Outbound Faxes fail intermittent with ATA186 and 6608

[ahopkins]

I am running CCM 3.3.3, using 6608 blades for PRI PSTN access and ATA186's connecting 48 fax machines. The ATA's are running SCCP version 3.2.0 and are configured for Fax-passthru as well as the 6608 blades being configured for fax-passthru. The faxes are of different brands and out of 48 we have troubles reported on 5 where outbound faxes fail 95% of the time but inbound faxes work 100% of the time. There are no errors on the PRI, switch ports or ATA ethernet port. I have swapped the faxes to locations of working faxes and they still fail, yet when connected to a POTS line they work fine. I have also taken a working fax and moved to the location of the failing fax, and the fax works everytime. The 6608 blades are rather difficult to trouble shoot since there are very few debugs that can be run. The HP faxes seem to work fine, but one of the failing faxes is Xerox. Has anyone experienced this type of trouble before, perhaps only with specific model/brand faxes.

Thanks

[dgahm]

Have you tried disabling Super G3 mode? Super G3 is really a V34 modem call, and will fail if your gateways don't do modem passthrough. Many faxes that attempt Super G3 through IP Telephony will drop the call before they downshift to G3. On some machines you can disable ECM which is required for Super G3, and achieve the desired result.

Good luck.

[dhingst · Accepted solution]

While I love ip telephony I just hate fax machines running over ip! I've had a lot of troubles with multiple brands of fax machines in this same configuration.

When using an ATA make sure you have the latest device load for the 6608's. That helped me in some cases.

Disable ECM, Super G3 and fix the baud rate to 9600. If that works you can try setting the speed up to 14.4k which works for some machines but not others. This has helped the most.

Different machines seem to be more sensitive to packet loss or delay. Make sure you have zero packet loss, especially across a wan. You can try turning on packet redundancy to see if that helps. If it does then you are probably losing packets somewhere. Don't forget to check the PRI's stats. We've had problems because of packet loss there, not just on the WAN/LAN.

My ultimate solution has been to move to FXS ports in the routers at remote sites and using VG248's here in the central site. (The 248's have had their share of similar problems!) I still have some machines that won't work right but it's far fewer than when using ATA's.

Here are the settings on my 6608. (While not perfect it's working most of the time.

Fax and Modem Parameters

Fax Relay Enable Not checked

Fax Error Correction Mode Override Not checked

Maximum Fax Rate 14400bps

Fax Payload Size 20

Non Standard Facilities Country Code 65535

Non Standard Facilities Vendor Code 65535

Fax/Modem Packet Redundancy Not checked

NSE Type IOS Gateways

Device load is D00404000006.

The one setting that has had the most impact is the Packet Redundancy. I've got it off right now and am having good results since I've found a couple of places where I was dropping packets that the Redundancy setting was covering over. (I had problems with the VG248's with older code until this setting was turned on.)

Any ATA's connecting to a gateway across the wan are put in seperate regions in CM so they can make a g711 call rather than g729 like the phones do. It eats more bandwidth but it's the only way they will work across the wan.

Hope this helps.

[ahopkins]

dhingst-

Thanks for the post. We went on your recommended settings, except left the baud rate set at 9600, and the 5 fax machines we were having problems outbound with, are now working. I agree with you. I would always prefer to leave the faxes off of the VOIP network.