CORDIS Archive : Real Time Streaming Protocol

Real Time Streaming Protocol

Is the Internet coming of age at last for real-time traffic?

On 14 October 1996 a consortium of 40 companies announced their support for the Real Time Streaming Protocol - RTSP. The companies include Progressive Networks - the developers of RealAudio, the market leader for audio broadcasting over the Internet - and Netscape, who need no introduction.

RTSP is a communications protocol for control and delivery of real-time media. Sources of data can include both live data feeds, such as live audio and video, and stored content, such as pre-recorded events. The protocol defines the connection between a streaming media client and a streaming media server, and also provides a standard way for clients and servers from multiple vendors to stream multimedia content. Widespread support for this unified protocol would help ensure interoperability and give application developers more flexibility in developing robust multimedia applications.

Other companies involved in RTSP include the main hardware and router vendors, plus multimedia developers - the roll call includes Apple Computer, Cisco Systems, Dolby Laboratories, Hewlett Packard, IBM, Macromedia, Silicon Graphics and Sun Microsystems. Microsoft is absent, which is not uncommon in consortia where Netscape is present - yet there has been collaboration in the past between Progressive Networks and Microsoft over audio servers, and the RealAudio client is bundled into Internet Explorer. Also absent at this stage are the small but charismatic companies Xing and VDOnet, who have piloted video servers for Internets and Intranets. This is a pity, since Xing are active in multimedia trials on the Finnish ATM service and could bring useful operational experience. Perhaps they will join later - we hope so.

The first draft of the protocol specification, RTSP 1.0, was submitted to the Internet Engineering Task Force (IETF) on October 9, 1996.

"Until now, each vendor of Internet multimedia systems had a different approach, which has led to confusion among developers and end-users. RTSP offers a strong framework for streaming-media applications and integrates well with advanced protocols that the Internet is moving to," said Jerry Michalski, managing editor of Release 1.0.

"RTSP will do for streaming multimedia, what HTTP did for text and graphics publishing," said Rob Glaser, founder and CEO of Progressive Networks. "Once you have a standard that allows for interoperability, like RTSP, the development of real-time multimedia on the Web will explode."

RTSP evolved from work done at Progressive Networks and Netscape. It incorporates aspects of the International Telecommunications Union's H.323 specification. RTSP will take advantage of Internet and Intranet infrastructure improvements, such as IP Multicast, RTP and RTCP. It is hoped that the affinity between H.323 and RTSP will make it easier for the industry to bring the worlds of telephony, conferencing and multimedia broadcasting together.

RTSP OVERVIEW

RTSP provides the following specific benefits to Internet content providers and users:

bidirectionality enabling full stream control
high reliability over current net infrastructure
low overhead on data delivery
full exploitation of emerging technologies and protocols
security
intellectual property rights protection
scalability
a design based on field-proven techniques.

TECHNICAL DETAILS

The Real Time Streaming Protocol, or RTSP, is an application-level protocol for control over the delivery of data with real-time properties. RTSP provides an extensible framework to enable controlled, on-demand delivery of real-time data, such as audio and video. Sources of data can include both live data feeds and stored clips. This protocol is intended to control multiple data delivery sessions, provide a means for choosing delivery channels such as UDP, multicast UDP and TCP, and delivery mechanisms based upon RTP (RFC 1889).

By Paul Bacsich, Sheffield Hallam University, 01.11.1996