RFC 3524 (rfc3524) - Page 2 of 6
Mapping of Media Streams to Resource Reservation Flows
Alternative Format: Original Text Document
RFC 3524 Mapping Media Streams to Resource Reservation Flows April 2003
1. Introduction
Resource reservation protocols assign network resources to particular
flows of IP packets. When a router receives an IP packet, it applies
a filter in order to map the packet to the flow it belongs. The
router provides the IP packet with the Quality of Service (QoS)
corresponding to its flow. Routers typically use the source and the
destination IP addresses and port numbers to filter packets.
Multimedia sessions typically contain multiple media streams (e.g. an
audio stream and a video stream). In order to provide QoS for a
multimedia session it is necessary to map all the media streams to
resource reservation flows. This mapping can be performed in
different ways. Two possible ways are to map all the media streams
to a single resource reservation flow or to map every single media
stream to a different resource reservation flow. Some applications
require that the former type of mapping is performed while other
applications require the latter. It is even possible that a mixture
of both mappings is required for a particular media session. For
instance, a multimedia session with three media streams might require
that two of them are mapped into a single reservation flow while the
third media stream uses a second reservation flow.
This document defines the SDP [1] syntax needed to express how media
streams need to be mapped into reservation flows. For this purpose,
we use the SDP grouping framework [2] and define a new "semantics"
attribute called Single Reservation Flow (SRF).
1.1 Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
[3] and indicate requirement levels for compliant SIP
implementations.
2. SRF Semantics
We define a new "semantics" attribute within the SDP grouping
framework [2]: Single Reservation Flow (SRF).
Media lines grouped using SRF semantics SHOULD be mapped into the
same resource reservation flow. Media lines that do not belong to a
particular SRF group SHOULD NOT be mapped into the reservation flow
used for that SRF group.
Camarillo & Monrad Standards Track