Session Description Protocol (SDP) Bandwidth Modifiers for RTP Control Protocol (RTCP) Bandwidth (RFC3556)
Original Publication Date: 2003-Jul-01
Included in the Prior Art Database: 2003-Jul-29
Internet Society Requests For Comment (RFCs)
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.
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 (C) The Internet Society (2003). All Rights Reserved.
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.
The Real-time Transport Protocol (RTP), RFC 3550 , 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
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 [Page 1]
RFC 3556 SDP Bandwidth Modifiers for RTCP Bandwidth July 2003
The RTP specification allows a profile to specify that the RTCP
bandwidth may be divided into two separate session parameters for
those participants which are active data senders and those which are
not. Using two parameters allows RTCP reception reports to be turned
off entirely for a particular session by setting the RTCP bandwidth
for non-data-senders to zero while keeping the RTCP bandwidth for
data senders non-zero so that sender reports...