Fax Modem with ATA186 via MGCP to PRI

[Burgal]

Hi there.

I have two configurations of fax. Standard analog fax machines plugged into one port of an ATA186.
I also have 2 fax modems on a server for fax broadcast. They're each plugged into a port on an ata186.

I find that a standard fax machine on an indentically configured ata will work flawlessly.

However, the fax modems fail 98% of the time after sending 1 or 2 pages of a multiple page document.

I'm using 8 ATA186's
a 2811 router with a vwic card for a PRI 23 channel
Cisco Callmanager v4.2(3)
PRI running MGCP
ATAs running SCCP

router MGCP config:
mgcp
mgcp call-agent 10.0.100.22 2427 service-type mgcp version 0.1
mgcp dtmf-relay voip codec all mode out-of-band
mgcp rtp unreachable timeout 1000 action notify
mgcp modem passthrough voip mode nse
mgcp package-capability rtp-package
no mgcp package-capability res-package
mgcp package-capability sst-package
no mgcp package-capability fxr-package
mgcp package-capability pre-package
no mgcp timer receive-rtcp
mgcp sdp simple
mgcp fax t38 inhibit
mgcp rtp payload-type g726r16 static
mgcp bind control source-interface FastEthernet0/0
mgcp bind media source-interface FastEthernet0/0
!
mgcp profile default
!
!
!
dial-peer voice 1 pots
description **** T1 PRI Inbound Outbound****
service mgpapp
port 0/0/0:23
!



ATA Audio Parameters
LBRCodec = 1
AudioMode = 0x00120012
ConnectMode = 0x90000400
FXSInputLevel = -1
FXSOutputLevel = -4

 

[pndscm]

We try not to run FAX machines/modems on ATA's. There is some kind of buffering problem with ATA's. Some fax machines work, some don't as you are finding out. Same problem, 1-2 page faxes are OK but longer faxes fail. We tell customers to use FXS ports for faxes.

Try reducing the speed on the FAX modems to 9600 and see what happens.

 

[Burgal]

What's a good way to limit the connection speed to 9600?

 

[pndscm]

It needs to be done in the Fax Machine or Fax Modem.

 

[Burgal]

Do you know a modem initialization string that will allow me to limit the fax transmission speed of a fax modem?

 

[pndscm]

Depends on the modem. Try a Google search with the modem type and you should be able to find the commands.

 

[ekrieger]

First thing is to limit the RX/TX of the FAX speed to 14400 or even 9600 bps.

Next, try the following (additional) settings on your MGCP Gateway:

voice service voip
fax protocol pass-through g711ulaw
modem passthrough nse codec g711ulaw

ccm-manager mgcp
no ccm-manager fax protocol cisco
mgcp modem passthrough voip mode nse
mgcp modem passthrough voip codec g711ulaw


Good luck.

 

[Burgal]

Thank you for your support.

I have contacted cisco tac and they suggested something similar. However, with modem passtrhough enabled, faxes from machines would be ok, but faxes from the fax modem still failed during handshaking.

I have updated my ATA to be 0x00120012 for audio settings and my PRI gateway config to read the following:

no ccm-manager fax protocol cisco
!
mgcp
mgcp call-agent 10.0.100.22 2427 service-type mgcp version 0.1
mgcp dtmf-relay voip codec all mode out-of-band
mgcp rtp unreachable timeout 1000 action notify
mgcp package-capability rtp-package
no mgcp package-capability res-package
mgcp package-capability sst-package
no mgcp package-capability fxr-package
mgcp package-capability pre-package
no mgcp timer receive-rtcp
mgcp sdp simple
mgcp fax t38 inhibit
mgcp rtp payload-type g726r16 static
mgcp bind control source-interface FastEthernet0/0
mgcp bind media source-interface FastEthernet0/0
!
mgcp profile default
!
!
!
dial-peer voice 1 pots
description **** T1 PRI Inbound Outbound****
service mgpapp
port 0/0/0:23