Internet DRAFT - draft-holmberg-mmusic-sdp-mmt-negotiation
draft-holmberg-mmusic-sdp-mmt-negotiation
MMUSIC Working Group C. Holmberg
Internet-Draft Ericsson
Intended status: Standards Track H. Alvestrand
Expires: April 11, 2013 Google
J. Lennox
Vidyo
October 8, 2012
Multiplexed Media Types (MMT) Using Session Description Protocol (SDP)
Port Numbers
draft-holmberg-mmusic-sdp-mmt-negotiation-00.txt
Abstract
This specification defines a new SDP Grouping Framework SDP grouping
framework extension, "MMT", and a new SDP media type, "anymedia".
Together they can be used with the Session Description Protocol (SDP)
Offer/Answer mechanism to negotiate the usage of multiplexed media
types, which refers to the usage of a single 5-tuple for different
media types.
This specification also defined a new SDP attribute, "mmtype", which
can be used within a "anymedia" SDP Media Description to map PT
(Payload Type) values to a specific media type.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on April 11, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
Holmberg, et al. Expires April 11, 2013 [Page 1]
Internet-Draft Multiplexed media types October 2012
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 4
5. SDP Grouping Framework MMT Extension Semantics . . . . . . . . 4
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.2. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 5
5.2.2. SDP Offer/Answer Usage . . . . . . . . . . . . . . . . 5
6. anymedia SDP Media Type . . . . . . . . . . . . . . . . . . . 6
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.2. SDP Extensions . . . . . . . . . . . . . . . . . . . . . . 6
6.3. SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 6
6.4. Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . 7
6.5. ICE Usage . . . . . . . . . . . . . . . . . . . . . . . . 7
6.6. RTP Sessions . . . . . . . . . . . . . . . . . . . . . . . 7
7. mmtype SDP attribute . . . . . . . . . . . . . . . . . . . . . 7
7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.3.1. General . . . . . . . . . . . . . . . . . . . . . . . 7
7.3.2. SDP Offer/Answer Usage . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 11
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
13.1. Normative References . . . . . . . . . . . . . . . . . . . 11
13.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Holmberg, et al. Expires April 11, 2013 [Page 2]
Internet-Draft Multiplexed media types October 2012
1. Introduction
In the IETF RTCWEB WG, a need to use a single 5-tuple for sending and
receiving media associated with multiple SDP Media Descriptions
[RFC4566] has been identified. This would e.g. allow the usage of a
single set of Interactive Connectivity Establishment (ICE) [RFC5245]
candidates for multiple media descriptions. Normally different media
types (audio, video etc) will be described using different SDP Media
Descriptions.
As defined in RFC 4566 [RFC4566], the semantics of using the same
port number for multiple SDP Media Descriptions is undefined.
Therefore, in order to be able to use the same port value for
multiple media types, it must be possible to describe multiple media
types within a single SDP Media Description.
This specification defines a new SDP Grouping Framework SDP grouping
framework [RFC5888] extension, "MMT", and a new SDP media type,
"anymedia". Together they can be used with the Session Description
Protocol (SDP) Offer/Answer mechanism [RFC3264] to negotiate the
usage of multiplexed media types, which refers to the usage of a
single 5-tuple for different media types.
This specification also defined a new SDP attribute, "mmtype", which
can be used within a "anymedia" SDP Media Description to map PT
(Payload Type) values to a specific media type.
When an endpoint generates an SDP Offer or SDP Answer, which
includeds one or more "MMT" groups, each group will contain one
"anymedia" SDP Media Description and one or more SDP Media
Descriptions for specific media types (audio, video, etc).
When media is transported using the Real-Time Protocol (RTP)
[RFC3550], each SDP Media Description is assumed to form a separate
RTP Session [RFC3550]. The same applies to media associated with a
"anymedia" SDP Media Description, ie all media types associated with
a "anymedia" SDP Media Description is by default assumed to form a
single RTP Session.
