The following points summarize the key concepts in this chapter:
- Three primary types of cables are used with networks: coaxial, twisted-pair, and fiber-optic.
- Coaxial cable comes in two varieties: thinnet and thicknet.
- Thinnet cable is about 0.64 centimeters (0.25 inches) thick and can carry a signal for a distance of up to 185 meters (607 feet).
- Thicknet cable is about 1.27 centimeters (0.5 inches) in diameter and can carry a signal for a distance of up to 500 meters (1640 feet).
- The BNC connector is used with both thinnet and thicknet cables.
- Coaxial cables come in two grades, classified according to how they will be used: PVC-grade cable is used in exposed areas; plenum-grade cable has a fire-safety rating and is used in enclosed areas such as ceilings and walls.
- Twisted-pair cable can be either shielded (STP) or unshielded (UTP).
- The number of twists per unit of length and the protective shielding provide protection from interference.
- Twisted-pair cables conform to five standards, called categories. Each category provides specifications for increasing the speed of data transmission and resistance to interference.
- Twisted-pair cables use RJ-45 connectors to connect to computers and hubs.
- Fiber-optic cables use light to carry digital signals.
- Fiber-optic cables provide the greatest protection from noise and intrusion.
- Data signals can be either baseband or broadband.
- Baseband transmission uses digital signals over a single frequency.
- Broadband transmission uses analog signals over a range of frequencies.
- IBM uses its own system of cabling and standards, but follows the same basic technology as other cables.
The Network Interface Card
- Network interface cards (NICs) are computer expansion cards that provide the interface between the network cabling and the computer.
- The function of the NIC is to prepare, send, receive, and—in a Ring topology—retransmit data on the network.
- A NIC is installed just like any other expansion card. You must properly set the IRQ, the base I/O port address, and the base memory address.
- In order for a NIC to be physically installed in the computer and connected to the network, it must both match the computer's expansion bus type and have the proper connector fittings for the network cabling.
- A network's performance is only as good as its weakest link. Many aspects of a NIC can either enhance or restrict the performance of the network. Be careful when selecting an economical card; it just might become the limiting factor in your network's performance.
- The wireless environment is an often appropriate, and sometimes necessary, networking option.
- Computers operating on a wireless network function like their wire-bound counterparts, except that the NIC is connected to a transceiver instead of a cable.
- A wireless segment can be either point-to-point (separated by short distances or in view of each other) or long-range.
- Wireless networks use infrared, laser, narrowband radio, or spread-spectrum radio signals for transmitting data.
- A wireless bridge can connect buildings that are situated as much as 40 kilometers (about 25 miles) apart.
- Cellular communications, satellite stations, and packet-radio communications are adding mobility to networks.