We're looking to generate some reports, to show the number of concurrent users, and duration of connections over a period of time. Sending the data to syslog obviously isn't a problem. Writing a script to manipulate the data into graphs, though is a bit tricky. Has anyone done this before? Would you be willing to share the code?
Take a look at Cacti ( http://www.cacti.net/ ).
With simple periodical snmp walk you can create the best graphs. Templates for IVE are available.