What is RTP?

RTP (Real-Time Transport Protocol) is used to encapsulate VoIP data packets inside UDP packets.

RTP is defined in RFC 3550 - RTP: A Transport Protocol for Real-Time Applications.

RTP provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. RTP does not address resource reservation and does not guarantee quality-of-service for real-time services. The data transport is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner scalable to large multicast networks, and to provide minimal control and identification functionality. RTP and RTCP are designed to be independent of the underlying transport and network layers. The protocol supports the use of RTP-level translators and mixers.

Other RFCs which document RTP include:

• RFC 3551 - RTP Profile for Audio and Video Conferences with Minimal Control
• RFC 2032 - RTP Payload Format for H.261 Video Streams
• RFC 3158 - RTP Testing Strategies
• RFC 3605 - Real Time Control Protocol (RTCP) attribute in Session Description Protocol (SDP)
• RFC 3611 - RTP Control Protocol Extended Reports (RTCP XR)
• RFC 3711 - The Secure Real-time Transport Protocol (SRTP)

Books on RTP

RTP: Audio and Video for the Internet

RTP (Real-time Transport Protocol) provides a framework for the delivery of audio and video across IP networks with unprecedented quality and reliability. In RTP: Audio and Video for the Internet, Colin Perkins provides readers with detailed technical guidance for designing, implementing, and managing any RTP-based system. By bringing together crucial information that was previously scattered or difficult to find, Perkins has created an resource that enables network professionals to leverage RTP's benefits in a wide range of Voice-over IP (VoIP) and streaming media applications. Colin demonstrates how RTP supports audio/video transmission in IP networks, and shares strategies for maximizing performance, robustness, security, and privacy. Comprehensive, exceptionally clear, and filled with examples, RTP: Audio and Video for the Internet is the definitive reference on RTP for every audio/video application designer, developer, researcher, and administrator. Key coverage in the book includes: RTP's goals, design philosophy, and relationships with other protocols The psychology of human perception in the design of media delivery systems RTP data transfer and control protocols, including framing, loss detection, reception quality feedback, and membership control Media playout, timing, and synchronization, including lip synchronization Mitigating network problems: error concealment, error correction, and congestion control Optimizing performance over low-speed links: header compression, multiplexing, and tunneling Integrating leading media codecs and standards into RTP systems Securing RTP sessions: encryption, authentication, and the new secure RTP profile for wireless networks Extensive references and practical examples