draft-ietf-mmusic-sdp-new-15.txt   draft-ietf-mmusic-sdp-new-16.txt 
Network Working Group M. Handley Network Working Group M. Handley
Internet-Draft UCL Internet-Draft UCL
Obsoletes: 2327, 3266 (if V. Jacobson Obsoletes: 2327, 3266 (if V. Jacobson
approved) Packet Design approved) Packet Design
Expires: April 26, 2004 C. Perkins Expires: November 2, 2004 C. Perkins
University of Glasgow University of Glasgow
October 27, 2003 May 4, 2004
SDP: Session Description Protocol SDP: Session Description Protocol
draft-ietf-mmusic-sdp-new-15.txt draft-ietf-mmusic-sdp-new-16.txt
Status of this Memo Status of this Memo
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and any of which I become aware will be disclosed, in accordance with
RFC 3668.
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Abstract
This memo defines the Session Description Protocol (SDP). SDP is This memo defines the Session Description Protocol (SDP). SDP is
intended for describing multimedia sessions for the purposes of intended for describing multimedia sessions for the purposes of
session announcement, session invitation, and other forms of session announcement, session invitation, and other forms of
multimedia session initiation. multimedia session initiation.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Glossary of Terms . . . . . . . . . . . . . . . . . . . . . 3 2. Glossary of Terms . . . . . . . . . . . . . . . . . . . . . 3
3. Examples of SDP Usage . . . . . . . . . . . . . . . . . . . 4 3. Examples of SDP Usage . . . . . . . . . . . . . . . . . . . 3
3.1 Multicast Announcement . . . . . . . . . . . . . . . . . . . 4 3.1 Multicast Session Announcement . . . . . . . . . . . . . . 3
3.2 Session Initiation . . . . . . . . . . . . . . . . . . . . . 4 3.2 Session Initiation . . . . . . . . . . . . . . . . . . . . 4
3.3 Streaming media . . . . . . . . . . . . . . . . . . . . . . 4 3.3 Streaming media . . . . . . . . . . . . . . . . . . . . . 4
3.4 Email and the World Wide Web . . . . . . . . . . . . . . . . 4 3.4 Email and the World Wide Web . . . . . . . . . . . . . . . 4
4. Requirements and Recommendations . . . . . . . . . . . . . . 5 4. Requirements and Recommendations . . . . . . . . . . . . . . 5
4.1 Media Information . . . . . . . . . . . . . . . . . . . . . 6 4.1 Media Information . . . . . . . . . . . . . . . . . . . . 5
4.2 Timing Information . . . . . . . . . . . . . . . . . . . . . 6 4.2 Timing Information . . . . . . . . . . . . . . . . . . . . 6
4.3 Private Sessions . . . . . . . . . . . . . . . . . . . . . . 7 4.3 Private Sessions . . . . . . . . . . . . . . . . . . . . . 6
4.4 Obtaining Further Information about a Session . . . . . . . 7 4.4 Obtaining Further Information about a Session . . . . . . 6
4.5 Categorisation . . . . . . . . . . . . . . . . . . . . . . . 7 4.5 Categorisation . . . . . . . . . . . . . . . . . . . . . . 6
4.6 Internationalization . . . . . . . . . . . . . . . . . . . . 7 4.6 Internationalization . . . . . . . . . . . . . . . . . . . 7
5. SDP Specification . . . . . . . . . . . . . . . . . . . . . 7 5. SDP Specification . . . . . . . . . . . . . . . . . . . . . 7
5.1 Protocol Version ("v=") . . . . . . . . . . . . . . . . . . 10 5.1 Protocol Version ("v=") . . . . . . . . . . . . . . . . . 9
5.2 Origin ("o=") . . . . . . . . . . . . . . . . . . . . . . . 10 5.2 Origin ("o=") . . . . . . . . . . . . . . . . . . . . . . 10
5.3 Session Name ("s=") . . . . . . . . . . . . . . . . . . . . 11 5.3 Session Name ("s=") . . . . . . . . . . . . . . . . . . . 11
5.4 Session and Media Information ("i=") . . . . . . . . . . . . 11 5.4 Session Information ("i=") . . . . . . . . . . . . . . . . 11
5.5 URI ("u=") . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.5 URI ("u=") . . . . . . . . . . . . . . . . . . . . . . . . 11
5.6 Email Address and Phone Number ("e=" and "p=") . . . . . . . 12 5.6 Email Address and Phone Number ("e=" and "p=") . . . . . . 11
5.7 Connection Data ("c=") . . . . . . . . . . . . . . . . . . . 13 5.7 Connection Data ("c=") . . . . . . . . . . . . . . . . . . 12
5.8 Bandwidth ("b=") . . . . . . . . . . . . . . . . . . . . . . 15 5.8 Bandwidth ("b=") . . . . . . . . . . . . . . . . . . . . . 14
5.9 Timing ("t=") . . . . . . . . . . . . . . . . . . . . . . . 16 5.9 Timing ("t=") . . . . . . . . . . . . . . . . . . . . . . 15
5.10 Repeat Times ("r=") . . . . . . . . . . . . . . . . . . . . 17 5.10 Repeat Times ("r=") . . . . . . . . . . . . . . . . . . 16
5.11 Time Zones ("z=") . . . . . . . . . . . . . . . . . . . . . 18 5.11 Time Zones ("z=") . . . . . . . . . . . . . . . . . . . 17
5.12 Encryption Keys ("k=") . . . . . . . . . . . . . . . . . . . 18 5.12 Encryption Keys ("k=") . . . . . . . . . . . . . . . . . 18
5.13 Attributes ("a=") . . . . . . . . . . . . . . . . . . . . . 20 5.13 Attributes ("a=") . . . . . . . . . . . . . . . . . . . 19
5.14 Media Announcements ("m=") . . . . . . . . . . . . . . . . . 21 5.14 Media Descriptions ("m=") . . . . . . . . . . . . . . . 21
6. Suggested Attributes . . . . . . . . . . . . . . . . . . . . 24 6. Suggested Attributes . . . . . . . . . . . . . . . . . . . . 24
7. Communicating Conference Control Policy . . . . . . . . . . 30 7. Communicating Conference Control Policy . . . . . . . . . . 29
8. Security Considerations . . . . . . . . . . . . . . . . . . 30 8. Security Considerations . . . . . . . . . . . . . . . . . . 30
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 32 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 31
9.1 The "application/sdp" media type . . . . . . . . . . . . . . 32 9.1 The "application/sdp" media type . . . . . . . . . . . . . 31
9.2 Registration of Parameters . . . . . . . . . . . . . . . . . 33 9.2 Registration of Parameters . . . . . . . . . . . . . . . . 32
A. SDP Grammar . . . . . . . . . . . . . . . . . . . . . . . . 36 9.3 Encryption Key Access Methods . . . . . . . . . . . . . . 36
B. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 41 A. SDP Grammar . . . . . . . . . . . . . . . . . . . . . . . . 37
Normative References . . . . . . . . . . . . . . . . . . . . 42 B. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 42
Informative References . . . . . . . . . . . . . . . . . . . 42 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 42
10.1 Normative References . . . . . . . . . . . . . . . . . . . 42
10.2 Informative References . . . . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 43 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 43
Intellectual Property and Copyright Statements . . . . . . . 44 Intellectual Property and Copyright Statements . . . . . . . 45
1. Introduction 1. Introduction
[Note to RFC Editor: All references to RFC XXXX should be replaced by [Note to RFC Editor: All references to RFC XXXX should be replaced by
the RFC number of this document, when published.] the RFC number of this document, when published.]
When initiating multimedia teleconferences, voice-over-IP calls, When initiating multimedia teleconferences, voice-over-IP calls,
streaming video, or other real-time sessions, there is a requirement streaming video, or other sessions, there is a requirement to convey
to convey media details, transport addresses, and other session media details, transport addresses, and other session description
description metadata to the participants. metadata to the participants.
SDP provides a standard representation for such information, SDP provides a standard representation for such information,
irrespective of how that information is transported. SDP is purely a irrespective of how that information is transported. SDP is purely a
format for session description - it does not incorporate a transport format for session description - it does not incorporate a transport
protocol, and is intended to use different transport protocols as protocol, and is intended to use different transport protocols as
appropriate, including the Session Announcement Protocol [8], Session appropriate, including the Session Announcement Protocol [8], Session
Initiation Protocol [9], Real-Time Streaming Protocol [10], Initiation Protocol [9], Real-Time Streaming Protocol [10],
electronic mail using the MIME extensions, and the Hypertext electronic mail using the MIME extensions, and the Hypertext
Transport Protocol. Transport Protocol.
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description. description.
2. Glossary of Terms 2. Glossary of Terms
The following terms are used in this document, and have specific The following terms are used in this document, and have specific
meaning within the context of this document. meaning within the context of this document.
Conference: A multimedia conference is a set of two or more Conference: A multimedia conference is a set of two or more
communicating users along with the software they are using to communicating users along with the software they are using to
communicate. communicate.
Session: A multimedia session is a set of multimedia senders and Session: A multimedia session is a set of multimedia senders and
receivers and the data streams flowing from senders to receivers. receivers and the data streams flowing from senders to receivers.
A multimedia conference is an example of a multimedia session. A multimedia conference is an example of a multimedia session.
Session Advertisement: See session announcement.
Session Announcement: A session announcement is a mechanism by which
a session description is conveyed to users in a pro-active
fashion, i.e., the session description was not explicitly
requested by the user.
Session Description: A well defined format for conveying sufficient Session Description: A well defined format for conveying sufficient
information to discover and participate in a multimedia session. information to discover and participate in a multimedia session.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1]. document are to be interpreted as described in RFC 2119 [1].
