MLPP on CCM 6.1(2)

Answered Question
Apr 21st, 2009

I am trying to set up MLPP on CCM 6.1(2) to support pre-emption of calls between IP phones.

I have used the instructions (How to setup basic MLPP section) in the document below.

http://cciev.wordpress.com/category/cm41-features/mlpp/

The pre-emption tones seem to be played ok but the precedence call does not pre-empt a normal call after 30 seconds has expired.

I have double checked all my settings and everything seems ok. Has anyone got this working and is there anything required that is missed in the document link? The document is for CCM4.x so I guess there might be.

Also can anyone confirm that non-precedence calls can be preempted or is it just calls with a lower precedence that can be preempted?

Correct Answer by dweiner about 7 years 10 months ago

When the call is preempted the preempted parties should hear preemption tone. The "acknowledgment" is the user hanging up the call, but if they don't the tone will time out (I believe it's the T.305 timer) and the preempting call will ring in.

What symptoms are you experiencing? Preemption should work just fine. Do you have max calls set to 1? Precedence calls will ring in on any available call instance ("line") before preempting another call.

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James Hawkins Tue, 04/21/2009 - 05:21

After some seraching on the I have found something that states "station to station precedence calls require acknowledging the destination user before the media connection"

http://books.google.co.uk/books?id=nTu9lA83v-4C&pg=PA495&lpg=PA495&dq=cisco+mlpp&source=bl&ots=Ke3qWHRX9C&sig=JT7fv89XNsAL_UWKfSoS5u1QdAQ&hl=en&ei=GMDtSZv9FeWQjAfm0_EJ&sa=X&oi=book_result&ct=result&resnum=7#PPA496,M1

This seems to imply that IP phone to IP phone calls for devices on the same cluster require the called user to hang up his existing call before accepting the precedence call. i.e. if the called user ignores the precedence call for 30 seconds it will not be automatically connected and the other call dropped.

Is this really how MLPP works for this type of call?

Correct Answer
dweiner Tue, 04/21/2009 - 05:33

When the call is preempted the preempted parties should hear preemption tone. The "acknowledgment" is the user hanging up the call, but if they don't the tone will time out (I believe it's the T.305 timer) and the preempting call will ring in.

What symptoms are you experiencing? Preemption should work just fine. Do you have max calls set to 1? Precedence calls will ring in on any available call instance ("line") before preempting another call.

James Hawkins Tue, 04/21/2009 - 05:37

Hi,

Thanks for the response. Max calls currently set to 2. I will change and report back.

James Hawkins Tue, 04/21/2009 - 05:59

Setting max calls to 1 has solved the problem - thank you very much!

The T.305 timer specifies the maximum time for precedence call failure announcements on H.323 intercluster trunks not for calls in the same cluster.

It would be good to be able to lower this from 30 seconds but none of the other service parameter timers seem to relate to this.

Thanks once again for your help.

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