T38 re-invites issue

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Asterisk Users 5 Comments

Hi all.

I have an issue with T.38 and re-invites.

Topology:
provider -> A (asterisk 1.6) -> B (asterisk 1.6) -> extension ->
-> (software fax, gateway whatever).

When between A and B trunk is canreinvite=no everything is working
smooth. When I switch canreinvite to yes, it stop working.

Do you have any idea where the issue can be?
Any help will be much appreciated.

Marek Soha

5 thoughts on - T38 re-invites issue

  • ‘canreinvite’ has *nothing* to do with T.38 re-INVITEs. ‘canreinvite’
    controls whether Asterisk is allowed to setup a direct media path
    between endpoints, or must keep the media flowing through itself.

    If you don’t need a direct media path, don’t enable ‘canreinvite’ (which
    in Asterisk 1.8 has been renamed to avoid this confusion). If you do
    need a direct media path, you’ll have a problem, because Asterisk cannot
    currently setup UDPTL (T.38) direct media paths, only RTP direct media
    paths.

  • Does it matter?
    Phones are working correctly…I tried also portforwarding.

    So corrected topology:
    provider -> A (asterisk 1.6) -> B (asterisk 1.6) -> extension ->
    -> NAT/FIREWALL -> (software fax, gateway whatever).

    Software fax ends with DIS sent, 9600Bbps

    Joel, d

  • Uf…

    you are perfectly clean about that confusion…

    Only thing I want to do, is to route “stream” out of local asterisk – to
    connect final extension directly to “sender” – provider.
    So what I can do if I need i.e:

    1) canreinvite=yes AND send T38 faxes through the same trunk?

    2) maybe canreinvite=no, but UDPTL routed outside local asterisk
    (called canreinvite in normal RTP traffic)?

    Yes and – many thanks Kevin for your perfect reply.

    Kevin, d

  • There is no solution today; as I said, Asterisk only knows how to
    transfer UDPTL traffic through itself right now. The changes to support
    direct media paths for UDPTL wouldn’t be terribly difficult, but nobody
    has done the work yet that I know of.