fax relay over IP - G.711, T.38

Hello group!

I wish to exchange experiences with someone who managed to successfully and reliably set up the fax relay over the IP - either running G.711 or T.38 on the IP side. Of special interest for me are the configurable parameters which influences the reliability of the transmission - both parameters on the gateways and on the faxes.

Network topology is as follows:

analog fax A - access GW - IP network - trunking GW - TDM network - trunking GW - IP network - access GW - analog fax B

Does it make sense to run T.38 in such configuration (4 GW conversion involved)? Is T.38 more suitable for 2 GW conversion only?

In general - how do standard analog faxes (e.g. Cannon, Brother, Panasonic) or analog fax modems (e.g. US Robotics, Zyxel) perform in an IP network? Can we configure them in any way to make them aware of the IP network? Any comment or experience is more than welcome.

Best regards,


rus(no spam)@iskratel.si

ommit (no spam) from e-mail address

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Sani Rus
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I'm using a VoIP provider that runs a G.711 codec by default. I can't tell you what their network backbone uses, for certain, other than to say I know its an IP backhaul from the Sipura SPA-2100 in my house to their IP POP.

Our fax machine is a 1994 era Brother. The fax transmission looks "clean" on the receiving side, but we believe we have seen a packet drop.

The status indication on our fax machine indicates "line condition problems", and when we hear the modem interaction there appears to be a bunch of white noise on the line, upon fax transmission initiation.

We could use "overseas mode" on that old fax machine should we encounter problems.

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