2000IPS calling Nextel cell-phones results in occasional dropped calls

[phadobas]

This is a strange scenario, and all usefull advice is appreciated:

I call a Nextel cell-phone from an IP phone of my 2000IPS, and about 30% of the calls gets disconnected within 1 minute, with an error message on the cell phone something like "busy 26"

I can call other carriers' cell phones, no disconnect. I can call land-lines, no disconnect...

My first idea: Nextel coverage or network overload. Except this is impossible to test for and next to impossible to fix. Especially considering the fact, the I never get disconnected if the call comes from somewhere else. I tested it for myself. I had somebody call my Nextel from the 2000IPS, 30% of the time = disconnects. I have had a Nextel for over a year, and never got disconnected during a call. Also, during these test calls, my phone showed 5 bars for good reception.

So we think it's not Nextel.

Is it my 2000IPS? How come I can call any other land lines or other cell-phone carriers with no problem?

Here is the route a call takes to a cell phone: it goes from my IP phone into a switch, then a router, accross a T1 (about 10 miles), arrives to a router, then switch, then the LAN port on the IPS. Then the IPS sends the call out on a trunk route to AT&T (or Verizon - I don't remember)...From there on, it's just a cloud for me, and I can only guess that AT&T or Verizon then routes to call onto Nextel's network.

My other suspicion then is somehow the setup between AT&T or Verizon and Nextel is not the best (maybe their signaling is not set up ideally?) Maybe somehow Nextel's network sends a "disconnect" signal to AT&T and so to my IPS2000, and the call gets dropped, when it shouldn't.

I called Nextel customer care, and they have network engineering checking out possible coverage issues.

Other than that, I'm totally lost. But my company is using Nextels, and my executives use IP phones, so it's the top who needs this resolved, and I can't suggest for my company to switch cell-phone carrier when we have over 200 phones, and certainly I can't replace out the IPS2000 with other brand.

Anybody with any clue? Or suggestions?

Thanks, Peter

 

[DrVuDu]

is the trunk route Analogue or Digital?

if its digital I can tell you it's most likely an issue and you will need to contact NTAC.

The call scenario you describe is a familiar one. you will probably find that the ISDN is stuck in "call proceeding" message on the ISDN leg. If the call is connected and you don't have a timely "connect" (within 2 seconds of connect) message from the the carrier for some reason the 2000 doesnt see a call bridge connection, and will kill the outbound leg of the call as a hung connection. This scanario seems to be limited to the IP phones only, dterm's and slt's are not affected. I went through this for 2 weeks with a Tbird in hand and phone on the ear to finally figure this one out.

I hope that this helps.


Regards,

Dr VuDu

 

[DrVuDu]

for what is worth my tests were on Sprint/Nextel.

the information I got from the carrier was. "they didn't send a connect message until the party was located on the sprint network and registered in their system"

I.E. "the call could be connected but the server farm had not pulled the sprint phone from the sleep table to active table in their billing system" fast enough for the NEAX to handle

The quotes are from the Sprint Top Tier Tech. Robert BTW who was wonderful in helping solve this problem!

Regards,

Dr VuDu

 

[phadobas]

Thanks for the tip. Yes, this is digital trunk, an ISDN-PRI.

If I understand you right, the call gets established, but the 2000 doesn't receive a signal from the Nextel network which tells it that the connection got established, right? And so the 2000 is wondering what's going on for a bit (maybe 2 seconds), and then after a while, thinking that the call never got connected, drops that connection.

Is that what you meant?

And you say you finally figured this out... Was there a solution you could impletent that fixed this problem? I would definitely be interested in that part of your story

One thing I have to note though, is that even if the call gets disconnected, it'll stay on for 30-60-90 seconds before it gets dropped.

Anyways, I have trouble ticket in with Nextel and with AT&T.

 

[DrVuDu]

yep you understand me ISDN messages from NEXTEL via AT&T are slow and at the outside of the limits for ISDN signaling. the NEAX waits for "CALL proceeding" info message from the network to give you network RBT, the second info packet is "call connected" is received but received late but the voice path is already connected.

now to the SOLUTION...
1) in the interim send out the NEXTEL calls on analogue trunks using LCR, no ISDN issues there.
2) alert NTAC! they should have this issue on file, and there is a Software patch fix for this but it's dependent on your Rev level.


As for the long disconnect time 30-60-90. its the NEAX cleardown timers, if you get disco'd early you'll wait 90 seconds, if you get 60 sec in to the conversation, you'll wait 30 sec for the disco.

Regards,

Dr VuDu

 

[phadobas]

Solved! System reset resolved the problem. Thanks.

 

[DrVuDu]

Glad your all fixed!! and wasn't as major as mine was! I'll drink to an easy fix!

Regards,

Dr VuDu