atcomsystems.ca/forum Forums TDM Business Telephone Systems Nortel Telephones & Systems Dual PRI & "all circuits are Busy..."

It's pretty complicated, but do my best to nutshell the pertinant details:

2 PRI's (46 voice channels) provider = Paetec
MICS 6.1 XC
2 0x16
2 T-1 cards
2 fiber combo cards
8 port Call Pilot (VM & AA)
16 port NAM (ACD only)

Problem:

Once the system gets around 22 inbound calls on the main target line, the callers get fast busy, or "all circuits are busy..." from telco. There are still 23,24,25... unused channels available. You can still access them outbound.

We have used a T-berd and Telco has set up traps to monitor calls.

The KSU is sending "cause code 44" (resouce unavailable) over the D-channel back to telco, promting them to issue the fast busy/"all circuits busy" message to the caller.

I have been told by one tech support source that any single target line can only handle 8 inbound calls simultaneously. Of this, I am not convinced yet; obviouly the system is handling almost 3 times that before the problem occurs.

This is a large company running a nat'l call center averaging a couple thousand calls per day. Monday's are particularly heavy getting upwards of 30,000 due the enormous amount of people calling back after getting the telco recording.

Any takers???????

First I would like to say the volume that you mention 30,000 calls per day it’s too much for the Norstar system if you calculate the traffic analysis its exceeds the capability of the Norstar, so I think you should consider upgrade to a bigger switch. You mentioned that you have 2 pri circuits, how many number do you have in the block (100, 25, 1....)you was taking only about one target line so I assume that you only having problem with one number or that’s the only number that you have (its not clear for me) however if you have only one number then per assumption you are using one target line you can have line appearances for that line as much as far as I remember up to 255 time however ITAS recommends 8 appearances only they treated like answer DN .That’s not mean that you can't have more line appearances you can however they will till unknown time when the system runs out of resources (heavy traffic or whatever ) but in normal condition maybe all they work ,as mention in the beginning your system most likely over stressed. Also you should check with the provider on how many calls they allow per one number sometimes they have some limitations, as you mention you have no problem with the outgoing so I assume your system as a hardware is working fine its just a matter of system limitation and capabilty.Thats my opinion anyway.

Whats your max in max out set at maybe your traffic out should be be reduced, sure sounds like an upgrade is on the way

Samh:

There are 100 DID's + 2 Add'l target lines for their main lines (admin & Cust. Serv.). Of the DID's they are using about half for actual private lines and they say they are rarely used at all for that. The rest of the DID's are assigned to stations that are not physically present on the system at this time.

The 2 main target lines are answered by the AA (CP) and there is no real line appearences to speak of except the receptionist has 6 for the admin number only. The customer service number has no line appearances anywhere on the system.

The 30,000 calls are only on mondays when the traffic goes up and the callers hear the telco message and then call back several times (theory, of course). so the math would indicate that the actual number of callers has risen, but only by a small margin. And the 30,000 calls are actually same callers calling in repeatedly.

Even so, why is the system over taxed after only 22 calls. This should only happen after 46 simultaneous calls. Right?

U-Tel-Us:

MAX IN-MAX OUT?????

This I NEED to know about. I've never heard of this.

Where do I set this parameter in the system programming?????

In theory you should be able to receive 46 calls on the 2 pri if no outgoing calls are made at this time ,however it will not happen on the same number or the same line ( in your case you have 2 DID numbers and you want 46 calls on these 2 numbers Do I understand you correct).If you can test it by having more than 2 numbers dialed in at the same time like 5 or 6 DID numbers and see how many calls you will receive ,and about the 22 calls I think that’s its not fixed maybe for that time only you got that number it could be less or more according to the system traffic condition and the resources that has been used at the time .I would like to ask what is the s/w version (The 6.1 has 2 releases maybe and I say maybe your s/w has a problem despite the new s/w doesn't cover such problem or issue but you never know). and regarding MAX in and MAX out that US -tell mentioned in the above post, you will find that under System programming CBC limits (call by call limits that’s determine how many calls are in and out for each PRI , by default its 23 in and 23 out so I will assume its not changed most people they don't touch that) And again I think the system is over worked that is my opinion.

[This message has been edited by samh (edited May 20, 2004).]

The S/W is rel 01

We consistantly recreated the problem including the 22 call max several times in the course of testing.

Yes I want as many calls as the T-1 will allow to come in via 2 target lines as the system stands now.

We have discussed the possibility of breaking up the inbound line group from 1 group of 46 channels to 5 or 6 groups each with a different DID that rolls over like an analog hunt group. That will be a first for Paetech, I understand.

I will test the system with via several DID's to see if I can breach the "magic number 22".


You may be right that the system is over-burdened, buit I'm not willing to cry "uncle" just yet as the they just bought this system and converted to T-1 from analog lines a few months ago and the system was ok with the amount of traffic until the last couple of weeks. (Call traffic increased????).

Thanks for your input & opinions. It is greatly appreciated.

There is a second release for the 6.1 as I mentioned before maybe you should try that (according to that release issues its not covering your problem but covering another ones but you never know, its fairly new so its not available from all vendors) Also I think you should let the provider break the DID to more groups maybe it helps. I also recommend waiting and seeing more opinions on the board, there are a lot of telecom professionals on this board with broad knowledge and great experience maybe them can help you or give you more ideas.
Good Luck.




[This message has been edited by samh (edited May 21, 2004).]

It's been awhile since I worked on a system as big as you seem to have, but here's a couple of options anyway, it seems like maybe only 1 of your t-1's seems to be handling incomming calls to a particular # Has your telco provider got it set up so that when the first t-1 is maxed out digets are recived by the 2nd t-1 ? are all your incomming calls handeled by the AA if so you only have 8 ports aviable what happens to the over flow ? naw forget that, you said it was your telco provider system that said all circuits busy ,is your customer paying for all 23 channels to be turned up per t-1 and are they enabled at both ends,the max in I was referring to is usually set so that only a max amount of out going calls can be made so that there is always lines aviable for incomming calls ,you would find this under system programming ,show next to cbc limits show ,public.show min in 0 min out o next max in ,the number of programmed channels max out is the number of programmed channels unless you want to save some spare for the incomming calls . good luck

Change your max in to 46 and your max out to 46 and you will be all set as previously discussed - default is probably 23 each and that is why you are sending resourse unavailable to the carrier on the d'channel