The mechanism is backward compatible. Entities that do not support
(or, for a given session, are not willing to use) the "MMT" grouping
extension and the "anymedia" media type, are expected to generate an
SDP Answer, which does not contain a "MMT" group, and where the
"anymedia" SDP Media Description is rejected.
Holmberg, et al. Expires April 11, 2013 [Page 3]
Internet-Draft Multiplexed media types October 2012
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 RFC 2119 [RFC2119].
5-tuple: A collection of the following values: source address, source
port, destination address, destination port and protocol.
Multiplexed media types: Two or more RTP streams, possibly of
different media types, using a single 5-tuple. The RTCP streams
associated with the RTP streams also use a single 5-tuple, which
might be the same, but can also be different, as the one used by the
RTP streams.
3. Conventions
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 BCP 14, RFC 2119
[RFC2119].
4. Applicability Statement
The mechanism in this specification only applies to the Session
Description Protocol (SDP) [RFC4566], when used together with the SDP
Offer/Answer mechanism [RFC3264].
5. SDP Grouping Framework MMT Extension Semantics
5.1. General
This section defines a new SDP Grouping Framework extension, "MMT".
The "MMT" extension can be indicated using a "group" SDP session-
level attribute. Each SDP Media Description ("m=" line) that is
grouped together, using a "mid" SDP media-level attribute, is part of
a specific "MMT" group.
A "MMT" group is not usable standalone. It MUST be used together
with a "anymedia" SDP Media Description.
Holmberg, et al. Expires April 11, 2013 [Page 4]
Internet-Draft Multiplexed media types October 2012
5.2. Usage
5.2.1. General
A "MMT" group MUST contain a "anymedia" SDP Media Description, and at
least one SDP Media Description for a specific SDP Media Type (audio,
video, etc).
An SDP Offerer [RFC3264] uses the "MMT" group to offer at least one
SDP Media Description for specific SDP Media Types, and a "anymedia"
SDP Media Description, which can contain multiple SDP Media Types
sharing a single SDP Media Description. From a "MMT" group the SDP
Answerer [RFC3264] will accept either the SDP Media Descriptions for
the specific SDP Media Types, or the "anymedia" SDP Media
Description.
It is RECOMMENDED that the capabilities of the "anymedia" SDP Media
Description match the capabilities (codecs, RTCP multiplexing etc) of
the SDP Media Descriptions for the specific SDP Media Types, in order
to provide the same capabilities no matter whether SDP Media
Descriptions for specific SDP Media Types, or the "anymedia" SDP
Media Description, is used to establish the session.
NOTE: An SDP Message Body can contain multiple "MMT" groups.
5.2.2. SDP Offer/Answer Usage
5.2.2.1. SDP Offererer Procedures
When an SDP Offerer generates an SDP Offer, which contains one or
more "MMT" groups, for each "MMT" group the SDP Offerer MUST:
1) Include a "anymedia" SDP Media Description; and
2) Include at least one SDP Media Description for a specific media
type (audio, video, etc).
5.2.2.2. SDP Answerer Procedures
When an SDP Answerer generates an SDP Answer, for each "MMT" group in
the associated SDP Offer it MUST either:
1) Accept the "anymedia" SDP Media Description, and reject all other
SDP Media Descriptions associated with the "MMT" group; or
2) Reject the "anymedia" SDP Media Description, and accept some or
all of the other SDP Media Descriptions associated with the MMT
group.
Holmberg, et al. Expires April 11, 2013 [Page 5]
Internet-Draft Multiplexed media types October 2012
NOTE: As described in [RFC3264], an SDP Media Description can be
rejected by setting the port value of the associated m- line to zero
in the SDP Answer.
NOTE: As described in [RFC3264] the SDP Answer must contain the same
number of SDP Media Descriptions as the associated SDP Offer.