3. Examples of SDP Usage 3. Examples of SDP Usage
3.1 Multicast Announcement 3.1 Multicast Session Announcement
In order to assist the advertisement of multicast multimedia In order to assist the advertisement of multicast multimedia
conferences and other multicast sessions, and to communicate the conferences and other multicast sessions, and to communicate the
relevant session setup information to prospective participants, a relevant session setup information to prospective participants, a
distributed session directory may be used. An instance of such a distributed session directory may be used. An instance of such a
session directory periodically sends packets containing a description session directory periodically sends packets containing a description
of the session to a well known multicast group. These advertisements of the session to a well known multicast group. These advertisements
are received by other session directories such that potential remote are received by other session directories such that potential remote
participants can use the session description to start the tools participants can use the session description to start the tools
required to participate in the session. required to participate in the session.
One protocol commonly used to implement such a distributed directory One protocol commonly used to implement such a distributed directory
is the Session Announcement Protocol, SAP [8]. SDP provides the is the Session Announcement Protocol, SAP [8]. SDP provides the
recommended session description format for such announcements. recommended session description format for such session
announcements.
3.2 Session Initiation 3.2 Session Initiation
The Session Initiation Protocol, SIP [9] is an application layer The Session Initiation Protocol, SIP [9] is an application layer
control protocol for creating, modifying and terminating sessions control protocol for creating, modifying and terminating sessions
such as Internet multimedia conferences, Internet telephone calls and such as Internet multimedia conferences, Internet telephone calls and
multimedia distribution. The SIP messages used to create sessions multimedia distribution. The SIP messages used to create sessions
carry session descriptions which allow participants to agree on a set carry session descriptions which allow participants to agree on a set
of compatible media types. These session descriptions are commonly of compatible media types. These session descriptions are commonly
formatted using SDP. When used with SIP, the offer/answer model [11] formatted using SDP. When used with SIP, the offer/answer model [11]
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properties. RTSP provides an extensible framework to enable properties. RTSP provides an extensible framework to enable
controlled, on-demand delivery of real-time data, such as audio and controlled, on-demand delivery of real-time data, such as audio and
video. An RTSP client and server negotiate an appropriate set of video. An RTSP client and server negotiate an appropriate set of
parameters for media delivery, partially using SDP syntax to describe parameters for media delivery, partially using SDP syntax to describe
those parameters. those parameters.
3.4 Email and the World Wide Web 3.4 Email and the World Wide Web
Alternative means of conveying session descriptions include Alternative means of conveying session descriptions include
electronic mail and the World Wide Web. For both email and WWW electronic mail and the World Wide Web. For both email and WWW
distribution, the use of the MIME content type "application/sdp" MUST distribution, the MIME content type "application/sdp" is used. This
be used. This enables the automatic launching of applications for enables the automatic launching of applications for participation in
participation in the session from the WWW client or mail reader in a the session from the WWW client or mail reader in a standard manner.
standard manner.
Note that announcements of multicast sessions made only via email or Note that announcements of multicast sessions made only via email or
the World Wide Web (WWW) do not have the property that the receiver the World Wide Web (WWW) do not have the property that the receiver
of a session announcement can necessarily receive the session because of a session announcement can necessarily receive the session because
the multicast sessions may be restricted in scope, and access to the the multicast sessions may be restricted in scope, and access to the
WWW server or reception of email is possible outside this scope. SAP WWW server or reception of email is possible outside this scope.
announcements do not suffer from this mismatch.
Session announcements made using SAP do not suffer from this
mismatch.
4. Requirements and Recommendations 4. Requirements and Recommendations
The purpose of SDP is to convey information about media streams in The purpose of SDP is to convey information about media streams in
multimedia sessions to allow the recipients of a session description multimedia sessions to allow the recipients of a session description
to participate in the session. SDP is primarily intended for use in to participate in the session. SDP is primarily intended for use in
an internetwork, although it is sufficiently general that it can an internetwork, although it is sufficiently general that it can
describe conferences in other network environments. describe conferences in other network environments. Media streams can
be many-to-many. The times during which the session is active need
A multimedia session, for these purposes, is defined as a set of not be continuous.
media streams that exist for some duration of time. Media streams
can be many-to-many. The times during which the session is active
need not be continuous.
Thus far, multicast based sessions on the Internet have differed from Thus far, multicast based sessions on the Internet have differed from
many other forms of conferencing in that anyone receiving the traffic many other forms of conferencing in that anyone receiving the traffic
can join the session (unless the session traffic is encrypted). In can join the session (unless the session traffic is encrypted). In
such an environment, SDP serves two primary purposes. It is a means such an environment, SDP serves two primary purposes. It is a means
to communicate the existence of a session, and is a means to convey to communicate the existence of a session, and is a means to convey
sufficient information to enable joining and participating in the sufficient information to enable joining and participating in the
session. In a unicast environment, only the latter purpose is likely session. In a unicast environment, only the latter purpose is likely
to be relevant. to be relevant.
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4.4 Obtaining Further Information about a Session 4.4 Obtaining Further Information about a Session
A session description should convey enough information to decide A session description should convey enough information to decide
whether or not to participate in a session. SDP may include whether or not to participate in a session. SDP may include
additional pointers in the form of Universal Resources Identifiers additional pointers in the form of Universal Resources Identifiers
(URIs) for more information about the session. (URIs) for more information about the session.
4.5 Categorisation 4.5 Categorisation
When many session descriptions are being distributed by SAP, or any When many session descriptions are being distributed by SAP, or any
other advertisement mechanism, it may be desirable to filter other advertisement mechanism, it may be desirable to filter session
announcements that are of interest from those that are not. SDP announcements that are of interest from those that are not. SDP
supports a categorisation mechanism for sessions that is capable of supports a categorisation mechanism for sessions that is capable of
being automated. being automated.
4.6 Internationalization 4.6 Internationalization
The SDP specification recommends the use of the ISO 10646 character The SDP specification recommends the use of the ISO 10646 character
sets in the UTF-8 encoding [3] to allow many different languages to sets in the UTF-8 encoding [3] to allow many different languages to
be represented. However, to assist in compact representations, SDP be represented. However, to assist in compact representations, SDP
also allows other character sets such as ISO 8859-1 to be used when also allows other character sets such as ISO 8859-1 to be used when
desired. Internationalization only applies to free-text fields desired. Internationalization only applies to free-text fields
(session name and background information), and not to SDP as a whole. (session name and background information), and not to SDP as a whole.
5. SDP Specification 5. SDP Specification
SDP session descriptions are entirely textual using the ISO 10646 An SDP session description is denoted by the MIME content type
"application/sdp" (See Section 9).
An SDP session description is entirely textual using the ISO 10646
character set in UTF-8 encoding. SDP field names and attribute names character set in UTF-8 encoding. SDP field names and attribute names
use only the US-ASCII subset of UTF-8, but textual fields and use only the US-ASCII subset of UTF-8, but textual fields and
attribute values MAY use the full ISO 10646 character set. Field and attribute values MAY use the full ISO 10646 character set. Field and
attribute values which use the full UTF-8 character set are never attribute values which use the full UTF-8 character set are never
directly compared, hence there is no requirement for UTF-8 directly compared, hence there is no requirement for UTF-8
normalization. The textual form, as opposed to a binary encoding normalization. The textual form, as opposed to a binary encoding
such as ASN.1 or XDR, was chosen to enhance portability, to enable a such as ASN.1 or XDR, was chosen to enhance portability, to enable a
variety of transports to be used (e.g, session description in a MIME variety of transports to be used (e.g, session description in a MIME
email message) and to allow flexible, text-based toolkits (e.g., Tcl/ email message) and to allow flexible, text-based toolkits (e.g., Tcl/
Tk) to be used to generate and to process session descriptions. Tk) to be used to generate and to process session descriptions.
However, since SDP may be used in environments where the maximum However, since SDP may be used in environments where the maximum
permissable size of a session description is limited (e.g. SAP permissable size of a session description is limited (e.g. SAP
announcements; SIP transported in UDP), the encoding is deliberately announcements), the encoding is deliberately compact. Also, since
compact. Also, since announcements may be transported via very announcements may be transported via very unreliable means or damaged
unreliable means or damaged by an intermediate caching server, the by an intermediate caching server, the encoding was designed with
encoding was designed with strict order and formatting rules so that strict order and formatting rules so that most errors would result in
most errors would result in malformed announcements which could be malformed session announcements which could be detected easily and
detected easily and discarded. This also allows rapid discarding of discarded. This also allows rapid discarding of encrypted session
encrypted announcements for which a receiver does not have the announcements for which a receiver does not have the correct key.
correct key.
An SDP session description may contain URIs which reference external
content in the "u=", "k=" and "a=" lines. These URIs may be
dereferenced in some cases, making the session description non-self
contained.
An SDP session description consists of a number of lines of text of An SDP session description consists of a number of lines of text of
the form: the form:
<type>=<value> <type>=<value>
where <type> MUST be exactly one case-significant character and where <type> MUST be exactly one case-significant character and
<value> is structured text whose format depends on <type>. In <value> is structured text whose format depends on <type>. In
general <value> is either a number of fields delimited by a single general <value> is either a number of fields delimited by a single
space character, or a free format string. Whitespace MUST NOT be used space character, or a free format string. Whitespace MUST NOT be used
either side of the "=" sign. either side of the "=" sign.
