asterisk users - Nov 2006 - T.38 - make conclusion

This is one long letter about T.38 and Asterisk. I hope it will help me, and
lots of other Asterisk users to understand some T.38 problems with Asterisk.
This is my situation:

I have Panasonic DX600 FAX machine. It's connected to Asterisk 1.2.13 thru
ATA adapter (I have used both, Cisco 186 and Grandstream HandyTone 386).
Asterisk is connected with my SIP provider. That link that my provider gives me
is dedicated for VoIP. QOS is up and it doesn't go thru Internet, it goes
thru dedicated line.

That Panasonic DX600 can receive FAX from everybody, but it can send FAX to 70%
of numbers. The numbers to who I can send FAX works all the time (none fax has
failed). The numbers I can't send fax newer work (all fax fails).

Every time I try to send fax to some number that fails, I get following warning:
WARNING[2237] chan_sip.c: Unknown SDP media type in offer: image 31358 udptl t38

As far as I understand, T.38 is VoIP protocol, so Panasonic DX600 on its analog
port shouldn't use T.38. My HT386 is in pass thru mode, so he shouldn't
use T.38 also. Cisco 186 ATA doesn't support T.38.

Big question is, who tries to establish T.38 connection?
- Panasonic DX600 - because it's connected on analog port, I believe he
doesn't
- ATA - Cisco doesn't support it and on HT386 it's turned off
- Asterisk - doesn't support it
So who tries to establish T.38 connection?

I'm not planning to use T.38. I'm only trying to make FAX work. To do
that I need to find out who is causing the problem that is giving me this
warning
WARNING[2237] chan_sip.c: Unknown SDP media type in offer: image 31358 udptl t38

I'll appreciate any info on this topic.



--
Tomislav Par?ina
Lama Computers Split
Stinice 12, 21000 Split
Tel.: +385(21)270248
Mob.: +385(91)1212148
SIP: tomo@sip.lama.hr
e-mail: tparcina#lama.hr
http://www.lama.hr

Tomislav Par?ina wrote:
> Asterisk is connected with my SIP provider.
>
> I'm not planning to use T.38. I'm only trying to make FAX work. To
do that I need to find out who is causing the problem that is giving me this
warning
> WARNING[2237] chan_sip.c: Unknown SDP media type in offer: image 31358
udptl t38
>   
I want to guess that it's your SIP provider. 

Faxing via VoIP (SIP) is not reliable unless you are using T38, my guess 
is your sip provider is providing this feature.

Doug


-- Ben Franklin quote: "Those who would give up Essential Liberty to 
purchase a little Temporary Safety, deserve neither Liberty nor Safety."

In article <455C5E2F.7050701@drdos.info>, support@drdos.info
says...
> I want to guess that it's your SIP provider. 
> 
> Faxing via VoIP (SIP) is not reliable unless you are using T38, my guess 
> is your sip provider is providing this feature.
Hi Doug!

Have I understand it right. You are saying that my provider, when it detects FAX
stream, he is trying to use T.38. And since my Asterisk doesn't support it I
get the error message? So, it does nothing to do with FAX machine that is (over
ATA) plugged to my Asterisk, or with FAX that is on the other side?

Please confirm or deny this.



--
Tomislav Par?ina
Lama Computers Split
Stinice 12, 21000 Split
Tel.: +385(21)270248
Mob.: +385(91)1212148
SIP: tomo@sip.lama.hr
e-mail: tparcina#lama.hr
http://www.lama.hr