Basics: 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 is a network?

  2. what are the components of a computer network?

  3. what are the different components of a communication system

  4. what are the different network topologies?

  5. what are the types of computer networks based on size?

  6. what are the types of line configuration used while networking?

  7. what do you understand by half-duplex and duplex transmission mode?

  8. what are the criteria for choosing a network?

  9. what do you understand by unicast, multicast and broadcast transmission?

  10. what is internet?

  11. what is the difference between lan, wan, man and pan?

  12. explain various elements of a protocol?

  13. what do you understand by asynchronous transfer mode?

  14. what is the difference between network edge and network core?

  15. what is ethernet?

  16. what is fdm and tdm?

  17. what are digital and analog signals?

  18. how can we convert digital signal to analog signal or vice versa?


Basics


Question 1) What is a network?

Answer) A network refers to an interconnection of two or more devices which share or exchange resources among themselves. The nodes in a network can be computer systems, printers, routers etc. The nodes in the network must be able to communicate with each other.

Example: Internet


computer network diagram in computer network class notes
Computer Network Diagram

 

Question 2) What are the components of a computer network?

Answer) A computer network contains both hardware and software components.

Hardware Components

a. Connecting Devices

The connecting devices are used to enable communication between the computers or other hardware components in the network. These devices act as middleware between the nodes in the network.

Example: Routers, Switches, Hubs etc.


b. Transmission Media

The transmission medium refers to the channel used for communication between the network nodes. The transmission medium carries the message signal in the form of bits, light or in the form of electromagnetic signals.

Example: Coaxial cable, optical fiber etc.


c. End Devices

The source or destination devices in a network are called end devices.

Example: PCs, web servers etc.


Software Components

a. Networking Operating System

A network operating system is a system software which is used to maintain the network resources and to establish peer-to-peer connection between the devices in the network.

Example: Microsoft Windows Server Linux, UNIX etc.


b. Protocol Suite

A protocol defines the rules that are to be followed by the devices in a network for communication. A protocol suite refers to a set of protocols used in a computer network.

Example: TCP/IP protocol suite


 

Question 3) What are the different components of a communication system

Answer) The different components of a communication system are:

Message

The data that has to be sent from the source to destination is called message.


Sender

The sender is a device in the network which initiates the data communication. It sends the message to a destination device.

Example: PC, web server etc.


Transmission medium

Transmission medium is a channel which is used to carry the message from sender to receiver.

Example: coaxial cable, optical fiber etc.


Receiver

The receiver is a network device to which the source (or sender) sends the message signal. It is an end device in a network.

Example: PC


components of computer network in computer networks class notes

 

Question 4) What are the different network topologies?

Answer) Network topologies refer to the way in which the network devices are connected to each other in a network. The different types of network topologies are:

Star Topology

In star topology, there is only one central controller (or server). The remaining devices in the network are connected directly to the server. These are considered as clients. The client nodes are not directly connected to one another.

The communication between two client devices in the network takes place through the central controller (or server).


star topology in computer networks class notes
Star Topology

Bus Topology

In bus topology, there is a cable which acts as backbone of the network. All the network devices are connected to the central cable. The message transfer happens through this cable.

As all the devices communicate through a single cable, this topology is not secure.


Bus Topology in computer networks class notes
Bus Topology

Ring Topology

In ring topology, each device is connected directly to exactly two devices (one on the right and the other on the left). Thus, the devices in the network form a ring structure.



Ring Topology  in computer networks class notes
Ring Topology

Mesh Topology

In mesh topology, every device in the network is connected to every other device in the network directly. As there is a direct link between all pairs of devices, it is more secure.


Mesh Topology in computer networks class notes
Mesh Topology

Hybrid Topology

Hybrid topology is the combination of two or more of the above mentioned network topologies.


 

Question 5) What are the types of computer networks based on size?

Answer) The computer networks are classified into four major categories based on size.

Local Area Network

A Local Area Network (LAN) is a computer network that covers a limited area or locality. Usually, the range of LAN is less than two miles and privately owned.

The network topologies used in LAN are star, bus and ring.

Example: a computer network in a building or office.


