draft-ietf-mmusic-sdp-media-content-05.txt   draft-ietf-mmusic-sdp-media-content-06.txt 
MMUSIC Working Group J. Hautakorpi MMUSIC Working Group J. Hautakorpi
Internet-Draft G. Camarillo Internet-Draft G. Camarillo
Expires: March 1, 2007 Ericsson Intended status: Standards Track Ericsson
August 28, 2006 Expires: March 26, 2007 September 22, 2006
The SDP (Session Description Protocol) Content Attribute The SDP (Session Description Protocol) Content Attribute
draft-ietf-mmusic-sdp-media-content-05.txt draft-ietf-mmusic-sdp-media-content-06.txt
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The Internet Society (2006).
Abstract Abstract
This document defines a new Session Description Protocol (SDP) media- This document defines a new Session Description Protocol (SDP) media-
level attribute, 'content'. The 'content' attribute defines the level attribute, 'content'. The 'content' attribute defines the
content of the media stream in more detailed level than the media content of the media stream in more detailed level than the media
skipping to change at page 2, line 13 skipping to change at page 2, line 13
(e.g., show it on a big screen or small screen) based on its content. (e.g., show it on a big screen or small screen) based on its content.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Related Techniques . . . . . . . . . . . . . . . . . . . . . . 3 3. Related Techniques . . . . . . . . . . . . . . . . . . . . . . 3
4. Motivation for the New Content Attribute . . . . . . . . . . . 4 4. Motivation for the New Content Attribute . . . . . . . . . . . 4
5. The Content Attribute . . . . . . . . . . . . . . . . . . . . 5 5. The Content Attribute . . . . . . . . . . . . . . . . . . . . 5
6. The Content Attribute in the Offer/Answer Model . . . . . . . 6 6. The Content Attribute in the Offer/Answer Model . . . . . . . 6
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Operation with SMIL . . . . . . . . . . . . . . . . . . . . . 7 8. Operation with SMIL . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
12.1. Normative References . . . . . . . . . . . . . . . . . . 9 12.1. Normative References . . . . . . . . . . . . . . . . . . 10
12.2. Informational References . . . . . . . . . . . . . . . . 9 12.2. Informational References . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . . . 12
1. Introduction 1. Introduction
The Session Description Protocol (SDP) [1] is a protocol that is The Session Description Protocol (SDP) [1] is a protocol that 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. One of the most typical use cases of multimedia session initiation. One of the most typical use cases of
SDP is the one where it is used with the Session Initiation Protocol SDP is the one where it is used with the Session Initiation Protocol
(SIP) [5]. (SIP) [5].
There are situations where one application receives several similar There are situations where one application receives several similar
media streams which are described in an SDP session description. The media streams which are described in an SDP session description. The
media streams can be similar in the sense that their content cannot media streams can be similar in the sense that their content cannot
be distinguished just by examining the media description lines (e.g., be distinguished just by examining their media description lines
two video streams). The 'content' attribute is needed, so that the (e.g., two video streams). The 'content' attribute is needed so that
receiving application can treat each media stream appropriately based the receiving application can treat each media stream appropriately
on its content. based on its content.
This specification defines the SDP 'content' media-level attribute, This specification defines the SDP 'content' media-level attribute,
which provides more information about the media stream than the 'm' which provides more information about the media stream than the 'm'
line in an SDP session description. line in an SDP session description.
The main purpose of this specification is to allow applications to
take automated actions based on the 'content' attributes. However,
this specification does not define those actions. Consequently, two
implementations can behave completely differently when receiving the
same 'content' attribute.
2. Terminology 2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED", In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [3] and indicate requirement levels for described in BCP 14, RFC 2119 [3] and indicate requirement levels for
compliant implementations. compliant implementations.
3. Related Techniques 3. Related Techniques
The 'label' attribute [9] enables a sender to attach a pointer to a The 'label' attribute [10] enables a sender to attach a pointer to a
particular media stream. The name space of the 'label' attribute particular media stream. The name space of the 'label' attribute
itself is unrestricted, so in principle it could also be used to itself is unrestricted; so, in principle it could also be used to
convey information about the content of a media stream. However, in convey information about the content of a media stream. However, in
practice, this is not possible because of the need for backward practice, this is not possible because of the need for backward
compatibility. Existing implementations of the 'label' attribute compatibility. Existing implementations of the 'label' attribute
already use values from that unrestricted namespace in an application already use values from that unrestricted namespace in an
specific way. So it is not possible to reserve portions of the application-specific way. So, it is not possible to reserve portions
'label' attribute's namespace without possible conflict with already of the 'label' attribute's namespace without possible conflict with
used, application specific labels. already-used application-specific labels.
