#Computer-Networks  #Computer-Networks  
# Topic covered
* Computer Network
* Types of computer networks
  * PAN, LAN, CAN, MAN, WAN
* Types of Transmission Media
  * Guided Media
  * Unguided Media
* Transmission Modes in Computer Networks
  * Simplex, Half-Duplex, Full-Duplex
* Types of Network Topology
  * P2P, Bus, Ring, Star, Tree, Mesh, Hybrid
* Data Transmission
  * Unicast, Broadcast, Multicast

1.1 What is Computer Network?

A computer network is a set of devices connected through links.

Computer networking refers to connected computing devices (such as laptops, desktops, servers, smartphones, and tablets) and an ever-expanding array of IoT devices (such as cameras, door locks, doorbells, refrigerators, audio/visual systems, thermostats, and various sensors) that communicate with one another.

1.2 Types of computer networks

https://www.javatpoint.com/types-of-computer-network

PAN(Personal Area Network)

  • Personal Area Network is a network arranged within an individual person, typically within a range of 10 meters.
  • Personal computer devices that are used to develop the personal area network are the laptop, mobile phones, media player and play stations.

LAN(Local Area Network)

  • Local Area Network is a group of computers connected to each other in a small area such as colleges, schools, hospitals, and so on.
  • LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc.

CAN(Campus Area Network)

  • Within University, Corporate office

MAN(Metropolitan Area Network)

  • A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network.
  • It covers a larger area than LAN such as small towns, cities, etc

WAN(Wide Area Network)

  • A Wide Area Network is a network that extends over a large geographical area such as states or countries.
  • The internet is one of the biggest WAN in the world.

1.3 Types of Transmission Media

https://www.geeksforgeeks.org/types-transmission-media/

Transmission media is a communication channel that carries the information from the sender to the receiver. Data is transmitted through the electromagnetic signals.

1. Guided Media

  • It is also referred to as Wired or Bounded transmission media.
  • Signals being transmitted are directed and confined in a narrow pathway by using physical links.

Twisted Pair Cable

  • It consists of 2 separately insulated conductor wires wound about each other.
  • Generally, several such pairs are bundled together in a protective sheath.
  • They are the most widely used Transmission Media
  • Eg: Telephone lines

Coaxial Cable

  • The name of the cable is coaxial as it contains two conductors parallel to each other.
  • The inner conductor of the coaxial cable is made up of copper, and the outer conductor is made up of copper mesh. The middle core is made up of non-conductive cover that separates the inner conductor from the outer conductor.
  • Eg: TV wire

Optical Fiber Cable

  • It uses the concept of refraction of light through a core made up of glass or plastic.
  • The core is surrounded by a less dense glass or plastic covering called the cladding.
  • A protective coating consisting of plastic is used known as a jacket.

2. Unguided Media

  • An unguided transmission transmits the electromagnetic waves without using any physical medium.
  • Therefore, it is also known as wireless transmission
  • In unguided media, air is the media through which the electromagnetic energy can flow easily.

Radio waves

  • Radio waves are the electromagnetic waves that are transmitted in all the directions of free space.
  • Radio waves are omnidirectional, i.e., the signals are propagated in all the directions.
  • The range in frequencies of radio waves is from 3Khz to 1 khz.
  • An example of the radio wave is FM radio.

Microwaves

  • Microwaves are the electromagnetic waves having the frequency in the range from 1GHz to 300 GHz.
  • Microwaves are unidirectional as the sending and receiving antenna is to be aligned, i.e., the waves sent by the sending antenna are narrowly focussed.
  • Types - Terrestrial microwave and Satellite microwave communication

Infrared

  • An infrared transmission is a wireless technology used for communication over short ranges.
  • The frequency of the infrared in the range from 300 GHz to 400 THz.

1.4 Transmission Modes in Computer Networks

https://www.javatpoint.com/computer-network-transmission-modes

  • Simplex
    • In Simplex mode, the communication is unidirectional, as on a one-way street.
    • Only one of the two devices on a link can transmit, the other can only receive.
    • Example: Keyboard and traditional monitors
  • Half-Duplex
    • In half-duplex mode, each station can both transmit and receive, but not at the same time.
    • When one device is sending, the other can only receive, and vice versa.
    • Example: Walkie-talkie
  • Full-Duplex
    • In full-duplex mode, both stations can transmit and receive simultaneously.

1.5 Types of Network Topology

https://www.guru99.com/type-of-network-topology.html

Network topologies describe the methods in which all the elements of a network are mapped. The topology term refers to both the physical and logical layout of a network.

Point to Point (P2P) Topology

Point-to-point topology is the easiest of all the network topologies. In this method, the network consists of a direct link between two computers

Bus Topology

Bus topology uses a single cable(common cable) which connects all the included nodes. The main cable acts as a spine for the entire network. One of the computers in the network acts as the computer server. When it has two endpoints, it is known as a linear bus topology.

In case if the common cable fails, then the entire system will crash down.

Ring Topology

In a ring network, every device has exactly two neighboring devices for communication purpose. It is called a ring topology as its formation is like a ring. In this topology, every computer is connected to another computer. Here, the last node is combined with a first one.

Break in a single ring can risk the breaking of the entire network and this topology less popular.

Star Topology

In the star topology, all the computers connect with the help of a hub. This cable is called a central node, and all other nodes are connected using this central node. It is most popular on LAN networks as they are inexpensive and easy to install.

Performance depends on the hub’s capacity

Tree Topology

Tree topologies have a root node, and all other nodes are connected which form a hierarchy. So it is also known as hierarchical topology.

This topology integrates various star topologies together in a single bus, so it is known as a Star Bus topology. Tree topology is a very common network which is similar to a bus and star topology.

Mesh Topology

The mesh topology has a unique network design in which each computer on the network connects to every other. It is developing a P2P (point-to-point) connection between all the devices of the network.

It offers a high level of redundancy, so even if one network cable fails, still data has an alternative path to reach its destination

Installation is complex, and it is expensive due to the use of more cables. No proper utilization of systems.

Hybrid Topology

Hybrid topology combines two or more topologies. You can see in the above architecture in such a manner that the resulting network does not exhibit one of the standard topologies.

The design of hybrid topology is complex. It is one of the costliest processes

1.6 Data Transmission

https://www.geeksforgeeks.org/difference-between-unicast-broadcast-and-multicast-in-computer-network/

Casting in computer networks means transmitting data (stream of packets) over a network.

Unicast Transmission (One-to-One)

In Unicast transmission, the data is transferred from a single sender (or a single source host) to a single receiver (or a single destination host).

Broadcast Transmission (One-to-All)

In Broadcast transmission, the data is transmitted from one or more senders to all the receivers within the same network or in other networks.

This type of transmission is useful in network management packets such as ARP (Address Resolution Protocol) and RIP (Routing Information Protocol) where all the devices must see the data.

Multicast Transmission (One-to-Many)

When the data is transmitted from a single source host to a specific group of hosts having the interest to receive the data, it is known as multicast transmission.

Multicast can be more efficient than unicast when different groups of receivers need to see the same data