Estimating the number of concurrent conference calls?

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Jun 1st, 2008

We are moving from a Nortel PBX front end to a full call manager 5.1(2)system. We are now planning the provisioning of the DSPs for the 3845 Gateway routers and we are trying to estimate the number of concurrent conference calls we may have in our office. The number of end users is 340 and there are six PRI's. Two of the six PRI's are dedicated to Long Distance service only. Any guidance would be greatly appreciated.

Thank you.

Rgds,

Vicky

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rob.huffman Sun, 06/01/2008 - 18:56

Hi Vicky,

How many NORTEL MERIDIAN NT8D17FA CONFERENCE TDS cards are in the current system? Each Conf/TDS cards supports 30 streams (10x3 Party conferences). This should tell you what your current capacity is. It is very likely that the built-in Software Conference setup will suffice for 340 users. (42x3 Party Conferences)

Here is the related information.

Software Conference Devices

For software conference devices, you can adjust the number of streams because software conference devices support a variable number of audio streams. You can create and configure a software conference device and choose the number of full-duplex audio streams that the device supports. To calculate the total number of conferences that a device supports, divide the number of audio streams by three. The maximum number of audio streams equals 128.

Cisco Conference Bridge Software

Software conference devices support G.711 codecs by default.

The maximum number of audio streams for this type equals 128. With 128 streams, a software conference media resource can handle 128 users in a single conference, or the software conference media resource can handle up to 42 conferencing resources with three users per conference.

If the Cisco IP Voice Media Streaming Application service runs on a different server than the Cisco CallManager service, a software conference cannot exceed the maximum limit of 128 participants.

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Caution If the Cisco IP Voice Media Streaming Application service runs on the same server as the Cisco CallManager service, a software conference should not exceed the maximum limit of 48 participants.

From this good doc (still applicable for CCM 5.x);

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/4_1_3/ccmsys/a05confb.html#wp1035397

DSP calculator:

http://www.cisco.com/cgi-bin/Support/DSP/dsp-calc.pl

Hope this helps!

Rob

iptuser55 Mon, 06/02/2008 - 02:41

It is not how many it supports but the number of concurrent calls at once. The DSP etc will only tell you how many you need based upon x conferences, the same with the number of Conference cards you have in the Nortel. unless they are on conference calls all the time then with 340 users then I would stick, for now, with the software version with 3 users, 40+ conferences and then monitor via RTMT. Remember if you ask an end user how many conferences are they in, they may say at least 50 per week times that by 20 user- seems a lot but how many do they just participate in as opposed to them actually setting up , creating a conference - probably not many

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