A session description consists of a session-level section followed by An SDP session description consists of a session-level section
zero or more media-level sections. The session-level part starts followed by zero or more media-level sections. The session-level
with a "v=" line and continues to the first media-level section. The part starts with a "v=" line and continues to the first media-level
media description starts with an "m=" line and continues to the next section. The media description starts with an "m=" line and
media description or end of the whole session description. In continues to the next media description or end of the whole session
general, session-level values are the default for all media unless description. In general, session-level values are the default for
overridden by an equivalent media-level value. all media unless overridden by an equivalent media-level value.
Some lines in each description are REQUIRED and some are OPTIONAL but Some lines in each description are REQUIRED and some are OPTIONAL but
all MUST appear in exactly the order given here (the fixed order all MUST appear in exactly the order given here (the fixed order
greatly enhances error detection and allows for a simple parser). greatly enhances error detection and allows for a simple parser).
OPTIONAL items are marked with a "*". OPTIONAL items are marked with a "*".
Session description Session description
v= (protocol version) v= (protocol version)
o= (owner/creator and session identifier). o= (owner/creator and session identifier).
s= (session name) s= (session name)
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Media description Media description
m= (media name and transport address) m= (media name and transport address)
i=* (media title) i=* (media title)
c=* (connection information - optional if included at c=* (connection information - optional if included at
session-level) session-level)
b=* (zero or more bandwidth information lines) b=* (zero or more bandwidth information lines)
k=* (encryption key) k=* (encryption key)
a=* (zero or more media attribute lines) a=* (zero or more media attribute lines)
The set of type letters is deliberately small and not intended to be The set of type letters is deliberately small and not intended to be
extensible -- an SDP parser MUST completely ignore any announcement extensible -- an SDP parser MUST completely ignore any session
that contains a type letter that it does not understand. The description that contains a type letter that it does not understand.
attribute mechanism ("a=" described below) is the primary means for The attribute mechanism ("a=" described below) is the primary means
extending SDP and tailoring it to particular applications or media. for extending SDP and tailoring it to particular applications or
Some attributes (the ones listed in this document) have a defined media. Some attributes (the ones listed in Section 6 of this memo)
meaning but others may be added on an application-, media- or have a defined meaning, but others may be added on an application-,
session-specific basis. An SDP parser MUST ignore any attribute it media- or session-specific basis. An SDP parser MUST ignore any
doesn't understand. attribute it doesn't understand.
An SDP session description may contain URIs which reference external
content in the "u=", "k=" and "a=" lines. These URIs may be
dereferenced in some cases, making the session description non-self
contained.
The connection ("c=") and attribute ("a=") information in the The connection ("c=") and attribute ("a=") information in the
session-level section applies to all the media of that session unless session-level section applies to all the media of that session unless
overridden by connection information or an attribute of the same name overridden by connection information or an attribute of the same name
in the media description. For instance, in the example below, each in the media description. For instance, in the example below, each
media behaves as if it were given a "recvonly" attribute. media behaves as if it were given a "recvonly" attribute.
An example SDP description is: An example SDP description is:
v=0 v=0
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u=http://www.example.com/seminars/sdp.pdf u=http://www.example.com/seminars/sdp.pdf
e=j.doe@example.com (Jane Doe) e=j.doe@example.com (Jane Doe)
c=IN IP4 224.2.17.12/127 c=IN IP4 224.2.17.12/127
t=2873397496 2873404696 t=2873397496 2873404696
a=recvonly a=recvonly
m=audio 49170 RTP/AVP 0 m=audio 49170 RTP/AVP 0
m=video 51372 RTP/AVP 31 m=video 51372 RTP/AVP 31
m=application 32416 udp wb m=application 32416 udp wb
a=orient:portrait a=orient:portrait
Text records such as the session name and information are octet Text fields such as the session name and information are octet
strings which may contain any octet with the exceptions of 0x00 strings which may contain any octet with the exceptions of 0x00
(Nul), 0x0a (ASCII newline) and 0x0d (ASCII carriage return). The (Nul), 0x0a (ASCII newline) and 0x0d (ASCII carriage return). The
sequence CRLF (0x0d0a) is used to end a record, although parsers sequence CRLF (0x0d0a) is used to end a record, although parsers
SHOULD be tolerant and also accept records terminated with a single SHOULD be tolerant and also accept records terminated with a single
newline character. By default these byte strings contain ISO-10646 newline character. If the "a=charset" attribute is not present,
characters in UTF-8 encoding, but this default MAY be changed using these octet strings MUST be interpreted as containing ISO-10646
the "charset" attribute. characters in UTF-8 encoding (the presence of the "a=charset"
attribute MAY force some fields to be interpreted differently).
5.1 Protocol Version ("v=") 5.1 Protocol Version ("v=")
v=0 v=0
The "v=" field gives the version of the Session Description Protocol. The "v=" field gives the version of the Session Description Protocol.
There is no minor version number. This memo defines version 0. There is no minor version number.
5.2 Origin ("o=") 5.2 Origin ("o=")
o=<username> <session id> <version> <network type> <address type> o=<username> <sess-id> <sess-version> <nettype> <addrtype>
<address> <unicast-address>
The "o=" field gives the originator of the session (her username and The "o=" field gives the originator of the session (her username and
the address of the user's host) plus a session id and session version the address of the user's host) plus a session identifier and version
number. number:
<username> is the user's login on the originating host, or it is "-" <username> is the user's login on the originating host, or it is "-"
if the originating host does not support the concept of user ids. if the originating host does not support the concept of user ids.
<username> MUST NOT contain spaces. The <username> MUST NOT contain spaces.
<sess-id> is a numeric string such that the tuple of <username>,
<session id> is a numeric string such that the tuple of <username>, <sess-id>, <nettype>, <addrtype> and <unicast-address> form a
<session id>, <network type>, <address type> and <address> form a globally unique identifier for the session. The method of
globally unique identifier for the session. The method of session <sess-id> allocation is up to the creating tool, but it has been
id allocation is up to the creating tool, but it has been
suggested that a Network Time Protocol (NTP) format timestamp be suggested that a Network Time Protocol (NTP) format timestamp be
used to ensure uniqueness [7]. used to ensure uniqueness [7].
<sess-version> is a version number for this session description. Its
<version> is a version number for this announcement. It is needed for usage is up to the creating tool, so long as <sess-version> is
proxy announcements to detect which of several announcements for increased when a modification is made to the session data. Again,
the same session is the most recent. Again its usage is up to the it is RECOMMENDED that an NTP format timestamp is used.
creating tool, so long as <version> is increased when a <nettype> is a text string giving the type of network. Initially "IN"
modification is made to the session data. Again, it is RECOMMENDED is defined to have the meaning "Internet", but other values MAY be
(but not mandatory) that an NTP format timestamp is used. registered in future (see Section 9).
<addrtype> is a text string giving the type of the address that
<network type> is a text string giving the type of network. follows. Initially "IP4" and "IP6" are defined, but other values
Initially "IN" is defined to have the meaning "Internet". MAY be registered in future (see Section 9).
<unicast-address> is the address of the machine from which the
<address type> is a text string giving the type of the address that session was created. For an address type of IP4, this is either
follows. Initially "IP4" and "IP6" are defined. the fully-qualified domain name of the machine, or the
<address> is the globally unique address of the machine from which
the session was created. For an address type of IP4, this is
either the fully-qualified domain name of the machine, or the
dotted-decimal representation of the IP version 4 address of the dotted-decimal representation of the IP version 4 address of the
machine. For an address type of IP6, this is either the machine. For an address type of IP6, this is either the
fully-qualified domain name of the machine, or the compressed fully-qualified domain name of the machine, or the compressed
textual representation of the IP version 6 address of the machine. textual representation of the IP version 6 address of the machine.
For both IP4 and IP6, the fully-qualified domain name is the form For both IP4 and IP6, the fully-qualified domain name is the form
that SHOULD be given unless this is unavailable, in which case the that SHOULD be given unless this is unavailable, in which case the
globally unique address may be substituted. A local IP address globally unique address MAY be substituted. A local IP address
MUST NOT be used in any context where the SDP description might MUST NOT be used in any context where the SDP description might
leave the scope in which the address is meaningful. leave the scope in which the address is meaningful.
In general, the "o=" field serves as a globally unique identifier for In general, the "o=" field serves as a globally unique identifier for
this version of this session description, and the subfields excepting this version of this session description, and the subfields excepting
the version taken together identify the session irrespective of any the version taken together identify the session irrespective of any
modifications. modifications.
5.3 Session Name ("s=") 5.3 Session Name ("s=")
s=<session name> s=<session name>
The "s=" field is the session name. There MUST be one and only one The "s=" field is the textual session name. There MUST be one and
"s=" field per session description. The "s=" field MUST NOT be empty only one "s=" field per session description. The "s=" field MUST NOT
and SHOULD contain ISO 10646 characters (but see also the "a=charset" be empty and SHOULD contain ISO 10646 characters (but see also the
attribute). If a session has no meaningful name, the value "s= " "a=charset" attribute). If a session has no meaningful name, the
SHOULD be used (i.e. a single space as the session name). value "s= " SHOULD be used (i.e. a single space as the session name).
5.4 Session and Media Information ("i=") 5.4 Session Information ("i=")
i=<session description> i=<session description>
The "i=" field is information about the session. There may be at The "i=" field provides textual information about the session. There
most one session-level "i=" field per session description, and at may be at most one session-level "i=" field per session description,
most one "i=" field per media. Although it may be omitted, this is and at most one "i=" field per media. If the "a=charset" attribute is
NOT RECOMMENDED for session announcements, and user interfaces for present, it specifies the character set used in the "i=" field. If
composing sessions should require text to be entered. If it is the "a=charset" attribute is not present, the "i=" field MUST contain
present it must contain ISO 10646 characters (but see also the ISO 10646 characters in UTF-8 encoding.
