There has been discussion around concurrency of connections for front end web servers for Project Server 2007. I wanted to provide a concurrency ratio:
Below is a link to a definition of concurrency provided by Wikipedia:
As one can see there are many models of concurrency. The best way to determine concurrency is to use one of these models and review the types and usage of the current users in an organization. Note: That is a difficult task at best.
From a Microsoft Technet Article:
User concurrency — A concurrency rate of 10% is assumed, with 1% of concurrent users making a request at a given moment. In other words, given 10,000 users, the assumption is that 1,000 users will be actively using the solution at the same time, and 10 users will be actively making a request.
So in order to reach say “500” concurrent users you would be looking at say “500,000” actual users.
For planning purposes “I” would only use the 10% rate in other words “500” concurrent users = “5,000” actual users maybe that’s just me being cautious but it seems correct.