This is a Java servlet filter (as per Servlet API 2.3). This filter lets you restrict the amount for concurrent HTTP sessions. So, you may use it for example as an access restriction tool, for load balancing etc. You have to use this filter together with Sessions stats listener (it must be installed too).

filter accepts two initial parameters:
limit - describes a maximal amount allowed sessions
redirect - describes an URI for page (site) bounced requests will be redirected to