asterisk users - Feb 2011 - T.38 negotiation error

Hi, I have asterisk 1.6.2.6 on a Debian Lenny system.
When I try to send a fax in T.38 mode I receive this error

ERROR[15035]: res_fax.c:795 set_fax_t38_caps: channel
'SIP/eutelia-sirio-out-00000000' is in an unsupported T.38 negotiation
state, cannot continue.

In my sip.config general section I have added this lines
t38pt_udptl=yes
t38pt_rtp=no 
t38pt_tcp=no 

If I comment this lines, the fax is sended by G711 but this modality is too
slow and instable.

How can I do to solve this problem?
Thank you
 
 

Dott. Marcello Colucci

Microsoft Certified Professional (70-176/70-155/70-100)

MColucci at SIRIOInformatica.it

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2011/2/3 Marcello Colucci (SIRIO Informatica s.a.s.)
<MColucci at sirioinformatica.it>:
> Hi, I have asterisk 1.6.2.6 on a Debian Lenny system.
> When I try to send a fax in T.38 mode I receive this error
>
> ERROR[15035]: res_fax.c:795 set_fax_t38_caps: channel
> 'SIP/eutelia-sirio-out-00000000' is in an unsupported T.38
negotiation
> state, cannot continue.
>
> In my sip.config general section I have added this lines
> t38pt_udptl=yes
> t38pt_rtp=no
> t38pt_tcp=no
>
> If I comment this lines, the fax is sended by G711 but this modality is too
> slow and instable.
It depends on who you're faxing with.

If you can control who you'll be T38-ing with, you might be able to
solve this particular problem.

But if you're T.38-ing with the whole world, in my opinion, there are
too many broken T.38 implementations for you to depend on this.

If you want reliable faxing, you should avoid voip altogether, and use a modem.

I've gotten pretty good faxing by using audio passthrough, over sip,
but it's only sip on a LAN, to a PRI gateway system. Trying to do voip
fax over internet is cheap, but it's not reliable.

On 02/03/2011 07:30 PM, Marcello Colucci (SIRIO Informatica s.a.s.)
wrote:
> Hi, I have asterisk 1.6.2.6 on a Debian Lenny system.
The current version is 1.6.2.16.1, and 1.6.2.17 is on the way (in 
release candidate mode). Is there some reason why you are running an old 
release?
> When I try to send a fax in T.38 mode I receive this error
>
> ERROR[15035]: res_fax.c:795 set_fax_t38_caps: channel
> 'SIP/eutelia-sirio-out-00000000' is in an unsupported T.38
negotiation
> state, cannot continue.
You have not reported the version of res_fax and res_fax_digium that you 
are using.

Given that your Asterisk version is quite old (nearly a year) and you 
may not be running the last FAX modules either, any attempt to help you 
out would be just guessing... because you could easily be experiencing a 
problem that has already been fixed. There have been many fixes to T.38 
negotiation in Asterisk since March of 2010.

If I had to guess, though, I would think that that receiver of this call 
has sent your system a T.38 re-INVITE before you started SendFAX 
running. If that is the case, this problem has already been solved and 
upgrading will take care of it.

-- 
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
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