Internet DRAFT - draft-dondeti-oma-sip-sdp-attrs
draft-dondeti-oma-sip-sdp-attrs
Network Working Group L. Dondeti, Ed.
Internet-Draft QUALCOMM, Inc.
Intended status: Informational A. Jerichow
Expires: April 18, 2008 Nokia Siemens Networks GmbH and
Co.KG
October 16, 2007
Session Description Protocol (SDP) Attributes for OMA BCAST Service and
Content Protection
draft-dondeti-oma-sip-sdp-attrs-02
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document provides descriptions of SDP attributes used by the
Open Mobile Alliance's Broadcast Service and Content Protection
specification.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. New SDP Attributes . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Registration of new SDP attributes . . . . . . . . . . . . 4
5.1.1. Registration of the attribute
a=bcastversion:<major>.<minor> . . . . . . . . . . . . 4
5.1.2. Registration of the attribute a=stkmstream:<id of
the stkm stream> . . . . . . . . . . . . . . . . . . . 5
5.1.3. Registration of the attribute
a=SRTPAuthentication:<id for SRTP authentication
algorithm value> . . . . . . . . . . . . . . . . . . . 5
5.1.4. Registration of the attribute
a=SRTPROCTxRate:<ROC transmission rate> . . . . . . . . 6
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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1. Introduction
The Open Mobile Alliance (OMA)'s Broadcast (BCAST) group is
specifying service and content protection mechanisms for broadcast
services over wireless networks. As part of that specification,
several new SDP attributes are necessary to allow the broadcast
server to signal the service and content protection parameters to
clients.
Section 8.2.4 of RFC 4566 [1] requires that new SDP attributes are
registered through IANA with name, contact information and
description (and other similar parameters). A standards track
specification is RECOMMENDED if the new attribute(s) will have
widespread use and interoperability considerations.
OMA BCAST specifications are expected to be used by 3GPP MBMS, 3GPP2
BCMCS and DVB-H based broadcast wireless systems.
This document provides descriptions of the SDP attributes used in the
OMA BCAST Service and Content Protection specification [2].
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 [3].
3. New SDP Attributes
The following new SDP attributes have been specified:
o a=bcastversion:<major>.<minor>
o a=stkmstream:<id of the stkm stream>
o a=SRTPAuthentication:<id for SRTP authentication algorithm value>
o a=SRTPROCTxRate:<ROC transmission rate>
See Section 5 for details on IANA considerations.
4. Security Considerations
In addition to the notes in Section 7 of RFC 4566 [1], the following
considerations may be applicable:
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Some of the new SDP parameters indicate the version, type of the key
management system used for service or content protection of broadcast
content. Others provide references to relevant key management
traffic streams so that receivers can map the media streams to key
streams and retrieve the necessary keys to decrypt media.
Modification of references to key streams will result in DoS attacks,
but nothing more. However, if the kmsversion parameter is sent
unprotected, there may be possibilities for downgrade attacks.
5. IANA Considerations
This document, following the guidelines of [5], instructs IANA to
register a number of SDP attributes.
5.1. Registration of new SDP attributes
This memo provides instructions to IANA to register a number of OMA
BCAST only attributes in the Session Description Protocol Parameters
registry [1]. The registration data, according to RFC 4566 [1]
follows.
Note to the RFC Editor: replace "RFC XXXX" with the RFC number of
this specification.
5.1.1. Registration of the attribute a=bcastversion:<major>.<minor>
Contact: Anja Jerichow <anja.jerichow@nsn.com>
Phone: +49 89 636-45868
Attribute name: bcastversion:<major>.<minor>
Long-form attribute name: BCAST version
Type of attribute: session-level
This attribute is not dependent on charset.
Description: This attribute specifies the OMA BCAST version
"bcastversion" Value in the format x.y. The Value field is of XML
data type Decimal.