It is possible to assign semantics to a media stream with an external It is possible to assign semantics to a media stream with an external
document that uses the 'label' attribute as a pointer. The downside document that uses the 'label' attribute as a pointer. The downside
of this approach is that it requires external document. Typically of this approach is that it requires an external document.
this kind of mechanism would be defined for some particular use case, Therefore, this kind of mechanism is only applicable to special use
for example centralized conferencing. cases where such external documents are used (e.g., centralized
conferencing).
Yet another way to attach semantics to a media stream is by using the Yet another way to attach semantics to a media stream is to use the
'i' SDP attribute, defined in [1]. However, values of the 'i' 'i' SDP attribute, defined in [1]. However, values of the 'i'
attribute are intended for human users and not for automata. attribute are intended for human users and not for automata.
4. Motivation for the New Content Attribute 4. Motivation for the New Content Attribute
Currently, SDP does not provide any means to describe what is the Currently, SDP does not provide any means to describe what is the
content of a media stream (e.g., speaker's image, slides, sign content of a media stream (e.g., speaker's image, slides, sign
language) in a form that the application can understand. Of course language) in a form that the application can understand. Of course,
the end user can see the content of the media stream and read its the end user can see the content of the media stream and read its
title, but the application cannot understand what the media stream title, but the application cannot understand what the media stream
contains. contains.
The application that is receiving multiple similar (e.g., same type The application that is receiving multiple similar (e.g., same type
and format) media stream needs, in some cases, to know what is the and format) media stream needs, in some cases, to know what is the
content of those streams. This kind of situation occurs, for content of those streams. This kind of situation occurs, for
example, in cases where presentation slides, the speaker's image and example, in cases where presentation slides, the speaker's image, and
sign language are transported as separate media streams. It would be sign language are transported as separate media streams. It would be
desirable that the receiving application could distinguish them in a desirable that the receiving application could distinguish them in a
way that it could handle them automatically in appropriate manner. way that it could handle them automatically in an appropriate manner.
+--------------------------------------+ +--------------------------------------+
|+------------++----------------------+| |+------------++----------------------+|
|| || || || || ||
|| speaker's || || || speaker's || ||
|| image || || || image || ||
|| || || || || ||
|+------------+| presentation || |+------------+| presentation ||
|+------------+| slides || |+------------+| slides ||
|| || || || || ||
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|+------------+| presentation || |+------------+| presentation ||
|+------------+| slides || |+------------+| slides ||
|| || || || || ||
|| sign || || || sign || ||
|| language || || || language || ||
|| || || || || ||
|+------------++----------------------+| |+------------++----------------------+|
+--------------------------------------+ +--------------------------------------+
Figure 1: Application's screen Figure 1: Application's screen
The Figure 1 presents a screen of a typical communication The Figure 1 presents a screen of a typical communication
application. The 'content' attribute enables the application to make application. The 'content' attribute makes it possible for the
the decision on where to show each media stream. From an end user's application to decide where to show each media stream. From an end
perspective, it is desirable that the user does not need to arrange user's perspective, it is desirable that the user does not need to
media stream every time the media session starts. arrange media stream every time a new media session starts.
The 'content' attribute could also be used in more complex The 'content' attribute could also be used in more complex
situations. This kind of complex situation could be e.g., an situations. An example of such a complex situation is an application
application that is controlling the equipment in an auditorium. An controlling equipment in an auditorium. An auditorium can have many
auditorium can have many different output channels for the video different output channels for video (e.g., main screen and two
(main screen and two smaller screens) and the audio (main speakers, smaller screens) and audio (e.g., main speakers, headsets for the
headsets for the participants). In this kind of environment, a lot participants). In this kind of environment, a lot of interaction
of interaction from the end user who is operating the application from the end user who operates the application would be required in
would be required in absence of cues from a controlling application. absence of cues from a controlling application. The 'content'
So, the possibility for such an application to handle the media attribute would make it possible, for example, for an end user needs
stream without end users' input is highly desirable. to specify, only once, which output each media stream of a given
session should use. The application could automatically apply the
same media layout for subsequent sessions. So, the 'content'
attribute can help to reduce the amount of required end user
interaction considerably.
