common network devices and cabling

                                                  Network Devices

Router: a specialized network device that determines the next network point to which it can forward a data packet towards the destination of the packet. Unlike a gateway, it cannot interface different protocols.



Bridge:  a device that connects multiple network segments along the data link layer.

Switch: a device that allocates traffic from one network segment to certain lines (intended destination(s)) which connect the segment to another network segment. So unlike a hub a switch splits the network traffic and sends it to different destinations rather than to all systems on the network.


Hub: connects multiple Ethernet segments together making them act as a single segment. When using a hub, every attached all the objects, compared to switches, which provide a dedicated connection between individual nodes.



Repeater: device to amplify or regenerate digital signals received while sending them from one part of a network into another.



                                 Network Cables

Twisted-pair cable- is the most common type of cabling you can see in todays LAN networks. A pair of wires forms a circuit that can transmit data. The pairs are twisted to provide protection against crosstalk, the noise generated by adjacent pairs. When a wire is carrying a current, the current creates a magnetic field around the wire. This field can interfere with signals on nearby wires. To eliminate this, pairs of wires carry signals in opposite directions, so that the two magnetic fields also occur in opposite directions and cancel each other out. This process is known as cancellation.

Coaxial cable- looks similar to the cable used to carry TV signal. A solid-core copper wire runs down the middle of the cable. Around that solid-core copper wire is a layer of insulation, and covering that insulation is braided wire and metal foil, which shields against electromagnetic interference. A final layer of insulation covers the braided wire.

Optical Fiber cables- use optical fibers that carry digital data signals in the form of modulated pulses of light. An optical fiber consists of an extremely thin cylinder of glass, called the core, surrounded by a concentric layer of glass, known as the cladding. There are two fibers per cable—one to transmit and one to receive. The core also can be an optical-quality clear plastic, and the cladding can be made up of gel that reflects signals back into the fiber to reduce signal loss.