Specification: RFC XXXX and OMA-TS-BCAST_SvcCntProtection, Section
10.1.1 [2]
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5.1.2. Registration of the attribute a=stkmstream:<id of the stkm
stream>
Contact: Anja Jerichow <anja.jerichow@nsn.com>
Phone: +49 89 636-45868
Attribute name: stkmstream:<id of the stkm stream>
Long-form attribute name: Short Term Key Message stream identifyer
Type of attribute: session-level or media-level attribute
The attribute can be at session level, in which case it applies to
all media streams, or it can be at media level, in which case it
only applies to the specified media and would overwrite possible
session level attribute.
This attribute is not dependent on charset.
Description: The stkmstream attribute specifies mapping Short Term
Key Message streams to media streams in the SDP.
Each session or media stream can have multiple stkmstream
attributes. Using this attribute, the terminal can lookup the
corresponding STKM stream announcements and figure out which one
to listen to and process. We note that this attribute is optional
and hence would not be there for unencrypted media streams.
This field specifies the type of keystream as a string. The valid
values are "stkm" for short term key messages and "ltkm" for long
term key messages.
Specification: RFC XXXX and OMA-TS-BCAST_SvcCntProtection, Section
10.1.3 [2]
5.1.3. Registration of the attribute a=SRTPAuthentication:<id for SRTP
authentication algorithm value>
Contact: Anja Jerichow <anja.jerichow@nsn.com>
Phone: +49 89 636-45868
Attribute name: SRTPAuthentication:<id for SRTP authentication
algorithm value>
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Long-form attribute name: SRTP authentication algorithm value
identifyer
Type of attribute: media-level
This attribute is not dependent on charset.
Description: When SRTP is used, the attribute SRTPAuthentication
states which authentication algorithm to use. Based on , the
identifier is a transform-independent parameter of the
cryptographic context for SRTP in integer format.
One of the following three integrity transforms registered for the
three modes MUST be used: value "2" for RCCm1, "3" for RCCm2 and
"4" for RCCm3.
Specification: RFC XXXX and OMA-TS-BCAST_SvcCntProtection, Section
10.4 [2]
5.1.4. Registration of the attribute a=SRTPROCTxRate:<ROC
transmission rate>
Contact: Anja Jerichow <anja.jerichow@nsn.com>
Phone: +49 89 636-45868
Attribute name: SRTPROCTxRate:<ROC transmission rate>
Long-form attribute name: ROC transmission rate
Type of attribute: media-level
This attribute is not dependent on charset.
Description: When SRTP is used, the attribute SRTPROCTxRate is used
to define the ROC transmission rate, R, which is given in network
byte order.
R MUST be a non-zero unsigned integer between 1 and 65535
inclusive, as specified in [4]. If the ROC transmission rate is
not included in the negotiation, the default value of 1 SHALL be
used.
Specification: RFC XXXX and OMA-TS-BCAST_SvcCntProtection, Section
10.4 [2]
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6. Acknowledgments
Many thanks to Charles Lo, Uwe Rauschenbach, David Castleford, Hosame
Abu-Amara, and Miguel Garcia for their help and support.
7. References
7.1. Normative References
[1] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[2] Open Mobile Alliance, "Service and Content Protection for Mobile
Broadcast Services", OMA OMA-TS-BCAST_SvcCntProtection-V1_0-
20070504-D, 2007.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[4] Lehtovirta, V., Naslund, M., and K. Norrman, "Integrity
Transform Carrying Roll-Over Counter for the Secure Real-time
Transport Protocol (SRTP)", RFC 4771, January 2007.
7.2. Informative References
[5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
Authors' Addresses
Lakshminath Dondeti (editor)
QUALCOMM, Inc.
5775 Morehouse Dr
San Diego, CA
USA
Phone: +1 858-845-1267
Email: ldondeti@qualcomm.com
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Anja Jerichow
Nokia Siemens Networks GmbH and Co.KG
Martinstr. 76
81541 Munich
Germany
Phone: +49 89 636-45868
Email: anja.jerichow@nsn.com
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