Real-Time Transport Protocol

RTP combines its data transport with a control protocol (RTCP), which makes it possible to monitor data delivery for large multicast networks. Monitoring allows the receiver to detect if there is any packet loss and to compensate for any delay jitter. Both protocols work independently of the underlying Transport layer and Network layer protocols. Information in the RTP header tells the receiver how to reconstruct the data and describes how the codec bit streams are packetized. As a rule, RTP runs on top of the User Datagram Protocol (UDP), although it can use other transport protocols. Both the Session Initiation Protocol (SIP) and H.323 use RTP.

RTP components include: a sequence number, which is used to detect lost packets; payload identification, which describes the specific media encoding so that it can be changed if it has to adapt to a variation in bandwidth; frame indication, which marks the beginning and end of each frame; source identification, which identifies the originator of the frame; and intramedia synchronization, which uses timestamps to detect different delay jitter within a single stream and compensate for it.

RTPC components include: quality of service (QoS) feedback, which includes the numbers of lost packets, round-trip time, and jitter, so that the sources can adjust their data rates accordingly; session control, which uses the RTCP BYE packet to allow participants to indicate that they are leaving a session; identification, which includes a participant's name, e-mail address, and telephone number for the information of other participants; and intermedia synchronization, which enables the synchronization of separately transmitted audio and video streams.

Compressed RTP (CRTP), specified in RFC 2509, was developed to decrease the size of the IP, UDP, and RTP headers. However, it was designed to work with reliable and fast point-to-point links. In less than optimal circumstances, where there may be long delays, packet loss, and out-of-sequence packets, CRTP doesn't function well for Voice over IP (VoIP) applications. Another adaptation, Enhanced CRPT (ECRPT), was defined in a subsequent Internet Draft document to overcome that problem.

Read more about Real-Time Transport Protocol: - The IETF provides the Real-Time Transport Protocol RFC. - The IETF provides the Real-Time Control Protocol Internet Draft. - The IETF provides the Compressed RTP Internet Draft. - The Department of Computer Science at Ohio State University discusses "Voice over IP: Protocols and Standards." - SearchNetworking offers "Bests Web Links about Voice/Data Convergence." - The Audio/Video Transport Working Group maintains an RTP Frequently-Asked Questions list.

Do you have something to add to this definition? Let us know. Send your comments to techterms@whatis.com

Digg This!     StumbleUpon     Del.icio.us

RELATED CONTENT How to set up a VLAN on multiple switches Learn how to establish a VLAN over multiple routers in this response from a networking expert. What makes a WAN different from a LAN and MAN? Learn the basics of networking in this expert explanation of the differences between WANs, LANs and MANs -- how they connect and which protocols they... Does each routing protocol have a different routing table? Learn from our routing and switching expert, Sudhanshu Gupta, whether different routing protocols such as RIP and IGRP have different routing tables...

RELATED GLOSSARY TERMS Terms from Whatis.com − the technology online dictionary 10-Gigabit Ethernet  (SearchNetworking.com) Asynchronous Pulsed Radiated Incident Light  (SearchNetworking.com) Asynchronous Pulsed Radiated Incident Light is a multi-duplicitous communication protocol (MDCP) used to configure wireless local area networks...