RFC 3556 (rfc3556) - Page 1 of 8
Session Description Protocol (SDP) Bandwidth Modifiers for RTP Control Protocol (RTCP) Bandwidth
Alternative Format: Original Text Document
Network Working Group S. Casner
Request for Comments: 3556 Packet Design
Category: Standards Track July 2003
Session Description Protocol (SDP) Bandwidth Modifiers
for RTP Control Protocol (RTCP) Bandwidth
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document defines an extension to the Session Description
Protocol (SDP) to specify two additional modifiers for the bandwidth
attribute. These modifiers may be used to specify the bandwidth
allowed for RTP Control Protocol (RTCP) packets in a Real-time
Transport Protocol (RTP) session.
1. Introduction
The Real-time Transport Protocol (RTP), RFC 3550 [1], includes a
control protocol RTCP which provides synchronization information from
data senders and feedback information from data receivers.
Normally, the amount of bandwidth allocated to RTCP in an RTP session
is 5% of the session bandwidth. For some applications, it may be
appropriate to specify the RTCP bandwidth independently of the
session bandwidth. Using a separate parameter allows rate-adaptive
applications to set an RTCP bandwidth consistent with a "typical"
data bandwidth that is lower than the maximum bandwidth specified by
the session bandwidth parameter. That allows the RTCP bandwidth to
be kept under 5% of the data bandwidth when the rate has been adapted
downward.
On the other hand, there may be applications that send data at very
low rates but need to communicate extra RTCP information, such as APP
packets. These applications may need to specify RTCP bandwidth that
is higher than 5% of the data bandwidth.
Casner Standards Track