LCS 2005 concurrent session limit

I often talk about LCS 2005 and how many more concurrent sessions we can support compared to LCS 2003.  We’ve greatly increased from the previous figures of 10,000 active sessions.  So when I was asked to quantify what I meant with Active concurent sessions after a previous blog entry.

Its important to distinguish between concurrent connections and concurrent sessions.  LCS standard and Enterprise edition can cope with up to about 25,000 concurrent connections.  This is limited by the type of hardware you’re using and the amount of processing power you have available.  To get beyond this, you need to scale out by adding servers, load balancing and creating user pools.  Then you can get to the million mark that we talk about during presentations.

Concurrent sessions are different.  They’re not really determined by the server, rather by the amount of active chats / audio / video / sharing activities that are actively going on at the time.  So this has an impact on your bandwidth and ultimately the message rate impacts the maximum number of sessions.  Here, you can use the capacity planning toolkit  and the resource kit to help you plan accordingly…