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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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
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retain all their rights.
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