Locations based Call Admission Control

Unanswered Question
Apr 3rd, 2007

I'm trying to do CAC calculations using locations and have found a contradiction. There are several postings like the one at: http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_implementation_design_guide_chapter09186a00806e8c1e.html

These postings state that you simply divide the amount of bandwidth you have set aside by the amount used in a codec to discover how many calls can be placed over that link.

However, I've also found a number of postings like the one at: http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide_chapter09186a00801ec5ac.html#59667.

These postings state that since audio has 2 streams (one each way), and video has between 4 and 6 streams, you need to take the amount of bandwidth afforded by a codec and double it to decide how many calls can be made over the WAN link.

Which concept is correct?

I have this problem too.
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alessandro.dona Tue, 04/03/2007 - 04:01

Hi,

I had a similar issue with an asymmetric DSL WAN LINK!I seized the number of calls over the wan taking into account the lower of the two speeds,that is in your case almost similiar to doubling the bandwith required for a call!

kelvin.blair Tue, 04/03/2007 - 05:26

I'm going to take a stab at this. Someone correct me if I'm wrong. If you have two sites connected over some type of dedicated leased line. For example a T1 between sites. For location A (HQ) you set unlimited and for location B (Branch) you set 48K. Keep in mind this is based on g729 across WAN. If location A calls an ipphone in location B 24K will be subtracted from both ends. So if you look at this 48K from location A to location B it is now 24K. FRom Location B to Location A it is also now down to 24k. Now, with that in mind only one more 24K call can be made to and from Location B. One more thing to take in account is the overhead. I've seen that some circuit use more overhead then others. For example, a Frame-Relay circuit is said to add 8k of overhead to the call.

I hope this helps some. Again IF anyone has any other thoughts, please provide.

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