NADetector monitors and analyzes the network traffic and displays statistical information pertaining to each IP address pair and protocol, helping network administrators and users troubleshoot network problems. It is a freeware network monitoring application that's helpful, well-designed, user friendly and advanced.
Here are some screenshots to illustrate the features and user interface of this application:
Net Monitor for Employees Professional
Network LookOut Administrator Pro
Advanced Host Monitor
Connection Keeper
MIB Browser