A protocol analyzer is a software utility that allows network traffic to be captured, and the contents of frames to be analyzed. A protocol analyzer often provides the best point of reference with respect to communication issues and errors that may be occurring on a network. The capabilities of protocol analyzers vary greatly, and range from enterprise products like Sniffer from Network Associates, to freeware tools like Ethereal.
A cable tester is a small handheld hardware device that can be used to troubleshoot a variety of physical connection and cabling issues. For example, a cable tester can be used to determine whether the pinouts of cables are correct, whether maximum distances have been exceeded, if a cable contains breaks, and so forth. Cable testers are available for a variety of different media (twisted pair, coax, fiber) and tend to be an invaluable resource in when troubleshooting physical layer issues.