"a=charset" attribute below).
A single "i=" field can also be used for each media definition. In A single "i=" field MAY also be used for each media definition. In
media definitions, "i=" fields are primarily intended for labeling media definitions, "i=" fields are primarily intended for labeling
media streams. As such, they are most likely to be useful when a media streams. As such, they are most likely to be useful when a
single session has more than one distinct media stream of the same single session has more than one distinct media stream of the same
media type. An example would be two different whiteboards, one for media type. An example would be two different whiteboards, one for
slides and one for feedback and questions. slides and one for feedback and questions.
5.5 URI ("u=") 5.5 URI ("u=")
u=<URI> u=<uri>
A URI is a Universal Resource Identifier as used by WWW clients [4]. A URI is a Universal Resource Identifier as used by WWW clients [4].
The URI should be a pointer to additional information about the The URI should be a pointer to additional information about the
conference. This field is OPTIONAL, but if it is present it MUST be conference. This field is OPTIONAL, but if it is present it MUST be
specified before the first media field. No more than one URI field is specified before the first media field. No more than one URI field is
allowed per session description. allowed per session description.
5.6 Email Address and Phone Number ("e=" and "p=") 5.6 Email Address and Phone Number ("e=" and "p=")
e=<email address> e=<email-address>
p=<phone number> p=<phone-number>
These specify contact information for the person responsible for the The "e=" and "p=" lines specify contact information for the person
conference. This is not necessarily the same person that created the responsible for the conference. This is not necessarily the same
conference announcement. person that created the conference announcement.
Inclusion of an email address or phone number is OPTIONAL. Note that Inclusion of an email address or phone number is OPTIONAL. Note that
the previous version of SDP specified that either an email field or a the previous version of SDP specified that either an email field or a
phone field MUST be specified, but this was widely ignored. The phone field MUST be specified, but this was widely ignored. The
change brings the specification into line with common usage. change brings the specification into line with common usage.
If the email addres or phone number are present, they MUST be If the email addres or phone number are present, they MUST be
specified before the first media field. More than one email or phone specified before the first media field. More than one email or phone
field can be given for a session description. field can be given for a session description.
Phone numbers SHOULD be given in the conventional international Phone numbers SHOULD be given in the form of an international public
format: preceded by a "+" and the international country code. There telecommunication number (see ITU-T Recommendation E.164) preceded by
must be a space or a hyphen ("-") between the country code and the a "+". Spaces and hyphens may be used to split up a phone field to
rest of the phone number. Spaces and hyphens may be used to split up aid readability if desired. For example:
a phone field to aid readability if desired. For example:
p=+44-171-380-7777 or p=+1 617 555 6011 p=+44-171-380-7777 or p=+1 617 555 6011
Both email addresses and phone numbers can have an optional free text
Both email addresses and phone numbers can have an OPTIONAL free text
string associated with them, normally giving the name of the person string associated with them, normally giving the name of the person
who may be contacted. This should be enclosed in parenthesis if it who may be contacted. This MUST be enclosed in parenthesis if it is
is present. For example: present. For example:
e=j.doe@example.com (Jane Doe) e=j.doe@example.com (Jane Doe)
The alternative RFC822 name quoting convention is also allowed for The alternative RFC 2822 name quoting convention is also allowed for
both email addresses and phone numbers. For example: both email addresses and phone numbers. For example:
e=Jane Doe <j.doe@example.com> e=Jane Doe <j.doe@example.com>
The free text string SHOULD be in the ISO-10646 character set with The free text string SHOULD be in the ISO-10646 character set with
UTF-8 encoding, or alternatively in ISO-8859-1 or other encodings if UTF-8 encoding, or alternatively in ISO-8859-1 or other encodings if
the appropriate charset session-level attribute is set. the appropriate session-level "a=charset" attribute is set.
5.7 Connection Data ("c=") 5.7 Connection Data ("c=")
c=<network type> <address type> <connection address> c=<nettype> <addrtype> <connection-address>
The "c=" field contains connection data. The "c=" field contains connection data.
A session announcement MUST contain either at least one "c=" field in A session description MUST contain either at least one "c=" field in
each media description (see below) or a single "c=" field at the each media description or a single "c=" field at the session level.
session-level. It MAY contain a single session-level "c=" field and It MAY contain a single session-level "c=" field and additional "c="
additional "c=" field(s) per media description, in which case the field(s) per media description, in which case the per-media values
per-media values override the session-level settings for the override the session-level settings for the respective media.
respective media.
The first sub-field is the network type, which is a text string The first sub-field ("<nettype>") is the network type, which is a
giving the type of network. Initially "IN" is defined to have the text string giving the type of network. Initially "IN" is defined to
meaning "Internet". have the meaning "Internet", but other values MAY be registered in
the future (see Section 9).
The second sub-field is the address type. This allows SDP to be used The second sub-field ("<addrtype>") is the address type. This allows
for sessions that are not IP based. Currently only IP4 and IP6 are SDP to be used for sessions that are not IP based. Currently only IP4
defined. and IP6 are defined, but other values MAY be registered in the future
(see Section 9).
The third sub-field is the connection address. Optional extra The third sub-field ("<connection-address>") is the connection
sub-fields MAY be added after the connection address depending on the address. OPTIONAL sub-fields MAY be added after the connection
value of the <address type> field. address depending on the value of the <addrtype> field.
For IP4 and IP6 addresses, the connection address is defined as When the <addrtype> is IP4 and IP6, the connection address is defined
follows: as follows:
o If the session is multicast, the connection address will be an IP o If the session is multicast, the connection address will be an IP
multicast group address. If the session is not multicast, then multicast group address. If the session is not multicast, then
the connection address contains the unicast IP address of the the connection address contains the unicast IP address of the
expected data source or data relay or data sink as determined by expected data source or data relay or data sink as determined by
additional attribute fields. It is not expected that unicast additional attribute fields. It is not expected that unicast
addresses will be given in a session description that is addresses will be given in a session description that is
communicated by a multicast announcement, though this is not communicated by a multicast announcement, though this is not
prohibited. prohibited.
o Conferences using an IPv4 multicast connection address MUST also o Conferences using an IPv4 multicast connection address MUST also
have a time to live (TTL) value present in addition to the have a time to live (TTL) value present in addition to the
multicast address. The TTL and the address together define the multicast address. The TTL and the address together define the
scope with which multicast packets sent in this conference will be scope with which multicast packets sent in this conference will be
sent. TTL values MUST be in the range 0-255. sent. TTL values MUST be in the range 0-255.
The TTL for the session is appended to the address using a slash as a The TTL for the session is appended to the address using a slash as a
separator. An example is: separator. An example is:
c=IN IP4 224.2.36.42/127 c=IN IP4 224.2.36.42/127
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only subscribing to a subset of these layers. Such layered encodings only subscribing to a subset of these layers. Such layered encodings
are normally transmitted in multiple multicast groups to allow are normally transmitted in multiple multicast groups to allow
multicast pruning. This technique keeps unwanted traffic from sites multicast pruning. This technique keeps unwanted traffic from sites
only requiring certain levels of the hierarchy. For applications only requiring certain levels of the hierarchy. For applications
requiring multiple multicast groups, we allow the following notation requiring multiple multicast groups, we allow the following notation
to be used for the connection address: to be used for the connection address:
<base multicast address>[/<ttl>]/<number of addresses> <base multicast address>[/<ttl>]/<number of addresses>
If the number of addresses is not given it is assumed to be one. If the number of addresses is not given it is assumed to be one.
Multicast addresses so assigned are contiguously allocated above the Multicast addresses so assigned are contiguously allocated above the
base address, so that, for example: base address, so that, for example:
c=IN IP4 224.2.1.1/127/3 c=IN IP4 224.2.1.1/127/3
would state that addresses 224.2.1.1, 224.2.1.2 and 224.2.1.3 are to would state that addresses 224.2.1.1, 224.2.1.2 and 224.2.1.3 are to
be used at a ttl of 127. This is semantically identical to including be used at a TTL of 127. This is semantically identical to including
multiple "c=" lines in a media description: multiple "c=" lines in a media description:
c=IN IP4 224.2.1.1/127 c=IN IP4 224.2.1.1/127
c=IN IP4 224.2.1.2/127 c=IN IP4 224.2.1.2/127
c=IN IP4 224.2.1.3/127 c=IN IP4 224.2.1.3/127
Similarly, an IPv6 example would be: Similarly, an IPv6 example would be:
c=IN IP6 FF15::101/3 c=IN IP6 FF15::101/3
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Multiple addresses or "c=" lines MAY be specified on a per-media Multiple addresses or "c=" lines MAY be specified on a per-media
basis only if they provide multicast addresses for different layers basis only if they provide multicast addresses for different layers
in a hierarchical or layered encoding scheme. They MUST NOT be in a hierarchical or layered encoding scheme. They MUST NOT be
specified for a session-level "c=" field. specified for a session-level "c=" field.
The slash notation described above MUST NOT be used for IP unicast The slash notation described above MUST NOT be used for IP unicast
addresses. addresses.
5.8 Bandwidth ("b=") 5.8 Bandwidth ("b=")
b=<modifier>:<bandwidth-value> b=<bwtype>:<bandwidth>
This specifies the proposed bandwidth to be used by the session or
media, and is OPTIONAL.
The <bandwidth-value> is in kilobits per second by default. Modifiers
MAY specify that alternative units are to be used (the modifiers
defined in this memo use the default units).
