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calls dropped after 35 seconds...need help badly

Discussion in '3CX Phone System - General' started by rpoffenbarger, Feb 26, 2007.

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  1. rpoffenbarger

    Jan 26, 2007
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    Im very new to phone switching, and having I hope an elementary problem. I can make outside calls, but they drop to a busy signal after 35 seconds...I don't know where to start...
  2. Anonymous

    Anonymous Guest


    Niether do I.

    Ok, several scenarios can be true:

    1. did you pay your bills?
    2. on and off hook voltage might be to low and causes the line to drop, you set this on your VoIP Gateway. In general you set this to 3
    3. NAT (yep NAT strikes again). 3+32 seconds is as follows. I assume that every 3 seconds your VoIP SP generates a SIP PING to see if you are still there. If you don't have port forwarding you won't see the ping.

    Generally 32 seconds is the magic number of seconds it takes most SIP stacks to go through a standard set of retransmissions and declare the packet undelivered. At this point, the connection is cut at the VoIP SP's end and you will be left talking to yourself. You won't even hear the busy tone as the VoIP SP will be unable to send you the "BYE" to tell your phone to terminate the call.

    Solution as previously stated is to either forward the SIP port on your router or to set your gateway to send SIP keep alive packets more frequently (may not work on some firewalls).

    Most likely the NAT stuff, but provide some more details if you can. Also have a search on your gateway and see if there is a setting that represents 35 seconds.

    Keep in mind that you need to provide traffic (eg bla bla bla on the line), if you are not talking (no traffic) the line will terminate due to no traffic, that is just how it works.
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