MMUSIC R. Gilman
Internet-Draft Avaya, Inc.
Intended status: Standards Track R. Even, Ed.
Expires: August 24, 2007 Polycom
F. Andreasen
Cisco Systems
February 20, 2007
SDP media capabilities Negotiation
draft-ietf-mmusic-sdp-media-capabilities-01.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 24, 2007.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Gilman, et al. Expires August 24, 2007 [Page 1]
Internet-Draft CMED February 2007
Abstract
Session Description Protocol (SDP) capability negotiation provides a
general framework for negotiating capabilities in SDP. The base
framework defines only capabilities for negotiating transport
protocols and attributes. In this document, we extend the framework
by defining media capabilities that can be used to negotiate media
types and their associated parameters.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. SDP Media capabilities . . . . . . . . . . . . . . . . . . . . 5
3.1. Solution Overview . . . . . . . . . . . . . . . . . . . . 5
3.2. Capability Attributes . . . . . . . . . . . . . . . . . . 8
3.2.1. Media Type and Subtype Capability Attribute . . . . . 8
3.2.2. The Capability Encoding Parameters Attribute . . . . . 9
3.2.3. The Media Format Parameter Capability Attribute . . . 10
3.3. Extensions to the Potential Configuration Attribute . . . 11
3.3.1. The Media Capability Extension to the Potential
Configuration Attribute . . . . . . . . . . . . . . . 11
3.3.2. The Payload Type Mapping Extension to the
Potential Configuration Attribute . . . . . . . . . . 12
3.4. Extensions to the Actual Configuration Attribute . . . . . 12
3.5. The Latent Configuration Attribute . . . . . . . . . . . . 13
3.5.1. The crypto: Attribute in Latent Configurations . . . . 14
3.6. Offer/Answer Model Extensions . . . . . . . . . . . . . . 14
3.6.1. Generating the Initial Offer . . . . . . . . . . . . . 14
3.6.2. Generating the Answer . . . . . . . . . . . . . . . . 14
3.6.3. Offerer Processing of the Answer . . . . . . . . . . . 14
3.6.4. Modifying the Session . . . . . . . . . . . . . . . . 14
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.1. Alternative Codecs . . . . . . . . . . . . . . . . . . . . 15
4.2. Latent Media Streams . . . . . . . . . . . . . . . . . . . 15
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7. Changes from version 00 . . . . . . . . . . . . . . . . . . . 18
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
Intellectual Property and Copyright Statements . . . . . . . . . . 22
Gilman, et al. Expires August 24, 2007 [Page 2]
Internet-Draft CMED February 2007
1. Introduction
Session Description Protocol (SDP) capability negotiation [SDPCapNeg]
provides a general framework for negotiating capabilities in
SDP[RFC4566]. The base framework defines only capabilities for
negotiating transport protocols and attributes. In this document, we
extend the framework by defining media capabilities that can be used
to negotiate media types and their associated parameters.
SDP Simple Capability Declaration (simcap) is defined in RFC 3407
[RFC3407]. It defines a set of SDP attributes that enables a limited
set of capabilities to be described at a session level or on a per
media stream basis. RFC 3407 defines capability declaration only -
actual negotiation procedures taking advantage of such capabilities
have not been defined. The SDP capability negotiation framework adds
this required functionality. This document updates RFC3407 and new
implementation SHOULD use the functionality defined in the current
draft to negotiate media capabilities.
Gilman, et al. Expires August 24, 2007 [Page 3]
Internet-Draft CMED February 2007
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119] and
indicate requirement levels for compliant RTP implementations.
Gilman, et al. Expires August 24, 2007 [Page 4]
Internet-Draft CMED February 2007
3. SDP Media capabilities
In this section we first provide an overview of the SDP media
Capability negotiation solution. This is followed by definitions of
new SDP attributes for the solution and its associated updated offer/
answer procedures [RFC3264]
3.1. Solution Overview
The solution consist of the following new attributes extending the
base attributes from [SDPCapNeg].
