Communication and Network

Physical Connection
Data packets are transmitted between computers on the network either as electrical signals in electric wires, as light signals in fibre optic cables, or as electromagnetic waves through space. The physical connection determines the kind of cable used, the way the cable is configured and the way information is transmitted over the cable.

• Twisted Pair refers to the use of cables that contain insulated copper wires twisted together in pairs for the physical layer of an Ethernet network—that is, a network in which the Ethernet protocol provides the data link layer. Twisted-pair cable is used by older telephone network and is the least expensive type of local area network(LAN) cable, most networks contain some twisted-pair cabling at some point along the network. Other types of cables used for LANs include coaxial cable and fiber optic cables.

• Coaxial cable Coaxial cable is used as a transmission line for radio frequency signals, in applications such as connecting radio transmitter and receivers with their antennas, computer network (Internet) connections, and distributing cable television signals. One advantage of coax over other types of transmission line is that in an ideal coaxial cable the carrying of electromagnetic field signal exists only in the space between the inner and outer conductors . This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other transmission lines, and provides protection of the signal from external electromagnetic interferences. Although it is more expensive than standard telephone wire, it is much less susceptible to interference and can carry much more data.

• Fiber Optic Cable transmit information from one place to another by sending pulses of light through optical fiber. The light in optical fiber forms an electromagnetic carrier wave that is modulated to carry information. Involves the following basic steps: Creating the optical signal involving the use of a transmitter, relaying the signal along the fiber, ensuring that the signal does not become too distorted or weak, receiving the optical signal, and converting it into an electrical signal. Data can be transmitted digitally rather than analogically.

Network terms

• node
• client
• server
• hub
• network interface card( NIC)
• network operating system(NOS)
• host computer
• network manager