[asterisk-users] T.38 - make conclusion

[Tomislav Parčina]

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