PRI/Fax Issue

[BogeyShooter]

Customer has a Coral II v9.89. Two days ago, they started having fax issues to some fax numbers. Nothing has changed in the Tadiran. The PRI comes from Cisco equipment. The Cisco guys tell me that they have not changed anything in their equipment either.

Any ideas?

 

[disturbedone]

Oh dear. Don't take the word for a Cisco tech They're worse than calling a telco. It's never their problem!

Fax/modem issues are 99% ISDN sync issues. You have probably lost sync on the PRI card. Loss of sync won't affect voice calls, just fax/modem calls that are synchronous. Check alarms in PI. Ensure in DTDB that you have sync set correctly. Ensure PRI card is in the correct PrmSync/SecSync slot - assuming that it's been working forever then this is probably all fine. But sync can be lost for a variety of reasons, even from the telco.

Resetting the PRI card will probably re-sync. But if you've lost sync from the Cisco box then it could be an issue with the Cisco box (don't let them tell you otherwise). That's the trouble with IT ppl trying to work on phone systems, they don't understand simple telephony

But check the PI alarms and it will tell you straight up. Also check the LEDs on the PRI card too.

 

[BogeyShooter]

I've checked the clocking and the sync on the PRI and everything looks fine. I can't think of anything that I could change in SLT programming,PRI programming, or Trunk Group programming that I can change that would have any effect on this. The cisco tech sent me a screen shot that says we are sending a "disconnect". I wonder if it is the fax machine.

Any suggestions?

 

[disturbedone]

It depends on what they say they're receiving. Are they simply receiving an ISDN Disconnect message? If they did an ISDN trace can you post that here? A Disconnect message will be followed with a Cause Code - cause 16 is normal clearing but if another code is there then there could be an issue.

Can you dial in to the Coral modem ok? If so, sync is ok. If not, sync is not ok.

Is this 100% of fax calls? Inbound and outbound? Just one fax machine or multiple?

 

[BogeyShooter]

Here is what the cisco tech sent me.
*Mar 6 15:36:36.398: ISDN Se0/0:23 Q931: RX <- SETUP pd = 8 callref = 0x069C

Bearer Capability i = 0x8090A2

Standard = CCITT

Transfer Capability = Speech

Transfer Mode = Circuit

Transfer Rate = 64 kbit/s

Channel ID i = 0xA98395

Exclusive, Channel 21

Calling Party Number i = 0x2180, '3172838522'

Plan:ISDN, Type:National

Called Party Number i = 0x81, '2255790'

Plan:ISDN, Type:Unknown

*Mar 6 15:36:36.430: ISDN Se0/0:23 Q931: TX -> CALL_PROC pd = 8 callref = 0x869C

Channel ID i = 0xA98395

Exclusive, Channel 21

*Mar 6 15:36:38.226: ISDN Se0/0:23 Q931: TX -> PROGRESS pd = 8 callref = 0x869C

Progress Ind i = 0x8188 - In-band info or appropriate now available

*Mar 6 15:36:39.030: ISDN Se0/0:23 Q931: RX <- DISCONNECT pd = 8 callref = 0x069A ß--------------------------------------------------------------

Cause i = 0x8090 - Normal call clearing

 

[disturbedone]

So it looks like the call isn't even answered, correct???

Are you sure that's all the trace? There appears to be messages missing. After a SETUP message you should receive a SETUP_ACK from the Cisco. I initially thought that you'd only supplied messages coming from the Coral to the Cisco but there's a CALL_PROC from the Cisco to the Coral so you're getting message in that direction. If this is the full trace then the Cisco isn't acknowleging the call setup. It should send a SETUP_ACK to the Coral so the Coral knows the Cisco has accepted the call and that the call can proceed. Without it, it's no surprise the Coral is sending a DISCONNECT.

What about the other questions...

Can you dial in to the Coral modem ok? If so, sync is ok. If not, sync is not ok.

Is this 100% of fax calls? Inbound and outbound? Just one fax machine or multiple?

But at this stage the Cisco isn't responding correctly to the call.

 

[BogeyShooter]

This is all the Cisco guy sent me. This does not happen on every fax call, however there are a few individual numbers (both local and long distance) that this happens on all the time. When I use a regular analog phone inplace of the fax to call these numbers, I can hear a fax answer then there is a disconnect.

