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VoIP "dead air" dialing.

Below is a recurring complaint that I am getting from end users. Has anyone seen this before?

"When attempting to call out on the phones ... Intermittant problems persist with not getting a line out. This happens periodically throughout the day on multiple phones, dialing local, long distant, or Voice Over Network lines, etc.

What happens is we dial the number ... The display shows as attempting to dial; but phone is 'dead' (nothing to hear). When this happens we can leave the phone in that status seems to be indefinately. The display will continue to look like it is dialing; but no sound in the earpiece (No busy signal, No dial tone, No ringing, nothing).

We then have tried to hang up and re-dial. In some cases the same problem; in others it will connect. This is not dependant on the number we are dialing; in fact, trying different numbers or types of numbers does not seem to matter. At times, no matter how many time you try it will not connect; then try later in the day and it will work fine.

This problem is very intermittant and unpredictable."

Are there any specifics in call tracing that I should be looking at that may help with this? I am looking into QOS, traffic shaping and queuing also to see if I can find any answers.

Any ideas?

5 REPLIES
Gold

Re: VoIP "dead air" dialing.

Does the call timer start incrementing on the phone display as if you're connected, or do you just see the dialed digit string?

If you never get to a connected state, and you can leave the phone in that state indefinitely, that sounds a bit more like a bug of some sort rather than a QoS issue. Even if there's an issue with broken PSTN trunks you should eventually fail the call, and you imply this happens phone to phone. You don't say what version of CallManager you're at. As a couple of shots-in-the-dark, make sure your CallManager is patched up to the latest service release for your version as available on CCO, and try the most recent version of phone loads, which is 5.0(2) as of this writing.

It's also somewhat possible that this could be caused by intermittent communication problems between the CallManager and the phone in question. You can check this by running a continuous ping from the CallManager that the phone is registered tt, to the phone. If the phone is slow to respond when in this state, it would support this theory.

If you do get to a connected state, you're having trouble passing RTP traffic back and forth and you should look for network issues between the phones or between the phone and the voice gateway. A more remote possibility is a problem with the phone loads. There's a bug in the 5.0(1) phone loads that can cause this sort of thing temporarily, for example. You can try upgrading to phone load 5.0(2) for this case as well.

New Member

Re: VoIP "dead air" dialing.

The call timer does not start incrementing, the only display is on the IP phone is the "ring out" moving icon.

I'm Running CallManager 3.2(2c) with 200.2.3SPE. Just received 3.3(3) yesterday and am planning the upgrade for next week. I am going to try upgrading first, 3.3(3) and 2000.2.5 OS plus SR1 and new phone loads and see if that helps.

I'll update whether that helps or not once I upgrade.

Thanks for the help.

Gold

Re: VoIP "dead air" dialing.

The upgrade to 3.3(3) is a pretty big ordeal. If you need a fix fast, you can try going to CCM 3.2(2c) service pack H and the 5.0(2) phone loads. I can't say for sure if that will fix it, but I can tell you that base 3.2(2c) without any service packs, if that's what you're running, has a lot of issues. You can accompish both upgrades with only one reboot on each CallManager and you have an easy back-out path.

New Member

Re: VoIP "dead air" dialing.

Just a hint. Do you have enough PSTN lines (timeslot)in/out. If someone is trying to connect to a outline PSTN line and all the line’s is busy the phone will just trying to connect and sometime time out. That could explain that is possible to connect later in the day

New Member

Re: VoIP "dead air" dialing.

i would look an a bad pstn connection if you receive supervision from co and no digits accepted you can set there forever. to test, when one phone locks up try to make other sets dup. the same trouble. if it's one pstn "trunk" it will not re-occur until phone "A" releases. no trunk avaible should give fast busy (all trunks busy)

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