Packet Analyzer

A packet analyzer is used to monitor, intercept, and decode data packets as they are transmitted across networks.  Some packet analyzers can be software while some of them can be hardware.  Other names for a packet analyzer are network analyzer, protocol analyzer, and packet sniffer.  As data is flowing through networks, the sniffer can look at each individual packet and decode the data.  By decoding the data, the sniffer can view the information in the packet and therefore analyze the information.

One example of a powerful network monitor and analyzer is CommView.  CommView is an easy network monitor and it is very flexible.  This application "captures every packet on the wire to display important information such as a list of packets and network connections, vital statistics, protocol distribution charts, and so on."  Since CommView gives a full analysis, it can help find network problems and troubleshoot software and hardware.  Network analyzers are important because they maintain efficient network data transmission, test firewalls, and identify problems.  In addition, CommView decodes network traffic which allows you to see what, where, and how the information you are sending leaves your computer.  Some of the many things that CommView is capable of doing are view detailed IP connections statistics, reconstruct TCP sessions, map packets to the application that is sending/receiving them, and view protocol distribution. 

http://www.veracode.com/security/packet-analyzer
http://www.tamos.com/products/commview/