Wide Area Network

A Wide Area network (WAN) is a computer network that covers a large geographical area. A WAN is an interconnection of LANs that are geographically far apart. It provides worldwide connectivity. A WAN usually uses wireless transmission media for communication(wired transmission media cannot be used as it covers a very large area).

Example: Internet


Metropolitan Area Network

A Metropolitan Area Network covers a city or a town. Its range is between LAN and WAN. MAN is used to provide connectivity within a city.


Personal Area Network

A Personal Area Network covers an individual’s workspace. A PAN extends over a very small area (less than 30 feet). A PAN usually consists of two or more PCs or mobile phones connected together.


 

Question 6) What are the types of line configuration used while networking?

Answer) The different types of line configurations in a network are:

Point-to-point Connection

In point-to-point communication, there is a direct link between two devices. Here, the entire capacity of the transmission channel is reserved for communication between the two devices. This type of communication is much faster and more secure.


Point to Point Line Configuration in computer networks class notes
Point to Point Line Configuration

Multipoint Connection

In multi-point communication, a communication channel is shared among two or more devices. It is also called multi-hop communication. This type of communication is less secure and less expensive.


Multipoint Connection in computer networks class notes
Multipoint Connection

 

Question 7) What do you understand by half-duplex and duplex transmission mode?

Answer) Half Duplex

In Half Duplex mode of communication, both the devices involved in communication can send and receive data. But, both the devices cannot send or receive at the same time.

While A transmits data to B, B cannot send data to A simultaneously. B can send data to A after A’s message has been received by B.

Example: Walkie-Talkie


half duplex in computer networks class notes

Full Duplex

In Full Duplex mode of communication, both the devices involved in communication can both send and receive data at the same time (simultaneously). Here, the channel is shared by the signals flowing in both the directions.

Example: Telephone


full duplex in computer networks class notes

 

Question 8) What are the criteria for choosing a network?

Answer) The following criteria must be considered before choosing a network:

Reliability

A network is considered reliable only if it gives the same results repeatedly under similar conditions. Reliability is also measured by the number of network failures and the network’s ability to recover from failure.

Scalability

Scalability of a network refers to its ability to adapt to the demand of the users. The network must be able to manage the increasing demand and change according to the needs.


Performance

The performance of a network is measured using the following parameters:

  • Efficiency

Efficiency of a network refers to the ability of the network to resist failures.

  • Transit time

Transit time refers to the amount of time taken by a message to travel from one device to another.

  • Response time

Response time is the time between enquiry and response.


Security

Security of a network indicates the ability of the network to prevent unauthorized users from accessing the network.


 

Question 9) What do you understand by unicast, multicast and broadcast transmission?

Answer) Unicast

In unicast communication, there is one sender and one receiver. The sender or source sends a message to only one of its interfaces. There exists a one-to-one relationship between the sender and receiver.


Multicast

In multicast communication, there is one sender and many receivers. There exists a one-to-many relationship between source and destination. Usually, the sender sends the message to a group address. The group address is used to identify the members of the group.


Broadcast

In broadcast communication, there is one sender and many receivers. Here, the sender sends message to all the other devices in the network. There exists a one-to-all relationship between the source and destination.


IP service in computer networks class notes
IP Service

 

Question 10) What is internet?

Answer) The internet is a Global Network (WAN) which connects devices all over the world. It provides worldwide connectivity. It allows exchange of information all over the world. In the internet, every device has a unique IP address. Internet allows the users to access the web. Hence, it allows exchange of data between computers all over the world.


 

Question 11) What is the difference between LAN, WAN, MAN and PAN?

Answer) Local Area Network

A Local Area Network (LAN) is a computer network that covers a limited area or locality. Usually, the range of LAN is less than two miles and privately owned.

The network topologies used in LAN are star, bus and ring.

Example: a computer network in a building or office.


Wide Area Network

A Wide Area network (WAN) is a computer network that covers a large geographical area. A WAN is an interconnection of LANs that are geographically far apart. It provides worldwide connectivity. A WAN usually uses wireless transmission media for communication(wired transmission media cannot be used as it covers a very large area).

Example: Internet


Metropolitan Area Network

A Metropolitan Area Network covers a city or a town. Its range is between LAN and WAN. MAN is used to provide connectivity within a city.


