Network Monitoring

[Dan]

To Whom It May Concern,     I work at  a local ISP here in Gallup, New Mexico and I am looking for some software that monitors network time and  as well as filtering software for a Public Access Computer Lab.  We woll be running OpenBSD or Debian  GNU/Linux the latest  version.   The  time monitoring will allow us to charge the customer for time used.  Any help will be greatly appreciated.  I know this kind of request is a bit odd, but it is highly needed information.   Thanks, Daniel Reinhardt