Terminology » Protocols » RTP vs RTCP vs RTSP: Key Differences Explained

RTP vs RTCP vs RTSP: Key Differences Explained

rtp rtcp rtsp multimedia protocol streaming

RTP (Real-Time Transport Protocol), RTCP (Real-Time Control Protocol), and RTSP (Real-Time Streaming Protocol) share a common foundation in facilitating real-time multimedia over IP communication. RTP and RTCP work in tandem, with RTP handling the transmission of audio and video data and RTCP providing essential control and feedback mechanisms to monitor and enhance the quality of media streams. Meanwhile, RTSP complements these protocols by managing the control aspects of multimedia sessions, allowing clients to initiate, control, and terminate streaming sessions.

Let’s compare RTP vs RTCP vs RTSP and then present a tabular summary of their differences.

RTP | Real-Time Transport Protocol

  • It is used for the transport of real-time data, specifically audio and video.
  • Applications: Media on demand, internet telephony.
  • RTP handles the multimedia data exchange, while RTCP handles the control aspects. RTCP is used to obtain feedback control information periodically.
  • RTP runs over UDP/IP.
  • RTP and its associated RTCP use consecutive transport layer ports over UDP. The video/audio to be transmitted are digitized using a specific codec.
  • The digitized data are assembled in blocks. These blocks are encapsulated in RTP packets with an RTP header and are carried by UDP and IP packets after suitable header insertion at respective layers.
  • RTP does not reserve bandwidth and does not guarantee QoS. RTCP handles QoS and synchronization of different media streams.

Refer to the RFC standard for the RTP header format.

Protocol Stack for RTP and RTSP

RTCP | Real-Time Control Protocol

  • It is a control protocol that works in conjunction with the RTP protocol.
  • In each RTP session, all the participants transmit RTCP packets to all the members in the same RTP session using multicast mode.
  • RFC 3550 defines RTCP packet types which are used to carry control information. These types include Receiver Report (RR), Sender Report (SR), SDES (Source Description Items), BYE (to indicate the end of participation), and APP (Application Specific functions).
  • RTCP packets are transmitted periodically among participants. RTCP packets contain sender reports and receiver reports which announce statistics such as packets sent, packets lost, and inter-arrival jitter.

RTSP | Real-Time Streaming Protocol

  • It is a client-server multimedia presentation protocol.
  • It is defined in RFC 2326. It has functionalities similar to a DVD player.
  • It is an application-level protocol that enables control over data delivery with real-time properties over IP.
  • It is designed to work in conjunction with RTP and RSVP to provide complete streaming service over the internet.
  • It was developed jointly by RealNetworks, Netscape Communications, and Columbia University.

RTSP and RTP Architecture

Tabular Difference between RTP, RTCP, and RTSP

The following table summarizes the major differences between these multimedia over IP protocols.

ParametersRTPRTCPRTSP
Full NameReal-Time Transport ProtocolReal-Time Control ProtocolReal-Time Streaming Protocol
Standard referenceRFC 1889, RFC 3550, ITU H.225.0RFC 3550 as part of RTP frameworkRFC 2326
PurposeReal-time transport of media dataControl and feedback for media streamsControl of streaming sessions
FunctionalityTransmits audio and video dataMonitors and manages stream qualityInitiates, controls, and manages media sessions
Transported ContentMedia content packetsControl and feedback informationControl commands for media playback
CharacteristicsUnicast or multicast transmissionPeriodic feedback reports sent to participantsControl of playback and session management
Transport protocolBoth RTP and RTCP uses UDP.RTCP does not have a dedicated transport protocol; it is typically multiplexed with RTP and shares the same transport protocol, often using UDP (User Datagram Protocol).RTSP uses RTP (over UDP) for stream and TCP for control.
Port numbersRTP/RTCP applications use UDP port numbers in the unprivileged range from 1024 to 65535. All RTP sent to an even numbered UDP port, 2p where as all RTCP sent to UDP port 2p+1.RTCP typically uses an adjacent odd port number to the RTP stream. For example, if RTP uses port number X, RTCP may use port number X+1.It uses 554 as default port for control messages.
Typical use casesVoIP, video conferencing, streamingQuality monitoring, feedbackMedia session control, IP cameras, servers

Conclusion

In summary, RTP (Real-Time Transport Protocol) is dedicated to the actual transmission of real-time audio and video data, while RTCP (Real-Time Control Protocol) works in tandem with RTP to provide control and feedback mechanisms, monitoring the quality of media streams. On the other hand, RTSP (Real-Time Streaming Protocol) is focused on managing the control aspects of multimedia sessions, enabling clients to initiate, control, and terminate streaming sessions but does not handle the actual transport of media content. Together, these protocols form a comprehensive framework for real-time multimedia communication, combining efficient data transport, quality monitoring, and session control.