Subject: Re: [Megaco] FAX on H.248/MEGACO

From: "Schwarz Albrecht" <[email-masked]>
Date: Fri, 1 Aug 2008 13:05:41 +0200

Andre,
 
facsimile is a voiceband data (VBD) service in PSTN/ISDN, there are
basically two transfer technologies in IP networks.
Before looking at the control aspects (= H.248), you should firstly
consider the bearer service options. See
 
V.152 (01/05)
<http://www.itu.int/rec/T-REC-V.152/recommendation.asp?lang=en&parent=T-
REC-V.152-200501-I>  Procedures for supporting voice-band data over IP
networks  
and
 
T.38 (04/07)
<http://www.itu.int/rec/T-REC-T.38/recommendation.asp?lang=en&parent=T-R
EC-T.38-200704-I>  Procedures for real-time Group 3 facsimile
communication over IP networks  
 
Both ITU-T Recommendations providing sections on H.248.
You may see that there are two options already for T.38.
 
/Albrecht

________________________________

	From: [email-masked] [mailto:[email-masked]]
On Behalf Of [email-masked]
	Sent: Donnerstag, 31. Juli 2008 17:13
	To: [email-masked]
	Subject: Re: [Megaco] FAX on H.248/MEGACO

	Appendix III (H.248 call establishment procedure examples for
facsimile-capable media gateways) from T.38 Spec should have what you
are looking for. I am looking at draft in force (04/2007).

________________________________

	From: [email-masked] [mailto:[email-masked]]
On Behalf Of Andre Rosa Stefanini
	Sent: Thursday, July 31, 2008 10:02 AM
	To: [email-masked]
	Subject: [Megaco] FAX on H.248/MEGACO

	Hi,

	I've been asked about something not clear on specs: When a MG
receives fax and/or modem tones on RTP port, it should change the codecs
in order to allow tones to be passed in a correct way to be decoded as a
fax or modem in the other side. There are some options (i.e. using G.711
or T.38). This way, the MG which detected the fax tone must set up a new
codec. For this, we have two options: automatic or negotiated. 

	It's not clear on RFC which of these options is mandatory for
the MG, or if both of them. Could you help me with this?

	Would someone could provide call-flows regarding fax/modem
detection?

	Thanks,

	ANDRE

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Megaco mailing list
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---

From: "Gunnar Hellstrom" <[email-masked]>
Date: Sun, 3 Aug 2008 21:23:14 +0200

H.248.2 also has the details on fax detection / T.38 procedure.

  _____  

From: [email-masked] [mailto:[email-masked]] On Behalf Of
[email-masked]
Sent: Thursday, July 31, 2008 5:13 PM
To: [email-masked]
Subject: Re: [Megaco] FAX on H.248/MEGACO

Appendix III (H.248 call establishment procedure examples for
facsimile-capable media gateways) from T.38 Spec should have what you are
looking for. I am looking at draft in force (04/2007).

  _____  

From: [email-masked] [mailto:[email-masked]] On Behalf Of
Andre Rosa Stefanini
Sent: Thursday, July 31, 2008 10:02 AM
To: [email-masked]
Subject: [Megaco] FAX on H.248/MEGACO

Hi,

I've been asked about something not clear on specs: When a MG receives fax
and/or modem tones on RTP port, it should change the codecs in order to
allow tones to be passed in a correct way to be decoded as a fax or modem in
the other side. There are some options (i.e. using G.711 or T.38). This way,
the MG which detected the fax tone must set up a new codec. For this, we
have two options: automatic or negotiated. 

It's not clear on RFC which of these options is mandatory for the MG, or if
both of them. Could you help me with this?

Would someone could provide call-flows regarding fax/modem detection?

Thanks,

ANDRE

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