Three attributes are used to make up media capabilities
o A new media attribute ("a=cmed") that lists media formats as
capabilities in the form a media type (e.g. "audio") and one or
more subtypes (e.g. "PCMU"), and associates a handle with each
subtype
o A new attribute ("a=cenc") that lists encoding parameter
capabilities associated with a particular media format capability.
o A new attribute ("a=cfmt") that lists media format parameter
capabilities associated with a particular media format capability.
A new attribute ("a=lcfg") that specifies latent configurations when
no corresponding media line is offered. An example is a latent
configuration for video even though no video is currently offered.
A new parameter type ("m=") to the potential configuration
("a=pcfg:") attribute and the actual configuration ("a=acfg:")
attribute defined in [SDPCapNeg], which permits specification of
media capabilities (including their associated parameters) and
combinations thereof for the configuration. For example, the
"a=pcfg:" line might specify PCUM and telephone events or G.729B and
telephone events as acceptable configurations. The "a=acfg:" line in
the answer would specify the accepted choice.
A new parameter type ("pt=") to the potential configuration
("a=pcfg:") attribute which associates RTP payload types with the
referenced media capabilities.
The document extends the base protocol extensions to the offer/answer
model that allow for capabilities and potential configurations to be
included in an offer. Media capabilities constitute capabilities
that can be used in potential and latent configurations. Whereas
potential configurations constitute alternative offers that may be
accepted by the answerer instead of the actual configuration(s)
Gilman, et al. Expires August 24, 2007 [Page 5]
Internet-Draft CMED February 2007
included in the "m=" line(s), latent configurations merely inform the
other side of possible configurations supported by the entity. Those
latent configurations may be used to guide subsequent offer/answer
exchanges.
The mechanism is illustrated by the offer/answer exchange below,
where Alice sends an offer to Bob:
Alice Bob
| (1) Offer (SRTP and RTP) |
|--------------------------------->|
| |
| (2) Answer (RTP) |
|<---------------------------------|
| |
Alice's offer includes RTP and SRTP as alternatives. RTP is the
default, but SRTP is the preferred one:
v=0
o=- 25678 753849 IN IP4 192.0.2.1
s=
c=IN IP4 192.0.2.1
t=0 0
a=creq:v1
a=cmed:1 audio g729 iLBC PCMU g729
a=cenc:2 8000
a=cfmt:1 annexb:no
a=ctrpr:1 RTP/SAVP
m=audio 3456 RTP/AVP 0 18
a=capar:1 a=crypto:1 AES_CM_128_HMAC_SHA1_32
inline:NzB4d1BINUAvLEw6UzF3WSJ+PSdFcGdUJShpX1Zj|2^20|1:32
a=pcfg:1 m=1,3|4,3 t=1 a=1 pt=1:100,4:101,3:102
a=pcfg:2 m=2 pt=2:103
The required base and extensions are provided by the "a=creq"
attribute defined in [SDPCapNeg], with the option tag "v1", which
indicates that the extension framework defined here, must be
supported. The Base level support is implied since it is required
for the extensions.
The "a=cmed:1" line defines four audio media subtype capabilities ,
to be numbered consecutively starting with 1. Note that the media
subtypes specified in the m-line (PCMU and G729) are explicitly
specified here.
The "a=cenc:2" line specifies the clock rate and encoding parmeters
Gilman, et al. Expires August 24, 2007 [Page 6]
Internet-Draft CMED February 2007
(see [RFC4566]) for capability 2, iLBC.
The "a=cfmt:1" line specifies media format parameter capabilities for
codec 1 ( no Annex B for G.729).
The "a=ctrpr:1" line, specified in the base protocol, defines a
transport protocol capability, in this case Secure RTP.
The "m=" line indicates that Alice is offering to use plain RTP with
PCMU or G.729. The media line implicitly defines the default
transport protocol (RTP/AVP in this case) and the default actual
configuration.
The "a=capar:1" line ,specified in the base protocol provides the
"crypto" attribute which provides the keying material for SRTP using
SDP security descriptions.
