Fax, VoiP, SIP trunks and T38

My SIP trunk provider supports t38. I am trying to do a direct sip registration to a virtual fax card. Are there any rules / proxy or config that are friendliest to support T38?

How important is QOS if the fax and voice traffic isolated to separate vlan?

Comments

  • I can't answer your T38 question.
    Consider opening a support incident to get help from a WG rep on this.

    QoS will prioritize traffic within the firewall - which will help when there is more traffic to go out a firewall interface than there is bandwidth for that interface.

  • James_CarsonJames_Carson Moderator, WatchGuard Representative

    Hi @lotty

    The firebox itself doesn't support T.38 via the SIP-ALG. However, most modern SIP devices don't need, or will explicitly state that you should not use a SIP-ALG with them.

    So long as you're using a packet filter, the firewall should allow the T.38 registration data out unhindered.

    -James Carson
    WatchGuard Customer Support

  • James_CarsonJames_Carson Moderator, WatchGuard Representative

    There is an open feature request (FBX-10170) to support T.38 in the SIP-ALG, in the event that you need that feature request information.

    -James Carson
    WatchGuard Customer Support

  • Appreciate the feedback.

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