Computer Networking Devices

Computer network devices also known as communication devices and they constitute a data communication network.  These devices are routers, switches, hubs, LAN cards, gateway, modems, hardware firewall, CSU/DSU, ISDN terminals and transceivers.  In an Ethernet or WAN network, the data communication cannot be performed without these devices.  Being an IT professional or a network administrator, you must have the good understanding of these devices.

Based on your business requirements, you have the select the best devices for your network and before selection, make sure that they are compatible with each other.  It is recommended that you select all the devices for your IT infrastructure from the same vendor.
The top vendors are Cisco, D-Link, LinkSys, Baynet, RealTek, 3Com, NetGear, Intel, Nortel, and Lucent etc.  A well designed IT infrastructure with the proper placement of the routers, servers, gateway and switches can reduce the operational cost and enhances the overall performance dramatically.

Routers
A router is a communication device that is used to connect two logically and physically different networks, two LANs, two WANs and a LAN with WAN.  The main function of the router is to sorting and the distribution of the data packets to their destinations based on their IP addresses. Routers provides the connectivity between the enterprise businesses, ISPs and in the internet infrastructure, router is a main device.  Cisco routers are widely used in the world.  Every router has routing software, which is known as IOS.  Router operates at the network layer of the OSI model.  Router does not broadcast the data packets.
Switches
Like the router, a switch is an intelligent device that maps the IP address with the MAC address of the LAN card.  Unlike the hubs, a switch does not broadcast the data to all the computers, it sends the data packets only to the destined computer.  Switches are used in the LAN, MAN and WAN.  In an Ethernet network, computers are directly connected with the switch via twisted pair cables.  In a network, switches use the three methods to transmit the data i.e. store and forward, cut through and fragment free.
Hubs
The central connecting device in a computer network is known as a hub.  There are two types of a hub i.e. active hub and passive hub.  Every computer is directly connected with the hub.  When data packets arrives at hub, it broadcast them to all the LAN cards in a network and the destined recipient picks them and all other computers discard the data packets.  Hub has five, eight, sixteen and more ports and one port is known as uplink port, which is used to connect with the next hub.
Modems
A modem is a communication device that is used to provide the connectivity with the internet.  Modem works in two ways i.e. modulation and demodulation. It coverts the digital data into the analog and analog to digital
LAN Cards
LAN cards or network adapters are the building blocks of a computer network. No computer can communicate without a properly installed and configured LAN card. Every LAN card is provided with a unique IP address, subnet mask, gateway and DNS (if applicable).  An UTP/STP cable connects a computer with the hub or switch.  Both ends of the cable have the RJ-45 connectors one is inserted into the LAN card and one in the hub/switch.  LAN cards are inserted into the expansion slots inside the computer.  Different LAN cards support different speed from 10/100 to 10/1000.
Multiplexer
Multiplexer is a device that is used to combining the several electrical signals into one signal.