weiqi228 at gmail.com
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 Posted: Wed Oct 29, 2014 11:10 am Post subject: [asterisk-users] My Asterisk can not send fax via T.38 |
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Hello,
I am a newer on asterisk. when I tried to send fax, I can not get success. After doing a lot of reseach, I decide to ask my question at here.
Instead of using old fax machine, I want my system can send fax via t.38. Could anyone give me some idea to correct my configuration?
Thanks a lot! Here is the detail:
my system: ubuntu 14.04 + asterisk 11.7
I use apt-get to install the ubuntu default version of asterisk 11.7. for easy debug, I just change a few param value with the default version sip.conf | Quote: | t38pt_udptl = yes,redundancy,maxdatagram=400
faxdetect = yes
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extension.conf | Quote: | [sendFAX]
exten => s,1,VERBOSE(sending fax...)
exten => s,n,Set(FAXOPT(headerinfo)=Fax from a Demo test)
exten => s,n,SendFAX(/tmp/demo.tiff,f)
;I get demo.tiff file from "$ gs -q -dNOPAUSE -dBATCH -sDEVICE=tiffg4 -sPAPERSIZE=letter -sOutputFile=<dest> <src>"
exten => s,n,VERBOSE(ok!)
exten => s,n,Hangup
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I use AMI to originate a fax call. In the CLI, everything looks well. I didn't get any error message. When I use wireshark to check the detail of this comunication, I found Asterisk used G711 instead of using T.38 which is expected.
however, at the receiver end, I didn't receive the fax, and I just got a error "Dcn No Dis" After a research, I got this:
T.30 Fax Signaling Messages In a Voip fax call, T.38 packets are preceded and succeeded by T.30 fax signaling messages. These messages include: | Quote: | - DIS: Digital Identification Signal indicating terminating fax capabilities (for example, data rate)
- DCS: Digital Command Signal indicating transmission mode that will be used by originating fax (for example, transfer rate)
- TCF: Training Check Sequences (sent for 1.5 seconds)
- CFR: Confirmation To Receive indicating the receiving fax is ready to receive the document
- MPS: MultiPage Signal (sent after each page if more than one page is sent)
- MCF: Message Confirmation indicating the page was received
- EOP: End Of Procedure message indicating there are no more pages to be sent
- DCN: Disconnect message
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Additional optional messages: | Quote: |
1.CSI: Called Subscriber Identification
2.TSI: Transmitting Subscriber Identification |
But I am still confused with what "Dcn No Dis" means what's wrong with my asterisk system.
I am sure of these: - the receiver is working well.
- My ISP provider is fully support fax termination both in g711 and t.38
- My testing server is not behind any firewall.
The demo.jpg is my wireshark's screenshot. form 19 to 1841, all traffic are RTP package.
The t.38 png diagram illustrates is a typical fax call. |
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