Hi,
Concurrent Sessions normally refers to maximum simultaneous connection from clients that ASA can handle. Each ASA model has different capacity to handle this connections.
New Sessions per second refers to how many new connections from clients can be accepted by ASA.
Example, if ASA5520 has 280,000 concurrent sessions with 9,000 new sessions per second, it tells you that this model can accept 9,000 new connections per second, but this connections is subjected to the limit of 280,000 max concurrent sessions. ASA will not accept new connetion if the concurrent sessions hits the max limit.
However, it will start to accept new connection(s) again if older session(s) is no longer active and terminated. This will open another space for new connection.
Rgds,
AK
