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New Member

Transfer Loop

Given that the default behavior of subscribers is to bypass the transfer rule when a call is forwarded by Unity, how easy is it to bypass that and accidentally create a transfer loop. This is more theoretical I suppose, but someone raised this question to me and I wasn't sure how to answer.

I suppose it's relatively easy if one is creating a number of Call Handlers that forward to subscribers, but it seems that the default behavior covers most possibilities.

Thanks

4 REPLIES
Cisco Employee

Re: Transfer Loop

You can either chain to handlers (or a handler/subscriber) together to force a loop like this or you can get clever and have the handler/subscriber's greeting be blank and then have the after greeting action set to "attempt transfer" to itself which will force it to ring the extension again.

You kinda have to go out of your way to make this happen, however - the way we handle it is pretty standard stuff that's employed by voice mail systems on most switches I've run into.

New Member

Re: Transfer Loop

Does adding the extension to the port in the sa under System>Ports have any impact on this behavior? I was told that there is a technote covering that subject but I'll be darned if I can find it.

Gold

Re: Transfer Loop

Adding a DN to the port is used to prevent a situation where a subscriber sets up notification to call their phone and their phone forwards back to Unity. This causes a situation where Unity ends of talking to itself and leaving new messages for the subscriber which causes a notification loop.

Please note that the logic used by Unity to determine if a call is from itself was changed in 4.0(1) and is a bit flawed in my opinion. It only works if you dedicate ports for notifications which are not configured to answer normal phone calls.

Pre 4.0(1) Logic:

NEW CALL

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DO WE ALLOW CALLS FROM VM? YES -> ANSWER CALL

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ELSE

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GET CALLER ID -- NO CALLER ID -> ANSWER CALL

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ELSE

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IS CALLER A VM PORT? NO -> ANSWER CALL

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ELSE

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DON'T ANSWER CALL

4.0(X) Logic:

NEW CALL

|

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DO WE ALLOW CALLS FROM VM? YES -> ANSWER CALL

|

|

ELSE

|

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GET CALLER ID -- NO CALLER ID -> ANSWER CALL

|

|

ELSE

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IS CALLER A VM PORT? NO -> ANSWER CALL

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ELSE

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IS CALLING VM PORT ALLOWED TO ANSWER CALLS? YES -> ANSWER CALL

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ELSE

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ASSUME UNITY IS CALLING ITSELF -> DON'T ANSWER CALL

There is an internal defect to get the logic cleaned up a bit.

Hope this helps...

Keith

New Member

Re: Transfer Loop

That helps, thanks.

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