[SR-Users] T.38 fax, rtpproxy, re-invite

[Daniel-Constantin Mierla]

Hello,


On 02.08.17 12:02, Yu Boot wrote:
> Hello. I'm using almost default kamailio.cfg with nathelper, rtpproxy,
> PSTN dialing and other default features. I have following scheme:
>
> FXS gateway -> (NAT) -> Kamailio -> FreeSwitch
>
> Voice calls work perfectly, no one-direction sound and so on.
>
>
> But with fax machine there was a problem. In wireshark I saw UDPTL
> from FS to Kamailio IP, and no UDPTL at all to FXS gw. I've guessed
> that something's wrong with a re-INVITE request processing in
> Kamailio. I've added this to WITHINDLG route:
>
>                 else if ( is_method("INVITE") ) {
>                         record_route();
>
> }
>
> And problem was magically solved, T.38 now works OK. Is this OK
> solution or this may break something elsewhere?
>
a re-INVITE should be get record route re-enforced, so likely you deal
with some broken CPE. Anyhow, doing the record_route() there should be
harmless for the other CPEs, so can be taken as an easy fix.

Cheers,
Daniel

-- 
Daniel-Constantin Mierla
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