[Freeswitch-users] Receiving faxes over sip trunk

David Witham david.witham at netsip.com.au
Thu Aug 20 05:37:58 MSD 2015


We operate fax2email services as well as end-to-end fax transmission using FreeSWITCH. There are a few things to be wary of:


1) If you are connecting over a public network, either to your customer or to your provider, t.38 on that leg is your only reliable solution. You can gateway between t.38 and G711 using FreeSWITCH if you have different needs on each leg. We have found this to work reliably.


2) Find out whether your provider supports t.38 or not and find out as much as you can about their network topology. With the way some providers deploy their networks, t.38 is the only viable solution. With others, where there may be only one or two hops from an ISDN gateway to your FreeSWITCH, G711 can work very well. Its also faster than t.38. We've also found providers with a VoIP only call path and who manage their networks well we can reliably use G711. For us we pick and choose whether to use t.38 or not based on the capability of the provider.


3) If you have private links to your customers go with G711. There is a lot of CPE that has poor t.38 support and it causes more problems than it solves.


4) When using G711, particularly to CPE, turn off any features that manipulate the media stream - adaptive jitter buffers, echo cancellation, silence suppression, fax-relay/bypass. You want an unadulterated G711 stream for it to have the best chance of success. With the right network connections G711 works very well.


David Witham?

________________________________
From: freeswitch-users-bounces at lists.freeswitch.org <freeswitch-users-bounces at lists.freeswitch.org> on behalf of Jai Rangi <jprangi at didforsale.com>
Sent: Thursday, 20 August 2015 02:31
To: FreeSWITCH Users Help
Subject: Re: [Freeswitch-users] Receiving faxes over sip trunk

Mike,
We are using Fax on freeswitch for some clients for receiving as well as sending faxes. Have not seen any problem except few incidents here and there.

-Jai Rangi
www.didforsale.com<http://www.didforsale.com>

On Wed, Aug 19, 2015 at 7:47 AM, Michael T Mowatt <mmowatt at nexxphase.com<mailto:mmowatt at nexxphase.com>> wrote:
HI all,
                Was wondering if anyone is using FreeSWITCH to receive faxes over a SIP trunk, and what the experience has been like.  I know I've heard this can be difficult, but was interested in real experiences.

Thanks,
Mike


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