The <modifier> is a single alphanumeric word giving the meaning of This OPTIONAL field denotes the proposed bandwidth to be used by the
the bandwidth figure. Two modifiers are initially defined: session or media. The <bwtype> is an alphanumeric modifier giving
the meaning of the <bandwidth> figure. Two values are initially
defined, but other values MAY be registered in future (see Section
9):
CT If the bandwidth of a session or media in a session is different CT If the bandwidth of a session or media in a session is different
from the bandwidth implicit from the scope, a "b=CT:..." line from the bandwidth implicit from the scope, a "b=CT:..." line
should be supplied for the session giving the proposed upper limit SHOULD be supplied for the session giving the proposed upper limit
to the bandwidth used. The primary purpose of this is to give an to the bandwidth used. The primary purpose of this is to give an
approximate idea as to whether two or more sessions can co-exist approximate idea as to whether two or more sessions can co-exist
simultaneously. When using the CT modifier with RTP, if several simultaneously. When using the CT modifier with RTP, if several
RTP sessions are part of the conference, the conference total RTP sessions are part of the conference, the conference total
refers to total bandwidth of all RTP sessions. refers to total bandwidth of all RTP sessions.
AS The bandwidth is interpreted to be application-specific (it will AS The bandwidth is interpreted to be application-specific (it will
be the application's concept of maximum bandwidth). Normally this be the application's concept of maximum bandwidth). Normally this
will coincide with what is set on the application's "maximum will coincide with what is set on the application's "maximum
bandwidth" control if applicable. For RTP based applications, AS bandwidth" control if applicable. For RTP based applications, AS
gives the RTP "session bandwidth" as defined in section 6.2 of gives the RTP "session bandwidth" as defined in section 6.2 of
[12]. [12].
Note that CT gives a total bandwidth figure for all the media at all Note that CT gives a total bandwidth figure for all the media at all
sites. AS gives a bandwidth figure for a single media at a single sites. AS gives a bandwidth figure for a single media at a single
site, although there may be many sites sending simultaneously. site, although there may be many sites sending simultaneously.
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be the application's concept of maximum bandwidth). Normally this be the application's concept of maximum bandwidth). Normally this
will coincide with what is set on the application's "maximum will coincide with what is set on the application's "maximum
bandwidth" control if applicable. For RTP based applications, AS bandwidth" control if applicable. For RTP based applications, AS
gives the RTP "session bandwidth" as defined in section 6.2 of gives the RTP "session bandwidth" as defined in section 6.2 of
[12]. [12].
Note that CT gives a total bandwidth figure for all the media at all Note that CT gives a total bandwidth figure for all the media at all
sites. AS gives a bandwidth figure for a single media at a single sites. AS gives a bandwidth figure for a single media at a single
site, although there may be many sites sending simultaneously. site, although there may be many sites sending simultaneously.
Tool writers MAY define experimental bandwidth modifiers by prefixing A prefix "X-" is defined for <bwtype> names. This is intended for
their modifier with "X-". For example: experimental purposes only. For example:
b=X-YZ:128 b=X-YZ:128
Use of the "X-" prefix is NOT RECOMMENDED: instead new modifiers Use of the "X-" prefix is NOT RECOMMENDED: instead new modifiers
SHOULD be registered with IANA in the standard namespace. SDP parsers SHOULD be registered with IANA in the standard namespace. SDP parsers
MUST ignore bandwidth fields with unknown modifiers. Modifiers MUST MUST ignore bandwidth fields with unknown modifiers. Modifiers MUST
be alpha-numeric and, although no length limit is given, they are be alpha-numeric and, although no length limit is given, they are
recommended to be short. recommended to be short.
The <bandwidth> is in kilobits per second by default. Modifiers MAY
specify that alternative units are to be used (the modifiers defined
in this memo use the default units).
5.9 Timing ("t=") 5.9 Timing ("t=")
t=<start time> <stop time> t=<start-time> <stop-time>
"t=" fields specify the start and stop times for a session. Multiple The "t=" lines specify the start and stop times for a session.
"t=" fields MAY be used if a session is active at multiple Multiple "t=" lines MAY be used if a session is active at multiple
irregularly spaced times; each additional "t=" field specifies an irregularly spaced times; each additional "t=" lines specifies an
additional period of time for which the session will be active. If additional period of time for which the session will be active. If
the session is active at regular times, an "r=" field (see below) the session is active at regular times, an "r=" line (see below)
should be used in addition to and following a "t=" field - in which should be used in addition to, and following, a "t=" line - in which
case the "t=" field specifies the start and stop times of the repeat case the "t=" line specifies the start and stop times of the repeat
sequence. sequence.
The first and second sub-fields give the start and stop times for the The first and second sub-fields give the start and stop times for the
session respectively. These values are the decimal representation of session respectively. These values are the decimal representation of
Network Time Protocol (NTP) time values in seconds [7]. To convert Network Time Protocol (NTP) time values in seconds [7]. To convert
these values to UNIX time, subtract decimal 2208988800. these values to UNIX time, subtract decimal 2208988800.
NTP timestamps are 64 bit values which wrap sometime in the year NTP timestamps are 64 bit values which wrap sometime in the year
2036. Since SDP uses an arbitrary length decimal representation, 2036. Since SDP uses an arbitrary length decimal representation,
this should not cause an issue (SDP timestamps will continue counting this should not cause an issue (SDP timestamps will continue counting
seconds since 1900, NTP will use the value modulo the 64 bit limit). seconds since 1900, NTP will use the value modulo the 64 bit limit).
If the stop-time is set to zero, then the session is not bounded, If the <stop-time> is set to zero, then the session is not bounded,
though it will not become active until after the start-time. If the though it will not become active until after the <start-time>. If
start-time is also zero, the session is regarded as permanent. the <start-time> is also zero, the session is regarded as permanent.
User interfaces SHOULD strongly discourage the creation of unbounded User interfaces SHOULD strongly discourage the creation of unbounded
and permanent sessions as they give no information about when the and permanent sessions as they give no information about when the
session is actually going to terminate, and so make scheduling session is actually going to terminate, and so make scheduling
difficult. difficult.
The general assumption may be made, when displaying unbounded The general assumption may be made, when displaying unbounded
sessions that have not timed out to the user, that an unbounded sessions that have not timed out to the user, that an unbounded
session will only be active until half an hour from the current time session will only be active until half an hour from the current time
or the session start time, whichever is the later. If behaviour or the session start time, whichever is the later. If behaviour
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Permanent sessions may be shown to the user as never being active Permanent sessions may be shown to the user as never being active
unless there are associated repeat times which state precisely when unless there are associated repeat times which state precisely when
the session will be active. In general, permanent sessions SHOULD the session will be active. In general, permanent sessions SHOULD
NOT be created for any session expected to have a duration of less NOT be created for any session expected to have a duration of less
than 2 months, and should be discouraged for sessions expected to than 2 months, and should be discouraged for sessions expected to
have a duration of less than 6 months. have a duration of less than 6 months.
5.10 Repeat Times ("r=") 5.10 Repeat Times ("r=")
r=<repeat interval> <active duration> <offsets from start-time> r=<repeat-interval> <active duration> <offsets from start-time>
"r=" fields specify repeat times for a session. For example, if a "r=" fields specify repeat times for a session. For example, if a
session is active at 10am on Monday and 11am on Tuesday for one hour session is active at 10am on Monday and 11am on Tuesday for one hour
each week for three months, then the <start time> in the each week for three months, then the <start-time> in the
corresponding "t=" field would be the NTP representation of 10am on corresponding "t=" field would be the NTP representation of 10am on
the first Monday, the <repeat interval> would be 1 week, the <active the first Monday, the <repeat interval> would be 1 week, the <active
duration> would be 1 hour, and the offsets would be zero and 25 duration> would be 1 hour, and the offsets would be zero and 25
hours. The corresponding "t=" field stop time would be the NTP hours. The corresponding "t=" field stop time would be the NTP
representation of the end of the last session three months later. By representation of the end of the last session three months later. By
default all fields are in seconds, so the "r=" and "t=" fields might default all fields are in seconds, so the "r=" and "t=" fields might
be: be:
t=3034423619 3042462419 t=3034423619 3042462419
r=604800 3600 0 90000 r=604800 3600 0 90000
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days, hours or minutes. The syntax for these is a number immediately days, hours or minutes. The syntax for these is a number immediately
followed by a single case-sensitive character. Fractional units are followed by a single case-sensitive character. Fractional units are
not allowed - a smaller unit should be used instead. The following not allowed - a smaller unit should be used instead. The following
unit specification characters are allowed: unit specification characters are allowed:
d - days (86400 seconds) d - days (86400 seconds)
h - hours (3600 seconds) h - hours (3600 seconds)
m - minutes (60 seconds) m - minutes (60 seconds)
s - seconds (allowed for completeness but not recommended) s - seconds (allowed for completeness but not recommended)
Thus, the above announcement could also have been written: Thus, the above session announcement could also have been written:
r=7d 1h 0 25h r=7d 1h 0 25h
Monthly and yearly repeats cannot be directly specified with a single Monthly and yearly repeats cannot be directly specified with a single
SDP repeat time - instead separate "t=" fields should be used to SDP repeat time - instead separate "t=" fields should be used to
explicitly list the session times. explicitly list the session times.
5.11 Time Zones ("z=") 5.11 Time Zones ("z=")
z=<adjustment time> <offset> <adjustment time> <offset> .... z=<adjustment time> <offset> <adjustment time> <offset> ....