 

[disturbedone]

Well, first I'd go back to the Cisco guys and ask why they're not responding to your SETUP with a SETUP_ACK. That's just wrong.

Secondly you've just proven that it's nothing to do with faxes. You can make a phone call and it still disconnects.

You still haven't answered the question about dialling in to the Coral modem. As you've proven that it's not faxes being the issue I doubt this will matter anymore as it's been proven not to be a fax/modem sync issue.

But the question about inbound faxes is still relevant. Do these fail? 100% of the time? What about different xtns to/from the same number?

You say there's a few local/long distance numbers you have issues with. Are these 100% failures?

Still, as the Cisco isn't responding correctly to the SETUP message it's not a surprise that the Coral is sending a DISCONNECT message. After that you should also receive a RELEASE from the Cisco and then a RELEASE_COMPLETE from the Coral.

 

[BogeyShooter]

The cisco tech told me that his cisco equipment doesnt the setup_ack. I dont believe him and think he doesn't really know what to do.

I can connect ok via modem.

Inbound faxes seem to work ok. If you call these particular fax numbers from a digital phone I get fax tone.

I have been given 1 long distance fax number and 1 local fax number that when dialed from all of their fax machines fail 100%. Other fax numbers work ok.

 

[disturbedone]

Hmmm, there's a surprise - a Cisco tech who thinks they're a telephony tech just cos they work on the CCM. I'd put money on they don't know what they're talking about and have no idea where to go from there so they're putting it back on you

If that trace was all there is then there's issues. There's no SETUP_ACK, no RELEASE and no RELEASE_COMPLETE.

I Googled and found this

http://www.cisco.com/en/US/tech/tk801/tk379/technologies_tech_note09186a008009454d.shtml

Is your trunk group set to ENBLOCK or OVERLAP? Is LCR setup correctly for the right number of digits for the number you're dialling?

I also found this

https://noppa.tkk.fi/noppa/kurssi/s-38.3115/luennot/notes_2.pdf

which is a general overview on ISDN setup messages.

If you're only having issues sending to these specific numbers then maybe there's a problem at their end????

Going on the info that cisco.com link above there could be an issue with your ENBLOCK or LCR config. But still, the Cisco should be sending a SETUP_ACK.

 

[BogeyShooter]

The cisco tech says that the trap I posted is complete. I can't convince him that his equipment has problems. He is going to break out analog lines to install on the fax machines.

I am only having problems on specific numbers. LCR is correct. Trunk group is set to Enblock.

I can send faxes to those numbers from our office and other locations.

 

[disturbedone]

The only thing I can think of now is

Calling Party Number i = 0x2180, '3172838522'

Plan:ISDN, Type:National

Called Party Number i = 0x81, '2255790'

Plan:ISDN, Type:Unknown

I don't know how you set things up in the US but in the rest of the world where I've installed Corals I always use Unknown in the LCR numbering plan. If it was my system outside the US I'd think I'd made a typo on that entry in LCR,5 but this may just be the way things are configured in the US.

Other than that, tell the Cisco tech to learn about telephony before going any further. From where I stand the Cisco is not responding with a SETUP_ACK when I believe it should be. Because the Coral hasn't received a SETUP_ACK it is probably thinking the call hasn't been acknowledged. Yes the Cisco is sending CALL_PROC and PROGRESS but it still hasn't sent the SETUP_ACK.

Do you have the ISDN debug software from Tadiran? You could do a trace yourself just to see what is really going on and not takin the Cisco guy's word for it. You need to get that software from Tadiran themselves though.

 

[BogeyShooter]

We can close this thread. The cisco tech broke out 4 analog trunks from his equipment and hooked the fax machines up to them. He thought that would be the easiest thing to do since he couldn't correct the problem.

 

[disturbedone]

Sounds like a Cisco-tech way of fixing things. Put something new in and pretend like the fault doesn't exist so it must be resolved.

At least things are working I suppose but the issue hasn't been addressed. I would imagine they'll probably try and push the Coral out of the way in the end and let Cisco take over. That'll be a sad day and users will wonder where all the features went.