[asterisk-users] Error 488 Not Acceptable Here

[Karsten Wemheuer]

Hi,

Am Donnerstag, den 23.05.2013, 20:48 +0200 schrieb Maximilian Grobecker:
> Am 22.05.2013 16:39, schrieb Andrew Colin:
> > Hi guys,
> > 
> > Any idea why I am getting this error when someone tries to send me a T38
> > Fax?
> Hi,
> 
> Maybe you have not allowed T.38 as acceptable codec ;-)
> You can try with "allow=all" in your sip.conf.

No, T.38 is not a codec and so allow=all will not help.

To use T.38 You have to enable T.38 with "t38pt_udptl = yes" in
sip.conf.

The reason, why You get a "488 Not Acceptable Here488 Not Acceptable
Here", is only detectable with a SIP Trace. There are many reasons e.g.
- Your asterisk version does not support T.38
- T.38 is not enabled (see above)
- T.38 is enabled, but not at the relevant peers (in most versions of
asterisk there is only support for T.38 passthrough, so both peers have
to support T.38)
- There are problems in the transmission and some peers wants to switch
back to audio level and the other or asterisk is not willing to support
this.
The last reason may occur, if You have NAT and do not correctly forward
the data ports of T.38 (UDPTL Ports).

Best way is to get a SIP Trace to analyse. If You provide one, You
should also tell, which version of asterisk.

HTH,

Karsten