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This specifies that at time 2882844526 the time base by which the This specifies that at time 2882844526 the time base by which the
session's repeat times are calculated is shifted back by 1 hour, and session's repeat times are calculated is shifted back by 1 hour, and
that at time 2898848070 the session's original time base is restored. that at time 2898848070 the session's original time base is restored.
Adjustments are always relative to the specified start time - they Adjustments are always relative to the specified start time - they
are not cumulative. Adjustments apply to all "t=" and "r=" lines in are not cumulative. Adjustments apply to all "t=" and "r=" lines in
a session description. a session description.
If a session is likely to last several years, it is expected that the If a session is likely to last several years, it is expected that the
session announcement will be modified periodically rather than session announcement will be modified periodically rather than
transmit several years worth of adjustments in one announcement. transmit several years worth of adjustments in one session
announcement.
5.12 Encryption Keys ("k=") 5.12 Encryption Keys ("k=")
k=<method> k=<method>
k=<method>:<encryption key> k=<method>:<encryption key>
If transported over a secure and trusted channel, the session If transported over a secure and trusted channel, the session
description protocol MAY be used to convey encryption keys. A simple description protocol MAY be used to convey encryption keys. A simple
mechanism for key exchange is provided by the key field ("k=") mechanism for key exchange is provided by the key field ("k=")
although this is primarily supported for compatibility with older although this is primarily supported for compatibility with older
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attribute conveys that the attribute is a property of attribute conveys that the attribute is a property of
the session. An example might be "a=recvonly". the session. An example might be "a=recvonly".
o value attributes: o value attributes:
A value attribute is of the form "a=<attribute>:<value>". A value attribute is of the form "a=<attribute>:<value>".
For example, a whiteboard could have the value attribute For example, a whiteboard could have the value attribute
"a=orient:landscape" "a=orient:landscape"
Attribute interpretation depends on the media tool being invoked. Attribute interpretation depends on the media tool being invoked.
Thus receivers of session descriptions should be configurable in Thus receivers of session descriptions should be configurable in
their interpretation of announcements in general and of attributes in their interpretation of session descriptions in general and of
particular. attributes in particular.
Attribute names MUST be in the US-ASCII subset of ISO-10646/UTF-8. Attribute names MUST be in the US-ASCII subset of ISO-10646/UTF-8.
Attribute values are octet strings, and MAY use any octet value Attribute values are octet strings, and MAY use any octet value
except 0x00 (Nul), 0x0A (LF), and 0x0D (CR). By default, attribute except 0x00 (Nul), 0x0A (LF), and 0x0D (CR). By default, attribute
values are to be interpreted as in ISO-10646 character set with UTF-8 values are to be interpreted as in ISO-10646 character set with UTF-8
encoding. Unlike other text fields, attribute values are NOT encoding. Unlike other text fields, attribute values are NOT
normally affected by the "charset" attribute as this would make normally affected by the "charset" attribute as this would make
comparisons against known values problematic. However, when an comparisons against known values problematic. However, when an
attribute is defined, it can be defined to be charset-dependent, in attribute is defined, it can be defined to be charset-dependent, in
which case it's value should be interpreted in the session charset which case it's value should be interpreted in the session charset
rather than in ISO-10646. rather than in ISO-10646.
Attributes MUST be registered with IANA (see Section 9). If an Attributes MUST be registered with IANA (see Section 9). If an
attribute is received that is not understood, it MUST be ignored by attribute is received that is not understood, it MUST be ignored by
the receiver. the receiver.
5.14 Media Announcements ("m=") 5.14 Media Descriptions ("m=")
m=<media> <port> <transport> <fmt list> m=<media> <port> <proto> <fmt>
A session description may contain a number of media descriptions. A session description may contain a number of media descriptions.
Each media description starts with an "m=" field, and is terminated Each media description starts with an "m=" field, and is terminated
by either the next "m=" field or by the end of the session by either the next "m=" field or by the end of the session
description. A media field has several sub-fields. description. A media field has several sub-fields.
The first sub-field is the media type. Currently defined media are The first sub-field ("<media>") is the media type. Currently defined
"audio", "video", "application", "data" and "control", though this media are "audio", "video", "text", "application", "data" and
list may be extended in future. The difference between "application" "control", though this list may be extended in future. The
and "data" is that the former is a media flow such as whiteboard difference between "application" and "data" is that the former is a
information, and the latter is bulk-data transfer such as media flow such as whiteboard information, and the latter is
multicasting of program executables which will not typically be bulk-data transfer such as multicasting of program executables which
displayed to the user. "control" is used to specify an additional will not typically be displayed to the user. "control" is used to
conference control channel for the session. specify an additional conference control channel for the session.
The second sub-field is the transport port to which the media stream The second sub-field ("<port>") is the transport port to which the
is sent. The meaning of the transport port depends on the network media stream is sent. The meaning of the transport port depends on
being used as specified in the relevant "c=" field, and on the the network being used as specified in the relevant "c=" field, and
transport protocol defined in the third sub-field. Other ports used on the transport protocol defined in the third sub-field. Other
by the media application (such as the RTCP port [12]) MAY be derived ports used by the media application (such as the RTCP port [12]) MAY
algorithmically from the base media port or MAY be specified in a be derived algorithmically from the base media port or MAY be
separate attribute (e.g. "a=rtcp:" as defined in [14]). specified in a separate attribute (e.g. "a=rtcp:" as defined in
[14]).
For applications where hierarchically encoded streams are being sent For applications where hierarchically encoded streams are being sent
to a unicast address, it may be necessary to specify multiple to a unicast address, it may be necessary to specify multiple
transport ports. This is done using a similar notation to that used transport ports. This is done using a similar notation to that used
for IP multicast addresses in the "c=" field: for IP multicast addresses in the "c=" field:
m=<media> <port>/<number of ports> <transport> <fmt list> m=<media> <port>/<number of ports> <transport> <fmt list>
In such a case, the ports used depend on the transport protocol. For In such a case, the ports used depend on the transport protocol. For
RTP, the default is that only the even numbered ports are used for RTP, the default is that only the even numbered ports are used for
data with the corresponding one-higher odd ports used for the RTCP data with the corresponding one-higher odd ports used for the RTCP
belonging to the RTP session, and the <number of ports> denoting the belonging to the RTP session, and the <number of ports> denoting the
number of RTP sessions. For example: number of RTP sessions. For example:
m=video 49170/2 RTP/AVP 31 m=video 49170/2 RTP/AVP 31
would specify that ports 49170 and 49171 form one RTP/RTCP pair and would specify that ports 49170 and 49171 form one RTP/RTCP pair and
49172 and 49173 form the second RTP/RTCP pair. RTP/AVP is the 49172 and 49173 form the second RTP/RTCP pair. RTP/AVP is the
skipping to change at page 22, line 28 skipping to change at page 22, line 15
If multiple addresses are specified in the "c=" field and multiple If multiple addresses are specified in the "c=" field and multiple
ports are specified in the "m=" field, a one-to-one mapping from port ports are specified in the "m=" field, a one-to-one mapping from port
to the corresponding address is implied. For example: to the corresponding address is implied. For example:
c=IN IP4 224.2.1.1/127/2 c=IN IP4 224.2.1.1/127/2
m=video 49170/2 RTP/AVP 31 m=video 49170/2 RTP/AVP 31
would imply that address 224.2.1.1 is used with ports 49170 and would imply that address 224.2.1.1 is used with ports 49170 and
49171, and address 224.2.1.2 is used with ports 49172 and 49173. 49171, and address 224.2.1.2 is used with ports 49172 and 49173.
The third sub-field is the transport protocol. The transport The third sub-field ("<proto>") is the transport protocol. The
protocol values are dependent on the address-type field in the "c=" transport protocol values are dependent on the address type field in
fields. Thus a "c=" field of IP4 defines that the transport protocol the "c=" fields. Thus a "c=" field of IP4 defines that the transport
runs over IP4. For IP4, it is normally expected that most media protocol runs over IP4. For IP4, it is normally expected that most
traffic will be carried as RTP over UDP. The following transport media traffic will be carried as RTP over UDP. The following
protocols are defined, but may be extended through registration of transport protocols are defined, but may be extended through
new protocols with IANA (see Section 9): registration of new protocols with IANA (see Section 9):
RTP/AVP - the IETF's Realtime Transport Protocol using the RTP/AVP - the IETF's Realtime Transport Protocol using the
Audio/Video profile carried over UDP. Audio/Video profile carried over UDP.
udp - User Datagram Protocol udp - User Datagram Protocol
TCP - Transmission Control Protocol TCP - Transmission Control Protocol
If an application uses a single combined proprietary media format and If an application uses a single combined proprietary media format and
transport protocol over UDP, then simply specifying the transport transport protocol over UDP, then simply specifying the transport
protocol as udp and using the format field to distinguish the protocol as udp and using the format field to distinguish the
combined protocol is recommended. If a transport protocol is used combined protocol is recommended. If a transport protocol is used
skipping to change at page 23, line 18 skipping to change at page 22, line 52
the same - a historical example is vat PCM audio and RTP PCM audio. the same - a historical example is vat PCM audio and RTP PCM audio.
In addition, relays and monitoring tools that are In addition, relays and monitoring tools that are
transport-protocol-specific but format-independent are possible. transport-protocol-specific but format-independent are possible.
For RTP media streams operating under the RTP Audio/Video Profile For RTP media streams operating under the RTP Audio/Video Profile
[13], the protocol field is "RTP/AVP". Should other RTP profiles be [13], the protocol field is "RTP/AVP". Should other RTP profiles be
defined in the future, their profiles will be specified in the same defined in the future, their profiles will be specified in the same
way. For example, the protocol field "RTP/XYZ" would specify RTP way. For example, the protocol field "RTP/XYZ" would specify RTP
operating under a profile whose short name is "XYZ". operating under a profile whose short name is "XYZ".
