Attenuation refers to the weakening of data signals as they travel through a respective media. Network media varies in its resistance to attenuation. Coaxial cable is generally more resistant than UTP, STP is slightly more resistant than UTP, and fiber-optic cable does not suffer from attenuation at all. That's not to say that a signal does not weaken as it travels over fiber-optic cable, but the correct term for this weakening is 'chromatic dispersion,' rather than attenuation.

It's important to understand attenuation or chromatic dispersion and the maximum distances specified for network media. Exceeding a media's distance without using repeaters can cause hard-to-troubleshoot network problems. Most attenuation or chromatic dispersion related difficulties on a network require using a network analyzer to detect them.

Data Transmission Rates

One of the more important media considerations is the supported data transmission rate or speed. Different media types are rated to certain maximum speeds, but whether or not they are used to this maximum depends on the networking standard being used and the network devices connected to the network.

Transmission rates are normally measured by the number of data bits that can traverse the media in a single second. In the early days of data communications, this measurement was expressed as bits per second (bps), but today's networks are measured in Mbps (megabits per second) and Gbps (gigabits per second).

The different network media vary greatly in the transmission speeds they support. Many of today's application-intensive networks require more than the 10Mbps offered by the older networking standards. In some cases, even 100Mbps, which is found in many modern LANs, is simply not enough to meet current network needs. For this reason, many organizations deploy 1Gbps networks, and some now even go for 10Gbps implementations.