T.38 Fax Over IAX2?

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Let’s assume we have this situation:

Call => SIP TSP => Asterisk1 => IAX2 => Asterisk2 => SIP/ATA => Fax

I have two Asterisk Servers in two branch offices, which are interconnected by IAX2 and the Switch functionality.

Asterisk1 is connected to the public phone network via a SIP provider which supports T.38

A fax is connected to a SIP T.38 capable ATA Box.

If that fax is connected to Asterisk1, then the call is transparently routed and received by this ATA box in T.38 mode.

If the fax is connectd to Asterisk2, then there is a IAX Link between the originating SIP T.38 Fax and the Destination which is also T.38
capable. But T.38 is refused by Asterisk1. Fax receptions falls back to g711 (sometimes) and is unreliable behind Asterisk2.

Google hints to me, that T.38 fax reception over IAX2 is possible with IAXMODEM. So I suppose udptl t.38 should also transparently be passed between SIP and IAX2. But I find no way to configure t38 on a IAX2

Am I missing something?

-BenoƮt Panizzon-

I m p r o W a r e A G – Leiter Commerce Kunden

One thought on - T.38 Fax Over IAX2?

  • Benoit Panizzon wrote:

    This would be incorrect.

    IAXMODEM does not support T.38.

    I’m currently using HylaFAX+ in several of our facilities that are connected by IAX2, what I do is to receive the incoming fax, convert to a print stream or pdf and print the fax out to the remote ‘fax printer’.

    Or, I email the converted PDF to the recipient.