Microsofts Message Analyzer 1.4 Build 4.0.8112.0

Microsoft Message Analyzer is a tool for capturing, displaying, and analyzing protocol messaging traffic. It is the successor to NetMon 3.x and a key component of the Protocol Engineering Framework (PEF), created by Microsoft to improve protocol design, development, documentation, testing, and support. With Message Analyzer, you can capture live data or retrieve archived message collections from saved files such as traces and logs. Message Analyzer also allows you to display data in a default tree grid view as well as selectable graphical views that employ grids, charts, and timeline visualizer components, providing high-level data summaries and other statistics.

Update: Microsoft Message Analyzer (MMA) was retired as of November 25, 2019. There is currently no Microsoft replacement for Microsoft Message Analyzer in development.

Note: I would say it is a must-have tool for any network administrator, given how much you can accomplish with it. A dedicated TechNet blog for Microsoft Message Analyzer is available.