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Versions: 00 draft-ietf-avt-rtp-gsm-hr

AVT Working Group                                             Rocky Wang
Internet Draft                                                Ying Zhang
Intended status: Standards Track                     Huawei Technologies
Expires: July 24, 2008                                  January 24, 2008



             Media Type Registration of GSM-HR payload Format
                       draft-rocky-avt-rtp-gsm-hr-00.txt


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Copyright Notice

   Copyright (c) The IETF Turst (2008).



Abstract

   This document registers a media type for the Real-time Transport
   protocol (RTP) payload format, which is used for the Group Special
   Mobile half-rate speech transcoding.




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Table of Contents


   Abstract........................................................1
   1. Introduction.................................................2
      1.1. Terminology.............................................2
   2. Registration of Media Type audio/GSM-HR......................2
   3. Mapping MIME Parameters into SDP.............................4
   4. Security Considerations......................................4
   5. IANA Considerations..........................................4
   6. References...................................................5
      6.1. Normative References....................................5
   Author's Addresses..............................................5
   Full Copyright Statement........................................5
   Intellectual Property Statement.................................6
   Acknowledgment..................................................6

1. Introduction

   Global System for Mobile Communication (GSM) network has been widely
   deployed in the last several years to provide mobile communication
   services.  GSM half rate codec (GSM-HR) is one of the compressed
   audio codecs which are used for the basic speech service in the GSM
   mobile networks.

   GSM-HR denotes GSM 06.20 half-rate speech transcoding, specified in
   ETS 300 969 which is available from ETSI at the address given in RFC
   3551 [1] Section 4.5.8.  This codec has a frame length of 112 bits.
   For transmission in RTP, each codec frame is packed into a 14
   octet(112 bit).  The packing is specified in ETSI Technical
   Specification TS 101 318.

   This document registers a media type for the Real-time Transport
   protocol (RTP) payload format for the GSM-HR codec to enabling the
   use of the codec in the Voice over IP (VoIP) application.

 1.1. 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 [2].

2. Registration of Media Type audio/GSM-HR

   Type name: audio

   Subtype name: GSM-HR


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   Required parameters: none

   Optional parameters:

         ptime: the recommended length of time (in milliseconds)
         represented by the media in a packet and the default value is
         20 milliseconds.  See Section 6 of RFC 4566 [3].

   Encoding considerations:

         This media type is framed binary data (see Section 4.8 in
         RFC4288 [4]).

   Security consideration:

         This media type does not carry active content.  It does
         transfer compressed data.  See Section 4.

   Interoperability considerations: none

   Published specification: RFC XXXX

   Applications that use this media type:

        Audio and video streaming and conferencing tools

   Additional information: none

   Person & email address to contact for further information:

        Rocky Wang <rocky.wang@huawei.com>

   Intended usage: COMMON

   Restrictions on usage:

         This media type depends on RTP framing, and hence is only
         defined for transfer via RTP (RFC 3550 [5]).  Transfer within
         other framing protocols is not defined at this time.

   Author:

        Rocky Wang

   Change controller:

        IETF Audio/Video Transport working group delegated from the IESG.


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3. Mapping MIME Parameters into SDP

   The information carried in the MIME media type specification has a
   specific mapping to fields in the Session Description Protocol (SDP)
   [3], which is commonly used to describe RTP sessions. When SDP is
   used to specify sessions employing the compact bundled format for GSM
   half-rate speech, the mapping is as follows:

       The MIME type ("audio") goes in SDP "m=" as the media name.

       The MIME subtype ("GSM-HR") goes in SDP "a=rtpmap" as the
       encoding name and the sampling rate for the GSM-HR codec is 8 KHz.

       The optional parameters "ptime" goes in the SDP "a=ptime"
       attributes, respectively.

   The payload type payload type value for GSM-HR is created dynamically
   and is used in the PT field of the RTP data header.

4. Security Considerations

   RTP packets using the GSM-HR payload format are subject to the
   security considerations discussed in the RTP specification [5].

   A potential denial-of-service threat exists for data encodings using
   compression techniques that have non-uniform receiver-end
   computational load.  The attacker can inject pathological datagrams
   into the stream which are complex to decode and cause the receiver to
   be overloaded.  However, this encoding does not exhibit
   anysignificant non-uniformity.

   As with any IP-based protocol, in some circumstances a receiver may
   be overloaded simply by the receipt of too many packets, either
   desired or undesired.  Network-layer authentication MAY be used to
   discard packets from undesired sources, but the processing cost of
   the authentication itself may be too high.

5. IANA Considerations

   It is requested that one new media subtype (audio/GSM-HR) is
   registered by IANA. For details, see Section 2.








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6. References

 6.1. Normative References

   [1]  Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
         Conferences with Minimal Control", RFC 3551, July 2003.

   [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [3]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
         Description Protocol", RFC 4566, July 2006.

   [4]  Freed, N. and J. Klensin, "Media Type Specifications and
         Registration Procedures", BCP 13, RFC 4288, December 2005.

   [5]  Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
         "RTP:  A Transport Protocol for Real-Time Applications", RFC
         3550, July 2003.



Author's Addresses

   Rocky Wang
   Huawei Technologies
   Huawei Industrial Base, Bantian Longgang
   Shenzhen, Guangdong Province 518129, P.R.China

   Email: <rocky.wang@huawei.com>


   Ying Zhang
   Huawei Technologies
   Huawei Industrial Base, Bantian Longgang
   Shenzhen, Guangdong Province 518129, P.R.China

   Email: <zhangying67324@huawei.com>


Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   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.


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