Strange "Zombie Call" issue

Lee Sharp

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#1
I got a real weird one that I want to run by y'all before I give up and buy some support. (And then they give up)

I have this odd behavior that only happens for one user (But he is the CEO, of course) and happens often, but is not repeatable.

Elastix 2.0.2 fully yum updated.
A US T1 trunk into an OpenVox DE115e card.
Aastra 6730i sip phone.
uLAW and aLAW codecs.
Moderatly crowded network...

He will be on a call, and the call will drop for him. The other party will still be on the call and unaware.

He picks up and dials any number or extension and is dumped back into the call. He can hear the other party, but they can not hear him.

No matter what he does (Hangup or stay on) the call will not terminate until the other party ends the call, or I yank the T1 from the card. (What I had to do on a conference call that would not end) Even repeated hangups and a call to voicemail *97 will dump him back in the call.

Going into "astersik -r" using "dahdi show channels" will NOT show that line as active. And the old "soft hangup" no longer seems to wok in 2.0.x so I could not do that.


Any hints? Should I kill the server before it starts to eat the brains of the mail system? Should I watch "Shaun of the Dead" again?
 

fmvillares

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#2
aastra firmware or hardware based issue....
 

Lee Sharp

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#3
I have about 50 Aastra phone on this system, and only one is having this issue. (Also 2 Grandstream ATAs and a bunch of soft phones)
 

dicko

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#4
An obvious question, and I'm sure you've tried it, have to swapped out all the hardware including patch cords, switch ports and the phone itself?

dicko
 

Bob

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#5
Lee,

the most common cause of a Zombie Call (especially with a non-voip carrier connection) is the network itself (although could be a crook phone - which is an easy test - switch them around)

Due to the fact that SIP is over UDP, as you know UDP is a connectionless protocol, which in very basic terms it works on the "blind faith" method of transmission. There is nothing to tell the PBX (or the phone for that matter) that the packet did not reach the phone.

So in simple terms, the PBX still thinks that the phone is working and has the call. SIP over TCP (not the RTP component) as per Asterisk 1.6 will remedy this situation if you wish to implement it.

The fact that he can dial any number and gets the call back again, is "one of those" things, but because the normal SIP call flow and sequence, their is generally no way of getting the call to "mesh" back up. The only method is to drop the call. This lessens the impact on everyone else.

You are correct, the call end function as you knew the command, no longer works.

The command (as part of Asterisk's re-organistion) is
channel request hangup [e.g. SIP/201] - have a read

They changed this to try and give some clear organisation of the commands. It has to do with the channel, therefore it comes under the CHANNEL command.

So just to recap on the other, while SIP is over UDP, there will always be Zombie calls, especially if their are network issues. Any Zombie calls I have seen the last few years, I have generally been able to attribute to a confirmed Network issue or power failure on the phone. It is still possible that there are going to be situations where Zombie calls will exist on SIP over TCP as well, but I think it will cut the number down considerably.

Hope this helps

Bob
 

fmvillares

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#6
Re: Re:Strange "Zombie Call" issue

my best guess is hardware issue.....especially in the nic part...
 

Lee Sharp

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#7
Re: Re:Strange "Zombie Call" issue

I would not think the nic, as it would effect more than one phone.

I did swap out the Aastra, and we will see if that helps. At least it will be me with the issue, not the CEO. :)
 

fmvillares

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#8
Re: Re:Strange "Zombie Call" issue

in the nic part i was referring to the nic in the aastra not the pbx...
 

64_Bit_Hacker

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#9
Hi Lee,

Did swapping the phones sort the issue for the CEO?

Regards
Carl
 

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