Important Networking Devices

Computer network 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. 

Major vendors / Manufacture are Cisco, D-Link, LinkSys, Baynet, RealTek, 3Com, NetGear, Intel, Nortel, and Lucent  

Routers

Is a communication device that is used to connect two logically and physically different networks like 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. Provides the connectivity between the enterprise businesses, ISPs and in the internet infrastructure, as main device. 

 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 converts 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

Bridge

A bridge is a network communication device that is used to connect one segment of the network with another that uses the same protocol.  It operates at the Data link layer of the OSI layers model.  In the Ethernet network, the bridge is also known as IEEE 802.1D.  A bridge process the information at the data link layer of the OSI layers model.  There are two types of the bridging.

• Transparent bridging
• Source route bridging

Bridges are fast devices for forwarding the data but not as fast as the routers and switches.  A bridge cannot be used as a firewall device as a router.  In the bridged network, the messages are sent to all the nodes and are picked up only by the destined computers. 

Broadband Router

A router is a network communication device that is used to connect two different networks and to provide the internet connectivity to the users. A broadband router is essential part of the home or office network where the high speed internet connectivity is required. 

Using a broadband router, the network computers can share the internet and send and receive the data with every other user on the network.  It shares the internet connection by using the NAT (Network Address Translation). There are the following three purposes of the broadband routers.

• To provide the high speed internet connectivity to the network users.
• To route the traffic between the network computers.
• To filter the traffic through the built-in firewall features.

It distributes the IP addresses dynamically thus it functions as a DHCP server.