[asterisk-dev] fallback to audio faxing when T.38 INVITE fail with 488/606 Not acceptable

[Kristijan Vrban]

> However, the original message was a bit unclear if it was a re-invite or an invite.
re-invite

And there is no difference if chan_sip get a 488 or 606 for the T.38
re-INVITE (both are valid response) . As far as i can see, there is
simply no logic that handle a fallback to audio fax when the caller
can not handle T.38? I examined how a Cisco/Linksys SPA2120 handel
this: It ACK the 488/606 for its rejected T.38 re-INVITE and send a
re-re-INVITE with PCMU, and then the fax is transported via audio RTP.

Kristijan