Network Devices: Computer Networks Class Notes

Updated: Aug 18

Mobiprep has created last-minute notes for all topics of Computer networks to help you with the revision of concepts for your university examinations. So let’s get started with the lecture notes on Computer networks.

  1. Computer Networks - Basics

  2. Network Devices

  3. Network Models

  4. Physical Layer

  5. Network Layer

  6. Transport Layer and Congestion control

  7. Application Layer

  8. Web Security

  9. Email and IP Security

Our team has curated a list of the most important questions asked in universities such as DU, DTU, VIT, SRM, IP, Pune University, Manipal University, and many more. The questions are created from the previous year's question papers of colleges and universities.


  1. what are the different network devices used in a computer network?

  2. what is a router? what are its functions?

  3. what is a switch?

  4. what is a hub?

  5. what is a gateway?

  6. what is a modem? why is it used?


Network Devices


Question 1) what are the different network devices used in a computer network?

Answer) The devices which enable communication between the hardware devices in a network are called network devices. The following are the different network devices used in a computer network:

  1. Hub

  2. Switch

  3. Bridge

  4. Router

  5. Modem

  6. Repeater

  7. Gateway

  8. Access points


 

Question 2) What is a router? what are its functions?

Answer) The router is a network device which operates in the network layer. It is used to enable communication between multiple LANs or WANs. The router routes the data packets from the source to destination using the IP address of the devices. The router stores the route from the source to destination in the form of a routing table. The routing table is updated dynamically.

The main functions of a router are:

Flooding

The router has the ability to flood or broadcast the data packet to all the devices in a network. This process is called flooding. Flooding enables the data to be sent to all the devices in a network in a short span of time.


Forwarding

The process of accepting the data packet on one interface and sending it to another interface is called forwarding. Forwarding is the main function of the router. It is used to send the packets from source to destination through the intermediate nodes.


Filtering

Packet filtering is a technique in which some data packets are forwarded and the other data packets are not forwarded by the router. The router decides whether the packet must be forwarded or not. This process is called filtering.

For example, an ARP request is not forwarded, instead it is sent back to the source with the MAC address requested by the source.


Router in Computer network class notes
Router

 

Question 3) What is a switch?

Answer) A switch is a network device which operates in the data link layer. The switch has multiple ports to which end devices can be connected.


Switch in computer network class notes
Switch

The main function of the switch is to receive the data frames from one of its interfaces, and forwarding them to their appropriate destinations. The switch uses the store and forward technique. i.e.the switch has memory.

The switch maintains a learning table which contains the mapping of IP address to the corresponding MAC address.


MAC address

Port

00:3E:41:5D:DF:FF


192.168.1.1

11:F3:DD:65:1F:88

192.168.1.5

If the MAC address of the destination is not known, the switch broadcasts the data packet to all the devices in the network. On receiving the packet, the destination device sends its MAC address as reply to the switch. In this way, the switch learns the MAC address of the devices in the network.


 

Question 4) What is a hub?

Answer) A hub is a network device which operates in the Physical layer. It functions as a multi-port repeater. It connects multiple devices in a network.

If a device in the network sends a data packet, it is forwarded to all the other devices in the network. Hub cannot send the data packet directly to the destination. Instead, the data is broadcasted to all the devices in the network. The destination device accepts the data packet, and the remaining devices discard the data.

The usage of hub leads to a lot of unnecessary traffic. It is not secure.


Hub in computer networks class notes
Hub

 

Question 5) What is a gateway?

Answer) The gateway is a device which connects two networks together. It acts as a gate between two networks. The gateway can also be used to connect two networks which operate on different protocols. The gateway enables the data flow between the two networks.

The gateway is usually a router, a server or a firewall.


Gateway in computer networks class notes
Gateway

 

Question 6) what is a MODEM? why is it used?

Answer) MODEM – Modulation and Demodulation

The modem is used to modulate the outgoing signals and demodulate the incoming signals. Modulation involves conversion of digital signals to analog signals. Demodulation involves the conversion of analog signals to digital signals.

The modem is used to provide internet facility to a PC. The modem can be connected only to one end device (PC). The modem is directly connected to the ISP through a dedicated channel (TV cables or telephone lines).


MODEM in computer networks class notes
MODEM



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