RTP represents a new style of protocol following the principles of
application level framing and integrated layer processing proposed by
Clark and Tennenhouse [1]. That is, RTP is intended to be malleable
to provide the information required by a particular application and
will often be integrated into the application processing rather than
being implemented as a separate layer. RTP is a protocol framework
that is deliberately not complete. This document specifies those
functions expected to be common across all the applications for which
RTP would be appropriate. Unlike conventional protocols in which
additional functions might be accommodated by making the protocol
more general or by adding an option mechanism that would require
parsing, RTP is intended to be tailored through modifications and/or
additions to the headers as needed. Examples are given in Sections
5.3 and 6.3.3.
Therefore, in addition to this document, a complete specification of
RTP for a particular application will require one or more companion
documents (see Section 12):
o a profile specification document, which defines a set of
payload type codes and their mapping to payload formats (e.g.,
media encodings). A profile may also define extensions or
modifications to RTP that are specific to a particular class of
applications. Typically an application will operate under only
one profile. A profile for audio and video data may be found in
the companion RFC TBD.
o payload format specification documents, which define how a
particular payload, such as an audio or video encoding, is to
be carried in RTP.
A discussion of real-time services and algorithms for their
implementation as well as background discussion on some of the RTP
design decisions can be found in [2].
Several RTP applications, both experimental and commercial, have
already been implemented from draft specifications. These
applications include audio and video tools along with diagnostic
tools such as traffic monitors. Users of these tools number in the
thousands. However, the current Internet cannot yet support the full
potential demand for real-time services. High-bandwidth services
using RTP, such as video, can potentially seriously degrade the
quality of service of other network services. Thus, implementors
should take appropriate precautions to limit accidental bandwidth
usage. Application documentation should clearly outline the
limitations and possible operational impact of high-bandwidth real-
Schulzrinne, et al Standards Track [Page 4]
RFC 1889 RTP January 1996
time services on the Internet and other network services.
2. RTP Use Scenarios
The following sections describe some aspects of the use of RTP. The
examples were chosen to illustrate the basic operation of
applications using RTP, not to limit what RTP may be used for. In
these examples, RTP is carried on top of IP and UDP, and follows the
conventions established by the profile for audio and video specified
in the companion Internet-Draft draft-ietf-avt-profile
2.1 Simple Multicast Audio Conference
