[asterisk-dev] State of FAX (primarily T.38) in Asterisk trunk (planning for 1.8 release)

asterisk at ntplx.net asterisk at ntplx.net
Thu Dec 3 15:46:57 CST 2009

Quoting "Kevin P. Fleming" <kpfleming at digium.com>:
> Over the past year, some of us at Digium have spent many (MANY) hours
> working on FAX support in Asterisk....

Thanks for all the hard work! I'm waiting for 1.8 before I upgrade from 1.4
It has enough new features it's worth the wait and the work to upgrade,
and it's getting harder to migrate my needed 1.6 features back to 1.4...

But somewhere along the line T.38 in Trunk became broken for me. I'm using
SPANDSP and app_fax with a Cisco AS5300. It used to work, but not any more.
Audio faxes still work.

On receiving a T.38 fax I now get this back from the Cisco:
  Got SIP response 420 "Bad Extension" back from 204.213.xxx.xxx
And it fails.

On sending a T.38 fax I now get:
  udptl.c:1054 ast_udptl_write: (SIP/860xxxxxxx): UDPTL asked to send  
23 bytes of IFP when far end only prepared to accept 19 bytes; data  
loss will occur.You may need to override the T38FaxMaxDatagram value  
for this endpoint in the channel driver configuration.
But it works... (may be it's just an old problem but a new warning)

I'm looking into the problem and if it's a true bug (vs. some type of
problem I caused), I'll open a bug report after I do some more testing.
This statement is mostly for the mailing list records and to see if anyone
else is now having problems with trunk/T.38 fax/cisco AS5300...


Andrew Lindh
<andrew at netplex.net>

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