[asterisk-users] FFA SendFax rejects T.38 reINVITE (488 Not acceptable here)

[Kevin P. Fleming]

On 10/20/2010 11:35 AM, VoIP Question wrote:
> On Wed, Oct 20, 2010 at 4:25 PM, Kevin P. Fleming <kpfleming at digium.com
> <mailto:kpfleming at digium.com>> wrote:
> 
> 
>     This was fixed in Asterisk 1.6.2.12 and later releases, so if you were
>     running the current version, you wouldn't have experienced this specific
>     problem. This was listed in the ChangeLog for 1.6.2.12, but
>     unfortunately the commit message the developer wrote did not explain why
>     the change was made or what problem it was addressing, so you wouldn't
>     have noticed it.
> 
>     In any case, upgrading to 1.6.2.12 or later will cure this problem.
> 
> I upgraded to 1.6.2.13 and now we get this error (with a specific
> destination, to which we occasionally need to send faxes):
> 
> WARNING[857]: udptl.c:1087 ast_udptl_write: (SIP/XXXXXXXXXXX): UDPTL
> asked to send 50 bytes of IFP when far end only prepared to accept 30
> bytes; data loss will occur.You may need to override the
> T38FaxMaxDatagram value for this endpoint in the channel driver
> configuration.
> 
> 
> How can we fix it, without risking incompatibility with other
> end-points? What's a "channel driver configuration" and where is it?

It appears that you need to spend some time learning the basics of
Asterisk. In this case, the channel driver is chan_sip, since the
channel involved is a SIP channel, and the 'channel driver
configuration' is the sip.conf file. It is unfortunate that you have
chosen to tackle a very complex task (T.38 interoperability is fraught
with problems due to widely varying implementations) as your first
experience with Asterisk... there's a lot you'll need to learn to be
able to diagnose and troubleshoot problems. Asterisk alone is not 'point
and click', and adding T.38 to the mix makes things more complicated.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kfleming at digium.com
Check us out at www.digium.com & www.asterisk.org