The "a=pcfg:" attributes provide the potential configurations
included in the offer by reference to the media capabilities,
transport capabilities, and associated payload type mappings. Two
explicit alternatives are provided; the first one, numbered 1 is the
preferred one. It specifies media capabilities 1 and 3, i.e. G.729
and PCMU, or media capability 4 and 3, i.e., G.729B and PCMU.
Furthermore, it specifies transport protocol capability 1 (i.e. the
RTP/SAVP profile - secure RTP), and the attribute capability 1, i.e.
the crypto attribute provided. Lastly, it specifies, a payload type
mapping for codecs 1, 3, and 4 thereby permitting the offerer to
distinguish between encrypted media and unencrypted media received
prior to receipt of the answer. For SRTP the offerer will still need
to receive the answer before being able to decrypt the stream.
The second alternative specifies media capability 2, i.e. iLBC, under
the default RTP/AVP profile . The media line, with any qualifying
attributes such as fmtp or rtpmap, is itself considered a valid
configuration; it is assumed to be the lowest preference.
Bob receives the SDP offer from Alice. Bob supports RTP, but not
SRTP, and hence he accepts the actual configuration for RTP provided
by Alice. Furthermore, Bob wants to use the iLBC codec and hence
generates the following answer:
v=0
o=- 24351 621814 IN IP4 192.0.2.2
s=
c=IN IP4 192.0.2.2
t=0 0
a=csup:v1
m=audio 4567 RTP/AVP 103
Gilman, et al. Expires August 24, 2007 [Page 7]
Internet-Draft CMED February 2007
a=rtpmap:103 8000
a=acfg:2
Bob includes the "a=csup" and "a=acfg" attribute in the answer to
inform Alice that he can support the v1 level of capability
negotiations. Note that in this particular example, the answerer
supported the capability extensions defined here, however had he not,
he would simply have processed the offer based on the offered PCMU
and G.729 codecs under the RTP/AVP profile only. Consequently, the
answer would have omitted the "a=csup" attribute line and chosen one
or both of the PCMU and G.729 codecs instead. The answer carries the
accepted configuration in the m line along with corresponding rtpmap:
and/or fmtp: parameters, as appropriate.
Note that per the base protocol, after the above, Alice should
generate a new offer with an actual configuration ("m=" line, etc.)
corresponding to the actual configuration referenced in Bob's answer
(not shown here).
3.2. Capability Attributes
In this section, we present the new attributes associated with
indicating the media capabilities for use by the SDP Capability
negotiation. The approach taken is to keep things similar to the
existing media capabilities defined by the existing media
descriptions ("m=" lines) and the associated "rtpmap" and "fmtp"
attributes, but using "media capability numbers" instead of payload
types to link the relevant media capability parameters.
3.2.1. Media Type and Subtype Capability Attribute
Media types and subtypes can be expressed as media format
capabilities by use of the "a=cmed" attribute, which is defined as
follows:
a=cmed:<med-cap-num> <type> <subtype>*[ <subtype>]
where <med-cap-num> is an integer between 1 and 2^31-1 (both
included) used to number the media format capabilities, <type> is a
media type (e.g., audio or video), and the <subtype> is the media
subtype e.g. H263-1998, PCMU (Editors' note: can specify in cmed
anything that can be specified in an m-line?). The <med-cap-num> is
the media capability number associated with the first subtype in the
list, the number associated with the second subtype is one higher,
etc. Each occurrence of the attribute MUST use a different value of
<med-cap-num>. Furthermore, when a "cmed" attribute indicates more
than one media format, the capability numbers implied MUST NOT be
used by any other "cmed" attribute in the entire session or media
Gilman, et al. Expires August 24, 2007 [Page 8]
Internet-Draft CMED February 2007
description (explicitly or implicitly). In ABNF, we have:
media-capability-line = "a=cmed:" media-cap-num WSP media-type
WSP media-cap *(WSP media-cap)
media-cap-num = 1*DIGIT
media-type = token ; Type name (audio, video, etc.)
media-cap = token ; Subtype name(PCMU, G729, etc.)