The fourth and subsequent sub-fields are media formats. For audio The fourth and subsequent sub-fields ("<fmt>") are media formats.
and video, these SHOULD reference a MIME sub-type describing the
format under the "audio" and "video" top-level MIME types. For audio, text and video, these SHOULD reference a MIME sub-type
describing the format under the "audio", "text" and "video" top-level
MIME types.
When a list of payload formats is given, this implies that all of When a list of payload formats is given, this implies that all of
these formats may be used in the session, but the first of these these formats may be used in the session, but the first of these
formats SHOULD be used as the default format for the session. formats SHOULD be used as the default format for the session.
For media whose transport protocol is not RTP or UDP the format field For media whose transport protocol is not RTP or UDP the format field
is protocol specific. Such formats should be defined in an is protocol specific. Such formats should be defined in an
additional specification document. additional specification document.
For media whose transport protocol is RTP, SDP can be used to provide For media whose transport protocol is RTP, SDP can be used to provide
skipping to change at page 24, line 49 skipping to change at page 24, line 37
For more details on RTP audio and video formats, see [13]. For more details on RTP audio and video formats, see [13].
Predefined application formats for the UDP protocol with non-RTP Predefined application formats for the UDP protocol with non-RTP
media are as below: media are as below:
wb: LBL Whiteboard (transport: udp) wb: LBL Whiteboard (transport: udp)
nt: UCL Network Text Editor (transport: udp) nt: UCL Network Text Editor (transport: udp)
6. Suggested Attributes 6. Suggested Attributes
The following attributes are suggested. Since application writers The following attributes are defined. Since application writers may
may add new attributes as they are required, this list is not add new attributes as they are required, this list is not exhaustive.
exhaustive.
a=cat:<category> a=cat:<category>
This attribute gives the dot-separated hierarchical category This attribute gives the dot-separated hierarchical category
of the session. This is to enable a receiver to filter of the session. This is to enable a receiver to filter
unwanted sessions by category. It is a session-level unwanted sessions by category. It is a session-level
attribute, and is not dependent on charset. attribute, and is not dependent on charset.
a=keywds:<keywords> a=keywds:<keywords>
skipping to change at page 26, line 8 skipping to change at page 25, line 43
size. This attribute is probably only meaningful for audio size. This attribute is probably only meaningful for audio
data, but may be used with other media types if it makes data, but may be used with other media types if it makes
sense. It is a media attribute, and is not dependent on sense. It is a media attribute, and is not dependent on
charset. Note that this attribute was introduced after RFC charset. Note that this attribute was introduced after RFC
2327, and non updated implementations will ignore this 2327, and non updated implementations will ignore this
attribute. attribute.
a=rtpmap:<payload type> <encoding name>/<clock rate> a=rtpmap:<payload type> <encoding name>/<clock rate>
[/<encoding parameters>] [/<encoding parameters>]
See Section 5.14. This may be a session or media attribute. See Section 5.14. This may be a session or media attribute
and is not dependent on charset.
a=recvonly a=recvonly
This specifies that the tools should be started in receive This specifies that the tools should be started in receive
only mode where applicable. It can be either a session or only mode where applicable. It can be either a session or
media attribute, and is not dependent on charset. Note that media attribute, and is not dependent on charset. Note that
recvonly applies to the media only, not to any associated recvonly applies to the media only, not to any associated
control protocol (e.g. an RTP based system in recvonly mode control protocol (e.g. an RTP based system in recvonly mode
SHOULD still send RTCP packets). SHOULD still send RTCP packets).
skipping to change at page 27, line 37 skipping to change at page 27, line 28
safely avoid displaying this session description to users. safely avoid displaying this session description to users.
The type attribute is a session-level attribute, and is not The type attribute is a session-level attribute, and is not
dependent on charset. dependent on charset.
a=charset:<character set> a=charset:<character set>
This specifies the character set to be used to display the This specifies the character set to be used to display the
session name and information data. By default, the ISO-10646 session name and information data. By default, the ISO-10646
character set in UTF-8 encoding is used. If a more compact character set in UTF-8 encoding is used. If a more compact
representation is required, other character sets may be used representation is required, other character sets may be used.
such as ISO-8859-1 for Northern European languages. In For example, the ISO 8859-1 is specified with the following
particular, the ISO 8859-1 is specified with the following
SDP attribute: SDP attribute:
a=charset:ISO-8859-1 a=charset:ISO-8859-1
This is a session-level attribute; if this attribute is This is a session-level attribute and is not dependent on
present, it MUST be before the first media field. The charset charset. The charset specified MUST be one of those registered
specified MUST be one of those registered with IANA, such as with IANA, such as ISO-8859-1. The character set identifier is
ISO-8859-1. The character set identifier is a US-ASCII string a US-ASCII string and MUST be compared against the IANA
and MUST be compared against the IANA identifiers using a identifiers using a case insensitive comparison. If the
case- insensitive comparison. If the identifier is not identifier is not recognised or not supported, all strings that
recognised or not supported, all strings that are affected by are affected by it SHOULD be regarded as octet strings.
it SHOULD be regarded as octet strings.
Note that a character set specified MUST still prohibit the Note that a character set specified MUST still prohibit the
use of bytes 0x00 (Nul), 0x0A (LF) and 0x0d (CR). Character use of bytes 0x00 (Nul), 0x0A (LF) and 0x0d (CR). Character
sets requiring the use of these characters MUST define a sets requiring the use of these characters MUST define a
quoting mechanism that prevents these bytes appearing within quoting mechanism that prevents these bytes appearing within
text fields. text fields.
a=sdplang:<language tag> a=sdplang:<language tag>
This can be a session level attribute or a media level This can be a session level attribute or a media level
skipping to change at page 32, line 49 skipping to change at page 32, line 36
RFC XXXX RFC XXXX
Applications which use this media type: Applications which use this media type:
Voice over IP, video teleconferencing, streaming media, instant Voice over IP, video teleconferencing, streaming media, instant
messaging, etc. See also section 3 of RFC XXXX. messaging, etc. See also section 3 of RFC XXXX.
Additional information: Additional information:
Magic number(s): None. Magic number(s): None.
File extension(s): The extension ".sdp" is commonly used. File extension(s): The extension ".sdp" is commonly used.
Macintosh File Type Code(s): Macintosh File Type Code(s): "sdp "
Person & email address to contact for further information: Person & email address to contact for further information:
Colin Perkins <csp@csperkins.org> Colin Perkins <csp@csperkins.org>
IETF MMUSIC working group IETF MMUSIC working group
Intended usage: COMMON Intended usage: COMMON
Author/Change controller: Author/Change controller:
Authors of RFC XXXX Authors of RFC XXXX
IETF MMUSIC working group IETF MMUSIC working group
skipping to change at page 35, line 22 skipping to change at page 34, line 48
expected to see widespread use and interoperability, SHOULD be expected to see widespread use and interoperability, SHOULD be
documented with a standards-track RFC that specifies the attribute documented with a standards-track RFC that specifies the attribute
more precisely. more precisely.
Submitters of registrations should ensure that the specification is Submitters of registrations should ensure that the specification is
in the spirit of SDP attributes, most notably that the attribute is in the spirit of SDP attributes, most notably that the attribute is
platform independent in the sense that it makes no implicit platform independent in the sense that it makes no implicit
assumptions about operating systems and does not name specific pieces assumptions about operating systems and does not name specific pieces
of software in a manner that might inhibit interoperability. of software in a manner that might inhibit interoperability.
IANA is requested to register the following initial set of attribute
names ("att-field" values), with definitions as in Section 6 of this
memo (these definitions update those in RFC 2327):
Name | Session or Media level? | Dependent on charset?
----------+-------------------------+----------------------
cat | Session | No
keywds | Session | Yes
tool | Session | No
ptime | Media | No
maxptime | Media | No
rtpmap | Either | No
recvonly | Either | No
sendrecv | Either | No
sendonly | Either | No
inactive | Either | No
orient | Media | No
type | Session | No
charset | Session | No
sdplang | Either | No
lang | Either | No
framerate | Media | No
quality | Media | No
fmtp | Media | No
9.2.5 Bandwidth specifiers ("bwtype") 9.2.5 Bandwidth specifiers ("bwtype")
A proliferation of bandwidth specifiers is strongly discouraged. A proliferation of bandwidth specifiers is strongly discouraged.
New bandwidth specifiers ("bwtype" fields) MUST be registered with New bandwidth specifiers ("bwtype" fields) MUST be registered with
IANA. The submission MUST reference a standards-track RFC specifying IANA. The submission MUST reference a standards-track RFC specifying
the semantics of the bandwidth specifier precisely, and indicating the semantics of the bandwidth specifier precisely, and indicating
when it should be used, and why the existing registered bandwidth when it should be used, and why the existing registered bandwidth
specifiers do not suffice. specifiers do not suffice.
IANA is requested to register the bandwith specifiers "CT" and "AS"
with definitions as in Section 5.8 of this memo (these definitions
update those in RFC 2327).
9.2.6 Network types ("nettype") 9.2.6 Network types ("nettype")
New network types (the "nettype" field) may be registered with IANA New network types (the "nettype" field) may be registered with IANA
if SDP needs to be used in the context of non-Internet environments. if SDP needs to be used in the context of non-Internet environments.
