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

[Bill Ross]

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 (claims T38 capable)

freeswitch - 1.4.18

x86_64

 

Topology:

 

FS#1: rossco.org, using FusionPBX web GUI to send fax

FS#2: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

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

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): https://pastebin.freeswitch.org/24115

 

Receiver(rossco.duckdns.org): 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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