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2834
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5
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28
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Calls get stuck in T1

hxmengmetro
Level 1
Level 1

Hi All,

I found one weird issue in our T1. We have one call center which has one number the customers can call in. I found out two calls which already ended several minutes ago. But they are still shown under the "show isdn active". They occupied the T1 slots. I called those two callers and they said they already hang up several minutes ago. At that time, the calls still show in active status.

We have a call queue setup in UCCX server. Is there any possiblity that the call ends actually but the queue still hold it for some time?

Thanks for your help!!!

Lou

28 Replies 28

Oh so the call isn't eternally stuck?

The problem is upstream of the gaetway, then.  The disconnect doesn't come from the H323 peer (CM I presume?) until 10:20:

7381844: Sep 10 10:20:20.712 CDT: H225.0 INCOMING PDU ::=

value H323_UserInformation ::=
    {
      h323-uu-pdu
      {
        h323-message-body releaseComplete :
        {
          protocolIdentifier { 0 0 8 2250 0 5 }
          callIdentifier
          {
            guid 'B54316E1BC2311DF901EFD8A79705EB9'H
          }
        }
        h245Tunneling FALSE
      }
    }

7381845: Sep 10 10:20:20.712 CDT: //1652696/B5427AB9991B/CCAPI/cc_api_call_disconnected:
   Cause Value=16, Interface=0x68589F00, Call Id=1652696

And then the call is torn down on ISDN right after that:

7381858: Sep 10 10:20:20.732 CDT: H225.0 OUTGOING PDU ::=

value H323_UserInformation ::=
    {
      h323-uu-pdu
      {
        h323-message-body releaseComplete :
        {
          protocolIdentifier { 0 0 8 2250 0 4 }
          callIdentifier
          {
            guid 'B54316E1BC2311DF901EFD8A79705EB9'H
          }
        }
        h245Tunneling FALSE
      }
    }

7381859: Sep 10 10:20:20.732 CDT: H225.0 OUTGOING ENCODE BUFFER::= 2580060008914A000411001100B54316E1BC2311DF901EFD8A79705EB910800100
7381860: Sep 10 10:20:20.732 CDT:
7381861: Sep 10 10:20:20.732 CDT: //1652696/B5427AB9991B/CCAPI/cc_api_call_disconnect_done:
   Disposition=0, Interface=0x68589F00, Tag=0x0, Call Id=1652696,
   Call Entry(Disconnect Cause=16, Voice Class Cause Code=0, Retry Count=0)
7381862: Sep 10 10:20:20.732 CDT: //1652696/B5427AB9991B/CCAPI/cc_api_call_disconnect_done:
   Call Disconnect Event Sent
7381863: Sep 10 10:20:20.732 CDT: //-1/xxxxxxxxxxxx/CCAPI/cc_free_feature_vsa:
  
7381864: Sep 10 10:20:20.732 CDT: :cc_free_feature_vsa freeing 6CA41DC0
7381865: Sep 10 10:20:20.732 CDT: //-1/xxxxxxxxxxxx/CCAPI/cc_free_feature_vsa:
  
7381866: Sep 10 10:20:20.732 CDT:  vsacount in free is 37
7381867: Sep 10 10:20:20.736 CDT: %ISDN-6-DISCONNECT: Interface Serial0/0/0:6  disconnected from 3147502946 , call lasted 880 seconds
7381868: Sep 10 10:20:20.736 CDT: ISDN Se0/0/0:23 Q931: TX -> DISCONNECT pd = 8  callref = 0x82FE
    Cause i = 0x8090 - Normal call clearing
7381869: Sep 10 10:20:20.768 CDT: ISDN Se0/0/0:23 Q931: RX <- RELEASE pd = 8  callref = 0x02FE
7381870: Sep 10 10:20:20.768 CDT: ISDN Se0/0/0:23 Q931: TX -> RELEASE_COMP pd = 8  callref = 0x82FE

You need to investigate why the release complete transmission from the node across from dial-peer 100 is delays by 12 minutes.  Detailed CM traces are the way to go.

Thanks a lot Steven. Right, the call would be released after some random delay. The dial peer 100 is to our cisco call manager. So you mean the call manager didn't send the disconnect message at correct time (10:08:29 AM)? It appears call manager itself knows this call is disconnected and sent out the disconnect message, but the message never reached the gateway. That's why CDR shows correct disconnected time but the gateway just hung there waiting for the disconnect message.

What kind of CM trace I should enable it to debug this issue? Thanks a lot Steven.

Lou

Steven Holl
Cisco Employee
Cisco Employee

That call disconnect from the H323 side, and the disconnect on the ISDN side looks normal.  CCAPI appears to clean itself up properly, as well.

If the call entry is getting hung in some show commands, it looks like a bug.  You can try running recent IOS and see if behavior still exists.  Perhaps the latest rebuild of 15.0(1)M?  If so, open a TAC SR and we'll work with development to diagnose towards root cause and get it fixed.

Since the ISDN channel frees up, though, it is really mostly a cosmetic bug, other than it potentially affecting CDR records.

-Steve

Get detailed CM traces.

There isn't anything proxying the h225 connection between CM and the gateway (TCP/1720), is there?  Like a firewall?

The router clock does match the clock on CM which is used for CDR, right?

There is no firewall or ACL setup between CM and gateway. All the ports are open. The gateway clock is pretty synchronized with CDR. I compared them when I looked at the debug output.

So I caught another stuck call. This time I collected debug from gateway and Call Manager. Here is the detail about this phone call:

Calling number: 3146527946

11:41:05  Call get into the greetings. CM trace: 119

11:41:49  Finished the greetings, the agent picked up the call. CM trace:122

11:42:04  The call ended but still stuck in T1. CM trace: 123

11:46:57  The call finally released in T1. CM trace: 144

I attached the zip file for CM trace and another text file for gateway trace. I'm trying to compare this to the normal call.

Thanks for the help.

Steven Holl
Cisco Employee
Cisco Employee

Is 10.101.1.100 IPCC?

No. IPCC is 10.101.1.13. 10.101.1.100 is another gateway. The gateway having stuck calls is 10.104.6.253

Well the call doesn't disconnect until 11:46:57 on the CM side, so the issue isn't with the gateway for sure.  The issue is at or upstream of CM.

The GUID for the issue is B3B1EAF1BF5511DF92C3FD8A79705EB9.

I don't have time to go through the entire trace and follow the other side of the CM leg.  The origin of the disconnect of the call needs to be traced in the CM traces, which may be occurring on another CM node.

Thanks Steven. Yes, the call got disconnected until 11:46:57 by CM. The origin you are talking is the end who hang up the call first?

Lou

I have looked at CDR and traces in CM. I found after the actual disconnection time, there is one call going from the gateway to another gateway. That's why the gateway in question holds the T1 slot. I'm trying to figure out why it works like this way.

Ok. Here is the deal. The agent made the transfer to another call center in the site and they dial the DID not the internal extension. That's why the calls to out through another gateway. So that "stuck" call actually is a transferred call. The agent should not do this way, we already suggest them just dial the internal number without wasting the T1 slots.

Thanks Steve and the other helper. At least, I figured out how to troubleshoot this kind of issue. This is really helpful!!!

Lou

Hailu, glad you got things straightened out.  Good job!!!

Thanks! :-) This issue is really a non-technical issue. Human issue again. Hehe. :-) But we need take technical way to find out human errors.

Cheers!

Lou

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