[Freeswitch-users] T.38 Secure Fax

[Brian West]

Not possible since t.38 doent take place over RTP!

On Sunday, March 22, 2015, Bill Ross <rossbcan at gmail.com> wrote:

> Folks;
>
>
>
> I am attempting to deploy T.38 Fax (ZRTP Secure) with FreeSwitch /
> FusionPBX and am seeking system architectural advice regarding how to
> approach this.
>
>
>
> Question #1: Recommended T.38 capable ATA (and settings) for reliable FAX.
>
>
>
> Approach #1 ZRTP mitm with T.38 SIP Extension (either T.38 capable ATA or
> soft endpoint) – preferred approach
>
>
>
> T.38 SIP endpoint <-> FS#1 / mitm <-> cloud <-> FS#2 mitm <-> T.38 SIP
> endpoint
>
>
>
> I am using a soft T.38 SIP endpoint, plugin for Windows Fax and Scan from
> faxback, available here:
>
>
>
>
> http://www.faxback.com/Products/Trialware.aspx?NET_SAT_EDITION=Small%20Business
>
>
>
> SIP Gateway, just prior to bridge:
>
> *<action application="export" data="fax_enable_t38_request=true"/>*
> *<action application="set" data="execute_on_answer=t38_gateway peer"/>*
>
>
>
> *Extension, just prior to bridge:*
>
>
>
> *<action application="set" data="fax_enable_t38_request=true"/>*
> *<action application="set" data="execute_on_answer=t38_gateway self"/>*
>
>
>
> *What I am seeing (two FS systems), each with T.38 soft extensions,
> attempting to fax each other.*
>
>
>
> *                ZRTP negotiation fails (Max retransmissions fail) ->
> NOZRTP*
>
> *                ONE SDP is T38Fax (extension or gateway), Other is
> PCMU/8000*
>
> *                The extension of T.38 enters state [ready] and
> immediately hangs up, I assume from SDP mismatch*
>
>
>
> Question #2: Anyone successfully done this, if so, how?
>
> Question #3: Is what I am attempting architecturally possible? Can T.38
> be mitm’d?
>
> Question #4: If so, advice regarding how to debug the ZRTP negotiation
> failure and SDP negotiation failure.
>
>
>
> Approach #2: FS terminates incoming T.38 fax, stores and forwards to fax
> extension, FS terminates outgoing T.38 fax, stores and forwards to SIP
> gateway to final destination.
>
>
>
> T.38 SIP endpoint <-> FS#1 / terminate fax <-> FS#1 forward fax <-> cloud
> <-> FS#2 / terminate fax <-> FS#2 forward fax <-> T.38 SIP endpoint
>
>
>
> Question #5: Will this work? Anyone done it, how? ZRTP gotcha’s?
>
>
>
> Thanks;
>
> Bill
>


-- 

*Brian West*
brian at freeswitch.org


*Twitter: @FreeSWITCH , @briankwest*
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