Whilst these are not normally the preserve of IANA, there may be Whilst these are not normally the preserve of IANA, there may be
circumstances when an Internet application needs to interoperate with circumstances when an Internet application needs to interoperate with
a non- Internet application, such as when gatewaying an Internet a non- Internet application, such as when gatewaying an Internet
telephony call into the PSTN. The number of network types should be telephony call into the PSTN. The number of network types should be
small and should be rarely extended. A new network type cannot be small and should be rarely extended. A new network type cannot be
registered without registering at least one address type to be used registered without registering at least one address type to be used
with that network type. A new network type registration MUST with that network type. A new network type registration MUST
reference an RFC which gives details of the network type and address reference an RFC which gives details of the network type and address
type and specifies how and when they would be used. Such an RFC MAY type and specifies how and when they would be used. Such an RFC MAY
be Informational. be Informational.
IANA is requested to register the network type "IN" to represent the
Internet, with definition as in Sections 5.2 and 5.7 of this memo
(these definitions update those in RFC 2327).
9.2.7 Address types ("addrtype") 9.2.7 Address types ("addrtype")
New address types ("addrtype") may be registered with IANA. An New address types ("addrtype") may be registered with IANA. An
address type is only meaningful in the context of a network type, and address type is only meaningful in the context of a network type, and
any registration of an address type MUST specify a registered network any registration of an address type MUST specify a registered network
type, or be submitted along with a network type registration. A new type, or be submitted along with a network type registration. A new
address type registration MUST reference an RFC giving details of the address type registration MUST reference an RFC giving details of the
syntax of the address type. Such an RFC MAY be Informational. syntax of the address type. Such an RFC MAY be Informational.
Address types are not expected to be registered frequently. Address types are not expected to be registered frequently.
IANA is requested to register the address types "IP4" and "IP6" with
definitions as in Sections 5.2 and 5.7 of this memo (these
definitions update those in RFC 2327).
9.2.8 Registration Procedure 9.2.8 Registration Procedure
In the RFC documentation that registers SDP "media", "proto", "fmt", In the RFC documentation that registers SDP "media", "proto", "fmt",
"bwtype", "nettype" and "addrtype" fields, the authors MUST include "bwtype", "nettype" and "addrtype" fields, the authors MUST include
the following information for IANA to place in the appropriate the following information for IANA to place in the appropriate
registry: registry:
o contact name, email address and telephone number o contact name, email address and telephone number
o name being registered (as it will appear in SDP) o name being registered (as it will appear in SDP)
o long-form name in English o long-form name in English
o type of name ("media", "proto", "fmt", "bwtype", "nettype", or o type of name ("media", "proto", "fmt", "bwtype", "nettype", or
"addrtype") "addrtype")
o a one paragraph explanation of the purpose of the registered name. o a one paragraph explanation of the purpose of the registered name.
o a reference to the specification (e.g. RFC number) of the o a reference to the specification (e.g. RFC number) of the
registered name. registered name.
IANA may refer any registration to the IESG Transport Area Directors IANA may refer any registration to the IESG Transport Area Directors
for review, and may request revisions to be made before a for review, and may request revisions to be made before a
registration will be made. registration will be made.
9.3 Encryption Key Access Methods
The IANA currently maintains a table of SDP encryption key access
method ("enckey") names. This table is obsolete and SHOULD be
removed, since the "k=" line is not extensible. New registrations
MUST NOT be accepted.
Appendix A. SDP Grammar Appendix A. SDP Grammar
This appendix provides an Augmented BNF grammar for SDP. ABNF is This appendix provides an Augmented BNF grammar for SDP. ABNF is
defined in [2]. defined in [2].
; SDP Syntax ; SDP Syntax
announcement = proto-version session-description = proto-version
origin-field origin-field
session-name-field session-name-field
information-field information-field
uri-field uri-field
email-fields email-fields
phone-fields phone-fields
connection-field connection-field
bandwidth-fields bandwidth-fields
time-fields time-fields
key-field key-field
skipping to change at page 38, line 33 skipping to change at page 39, line 4
; sub-rules of 'u=' ; sub-rules of 'u='
uri = URI-reference; see RFC1630 and RFC2732 uri = URI-reference; see RFC1630 and RFC2732
; sub-rules of 'e=' ; sub-rules of 'e='
email-address = email *SP "(" 1*email-safe ")" / email-address = email *SP "(" 1*email-safe ")" /
1*email-safe "<" email ">" / 1*email-safe "<" email ">" /
email email
email = addr-spec ; defined in RFC2822 email = addr-spec ; defined in RFC2822
; modified to remove CFWS ; modified to remove CFWS
; sub-rules of 'p=' ; sub-rules of 'p='
phone-number = phone *SP "(" 1*email-safe ")" / phone-number = phone *SP "(" 1*email-safe ")" /
1*email-safe "<" phone ">" / 1*email-safe "<" phone ">" /
phone phone
phone = "+" POS-DIGIT 1*(SP / "-" / DIGIT) phone = "+" POS-DIGIT 1*(SP / "-" / DIGIT)
;there must be a space or hyphen between
;the international code and the rest of
;the number.
; sub-rules of 'c=' ; sub-rules of 'c='
connection-address = multicast-address / unicast-address connection-address = multicast-address / unicast-address
; sub-rules of 'b=' ; sub-rules of 'b='
bwtype = token bwtype = token
bandwidth = 1*DIGIT bandwidth = 1*DIGIT
; sub-rules of 't=' ; sub-rules of 't='
start-time = time / "0" start-time = time / "0"
stop-time = time / "0" stop-time = time / "0"
time = POS-DIGIT 9*DIGIT time = POS-DIGIT 9*DIGIT
; 10-digit NTP time represents times between ; 10-digit NTP time represents times between
; 1931 and 5068 AD. 9* allows times after ; 1931 and 5068 AD. 9* allows times after
; that as well. ; that as well.
skipping to change at page 39, line 37 skipping to change at page 40, line 4
base64 = *base64-unit [base64-pad] base64 = *base64-unit [base64-pad]
base64-unit = 4base64-char base64-unit = 4base64-char
base64-pad = 2base64-char "==" / 3base64-char "=" base64-pad = 2base64-char "==" / 3base64-char "="
base64-char = ALPHA / DIGIT / "+" / "/" base64-char = ALPHA / DIGIT / "+" / "/"
key-method = token key-method = token
; sub-rules of 'a=' ; sub-rules of 'a='
attribute = (att-field ":" att-value) / att-field attribute = (att-field ":" att-value) / att-field
att-field = token att-field = token
att-value = byte-string att-value = byte-string
; sub-rules of 'm=' ; sub-rules of 'm='
media = token media = token
;typically "audio", "video", "application" ;typically "audio", "video", "text",
;or "data" ;"application" or "data"
fmt = token fmt = token
;typically an RTP payload type for audio ;typically an RTP payload type for audio
;and video media ;and video media
proto = token "/" token proto = token "/" token
/ token / token
;typically "RTP/AVP" or "udp" for IP4 ;typically "RTP/AVP", "udp" or "tcp"
port = 1*DIGIT port = 1*DIGIT
;should be either "0" or in the range "1024" ;should be either "0" or in the range "1024"
;to "65535" inclusive for UDP based media ;to "65535" inclusive for UDP based media
;(a value of "0" is used to signal special ;(a value of "0" is used to signal special
;conditions in some uses of SDP) ;conditions in some uses of SDP)
; generic sub-rules: addressing ; generic sub-rules: addressing
unicast-address = IP4-address / IP6-address / FQDN / extn-addr unicast-address = IP4-address / IP6-address / FQDN / extn-addr
skipping to change at page 41, line 49 skipping to change at page 42, line 15
; ALPHA, DIGIT, CRLF, SP, VCHAR: from RFC 2234 ; ALPHA, DIGIT, CRLF, SP, VCHAR: from RFC 2234
; URI-reference: from RFC1630 and RFC2732 ; URI-reference: from RFC1630 and RFC2732
; addr-spec: from RFC 2822 ; addr-spec: from RFC 2822
Appendix B. Acknowledgments Appendix B. Acknowledgments
Many people in the IETF MMUSIC working group have made comments and Many people in the IETF MMUSIC working group have made comments and
suggestions contributing to this document. In particular, we would suggestions contributing to this document. In particular, we would
like to thank Eve Schooler, Steve Casner, Bill Fenner, Allison like to thank Eve Schooler, Steve Casner, Bill Fenner, Allison
Mankin, Ross Finlayson, Peter Parnes, Joerg Ott, Carsten Bormann, Mankin, Ross Finlayson, Peter Parnes, Joerg Ott, Carsten Bormann,
Steve Hanna and Jonathan Lennox. Steve Hanna, Jonathan Lennox and Keith Drage.
Normative References 10. References
10.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and P. Overell, "Augmented BNF for Syntax [2] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[3] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC [3] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC
2279, January 1998. 2279, January 1998.
[4] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource [4] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998. Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[6] Alvestrand, H., "Tags for the Identification of Languages", BCP [6] Alvestrand, H., "Tags for the Identification of Languages", BCP
47, RFC 3066, January 2001. 47, RFC 3066, January 2001.
Informative References 10.2 Informative References
[7] Mills, D., "Network Time Protocol (Version 3) Specification, [7] Mills, D., "Network Time Protocol (Version 3) Specification,
Implementation", RFC 1305, March 1992. Implementation", RFC 1305, March 1992.
[8] Handley, M., Perkins, C. and E. Whelan, "Session Announcement [8] Handley, M., Perkins, C. and E. Whelan, "Session Announcement
Protocol", RFC 2974, October 2000. Protocol", RFC 2974, October 2000.
[9] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., [9] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002. Session Initiation Protocol", RFC 3261, June 2002.
skipping to change at page 44, line 8 skipping to change at page 45, line 8
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