5. The Content Attribute 5. The Content Attribute
This specification defines a new media-level value attribute, This specification defines a new media-level value attribute,
'content'. Its formatting in SDP is described by the following BNF 'content'. Its formatting in SDP is described by the following BNF
[2]: [2]:
content-attribute = "a=content:" mediacnt-tag content-attribute = "a=content:" mediacnt-tag
mediacnt-tag = mediacnt *("," mediacnt) mediacnt-tag = mediacnt *("," mediacnt)
mediacnt = "slides" / "speaker" / "sl" / "main" mediacnt = "slides" / "speaker" / "sl" / "main"
/ "alt" / mediacnt-ext / "alt" / mediacnt-ext
mediacnt-ext = token mediacnt-ext = token
The 'content' attribute contains a token, which MAY be attached to a The 'content' attribute contains a token, which MAY be attached to a
media stream by a sending application. It describes the content of media stream by a sending application. An application MAY attach a
the transmitted media stream to the receiving application. Multiple content attribute to any media stream it describes. That attribute
'content' attribute values MAY be attached to a single media stream. contains one or more tokens describing the content of the transmitted
media stream to the receiving application.
This document provides a set of pre-defined values for the 'content' This document provides a set of pre-defined values for the 'content'
attribute. Other values can be defined in the future. The pre- attribute. Other values can be defined in the future. The pre-
defined values are: defined values are:
slides: This is a media stream that includes presentation slides. slides: the media stream includes presentation slides. The media
The media type can be e.g., a video stream or a set of instant type can be, for example, a video stream or a number of instant
message with pictures. A typical use case for this is e.g., messages with pictures. Typical use cases for this are online
online seminars and courses. This is similar to the seminars and courses. This is similar to the 'presentation' role
'presentation' role in H.239 [11]. in H.239 [12].
speaker: This is a image from the speaker. The media can be e.g., a speaker: the media stream contains the image of the speaker. The
video stream or a still image. Typical use case for this is e.g, media can be, for example, a video stream or a still image.
online seminars and courses. Typical use case for this are online seminars and courses.
sl: This means that the media stream contains sign language. The sl: the media stream contains sign language. A typical use case for
media type is a video stream. A typical use case for this is one this is an audio stream that is translated into sign language,
where the audio stream is translated into sign language. which is sent over a video stream.
main: This means that the media stream is taken from the main source. main: the media stream is taken from the main source. A typical use
A typical use case for this is a concert, where the camera is case for this is a concert where the camera is shooting the
shooting the performer. performer.
alt: This means that the media stream is taken from the alternative alt: the media stream is taken from the alternative source. A
source. A typical use case for this is an event, where there is a typical use case for this is an event where the ambient sound is
separate ambient sound and the main sound. The alternative audio separated from the main sound. The alternative audio stream could
stream could be e.g., the sound of a jungle. Another example is be, for example, the sound of a jungle. Another example is the
the video of the conference room while the main is the video of video of a conference room while the main stream carries the video
the speaker. This is similar to the 'live' role in H.239. of the speaker. This is similar to the 'live' role in H.239.
All of these values can be used with any media type. The application All these values can be used with any media type. The application
can make decisions on how to handle a single media stream based on can make decisions on how to handle a single media stream based on
both the media type and the value of the 'content' attribute. both the media type and the value of the 'content' attribute.
Therefore the situation where one value of 'content' attribute occurs Therefore the situation where one value of 'content' attribute occurs
more than once in a single session descriptor is not problematic. more than once in a single session descriptor is not problematic.
6. The Content Attribute in the Offer/Answer Model 6. The Content Attribute in the Offer/Answer Model
This specification does not define a means to discover whether or not This specification does not define a means to discover whether or not
the peer endpoint understands the 'content' attribute because the peer endpoint understands the 'content' attribute because
'content' values are informative only at the offer/answer model [7] 'content' values are just informative at the offer/answer model [8]
level. The fact that the peer endpoint does not understand the level. The fact that the peer endpoint does not understand the
'content' attribute does not keep the media session from being 'content' attribute does not keep the media session from being
established. The only consequence is that end user interaction on established. The only consequence is that end user interaction on
the receiving side may be required to direct the individual media the receiving side may be required to direct the individual media
streams appropriately. streams appropriately.
Since the 'content' attribute does not have to be understood, an SDP Since the 'content' attribute does not have to be understood, an SDP
answer MAY contain 'content' attributes even if none were present in answer MAY contain 'content' attributes even if none were present in
the offer. Similarly, the answer MAY contain no 'content' attributes the offer. Similarly, the answer MAY contain no 'content' attributes
even if they were present in the offer. even if they were present in the offer. Furthermore, the values of
'content' attributes does not need to match in an offer and an
answer.
The 'content' attribute can also be used in scenarios where SDP is The 'content' attribute can also be used in scenarios where SDP is
used in declarative style. For example, 'content' attributes can be used in a declarative style. For example, 'content' attributes can
used in SDP session descriptors that are distributed with Session be used in SDP session descriptors that are distributed with Session
Announcement Protocol (SAP) [8]. Announcement Protocol (SAP) [9].
