not able to guarantee that Real-Time media will arrive properly timed, and with all audio and image packets intact. The Internet Engineering Task Force's (IETF) Audio-Video Transport Working Group is adapting the IP protocol stack to the unique needs of interactive media streams. Several Internet standards have been the result, with more on the way. This chapter examines the most widely-implemented, the User Datagram Protocol (UDP), the Real-Time Transport Protocol (RTP), the Real-Time Transport Control Protocol (RTCP) and the Resource Reservation Protocol (RSVP). We will also discuss the Real-Time Streaming Protocol (RTSP), IP multicasting. Overview of UDP The User Datagram Protocol (UDP) is a streaming IP protocol that is being substituted for TCP in Real-Time multimedia applications. UDP is unidirectional; no mechanism is available at the sender to know if a packet has been successfully received. Thus, UDP does not wait for transmission acknowledgements. It carries the packets presented to it but, if those packets are dropped or duplicated, or arrive out of sequence, UDP takes no corrective action. On the other hand, UDP increases the throughput of an IP network. Since there is no need to wait for acknowledgement by receivers, the UDP is an efficient mechanism for delivering multiple streams of information. TCP, on the other hand, has an inherent need to track and retransmit dropped or corrupted packets. The service that TCP provides has, unfortunately, no value for Real-Time applications. Video communication sequence and timing does not allow for a lost frame of video or packet of audio, to be re-sent and re-inserted in the data stream. Today, UDP provides the foundation for the other IETF protocols that are being developed to support video communication over the Internet. These include the RTP, the RTCP, and RSVP. UDP is also being used for IP multicasting. Applications Video Communications: The Whole Picture developed in accordance with the IETF protocols rely on codecs to detect and recover from packet los