Learn how computer networks connect devices and let us share information and work together easily.
Introduction
Have you ever wondered how your WhatsApp message reaches your friend within seconds, or how streaming services like Netflix deliver high-quality video to millions of users simultaneously? The answer lies in Computer Networks.
A computer network is a set of interconnected devices that share resources and data using specific communication protocols. This blog will take you through the basics of computer networks, from their origins to the technical layers that make it all possible.
Networks
A network is a collection of devices connected through communication media to share resources or data.
For example, your home Wi-Fi network connects your phone, laptop, and smart TV to the internet. This process of sharing is often referred to as data communication.
How Did It Start?
The concept of networking began during the Cold War when the United States and Russia were in a technological race. Russia launched the first satellite, pushing the United States to innovate further. This led to the creation of ARPA (Advanced Research Projects Agency), which developed ARPANET, the precursor to the internet.
Initially, ARPANET connected four locations: UCLA, the Stanford Research Institute, UC Santa Barbara, and the University of Utah. It used TCP (Transmission Control Protocol) for communication.
As more computers joined ARPANET, the need for better organization arise, leading to the invention of the World Wide Web.
WWW (World Wide Web)
The World Wide Web (WWW), developed by Tim Berners-Lee, revolutionized the way information was stored and accessed. It allowed users to reference other documents via hyperlinks. The world's first website was a simple text-based page without any search engine functionality. Today, the web enables everything from social media to online shopping
Protocols
Communication in networks relies on a set of rules called protocols. Without them, devices running different software wouldn’t be able to exchange data. Protocols are defined by the Internet Society. Anyone can able to suggest about the internet by RFC(Request for comments).
There are some protocols
TCP(Transmission Control Protocol)
It will ensure the data reaches to destination and is not corrupted.
UDP
When you do not want to care about your 100% of your data is reaching or not. Ex: Video conferencing
HTTP
HTTP, or Hypertext Transfer Protocol, is the foundation of how web browsers and servers communicate to share information on the internet.
OSI(Open System Interconnection) Model
The OSI model illustrates how computers communicate in a structured manner across seven layers. Let’s break them down:
Application Layer
The application layer allows the users to access the network. It provides a user interface. It's implemented in software. Users interact with the application layer like browsers, messages, etc.
Design issues of the Application Layer
Client-server paradigm
All the application layer programs are based on the client and server.
A user at a local site wants to receive a service from a computer of a remote site.
Ex: A user wants to retrieve a file from remote computers both computers run the programs.
The local computer runs a program(client) that requests service from another remote program computer(server).
Addressing
Addressing is different based on mechanisms.
Client-servers communicate with each other using addressing.
Each application has its own address format.
Ex: The application program user uses an alias name instead of an IP address to make the environment convenient for the user by using DNS.
DNS is a Domain Name System, DNS maps names to IP addresses of that particular name.
Different services
The Application Layer is designed to give different services to he user or user programs.
The common service of the Application layer is SMTP, FTP, and HTTP.
Presentation Layer
We get the data from an application layer, the data is in the form of words or characters. The presentation converts it into a machine-readable format.
The presentation layer is concerned with the syntax and semantics of the information exchange between two systems.
The presentation layer acts as a Data translator and it performs encoding and decoding and it compresses the data.
Functions of the presentation layer
- Translation
- Encryption -Protecting the data
- Compression-Reducing the size of the data, in order to reduce the load on the network.
Session Layer
It helps in setting and managing the connections and it enables sending and receiving of data followed by the termination of the connected session.
It is used to establish, maintain and synchronize the interaction between the communicating devices.
Functions of Session Layer
- Dialogue control
- Synchronization
Transport Layer
It is responsible for the process to process delivery.
Design issues of the Transport layer
Packetizing
Data received from the session layer is divided into small data units called segments. Every segment contains the port number of the source and destination and sequence number(Resemble the segments in the correct order). Dividing data into smaller units (segments) for efficient transmission is known as packetizing.
Connection control
Transport layer protocols are divided into two categories:
- Connection-oriented
- Connection less
In Connection-oriented, the path is chosen from source to destination.
In connectionless, no path is chosen and the data can move in any direction.
TCP is connection-oriented and UDP is connectionless.
Addressing
In the transport layer, addressing is port addressing. A computer may be running several programs at the same time. The communication at the transport layer is done by the client-server paradigm.
Reliability
Reliability means having error control and flow control. Sending transport layer makes sure that the entire message arrives at the receiving transport layer without error. Error control is usually carried out by retransmission.
Network Layer
It works for the transmission of the received data segment from one computer to another that is located in a different computer.
The network layer is a host-to-host delivery.
Design issues of Network Layer
Internetworking
Internetworking is the logical connecting of heterogeneous physical networks together to look like a single network to the upper layer protocols.
It supports data transmission from one network to another network.
Packetizing
The network layer encapsulates packets received from upper-layer protocols and makes new packets out of them.
Routing
Routing means making or choosing the path
Whenever there are multiple routes to the destination, we must make a decision and choose one route.
Each IP packet normally reaches the destination via several routes.
The packet can't choose the route, the routes connecting LAN, and WAN make the decision.
Addressing
The network layer supports only IP addresses. The address used in the network layer must uniquely and universally define the connection of a host or router to the internet.
Fragmentation
Simply fragmentation means dividing.
A packet can travel through different networks,each router decapsulates the IP packet, process it, and encapsulates it in another frame.
Data Link Layer
The data link layer allows you to directly communicate with the computers. The data unit in the data link layer is called a frame. The main responsibility of the data link layer is the node-to-node delivery of data.
Design issues of the Data link layer
Framing
The process of encapsulating the data in a frame coming from an upper layer is called framing. A frame is a manageable unit.
Error control
It is used to find out if the data is lost or corrupted. Error control is divided into two categories. Error Detection and Error Correction.
Flow control
It controls the flow of data. It means, how much data the sender has to send before receiving an acknowledgment.
Addressing
In the data link layer, physical addressing is used. Physical addressing is also called MAC address and local address. The Mac address is 48 bits.
Media Access Control
The data link layer allows the upper layers of the OSI model to access these frames and it also controls how the data is placed and received from the media using media access controllers.
Physical Layer
The physical layer is the bottom-most layer of the OSI model. It transmits the data bits from one computer to another computer through a physical medium. It establishes, maintains, and deactivates the physical connections. It also performs the synchronization of the bits. And it is directly connected to transmission media.
Functions of the physical layer
- It defines the transmission mode.
- It defines the type of signal used for transmission.
- It performs the bit-to-signal transformation.
- It defines the way, how two or more devices are connected physically. The data in the physical layer is in the form of a sequence of bits and it is transmitted in the form of signals.
TCP/IP Network model
The TCP/IP model, older but still widely used, simplifies networking into five layers:
Protocols in TCP
- In the Application layer, the protocols used are SMP, HTTP, FTP, DNS, and SNMP.
- In the Transport layer, the protocols are TCP and QDP.
- In Network layer,the protocols are ARP,IP,IGMP,RARP,ICMP.
Conclusion
Computer networks are the backbone of the digital world. They make it possible for us to share files, browse the internet, and communicate across the globe. Learning the basics of networks, their layers, and how they work helps you understand the internet better.
Thanks for reading the blog and investing your time 😊. I hope you find this blog insightful and you learn something out of this. If you did, then shower some support by giving a reaction to the blog.
Top comments (2)
Nice explanation
Thank you Avinash