6. anymedia SDP Media Type
6.1. General
This section describes a new SDP media type [RFC4566], "anymedia",
for SDP Media Descriptions [RFC4566]. "anymedia" does not refer to a
specific media type, but allows multiple media types (audio, video
etc) to be associated with a single SDP Media Description. All media
associated with a "anymedia" SDP Media Description will share the
same IP address+port, protocol (e.g. RTP/AVP) and other information
(e.g. ICE candidates) associated with the SDP Media Description. It
allows, if both endpoints support the mechanism, multiple media typex
to be multiplexed on a single 5-tuple. PT (Payload Type) values will
be listed in a normal fashion in the format list of the SDP Media
Description. The SDP rtpmap attribute [RFC4566] will be used in a
normal fashion to map each PT to a codec, and the SDP mmtype
attribute will be used to map each PT to a specific media type (e.g.
audio, video, etc).
Within a "anymedia" SDP Media Description, each PT value SHOULD be
described using an "rtpmap" SDP Attribute [RFC4566], even if the PT
value is static. In addition, as it might not always be possible to
retreive the media type from the "rtpmap" SDP Attribute value, each
PT value MUST be mapped to a specific media type, using the "mmtype"
SDP Attribute.
6.2. SDP Extensions
OPEN ISSUE: Which, if any, SDP Extensions shall we require support
of?
6.3. SDP Attributes
In a normal fashion, any media level SDP Attribute (e.g. the
directionality attributes) associated with the "anymedia" SDP Media
Description applies to all media associated with the SDP Media
Description.
NOTE: Additional extensions are needed in order to specify SDP
Attribute values for individual media types, or individual media
Holmberg, et al. Expires April 11, 2013 [Page 6]
Internet-Draft Multiplexed media types October 2012
sources, associated with the "anymedia" SDP Media Description.
6.4. Bandwidth
The SDP bandwidth parameter, b=, is used in a normal fashion, as
described in [RFC4566]
NOTE: Additional extensions are needed in order to specify SDP
Bandwidth values for individual media types, and for a specific media
direction.
6.5. ICE Usage
ICE [RFC5245], if supported, will be used in a normal fashion, and
the ICE Candidate information will apply to all media types
associated with the "anymedia" SDP Media Description.
6.6. RTP Sessions
By default, all media associated with a "anymedia" SDP Media
Description is considered to be part of a single RTP Session
[RFC3550].
7. mmtype SDP attribute
7.1. General
This section defines a new SDP media level attribute [RFC4566],
"mmtype" (Multiplexed Media Type). The attribute is used within
"anymedia" SDP Media Descriptions to indicate the media type
associated with a specific PT value.
7.2. Syntax
a=mmtype: format media
format and media as defined in [RFC4566].
7.3. Usage
7.3.1. General
The attribute is used within "anymedia" SDP Media Descriptions to
indicate the media type associated with a specific PT value. This
specification does not define the usage of the attribute within other
types of SDP Media Descriptions.
Holmberg, et al. Expires April 11, 2013 [Page 7]
Internet-Draft Multiplexed media types October 2012
For each instance of the "mmtype" attribute, the associated PT value
MUST also be listed in the format list of the associated SDP m- line.
Within a given SDP Media Description, there MUST only be one 'mmtype'
attribute associated with a given PT value. An entity MUST either
reject or discard an SDP Media Description that contains 'mmtype'
attributes with PT values not listed in the associated m- line. An
entity MUST either reject or discard an SDP Media Description that
contains multiple 'mmtype' attributes for the same PT value.
7.3.2. SDP Offer/Answer Usage
There are no SDP Offer/Answer specific procedures defined for the
"mmtype" SDP attribute.
8. Security Considerations
TBA
9. Example
The example below shows an SDP Offer, where multiplexed media types
is offered. The example also shows two SDP Answer alternatives: one
where multiplexed media types is accepted, and one where multiplexed
media types is rejected (or, not even supported) by the SDP Answerer.