7. Examples 7. Examples
There are two examples in this section. The first example, shown There are two examples in this section. The first example, shown
below, uses only one 'content' attribute value per media stream: below, uses a single 'content' attribute value per media stream:
v=0 v=0
o=Alice 292742730 29277831 IN IP4 131.163.72.4 o=Alice 292742730 29277831 IN IP4 131.163.72.4
s=Second lecture from information technology s=Second lecture from information technology
c=IN IP4 131.164.74.2 c=IN IP4 131.164.74.2
t=0 0 t=0 0
m=video 52886 RTP/AVP 31 m=video 52886 RTP/AVP 31
a=rtpmap:31 H261/9000 a=rtpmap:31 H261/9000
a=content:slides a=content:slides
m=video 53334 RTP/AVP 31 m=video 53334 RTP/AVP 31
a=rtpmap:31 H261/9000 a=rtpmap:31 H261/9000
a=content:speaker a=content:speaker
m=video 54132 RTP/AVP 31 m=video 54132 RTP/AVP 31
a=rtpmap:31 H261/9000 a=rtpmap:31 H261/9000
a=content:sl a=content:sl
The second example, below, shows a case where there is more than one The second example, below, shows a case where there is more than one
'content' attribute value per media stream. The difference to the 'content' attribute value per media stream. The difference with the
previous example is that now the conferencing system automatically previous example is that now the conferencing system might
mixes the video streams from the presenter and slides: automatically mix the video streams from the presenter and slides:
v=0 v=0
o=Alice 292742730 29277831 IN IP4 131.163.72.4 o=Alice 292742730 29277831 IN IP4 131.163.72.4
s=Second lecture from information technology s=Second lecture from information technology
c=IN IP4 131.164.74.2 c=IN IP4 131.164.74.2
t=0 0 t=0 0
m=video 52886 RTP/AVP 31 m=video 52886 RTP/AVP 31
a=rtpmap:31 H261/9000 a=rtpmap:31 H261/9000
a=content:slides,speaker a=content:slides,speaker
m=video 54132 RTP/AVP 31 m=video 54132 RTP/AVP 31
a=rtpmap:31 H261/9000 a=rtpmap:31 H261/9000
a=content:sl a=content:sl
8. Operation with SMIL 8. Operation with SMIL
The values of 'content' attribute, defined in Section 5, can also be The values of 'content' attribute, defined in Section 5, can also be
used with SMIL [10]. SMIL contains a 'param' element, which is used used with SMIL [11]. SMIL contains a 'param' element, which is used
for describing the content of a media flow. However, this 'param' for describing the content of a media flow. However, this 'param'
element provides only application specific description of media element, like 'content' attribute, provides application specific
content. By using the values of the 'content' attribute, this description of media content.
'param' element can also be used to describe the media content in
globally interpretable way.
Details on how to use the values of the 'content' attribute with Details on how to use the values of the 'content' attribute with
SMIL's 'param' element are outside the scope of this specification. SMIL's 'param' element are outside the scope of this specification.
9. Security Considerations 9. Security Considerations
An attacker may attempt to add, modify, or remove 'content' An attacker may attempt to add, modify, or remove 'content'
attributes from a session description. This could result in an attributes from a session description. Depending on how an
application behaving in an undesirable way. So, it is strongly implementation chooses to react to the presence or absence of a given
RECOMMENDED that integrity protection be applied to the SDP session 'content' attribute, this could result in an application behaving in
descriptions. For session descriptions carried in SIP [5], S/MIME an undesirable way. So, it is strongly RECOMMENDED that integrity
[6] is the natural choice to provide such end-to-end integrity protection be applied to the SDP session descriptions.
protection, as described in RFC 3261 [5]. Other applications MAY use
a different form of integrity protection. Integrity protection can be provided for session description carried
in SIP [5] e.g., by using S/MIME [6] or Transport Layer Security
(TLS) [7].
It is assumed that values of 'content' attribute do not contain data
that would be truly harmful if it is exposed to an possible attacker.
It must be noted that the initial set of values does not contain any
data that would require confidentiality protection. However, S/MIME
and TLS can be used to protect confidentiality, if needed.
10. IANA Considerations 10. IANA Considerations
This document defines a new 'content' attribute for SDP. It also This document defines a new 'content' attribute for SDP. It also
defines an initial set of values for it. Some general information defines an initial set of values for it. Some general information
regarding 'content' attribute is presented in the following: regarding 'content' attribute is presented in the following:
Contact name: Jani Hautakorpi Jani.Hautakorpi@ericsson.com. Contact name: Jani Hautakorpi Jani.Hautakorpi@ericsson.com.
