IPNetMonitor for Mac

From Sustainable Softworks:

IPNetMonitor provides a set of twelve integrated Internet tools which allow Macintosh users to monitor their connection to the Internet. The tools are designed to help users quickly identify problems, locate where the problem is, and gather data which can be used to solve the problem, either directly or through their Internet Service Provider. The tools include Ping, Trace Route, Name Server Lookup, Who Is, Finger, Monitor, TCP Info, Connection List, Address Scan, and Subnet Calculator, DHCP Lease Renewal and DHCP Test Window. With IPNetMonitor, you can see how the Internet is working, monitor the flow of data to and from your computer, and trace the route by which the data is flowing. This gives you the information to both optimize internet service and diagnose problems. Once you have located a problem, the tool's Who Is feature gives you the name, and often the e-mail address, of the person responsible for that part of the network.