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.
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.
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.
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
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 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 is a device that is used to combining the several
electrical signals into one signal.