[SIPForum-discussion] SIP T.38

[Deepak Baskaran]

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:

> Inline comments…
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> *From:* discussion-bounces at sipforum.org [mailto:
> discussion-bounces at sipforum.org] *On Behalf Of *vamshi krishna
> *Sent:* Saturday, May 28, 2011 11:27 AM
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> *Cc:* discussion at sipforum.org
> *Subject:* [SIPForum-discussion] SIP T.38
>
>
>
> 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.
>
> [m]could be TDM/IP. If you are using fax device which connects to FXS port
> then GW to FAX is on TDM call flow. The GW should support for T.38 and for
> IP-to-Tel routing. You can refer the GW diagnostic tools for analysis.
>
> 2.Type of UA to support FOIP.
>
> [m]UA should support T.38
>
> 3.Can any one suggest test bed setup to test the GW.
>
> [m] If you have FXS ports available in GW then you can connect the fax
> device to GW and test.
>
>
>
> If possible can any provide the links related to protocol flows btw GW &
> FAX.
>
> [m] to my knowledge the call flow is similar to fax call flow on TDM. You
> can search for ITU-T standard for T.38 you will get better understanding.
>
>
>
> Thanks in Advance.
>
> VAMSHI KRISHNA
>
>
>
>
>
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-- 
Deepak Baskaran,
Senior Engineer, GSX-SVT Trunking,
Sonus Networks,
Crescent 4,
Prestige Shantiniketan,
EPIP Zone, Whitefield,
Bengaluru-560066
Tel:- +91 806 789 5107
Mob:- +91 973-921-1911

Check out my New posts @ http://deepuscandybox.blogspot.com
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