SDP Offer (multiplexed media types offered)
v=0
o=alice 2890844526 2890844526 IN IP4 host.atlanta.com
s=
c=IN IP4 host.atlanta.com
t=0 0
a=group:MMT foo bar zoe
m=audio 10000 RTP/AVP 0 8 97
a=mid:foo
b=AS:200
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:97 iLBC/8000
m=video 20000 RTP/AVP 31 32
a=mid:bar
b=AS:1000
a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000
m=anymedia 30000 RTP/AVP 0 8 97 31 32
a=mid:zoe
Holmberg, et al. Expires April 11, 2013 [Page 8]
Internet-Draft Multiplexed media types October 2012
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:97 iLBC/8000
a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000
a=mmtype: 0 audio
a=mmtype: 8 audio
a=mmtype: 97 audio
a=mmtype: 31 video
a=mmtype: 32 video
SDP Answer (multiplexed media types accepted)
v=0
o=bob 2808844564 2808844564 IN IP4 host.biloxi.com
s=
c=IN IP4 host.biloxi.com
t=0 0
a=group:MMT foo bar
m=audio 0 RTP/AVP 0
a=mid:foo
a=rtpmap:0 PCMU/8000
m=video 0 RTP/AVP 32
a=mid:bar
a=rtpmap:32 MPV/90000
m=anymedia 60000 RTP/AVP 0 32
a=mid:zoe
a=rtpmap:0 PCMU/8000
a=rtpmap:32 MPV/90000
a=mmtype: 0 audio
a=mmtype: 32 video
SDP Answer (multiplexed media types not accepted)
v=0
o=bob 2808844564 2808844564 IN IP4 host.biloxi.com
s=
c=IN IP4 host.biloxi.com
t=0 0
a=group:MMT foo bar
m=audio 40000 RTP/AVP 0
a=mid:foo
a=rtpmap:0 PCMU/8000
m=video 50000 RTP/AVP 32
a=mid:bar
a=rtpmap:32 MPV/90000
m=anymedia 0 RTP/AVP 0 32
Holmberg, et al. Expires April 11, 2013 [Page 9]
Internet-Draft Multiplexed media types October 2012
a=mid:zoe
SDP Offer with ICE (multiplexed media types offered)
v=0
o=alice 2890844526 2890844526 IN IP4 host.atlanta.com
s=
c=IN IP4 host.atlanta.com
t=0 0
a=group:MMT foo bar zoe
m=audio 10000 RTP/AVP 0 8 97
a=mid:foo
b=AS:200
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:97 iLBC/8000
a=candidate:1 1 UDP 1694498815 host.atlanta.com 10000 typ host
m=video 20000 RTP/AVP 31 32
a=mid:bar
b=AS:1000
a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000
a=candidate:1 1 UDP 1694498815 host.atlanta.com 20000 typ host
m=anymedia 30000 RTP/AVP 0 8 97 31 32
a=mid:zoe
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:97 iLBC/8000
a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/9000
a=mmtype: 0 audio
a=mmtype: 8 audio
a=mmtype: 97 audio
a=mmtype: 31 video
a=mmtype: 32 video
a=candidate:1 1 UDP 1694498815 host.atlanta.com 30000 typ host
10. IANA Considerations
This document requests IANA to register the new SDP Grouping semantic
extension called MMT.
Holmberg, et al. Expires April 11, 2013 [Page 10]
Internet-Draft Multiplexed media types October 2012
11. Acknowledgements
The usage of the SDP grouping mechanism is based on a similar
alternative proposed by Harald Alvestrand. The SDP examples are also
modified versions from the ones in the Alvestrand proposal.
The usage of a dedicated SDP media type to described multiplexed
media types types is based on input from Jonathan Lennox.
12. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-holmberg-mmusic-sdp-mmt-negotiation-xx
o Add change.
13. References
13.1. 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.
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
13.2. Informative References
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245,
April 2010.
Holmberg, et al. Expires April 11, 2013 [Page 11]
Internet-Draft Multiplexed media types October 2012
Authors' Addresses
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
Harald Tveit Alvestrand
Google
Kungsbron 2
Stockholm 11122
Sweden
Email: harald@alvestrand.no
Jonathan Lennox
Vidyo, Inc.
433 Hackensack Avenue
Seventh Floor
Hackensack, NJ 07601
US
Email: jonathan@vidyo.com
Holmberg, et al. Expires April 11, 2013 [Page 12]