Attribute name: 'content'. Attribute name: 'content'.
skipping to change at page 8, line 49 skipping to change at page 9, line 32
the following, and IANA is requested to add them into its database: the following, and IANA is requested to add them into its database:
Value of 'content' attribute Reference Description Value of 'content' attribute Reference Description
---------------------------- --------- ----------- ---------------------------- --------- -----------
slides RFC xxxx Presentation slides slides RFC xxxx Presentation slides
speaker RFC xxxx Image from the speaker speaker RFC xxxx Image from the speaker
sl RFC xxxx Sign language sl RFC xxxx Sign language
main RFC xxxx Main media stream main RFC xxxx Main media stream
alt RFC xxxx Alternative media stream alt RFC xxxx Alternative media stream
Note for the RFC Editor: The 'RFC xxxx' in the above should be a Note for the RFC Editor: 'RFC xxxx' above should be replaced by a
reference to the coming RFC number of this draft. reference to the coming RFC number of this draft.
As per the terminology in RFC 2434 [4], the registration policy for As per the terminology in RFC 2434 [4], the registration policy for
new values for the 'content' parameter shall be 'Specification new values for the 'content' parameter shall be 'Specification
Required'. Required'.
If new values for the 'content' attribute are specified in the If new values for 'content' attribute are specified in the future,
future, they should consist of a meta description of the contents of they should consist of a meta description of the contents of a media
a media stream. New values for the 'content' attribute should not stream. New values for 'content' attribute should not describe
describe things like what to do in order to handle a stream. things like what to do in order to handle a stream.
11. Acknowledgements 11. Acknowledgements
Authors would like to thank Arnoud van Wijk and Roni Even, who Authors would like to thank Arnoud van Wijk and Roni Even, who
provided valuable ideas for this document. We wish to thank also Tom provided valuable ideas for this document. We wish to thank also Tom
Taylor for a thorough review. Taylor for a thorough review.
12. References 12. References
12.1. Normative References 12.1. Normative References
[1] Handley, M., "SDP: Session Description Protocol", [1] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
draft-ietf-mmusic-sdp-new-26 (work in progress), January 2006. Description Protocol", RFC 4566, July 2006.
[2] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [2] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement [3] 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.
[4] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [4] 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.
12.2. Informational References 12.2. Informational References
[5] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., [5] 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.
[6] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions [6] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions
(S/MIME) Version 3.1 Message Specification", RFC 3851, (S/MIME) Version 3.1 Message Specification", RFC 3851,
July 2004. July 2004.
[7] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with [7] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
Protocol Version 1.1", RFC 4346, April 2006.
[8] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002. Session Description Protocol (SDP)", RFC 3264, June 2002.
[8] Handley, M., Perkins, C., and E. Whelan, "Session Announcement [9] Handley, M., Perkins, C., and E. Whelan, "Session Announcement
Protocol", RFC 2974, October 2000. Protocol", RFC 2974, October 2000.
[9] Levin, O. and G. Camarillo, "The SDP (Session Description [10] Levin, O. and G. Camarillo, "The Session Description Protocol
Protocol) Label Attribute", (SDP) Label Attribute", RFC 4574, August 2006.
draft-ietf-mmusic-sdp-media-label-01 (work in progress),
January 2005.
[10] Michel, T. and J. Ayars, "Synchronized Multimedia Integration [11] Michel, T. and J. Ayars, "Synchronized Multimedia Integration
Language (SMIL 2.0) - [Second Edition]", W3C REC REC-SMIL2- Language (SMIL 2.0) - [Second Edition]", W3C REC REC-SMIL2-
20050107, January 2005. 20050107, January 2005.
[11] ITU-T, "Infrastructure of audiovisual services - Systems [12] ITU-T, "Infrastructure of audiovisual services - Systems
aspects; Role management and additional media channels for aspects; Role management and additional media channels for
H.300-series terminals", Series H H.239, July 2003. H.300-series terminals", Series H H.239, July 2003.
Authors' Addresses Authors' Addresses
Jani Hautakorpi Jani Hautakorpi
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland Finland
skipping to change at page 12, line 5 skipping to change at page 12, line 5
Email: Jani.Hautakorpi@ericsson.com Email: Jani.Hautakorpi@ericsson.com
Gonzalo Camarillo Gonzalo Camarillo
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland Finland
Email: Gonzalo.Camarillo@ericsson.com Email: Gonzalo.Camarillo@ericsson.com
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