Day-7: OSI Model Part-1

By | May 7, 2022

What is Protocol?

Before we understand the OSI Model we need to understand the protocol. A protocol is a set of rules of operation it means there is something that has been predefined or pre-programmed In order for computers to exchange information, there must be a preexisting agreement as to how the information will be structured and how each side will send and receive it.

In networking, there are lots of protocols we have, and each protocol has been designed to accomplish its respective task. For example, we have a web server, File server, Mail server, etc, these servers are built with the help of some sort of protocol. Network protocols are typically created according to industry-standard by various networking or information technology organizations.

Protocol can be proprietary or it can be open standard. Proprietary means it is strict to the organization and that can be used by them only. open standard means that can be used by everyone in the world.

In networking, Protocols are used for exchanging resources, Communicating with each other and also we use them for troubleshooting the network.

There are few organizations that are involved in this project of writing the open standard protocols.Like IEEE,IETF,IANA etc etc.

In the Computer network industry, Also there is some set of routing protocols we have, that are basically playing a key role in communication.

The architecture of communication is going to be controlled by the OSI layer . International Organization for Standardization (ISO) researched different network models and the result is the OSI model which was released in 1984.

Some Common Protocols.

TCP: TCP is a transport layer protocol that ensures reliable data delivery. TCP is meant to be used with IP, and the two protocols are often referenced together as TCP/IP.

HTTP: The Hypertext Transfer Protocol (HTTP) is the foundation of the World Wide Web, the Internet that most users interact with this protocol.

HTTPS: The problem with HTTP is that it is not encrypted — any attacker who intercepts an HTTP message can read it. HTTPS (HTTP Secure) corrects this by encrypting HTTP messages.

TLS/SSL: Transport Layer Security (TLS) is the protocol HTTPS uses for encryption. TLS used to be called Secure Sockets Layer (SSL).

UDP: The User Datagram Protocol (UDP) is a faster but less reliable alternative to TCP at the transport layer. It is often used in services like video streaming and gaming, where fast data delivery is paramount.
ICMP: The Internet Control Message Protocol (ICMP) reports errors and provides status updates. For example, if a router is unable to deliver a packet, it will send an ICMP message back to the packet’s source.

A protocol has its own unique protocol number and they work on layer hierarchy as per the OSI model.

OSI Model Introduction.

OSI has 7 layers and it was developed by the ISO, Normally OSI model is a standard of communication in the network, It means whatever the communication is going to have occurred in the network from source to destination, that is going to be followed by the OSI layers.

What is an ISO?

  • ISO Stands for the “International Organization for Standardization”.
  • World’s largest developer of international standards for a wide variety of products and services.
  • ISO is not an acronym but is based on the Greek word ISOS, meaning equal.
  • ISO is best known for its Open Systems Interconnection (OSI) reference model.
  • ISO published the OSI reference model in 1984 to develop a layered framework for networking protocols.

Advantages of OSI Model

At the beginning of the computer network industry, the development of networks was very difficult. Because Each networking product vendor had its own proprietary solution. The bad part was that one vendor’s device was not compatible with another vendor’s network devices. This is where the idea for the OSI model was born, having a layered approach to networks our hardware vendors would design hardware for the network, and others could develop software for the application layer. Using an open model which everyone agrees on means we can build networks that are compatible with each other.

So the end result would be Juniper device can be interoperable with cisco devices and vice versa and the apple device can talk with Microsoft and vice versa.

OSI Model » CS Taleem


Normally when we talk about the communication in the network we go from top to bottom and bottom to top.

The top three layers we called Upper layers and the bottom 4 layer we called lower layers.

Normally when we talk about the Upper layer, they normally deal with the network-aware applications like your browser, google chrome, Outlook, Ftp client, RDP, etc.

Once the Upper layer will accomplish its work the data will move to the lower layer. the lower layer which is basically the most important and you as a network engineer normally have to deal with it.

The lower layer is basically taking the major responsibility in the network for carrying the data in the network. and each and every layer in the lower layer is going to play a major role in the network and you as a network engineer need to take care of these layers.


Leave a Reply

Your email address will not be published.