used to relay feedback information between client and server. Feedback messages are used as a basis for quality of service monitoring and multimedia adaptation. The Real-time Streaming Protocol (RTSP) is used to relay control information. Such control information allows for connection establishment and negotiation of session parameters. The session parameters are typically conveyed through a session description using the Session Description Protocol (SDP). The main problem with UDP/IP as a transport mechanism is that there is no guarantee that the packets will arrive, and once lost or delayed past their playtime they are discarded. However using another transport mechanism such as TCP/IP would be wasteful, as it has a larger header overhead and requests retransmission of all lost or delayed packets. Retransmission of all lost packets is usually unsuitable for real-time applications, as this would cause undue traffic on the network and the retransmitted packets may be too late in any case. To solve this, RTP was designed for the transport of real-time data, including audio and video [1][2][3]. RTP consists of two closely linked parts: o The real-time transport protocol (RTP), to carry data that has real-time properties. o The RTP control protocol (RTCP), to monitor the quality of service and to convey information about the participants in an ongoing session. RTP employs the principles of application level framing and integrated layer processing. RTP is designed to be flexible enough to provide the relevant information required by the application and its processing. RTP is often typically implemented at the application layer. RTP is a protocol framework that is deliberately incomplete as it is very generalized so that Appendix A – Transport Protocols 2 it can be tailored through modifications and/or additions to the headers as needed to make it more specific to its application. RTP is a transport protocol for real-time applications and provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video etc. over multicast or unicast network networks. RTP can be used with other network protocols such AAL5/IP, UDP/IP and TCP/IP [4]. RTP does not: …