atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's Faxing and PRI issues

We have a PRI in service frpm Verizon and cannot seem to get faxes to go through on a consistant basis. it seems like every third or fourth fax does not go through and large multiple page faxes (like 15 pages) gets about half way through and the fax machine itself gives an error message and terminates the call.

This is happening at several different faxes and at three of our seperate campuses.

Of course Verison says "Duh--I Dunno!!"

Any help would be appreciated.

John

This is a classic symptom of frame slips on the circuit. Voice calls are not affected but fax/modem traffic is. Check your alarm/error registers. And slips are always the premise equipment's problem. Make sure your PRI card is slave to the carrier's timing.
Mike

Do you have a regular PRI or is it one of the newer IP PRI's? The IP PRI's seem to still have issues with faxing. I do not know if Verizon does, but most of the major CLECs have issues with faxing over the IP PRI's.

Steve

TampaSTEVE: I am assuming it is a regular PRI...does that help?

as mforrence said, check your circuit for errors. then double check your equipment configuration. and, watch those assumptions, they'll bite you.

Check for timing errors, they will have minimal effect on voice calls but cause tons of issues with fax and data transmission. As mentioned you want to make sure you are clocking from the network

No.

How long has this been happening?
How old is the circuit?
What type of interface do you have between your telecom hardware and the telco network? List any pieces of equipment that are sitting between your equipment and telco.

I have been beating my head against the wall on this subject for years. Regardless of the carrier or the equipment being used, VoIP does not carry analog data (fax/modem) reliably. The longer the call, the less-reliable it becomes. This is because the buffers that handle data errors become full. Once this occurs, it is anyone's guess as to whether the call will be successful. We have been discussing this here for at least two years.

These questions are difficult to answer since the equipment that existed when the customer purchased the circuit and today may have changed. Many LECs and CLECs change their PRI circuits to VoIP or "soft switches" without the customer having any knowledge of such activity. Worse yet, toll switches (CO-type switches between central offices) get converted to VoIP where even the owner of the end-office switch doesn't have a clue. That is when the troubleshooting process really gets fun.

"We can send or receive faxes in town, but if we try to send or receive one anywhere else, they usually fail."

This is because any analog data sent out of the local central office is routed through one or several VoIP toll switches handling the call.

We had an incident here about three years ago where the simple "beep" of a particular brand of voice mail was of a frequency that was interpreted by a new Verizon-owned Nortel soft switch as a disconnect signal. A call from anywhere that happened to be routed through that toll switch got knocked down as soon as the VM said "beep".

MarkK probably remembers this one.

Until VoIP is a universal transmission medium that works, and is managed by people who are speaking the same language, I can assure you that it is not our friend.

Checked the clock issue and it is set properly (actually it was doen that way at the time of the install) and still no luck.l...called Verizon and got the usul blah-blah talk.

I am really in a pinch as the customers seem to think that we do not know what the heck we are doing.

Funny thing our sites that use AT&T PRI as the local provider do NOT have any problems at all, just those sites thatuse Verizon PRI..

Any thought?

Thanks as always

John

Oh, I remember that type of incident too. We had exactly the same issue with a Verizon Nortel soft switch and the beep...about two years ago if I remember correctly.

Steve