[Freeswitch-users] Freeswitch / FusionPBX T.38 Fax

[Michael Jerris]

you probably don't want to use fax_enable_t38_request = true unless you know for sure that you need it, and you would NEVER want that on both sides.


> On Apr 11, 2015, at 12:04 PM, Bill Ross <rossbcan at gmail.com> wrote:
> 
> Hi;
>  
> I am attempting to get T38 Fax working between two FS/FusionPBX installations using mod_spandsp. I am unable to get into T.38 mode, T.30 used, successful fax.
> Note that zrtp is disabled for fax calls, due to T38 udpl (not rtp media) incompatibility
> Thanks Brian West!: “T.38 Fax takes place over UDPTL, There for it can NOT be encrypted as there was never really a standard for doing so.”
>  
> Details (both FS’s):
>  
> SIP Provider: freephoneline.ca <http://freephoneline.ca/> (claims T38 capable)
> freeswitch - 1.4.18
> x86_64
>  
> Topology:
>  
> FS#1: rossco.org <http://rossco.org/>, using FusionPBX web GUI to send fax
> FS#2:rossco.duckdns.org <http://rossco.duckdns.org/>, using spandsp extension to receive fax
>  
> (spandsp txfax, x1020)FS#1 -> cloud  -> FS#2(spandsp rxfax, x9000)
>  
> Key variables for fax sender (FS#1), during call:
> $domain= rossco.org <http://rossco.org/>
> Spandsp Fax extension: 1020
> t38_passthru = false
> zrtp_secure_media = false
> fax_enable_t38 = true
> fax_enable_t38_request = true
> fax_use_ecm = off
> inbound-late-negotiation = true
> ignore_early_media = false
>  
> Key variables for fax receiver (FS#2), during call:
> $domain= rossco.duckdns.org <http://rossco.duckdns.org/>
> Spandsp Fax extension: 9000
> t38_passthru = false
> zrtp_secure_media = false
> fax_enable_t38 = true
> fax_enable_t38_request = true
> fax_use_ecm = off
> inbound-late-negotiation = true
> ignore_early_media = false
>  
> Full Logs w/siptrace:
>  
> Sender(rossco.org <http://rossco.org/>): https://pastebin.freeswitch.org/24115 <https://pastebin.freeswitch.org/24115>
>  
> Receiver(rossco.duckdns.org <http://rossco.duckdns.org/>): https://pastebin.freeswitch.org/24116 <https://pastebin.freeswitch.org/24116>
>  
> Note that the SDP’s are correct for T38:
>  
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 v=0
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 o=FreeSWITCH 1428750600 1428750602 IN IP4 198.48.238.130
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 s=FreeSWITCH
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 c=IN IP4 198.48.238.130
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 t=0 0
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 m=image 16448 udptl t38
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 a=T38FaxVersion:0
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 a=T38MaxBitRate:14400
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 a=T38FaxFillBitRemoval
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 a=T38FaxRateManagement:transferredTCF
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 a=T38FaxMaxBuffer:2000
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 a=T38FaxMaxDatagram:400
> 590fc4c4-3035-438e-a4c7-4a9d8e51ee42 a=T38FaxUdpEC:t38UDPRedundancy
>  
> Questions:
>  
> 1 - According to my interpretation of logs, T38 is not negotiated, despite T38 SDP’s
> 2 - What am I missing?
>  
> Thanks;
> Bill Ross
>  
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