[SIPForum-discussion] SIP T.38

Thu Jun 2 04:39:03 UTC 2011

http://www.cisco.com/en/US/tech/tk652/tk777/technologies_tech_note09186a
0080114565.shtml

From: Deepak Baskaran [mailto:deepu.sarmatian at gmail.com] 
Sent: Thursday, June 02, 2011 9:07 AM
To: Mahudeswaran; vamshi krishna
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] SIP T.38

Hope this helps you

Hi every one in the forum.

Am trying to test a VOIP gateway which works with legacy PSTN & T.38.

UA<--------(SIP)---------->GW<---------?---------->FAX.

My question is what will be the call flow between the GW & FAX and what
type of tool is to capture flow.

      (Deepak)  The call flow depends on the type of FAX device you use.
There are as of now two types of fax devices, G3FE and Super G3FE. G3FE
speed is around 11.4 KBps. Super G3 speed around 33.5 kBps. Any way,
setting up fax call is done by transmitting/receiving tones inband. 

This is the call flow.

(FAX) CNG Tone ------------->(GW)-------------------->INVITE/RE-INVITE
with media - T38 UDPTL in SDP

When the SIP UA answers with SDP in 200 OK, and also sends CED tone, the
tone will make the FAX device ready with data transfer limit,speed ....

And then SIP UA sends V.21 preamble flag to FAX device via GW, which
makes the FAX device ready t transmit FAX data.

For CNG, CED and V.21, refer T.30 signalling in ITU.

2.Type of UA to support FOIP.

       (Deepak)  If you are testing only the signalling, any SIP tool
whould be Ok, coz the main part is the SDP content.

If you want fax payload as well, kapanga is the one which I know of.

3.Can any one suggest test bed setup to test the GW.

          (Deepak) Kapanga (SIP UA)
----------------->GW----------------------------->FAX Logic(tool for
T.30 FAX over TDM)

If possible can any provide the links related to protocol flows btw GW &
FAX.

        (Deepak)  Can search T.30(T.30, not T.38) standard in ITU. Will
help you a lot.

Thanks in Advance.

VAMSHI KRISHNA

On Wed, Jun 1, 2011 at 9:07 PM, Mahudeswaran <mahudeswarana at acqueon.com>
wrote:

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[mailto:discussion-bounces at sipforum.org] On Behalf Of vamshi krishna
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Cc: discussion at sipforum.org
Subject: [SIPForum-discussion] SIP T.38