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Summary:ASTERISK-15578: T.38 with devices behind NAT does not work
Reporter:Ilya Pichugin (ipich)Labels:
Date Opened:2010-02-04 07:42:00.000-0600Date Closed:2011-06-07 14:08:02
Priority:MinorRegression?No
Status:Closed/CompleteComponents:Channels/chan_sip/T.38
Versions:Frequency of
Occurrence
Related
Issues:
Environment:Attachments:( 0) bug_asterisk_t38_real.log
( 1) t38_172.31_for_mantis.log
( 2) t38_192.168_for_mantis.log
Description:I've found trouble described in https://issues.asterisk.org/view.php?id=10417
There is patch for 1.4, but I have 1.6.2, so it does not work

Scenario is :
Host1 192.168.x.x (NAT IP 100.100.100.100) sends fax host2 200.200.200.200 but after re-invite t.38 session asterisk transmits udptl packets to internal IP 192.168.x.x
Comments:By: Joshua C. Colp (jcolp) 2010-02-04 08:38:06.000-0600

The patch you are referencing added a configuration option which caused Asterisk to send UDPTL to the IP address of the RTP, and to the port negotiated for UDPTL. If the port was forwarded then it could work.

Have you done so? Otherwise this trace looks normal, we get no packets from the other side so we can't use the source IP address/port of them for sending UDPTL and have to use what was given in the SDP.
By: Ilya Pichugin (ipich) 2010-02-05 02:52:26.000-0600

"The patch you are referencing added a configuration option which caused Asterisk to send UDPTL to the IP address of the RTP, and to the port negotiated for UDPTL. If the port was forwarded then it could work."

It's correct.
So I've made new tests with another device - Addpac. This device advertises the same udp port for UDPTL session as the RTP session, therefore socket is alive and it must faxing but asterisk still transmits to internal IP rtp port, not nat IP and rtp port. Check my t38_192.168_for_mantis.log trace

"we get no packets from the other side so we can't use the source IP address/port"

Sorry for my knowledge base, what do you mean 'we get no packets from the other side'? What type of packets? I've made test for available host from Asterisk - this is 172.31.255.250, this is not NAT ip and Asterisk pings that

I've seen that first UDPTL packet from Addpac follows after UDPTL packets from Asterisk and fax passes. Check my t38_172.31_for_mantis.log trace

So my question is why asterisk transmits to internal IP, I do not see any attemps (even fail attemps) to transmit to NAT IP.


By: Ilya Pichugin (ipich) 2010-02-09 00:35:28.000-0600

any ideas why this might be?
By: Leif Madsen (lmadsen) 2010-03-23 12:27:57

I'd suggest you try this again with the latest 1.6.2 version as T.38 has been an ongoing process. In fact, because 1.6.2.2 is quite old now, I'm going to close this issue and suggest you open a new issue if you're continuing to have problems. That way we can address it with a fresh start.