Strange max-conn behaviour

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    This document was generated from CDN thread

    Created by: Mark Alliban on 09-08-2012 05:54:51 AM
    I seem to have a problem with max-conn on a dial-peer. This is a 3745, IOS 12.4 r4.

    Router#sh run | begin dial-peer voice 18
    dial-peer voice 18 voip
     service MyTCLService
     max-conn 400
     incoming called-number .T

    After a busy night of traffic, I get complaints that this gateway is refusing calls. So I run the following - results cropped to show relevant info:
    Router#sh dial-peer voice 18
            incoming called-number = `.T', connections/maximum = 400/400,

    Router#sh call acti voi bri

    Telephony call-legs: 0
    SIP call-legs: 0
    H323 call-legs: 0
    Call agent controlled call-legs: 0
    SCCP call-legs: 0
    Multicast call-legs: 0
    Total call-legs: 0

    Router#sh call appl voi | inc Instances
           Exec Instances: 0

    Clearly it is refusing calls because the max-conn has been reached. Yet there are no calls in progress and no instances of the TCL code running. So it seems the calls are clearing properly, and the TCL code is terminating properly. Yet the max-conn counter is not being reset for some calls. What should I be looking at here? How can I find out why the connections are not being freed up after the calls finish? And is there any way of finding out which calls are not freeing up their connection slots?

    When I run it in a test environment it all works fine, ie. I make a call, end it, the max-conn DOES go back to zero. In fact multiple test calls all seem to indicate that everything is fine. But after a busy night of traffic, the max-conn is always run out. In fact it is not a case of the first 400 calls get in and subsequent ones are refused; the gateway routes about 50,000 calls in a night... but it seems on some calls the connection is not freed up... so over the course of a night this number steadily increases to 400, and then it rejects calls.

    Subject: RE: Strange max-conn behaviour
    Replied by: Grant Bagdasarian on 15-09-2012 07:45:16 AM

    Did you find a solution to your problem, because I think our system is also experiencing the same issue. It seems the maxcon slots arent being freed when the system is under a heavy load. But I havent yet concluded that this is the problem. Perhaps you could point me into the right direction if you have a solution for this.



    Subject: RE: Strange max-conn behaviour
    Replied by: Anusha Kannappan on 17-09-2012 05:09:05 AM
    Hi Mark/Grant,

    You may be encountering the following Defect CSCsb81156. Please make sure you are using the versions that has the fix for the defect.

    Hope it is useful !


    Subject: RE: Strange max-conn behaviour
    Replied by: Grant Bagdasarian on 26-09-2012 05:55:25 AM
    Thanks!. We are using 15.2.3T.

    I'm now using a SIP proxy(Kamailio) to control the maximum simultaneous calls, so max-conn doesn't have to be configured on the cisco machines anymore. The SIP proxy does a much better job at controlling this.