Computer Network is an interconnection of Computers and other devices which are capable of communicating to the Internet world. The Network can be Wired Network or Wireless Network. The main Component of Computer Network is a Computer, also known as Work Station. However there are some other devices which makes this communication possible.
Modem
MODEM refers to Modulator-Demodulator. It is a device which can convert one form of signal into another form.
(i) Telephone Modem/Dialup Modem
The earlier days, Telephone lines were used to connect Computers to the Internet. We know that computer are digital devices and Telephone lines on those days were Analog Type. Now we need something to convert the Digital Data into Analog form and vice verse. The Device used for this purpose is known as Modem. The circuitry for the same is incorporated in the Network Card of Computers and Laptops.
(ii) GSM Modem/Mobile Broadband Modem
This is an electronic wireless device, which can be connected to a Computer or a Laptop. This device is also known as a Dongle. It has a Sim Card slot through which it can communicate to the internet via the Mobile Service Provider. It can be considered as a dedicated Mobile Phone for Internet access connected to a Computer.
(iii) Wireless Modem/Wi-Fi Modem
This is another electronic wireless device, which can be connected to a Router, or a Broadband line to convert the signals into Wireless Signals (Wi-Fi) in Micro Wave Frequency. The signals arriving at the Router or Broadband line are mainly in Radio Frequency Range. The main purpose of this device is to convert this radio frequency signals into a smaller frequency, which is known as
Hub
Hub is also known as a repeater which work in the Physical Layer of the OSI Model. It has many input/output ports. It is mainly used for Network sharing. Consider you have an Wired Broadband BSNL internet connection to your room. You want to share the internet with your room mates. A Hub is useful in this situation. We will connect the external internet connection to one of the port. This internet connection will be shared now and available to all the other ports in the Hub. Your room mates can connect Ethernet cable from the other ports of the Hub to their Computer. RJ45 is the connector used to connect the Ethernet cable to the Hub.
Switch
Switch is also known as MAC bridge, which work in the Datalink Layer of the OSI Model. Like Hub, Switch also has lot of input/output ports. The main difference between Hub and Switch is that, Hub will simply broadcast the messages arriving at the input. However, Switch has the capability to selectively route the message to specific ports. The routing is done using the MAC address of each devices connected to it.
Router
Router is a traffic directing device which works in the Network Layer of the OSI Model. When a packet data arrives at the input port of the Router, it will forward the data to the next destination of the data based on the information available in the Routing Table. The traffic directing is carried in Router using IP Address of the Destination. The main purpose of Router is to connect multiple networks and direct the packets to same network or another network.
Gateway
Gateway is a Network device which can operate in any layer of the OSI Model. It is device used to connect different networks, operating with different protocols. Gateway is a complex device than Router.
