[asterisk-users] Asterisk T.38 Pass-Through doesn't work

[Larry Moore]

On 3/06/2013 8:04 PM, Andrey Polovov wrote:
> Thank you for reply, Larry!
>
> On 06/03/2013 05:14 AM, Larry Moore wrote:
>> 1) On SPA112 set "FAX T38 Redundancy" = 3
> I have tried to change this value with no effect.
>> 2) Add t38pt_usertpsource=yes in [mtt] section
> This option take no positive effect for me, asterisk continues to use
> ports from udptl.conf range. But in the oser side, I think, that there
> are no problems with network, because:
> * on router, that provide internet for asterisk configured full DNAT
> from white IP to asterisk server,
> * fax between asterisk cmd SendFax and PSTN fax works great.
>> 3) Change maxdatagram=200 to maxdatagram=1400
>> 4) In udptl.conf change T38FaxMaxDatagram to a value of 1400
>> 5) In udptl.conf change use_even_ports to yes
> This settings doesnt help me.
>> You don't appear to list the sip.conf entry for the SPA112.
> I`m sorry, spa112 peer settings are in mysql extconfig, config file
> analogue:
> [297]
> context=office
> secret=xxx
> host-dynamic
> nat=yes
> type=friend
> callerid=297
> disallow=all
> allow=alaw
>> Where did t38pt_rtp & t38_tcp come from?
> This settings I have googled on some forum and then add to my config
> with despair.
>> You may also want to experiment with the SPA112 setting "FAX T38 ECM
>> Enable"
> This option doesnt help me too :(.
>
> Additional info: fax between two SPA112 works perfect! Now I returned
> settings to original state as described in first letter.
>


Have you checked the installed version of firmware against the latest 
available from Cisco?

Looking at your SIP information when your ITSP initiated a T.38 session 
it did not indicate a maxmimum bitrate, it would appear your spa112 
attempted to negotiate a connection at 2400bps.

Do you have a sip debug session when you sent a fax from your Asterisk 
box to the PSTN, it would be interesting to see if it sends it as a t.38 
or reverts to G711 audio.

You will only want to experiment with the ECM option once you have t.38 
working.

Larry.