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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