[Asterisk-Users] Development news :: T38 passthrough support

[George Pajari]

Olle E Johansson wrote:
>
> 11 mar 2006 kl. 23.44 skrev George Pajari:
>
>>
>>>>> *** ITU T.38 -- Fax over VoIP
>>
>> It's not clear from the bug tracker if the problem with a T.38 
>> endpoint (say ATA) behind NAT is working yet (with sip.conf 
>> specifying nat=yes/qualify=yes). Is this working or do both T.38 
>> endpoints have to have public routable IP addresses still?
>
> I wasn't aware of this problem. Please tell me more!

"I can see at least one report so far confirming that T.38 doesn't work 
for nat=yes and canreinvite=no.

I have the same problem. I am using the 
asterisk-1.2.4-t38-20060216.tar.bz2 patch against 1.2.4. Only one of the 
edinpoints is behind NAT.

I did some sniffing and discovered that the problem appears after the 
asterisk server gets reINVITE for the T.38 session. Before the reINVITE 
asterisk will relay all RTP packets to the public IP of the NATed 
endpoint. After the T.38 reINVITE it will indeed switch to T.38 but all 
T.38 packets for the NATed endpoint suddenly start being sent to the 
private IP instead of the public one, never really reching that endpoint 
and resulting in failed fax transmission."

See http://bugs.digium.com/view.php?id=5090

-- 
George Pajari, netVOICE communications    604 484 VOIP (484 8647 x102)
Open Source VoIP/Telephony Specialists  1 877 NET VOIP (638 8647 x102)
                  www.netvoice.ca  www.ip-centrex.ca
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