NAVODAYA VIDYALAYA SAMITI, NOIDA�
E-Content for Class XII (Informatics Practices)�Topic: Network Devices
BY
Jitendra Kumar, PGT IT
JNV, Medak
Learning Objectives
Hub
A hub, also called a network hub, is a common connection point for devices in a network.
Hubs are devices commonly used to connect segments of a LAN. The hub contains multiple ports. A computer which intends to be connected to the network is plugged in to one of these ports
A hub has a simple job i.e anything that comes in one port is sent out to the others
If a message comes in destined for computer “A”, that message is sent out to all the other computers/devices connected to hub, regardless of which computer “A” is.
Switch
A network switch connects devices (such as computers, printers, wireless access points) in a network to each other,
A switch can detect specific devices that are connected to it and keeps a record of the mac addresses of these devices. So data is always directed to intended port.
Hub v/s Switch
A switch does what a hub does, but more efficiently. By paying attention to the traffic that comes across it, it learns which computers are connected to which port.
Initially, a switch knows nothing, and simply sends on incoming messages to all ports.
So,just by accepting that first message, the switch has learned something: it knows on which connection the sender of the message is located. Thus, when machine “A” responds to the message, the switch only needs to send that message out to the one connection.
By processing the response, the switch has learned something else: it now knows on which connection machine “A” is located. That means subsequent messages destined for machine “A” need only be sent to that one port.
Switches learn the location of the devices they are connected to it almost instantaneously and this lead to less network traffic as now most network traffic only goes where it needs to, rather than to every port
Router
A router is a physical or virtual device that passes information between two or more computer networks. A router inspects a given data packet's destination Internet Protocol address (IP address), calculates the best way for it to reach its destination and then forwards it accordingly.
Modem
Modem (Modulator-Demodulator), is a network device that allows a computer or another device, such as a router or switch, to connect to the Internet.
The first modems were "dial-up," meaning they had to dial a phone number to connect to an ISP. These modems operated over standard analog phone lines and used the same frequencies as telephone calls, which limited their maximum data transfer rate to 56 Kbps.
Modern modems are typically DSL or cable modems, which are considered "broadband" devices. DSL modems operate over standard telephone lines, but use a wider frequency range.
Modem
Gateway
A gateway is a networking device that connects two networks using different protocol.
Network gateways, known as protocol translation gateways or mapping gateways, can perform protocol conversions to connect networks with different network protocol technologies.
For example, a network gateway connects an office or home intranet to the Internet. If an office or home computer user wants to load a web page, at least two network gateways are accessed—one to get from the office or home network to the Internet and one to get from the Internet to the computer that serves the web page.
Note: Gateways are network points that acts as an entrance to another network.
Gateway
Repeater
A repeater is an electronic device that receives a signal before it becomes too weak and regenerates the original signal.
As a signal travels a fixed distance, before attenuation of the signal, a repeater is used which amplifies and restores signals for long-distance transmission.