Ethereal

Ethereal is a network Protocol Analyzer for Windows Operating Systems.  This software is utilized heavy in China, India and the United States and needs less storage than most other programs in the Networking Software arena.  Ethereal is an application that can capture packets that are sent through a network and then interprets them so that you can see what tasks are being done throughout the network.  At its core, Ethereal is a packet analyzer that uses a tcpdump system to carry out the captures which will then display on 3 information windows.  Once the Ethereal Network Protocol Analyzer is complete, you can access the list of all of the packets and which ports were used.  

Ethereal has been used by network professionals to troubleshoot, analyze and teach software and protocol development.  Compared to other network Protocol Analyzers, Ethereal is infinitely easier to use and has the added benefit of being free.

Features:

Ethereal needs less storage than other programs

• Supports over 20 different Formats
• Supports more than 300 Protocols (including SMTP, ATM, IGRP, PPP, IPX)
• Capture data from network and disc capture
• Results display on 3 information windows
• Results display what Ports were used
• Free (open source) and Easy to use
• Real-Time Scanning of Ethernet, FDDI, Token Ring, IP over ATM and Loopback Interfaces

Ethereal lets you examine at a packet level, the specific details of network traffic.  It is very easy to use and free which makes this software better than most.  Data from a network scan and we scanned using Ethereal in real time or saved for analyzing later.  You have the option to set up a script or schedule a later scan to target something specific on the network.  The Ethereal application is distributed in binary form so it can be used on a wide variety of platforms including Windows, Linux, and Mac OS X.