Media subtypes identified in "a=cmed" lines may be qualified via the
attributes, "a=cenc" and "a=cfmt", in much the same way as media
formats in "m=" lines payload types can have their clock rate and
encoding parameters qualified by an "a=rtpmap" line and media format
specific parameters can be provided by "a=fmtp" lines.
3.2.2. The Capability Encoding Parameters Attribute
Media format capabilities may require additional encoding parameters,
such as sample rate, to be precisely defined. The "a=cenc" encoding
attribute is defined as
a=cenc:<med-cap-num> <clock rate>[/<encoding parameters>]
The clock rate and other encoding parameters are as defined for the
"a=rtpmap:" attribute defined in RFC 4566 [RFC4566]. For example, a
capability for low-bit-rate encoding at 8000 samples per second could
be specified by
a=cmed:1 iLBC
a=cenc:1 8000
The encoding becomes part of the media capability. Thus, if it is
desirable to specify the same subtype with, e.g., two different
encoding rates, then the subtype should be listed twice, and each
should be modified appropriately. For example:
a=cmed:1 L16 L16
a=cenc:1 8000
a=cenc:2 16000/2
defines two low-data-rate codecs, codec 1 uses 8000 samples per
second, and codec 2 uses 16000 samples per second and 2 channels.
[EDITOR'S NOTE: I'm thinking that it might be better to put the
encoding information in the cmed line pcfg "pt", along with the media
subtype, and eliminate the cenc attribute. This would make the above
example look like:
a=cmed:1 L16/8000 L16/16000/2
Gilman, et al. Expires August 24, 2007 [Page 9]
Internet-Draft CMED February 2007
or
a=pcfg:1 m=1,3|4,3 t=1 a=1 pt=1:100/8000, 4:101/16000/2, 3:102
This can be done so long as the encoding attributes never contain
whitespace. Is this the case? or instead use semi colon as
separator]
A media capability merely indicates possible support for the media
type and media format(s) in question. In order to actually use a
media capability in an offer/answer exchange, it must be referenced
in a potential configuration (see Section 2.3.1. ).
Media capabilities can be provided at the session-level and the
media-level. Media capabilities provided at the session level apply
to the session description in general, whereas media capabilities
provided at the media level apply to that media stream only. In
either case, the scope of the <med-cap-num> is the entire session
description. This enables each media capability to be referenced
across the entire session description (e.g. in a potential
configuration.)
3.2.3. The Media Format Parameter Capability Attribute
This attribute is used to associate media format parameters with a
media capability. The form of the attribute is:
a=cfmt:<med-cap-num> <list of format parameters>
where the format parameters are specific to the type of codec, as
described for the fmtp: attribute defined in RFC 4566. As an
example, a G.729 capability is, by default, considered to support
comfort noise as defined by Annex B. Capabilities for G.729 with and
without comfort noise support may thus be identified by:
a=cmed:1 audio G729 G729
a=cfmt:2 annexb:no
Example for H.263 video:
a=cmed:1 video H263-1998 H263-2000
a=cfmt:1 CIF=4;QCIF=2;F=1;K=1
a=cfmt:2 profile=2;level=2.2
Gilman, et al. Expires August 24, 2007 [Page 10]
Internet-Draft CMED February 2007
3.3. Extensions to the Potential Configuration Attribute
The extension protocol of capabilities negotiation requires two new
extensions for the pcfg: attribute defined in the base protocol. One
extension permits the specification of media capabilities, or
combinations thereof; the other permits the assignment of payload
types to those capabilities when used in the specified configuration.
3.3.1. The Media Capability Extension to the Potential Configuration
Attribute
The potential configuration attribute ("a=pcfg") as defined in SDP
capabilities negotiation, permits alternate attributes to be
associated with the media types defined in a media line. In this
extension (this document), we define an extension parameter for the
specification of media configurations in addition to the one
specified on the media line.
