Skype Business Server 2015 Planning Tool Conferencing Values

Whenever I see a customer going through the Skype for Business Server 2015 Planning tool I always pause for a moment and make sure that there are not changing too many default options in the user profile section; one of those areas in particular is the conferencing section.  Conferencing is one of the key modalities for Skype for Business 2015 and with that should be taken into careful consideration with the thought of changing the default values that have been designated for you.  I will touch upon some key aspects that if changed could render a different than expected outcome for your proposed Skype Business server 2015 design. 

Let’s take a look at the following areas:

Why the number 5%?

The percentage of 5% was not just made up by the Microsoft Skype Product Group.  But rather a number or value that has been around since Office Communicator Server 2007 days.  Now you may be saying, “That’s a long time ago.”  And I wouldn’t disagree with you either.  The Lync or Skype capacity user profile contains conferencing for an organization value and that value is 5%.  So basically Microsoft is saying based on their standard best practice 5% of your organization that is enabled for Skype could be in a conference at any point of time from a planning point of view.  Now it’s difficult to talk about 5% without talking about the 250 conferencing limit. To read my previous article that addresses the 250 conferencing limit you can go here Lync Server 2013 Conferencing Limits.

Let’s also keep in mind what a conference really is.   Whenever there are more than 2 participants in a modality is what defines a conference.   Reason being is that particular MCU (multipoint control unit) kicks in to action and the communication is happening across the front end servers.

So when we go back to the 5% of users are in a conference at any point in time and do the math with numbers besides the typical 80,000 users for not everybody’s organizations have that many users, we will see how the numbers turn out.  We will use 25,00 users based on a medium size organization that has users spread across regions or possibly in different countries.  So now we have (5% / 25000) = 1250 concurrent users in a conference for that pool.  (1250 users / 5 Front End servers) gets us to approximately 250 users per Front End server in a conference.  Then we take the average number of users for an ad hoc conference, which is about 4 taken from the (4-6) users in an ad hoc conference profile.  So now we have (1250 users per FE / 4 users per conference) = 312.5 concurrent conferences per Front End server is the number of ad hoc conferences each Front End server can handle safely.
Note: Some of the math was taken from my previous article on Lync Server 2013 Conferencing Limits.

Existing Capacity User Model

The 312 conferencing sessions per Front end server is slightly lower than the actual suggested limit of what a Front End server can handle which is approximately 333 conferencing users per Front End server taken from the model of 5% users in a conference based on the 5% user model and number of Front End servers that we deployed in this example.

Note: Excerpt taken from my previous WindowsITPro article Lync Server 2013 Conferencing Limits.

The Microsoft suggested max capacity of users in a pool of 80,000 users; (5% / 80,000) = 4,000 users in a pool in a conference concurrently; based on Skype for Business server 2015. Then we take (4,000 users / 12 max front end servers in a pool) = 333 conferencing users per Front End server; (4 avg users in a conference/ 333 conferencing users per front end server) = 83 concurrent meetings per Skype Front End server.

Despite the supported limit of users per pool decreasing from OCS 2007 R2 (100,00) to Skype for Business server 2015 (80,000) users; the supportability of the pool increasing from Front End server count from (8) in OCS 2007 R2 to (12) Skype for Business server 2015 now almost has a factor of approximately 1,000 users in a conference; 20,000 / 5% = 1,000.  The 1,000 users spread across the 4 Front End servers that are available now compared to OCS 2007 R2 comes out to 250 users in a conference per Front End server. (There is that magical 250 # that I’ve spoken about before :) )

Note:  My recommendation is to leave the setting as is unless your organization calls for a specific need a high conference value that would exceed 5%.

Skype Business Server 2015 Conferencing Justification

At the end of the day, through all of my deployments, dating back from LCS 2005 days to Skype for Business server 2015 I have not really had a reason to change the 5% value for planning a deployment.  Actually I have only needed to change it a couple of times, but that is what I would like to think was justified based on the customer requirements they had specifically around conferencing that were very unique.  Keep in mind that if the value is changed, make sure there is ample reason to and it will affect the outcome of the planning with regards to expected usage compared to Microsoft’s standard user model.