Personal Area Network

A Personal Area Network covers an individual’s workspace. A PAN extends over a very small area (less than 30 feet). A PAN usually consists of two or more PCs or mobile phones connected together.


 

Question 12) Explain various elements of a protocol?

Answer) Every protocol has three key elements. They are:

Syntax

Syntax defines the way in which the data has to be represented. It defines the structure of data.


Semantics

Semantics defines the logical meaning of each block of data. It also explains how the data has to be interpreted and the actions to be taken after interpretation.


Timing

Timing refers to the speed of data transfer between the sender and receiver. The sender and receiver must be synchronized at a particular speed to avoid data loss and data overloading.


 

Question 13) What do you understand by asynchronous transfer mode?

Answer) The Asynchronous Transfer Mode (ATM) is a connection oriented protocol that is used for switching in telecommunication networks. It uses asynchronous time division multiplexing to encode data. ATM networks support audio, video and data transmission.

ATM is used to employ cell switching. ATM cells are fixed size packets with 48 bytes of payload. It enables fast switching.



 

Question 14) What is the difference between network edge and network core?


Answer)

Network Edge

Network Core

Network edge refers to the end devices in a network.

Network core refers to the backbone or center of the network

Network edge contains the end-points and the first hop from the end-points into the core of the network.

Network core is used to connect various zones within the datacenter and to other datacenters.

Network edge consists of PCs, network adaptors, modems etc.

Network core consists of routers, switches etc.



 

Question 15) What is ethernet?

Answer) Ethernet is used to connect the PCs within a Local Area Network (LAN). The Ethernet uses a cable to connect the computers within a LAN. Ethernet connection can be extended upto a maximum of 10 kilometers. Setting up Ethernet in a LAN is much expensive. Ethernet provides high security.

Ethernet uses the Rj-45 cable for data transmission. It operates in both half-duple and full-duplex mode. Ethernet supports star and bus topologies.


ethernet in computer networks class notes


 

Question 16) What is FDM and TDM?

Answer) FDM (Frequency Division Multiplexing)

In FDM, the channel bandwidth is divided among many data signals. The signals occupy different frequency bands. The signals are transmitted simultaneously through the channel. FDM does not require synchronization. The circuitry for FDM is complex. FDM channels suffer from crosstalk as they are prone to interference. FDM is usually used for transmitting analog signals.


circuit switching in computer networks class notes

TDM (Time Division Multiplexing)

In TDM, the entire bandwidth is occupied by a single data signal. The signals are transmitted through the channel at different time slots. TDM requires synchronization. The circuitry for TDM is simpler than that of FDM. TDM does not suffer from crosstalk. TDM can be used for both analog and digital signals.


circuit switching in computer networks class notes

 

Question 17) What are digital and analog signals?

Answer) Digital Signal

Digital signals are continuous in time, but discrete in amplitude. Digital signals are used to represent data as a sequence of values. Usually, the digital signals use 0 or 1 (discrete values) to represent the data.


Digital signals in computer network class notes
Digital Signals

Analog Signal

Analog signals are continuous time-varying signals. These signals are continuous both in time and amplitude. Most of the physical signals are analog signals.

Example: Heartbeat signal, earthquake signal etc.


Analog signals in computer networks class notes
Analog Signals

 

Question 18) How can we convert digital signal to analog signal or vice versa?

Answer) Analog to Digital Conversion

The process of converting analog signal to digital signal involves the following steps:

a. Sampling

Sampling is the process of recording the amplitude of the given analog signal at discrete time intervals. Sampling involves discretization in time domain.


b. Quantization

Quantization is the process of converting non-integral amplitude values to discrete integral values. Quantization involves discretization in amplitude.


c. Encoding

Encoding converts the sampled and quantized samples to ‘n’ bit code. It converts the discrete samples into a digital signal.


Analog to Digital conversion in computer networks class notes
Analog to Digital conversion

Digital to Analog Conversion

Digital to analog conversion involves the reconstruction of the sampled signal using the Nyquist sampling theorem. Methods like Successive Approximation register, R-2R ladder are used for converting digital signal to analog signal.


digital to analog conversion in computer networks class notes



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