We define the media capability configuration parameter, pot-media-
config, in accordance with the following format:
m=<med-cap-list> *["|"<med-cap-list>]
where <med-cap-list> is a comma-separated list of media capability
numbers (media-cap-num) as defined by a=cmed: lines and media lines.
In ABNF form (adhering to the ABNF for pot-extension-config in
[SDPCapNeg]:
pot-media-config = "m=" med-cap-list *(BAR med-cap-list)
med-cap-list = med-cap-num *("," med-cap-num)
med-cap-num = 1*DIGIT ; defined in SDP
BAR = *WSP "|" *WSP
Each potential media configuration is a comma-separated list of media
capability numbers where med-cap-num refers to media capability
numbers defined explicitly by a=cmed attributes or implicitly by the
media line, and hence MUST be between 1 and 2^31-1 (both included).
Alternative potential media configurations are separated by a
vertical bar ("|"). The alternatives are ordered by preference.
When media capabilities are not included in a potential configuration
at the media level, the media type and media format from the
associated "m=" line will be used.
For example:
Gilman, et al. Expires August 24, 2007 [Page 11]
Internet-Draft CMED February 2007
v=0
o=- 25678 753849 IN IP4 192.0.2.1
s=
c=IN IP4 192.0.2.1
t=0 0
a=creq:v1
a=cmed:1 audio PCMU g729 telephone-event
m=audio 3456 RTP/AVP 0 18 100
a=rtpmap:100 telephone-events
a=fmtp:100 0-15
a=pcfg:1 m=2,3|1,3 pt=1:0, 2:18, 3:100
In this example, G729 is media capability 2, PCMU is media capability
1, and events is media capability 3. The a=pcfg: line specifies that
the preferred configuration is G.729 with dtmf events, second is
G.711 mu-law with dtmf events. Intermixing of G.729, G.711, and dtmf
events is least preferred (the actual configuration provided by the
"m=" line, which is always the least preferred configuration).
3.3.2. The Payload Type Mapping Extension to the Potential
Configuration Attribute
When media capabilities defined in cmed: attributes are used in
potential configuration lines, it is necessary to assign payload
types to them. In some cases, it is desirable to assign different
payload types to media capabilities defined in the media line. One
example of the latter is when configurations for AVP and SAVP are
offered: the offerer would like the answerer to use different payload
types for encrypted and unencrypted media so that it (the offerer)
can decide whether or not to render early media which arrives before
the answer is received.
We define the media type mapping configuration parameter, pot-media-
map, in accordance with the following format:
pot-media-map = "pt=" med-map-num *("," *WSP med-map-num)
med-map-num = 1*DIGIT ":" 1*DIGIT ;
The example in the previous section shows how the parameters from the
cmed line are mapped to payload type in the pcfg "pt" parameter.
3.4. Extensions to the Actual Configuration Attribute
We define an actual configuration extension parameter act-media-
config in accordance with the following ABNF:
a=acfg:<med-cap-num> *WSP "m=" <med-cap-list>
Gilman, et al. Expires August 24, 2007 [Page 12]
Internet-Draft CMED February 2007
A response to the previous offer example in the above section might
be:
v=0
o=- 24351 621814 IN IP4 192.0.2.2
s=
c=IN IP4 192.0.2.2
t=0 0
a=csup:v1
m=audio 5432 RTP/AVP 18 100
a=rtpmap:100 events
a=fmtp:100 0-15
a=acfg:1 m=2,3
Note that the capability numbers expressed in the acfg: attribute are
based on the offered capability numbering, not on those listed in the
answer. The acfg identify to the offrer which potetial configuration
was selected by the answerer.
3.5. The Latent Configuration Attribute
One of the goals of this work is to permit the exchange of media
configurations in addition to those offered for immediate use. Such
configurations are referred to as "latent configurations". For
example, a party may offer to establish an audio session, and, at the
same time, announce its ability to support a video session.
Latent configurations may be announced by use of the latent
configuration attribute, which is defined in a manner very similar to
the potential configuration attribute:
a=lcfg:<preference> ["m="<media-caps>] ["t="<transport>]
["a="<attributes>]
The m=, t= and a= parameters are identical in format and meaning to
those defined for the pcfg: attribute. Note that the pt= parameter
is not permitted in the lcfg: attribute because no actual media
session is being offered or accepted.
