The Connection-limit setting is enforced at the TCP level by the ProxySG's IP stack. It's simply a hard limit on the number of TCP connections from a given IP address.
Above enforcement is executed when number of simultaneous TCP connections and/or excessive repeated failed requests from each client IP address that can be established within a specified time frame. If the limits are met the appliance either does not respond to connection attempts from a client already at this limit or resets the connection.
Configuration for the setting is only configurable from Command Line Interface.
Detailed command explanation can be found on SGOS admin guide.
ProxySG CLI admin guide : DOC10456
ProxySG Admin Guide : DOC10459