UIT - Secteur de la normalisation des télécommunications
ITU - Telecommunication Standardization Sector
UIT - Sector de Normalización de las Telecomunicaciones

Study Period 1997-2000

  16	 

Geneva, 14-25 September
	  E
Question(s):	13/16

SOURCE*:	
	　　　 Canon Inc.
              Matsushita Electric Industrial Co., Ltd.
              Mitsubishi Electric Corp.
              NEC Corporation
	       NTT Corporation
　            Oki Electric Industry Co., Ltd.
              Ricoh Co., Ltd.
　            Toshiba Corporation

TITLE:	PROPOSAL FOR CORRECTION OF H.323 ANNEX D

PURPOSE:	Proposal
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1.ABSTRACT
This contribution proposes some corrections to the text of H.323 Annex D  in COM16-60-E. 
2.DISCUSSION
We find some inconsistencies among the texts of H. 323 Annex D, in H.323 main body and T.38 Annex B in the following respects:  
(1)Voice Channel
(2)DTMF Transmission
(3)Non-Fast Start Procedures
These may affect the interworking between H.323 Annex D implementation and T.38 Annex B implementation. In the following, we propose some corrections with comments. 

2.1 Voice Channel
T.38 Annex B Section3.1.1 “Call Setup” describes that “A facsimile-only over IP environment. In this environment, no voice support is provided. The procedures and requirements of this Annex shall apply to implementations operating in this environment unless they are superseded by a Rec.H.323 Annex D implementation.”
COM16-60-E H.323 Annex D Section4.1 “Opening the Voice channel” describes that  “Zero, one, or two logical channels for voice can be opened depending on the capability of the sender and the receiver” and that “Support of voice by facsimile applications is not mandatory”.
Above two descriptions mention that facsimile application does not require voice support and define the interoperability between  H.323 Annex D and T.38 Annex B. However, H.323 main body specifies that “support of voice is mandatory”. We are concerned with this apparent contradiction between the main body and Annex D.
To clarify the definition of voice support in H.323 Annex D which describes facsimile protocol using H.323 we propose to add “H.323 Annex D”.
2.2 DTMF Transmission
COM16-60-E H.323 Annex D Section4.3 “DTMF Transmission” describes that “DTMF tones shall be exchanged with T.38 Annex B terminals using the RTP DTMF payload type over the same channel as the voice (this does not involve the usage of H.245), or in-band with the voice at the discretion of the manufacture.”.
But, T.38 Annex B has no descripton about DTMF. Furthermore, Recommendation T.38 does not use RTP to transfer IFP(Internet Facsimile Protocol).
In these descriptions, the interoperability between H.323 Annex D and T.38 Annex B is not guaranteed.
Therefore, we propose  that DTMF transmission using RTP for interworking of H.323 Annex D and T.38 Annex B be left for further study in H.323 Annex D.

2.3 Non-Fast Start Procedures
COM16-60-E H.323 Annex D Section5 “Non-Fast Start Procedure” describes that “It is noted that in non-fast start, the normal H.245 based OpenLogicalChannel Procedures can be used to open and close both UDP and TCP fax channels.”.
But, T.38 Annex B Section3.7 “Interoperability” describes that this annex implementation will disconnect from any H.323 implementation as it will not find the fast connect OLCs in the messages.  
Use of Non-Fast Start Procedures assumes fax-detect, but existing T.38 deals with the fax-detect function as further study.
In these descriptions, the interoperability between H.323 Annex D and T.38 Annex B is not guaranteed.
Therefore, we propose  that use of  Non-Fast Start Procedures for interworking of H.323 Annex D and T.38 Annex B be left for further study.

3.PROPOSAL
We propose the following corrections in COM16-60-E H.323 Annex D.
3.1 Section4.1 Voice Channel
“Support of voice by facsimile applications is not mandatory” in H.323 Annex D.

3.2 Section4.3 DTMF transmission second paragraph.
“DTMF tones shall be exchanged with T.38 Annex B terminals using RTP DTMF payload type over the same channel as the voice(this does not involve the usage of H.245), or in-band with the voice at the discretion of the manufacture. In the interworking of this annex implementation and T.38 Annex B implementation, using RTP DTMF payload type over the same channel as the voice is for further study.”

3.3 Section5 Non-Fast Start Procedures
“It is noted that in non-fast start, the normal H.245 based OpenLogicalChannel procedures can be used to open and close both UDP and TCP fax channels. Tunnelled H.245 can also be used to open and close channels. In the interworking of this annex implementation and T.38 Annex B implementation, use of Non-Fast Start Procedures  is for further study.”

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