Latent Configurations may be specified at the session level in offers
and in answers.
[Editor's note: Do you have a good example of an offer of an audio
stream with a latent video stream?][Editor's note (rrg): What if, as
Roni suggested, we exclude the a= parameters from the lcfg: lines?
We can include the t= parameter as the 'cheapest' way to indicate
SRTP. That conveys most of the necessary info; the details can be
firmed up in the actual offer when/if it's actually made.]
Gilman, et al. Expires August 24, 2007 [Page 13]
Internet-Draft CMED February 2007
3.5.1. The crypto: Attribute in Latent Configurations
If the sdescriptions crypto: attribute is necessary as part of any
latent configuration which announces sdescriptions capabilities. then
it presents a slight problem in that the rather long key/salt string
is useless and should be ignored. This problem is avoided if we
exclude the a= parameters from the lcfg: attribute. [Editor's note:
should we define a new crypto: key-method, e.g. "latent", in which
the key-salt portion of key-info is empty? I think it may be
sufficient to just include the RTP/SAVP transport to indicate SRTP
capability]
3.6. Offer/Answer Model Extensions
In this section, we define extensions to the offer/answer model
defined in RFC3264 to allow for media capabilities to be used with
the SDP Capability Negotation framework.
3.6.1. Generating the Initial Offer
3.6.2. Generating the Answer
3.6.3. Offerer Processing of the Answer
3.6.4. Modifying the Session
Gilman, et al. Expires August 24, 2007 [Page 14]
Internet-Draft CMED February 2007
4. Examples
In this section, we provide examples showing how to use the Media
Capabilities with the SDP Capability Negotiation.
4.1. Alternative Codecs
4.2. Latent Media Streams
Gilman, et al. Expires August 24, 2007 [Page 15]
Internet-Draft CMED February 2007
5. IANA Considerations
Gilman, et al. Expires August 24, 2007 [Page 16]
Internet-Draft CMED February 2007
6. Security Considerations
Gilman, et al. Expires August 24, 2007 [Page 17]
Internet-Draft CMED February 2007
7. Changes from version 00
The major changes include taking out the "mcap" and "cptmap"
parameter. The mapping of payload type is now in the "pt" parameter
of "pcfg". Media subtype need to explictly definesd in the "cmed"
attribute if referenced in the "pcfg"
Gilman, et al. Expires August 24, 2007 [Page 18]
Internet-Draft CMED February 2007
8. Acknowledgements
This document is heavily influenced by the discussions and work done
by the SDP Capability Negotiation Design team. The following people
in particular provided useful comments and suggestions to either the
document itself or the overall direction of the solution defined
herein: Cullen Jennings, Matt Lepinski, Joerg Ott, Colin Perkins, and
Thomas Stach.
Gilman, et al. Expires August 24, 2007 [Page 19]
Internet-Draft CMED February 2007
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
June 2002.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[SDPCapNeg]
Andreasen, F., "SDP Capability Negotiation",
draft-ietf-mmusic-sdp-capability-negotiation-02 (work in
progress), February 2007.
9.2. Informative References
[RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple
Capability Declaration", RFC 3407, October 2002.
Gilman, et al. Expires August 24, 2007 [Page 20]
Internet-Draft CMED February 2007
Authors' Addresses
Robert R Gilman
Avaya, Inc.
1300 West 120th Avenue
Westminster, CO 80234
USA
Email: rrg@avaya.com
Roni Even (editor)
Polycom
94 Derech Em Hamoshavot
Petach Tikva 49130
Israel
Email: roni.even@polycom.co.il
Flemming Andreasen
Cisco Systems
Edison, NJ
USA
Email: fandreas@cisco.com
Gilman, et al. Expires August 24, 2007 [Page 21]
Internet-Draft CMED February 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Gilman, et al. Expires August 24, 2007 [Page 22]
