Internet Engineering Task Force (IETF) J. Rosenberg
Request for Comments: 5688 Skype
Category: Standards Track January 2010
ISSN: 2070-1721
A Session Initiation Protocol (SIP) Media Feature Tag for MIME
Application Subtypes
Abstract
The caller preferences specification for the Session Initiation
Protocol (SIP) allows a caller to express preferences that the call
be routed to a User Agent (UA) with particular capabilities.
Similarly, a specification exists to allow a UA to indicate its
capabilities in a registration. Amongst those capabilities are the
type of media streams the agent supports, described as top-level MIME
types. The 'application' MIME type is used to describe a broad range
of stream types, and it provides insufficient granularity as a
capability. This specification allows a UA to indicate which
application subtypes the agent supports.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5688.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Rosenberg Standards Track [Page 1]RFC 5688 Application Subtype Tag January 2010
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. sip.app-subtype Media Feature Tag . . . . . . . . . . . . . . . 3
4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . . 7
1. Introduction
The caller preferences specification [RFC3841] for the Session
Initiation Protocol (SIP) [RFC3261] allows a user to express
preferences for the routing of SIP requests. These preferences are
expressed as a set of desired capabilities and characteristics of a
receiving agent. When a user agent registers to the SIP network, it
includes, as part of its registration, its own capabilities and
characteristics [RFC3840]. These capabilities are stored as part of
the registration, and then made available to the proxy in the
network. When a request arrives at the proxy with caller
preferences, the preferences in the request are compared with the
supported characteristics and capabilities stored in the
registrations, and the result is used to select the target user
agents for the request.
RFC 3840 makes use of media feature tags [RFC2506]. Each tag has a
name and a type. The tags defined in RFC 3840 describe some of the
datatracker.ietf.org