OPEN SYSTEMS INTERCONNECTION MODEL (OSI MODEL)

Open Systems Interconnection model (ISO-OSI model 7 layers)

Generally, you found that this article is a feature on OSI models. Pay attention above the to the blog’s featured image; you shall see the network word labelled. So the whole thing is based on computer networks. When network word comes in our mind, it strikes the internet and all, connect one place to another. Yes, you are right. Now let us come to examples to make you understand faster.

Movie Scenario:

Suppose you are using a computer and you want to send your movie’s file collection to your other drive. So you have movies in your C:/ drive, and you want to send your movie’s file to D:/ drive. In this scenario, C:/ became sender and  D:/  became the receiver.

Movie Scenario
Another example:

Another such example, suppose the sender or the receiver is not in the same place, but they should work together as both of them are in a single host. Like your workstation co-exists with hardware and software the same way it works between sender and receiver.

We can place hardware or software or both of them, to implement a connection between them as a single host. After implementing the connection between them, lot of problems may arise like, a sender can send unlimited data to the receiver, and we also don’t need over-limit, or at a time you have many systems to access, so you also need access control.

To control the error in the system, you also need error control. So there are almost 70 functionalities, which are essential and which may not be necessary in some cases. So those functionalities are implemented in hardware and software.

iso-osi models

Suppose you need 70 responsibilities. You cannot implement 70 functionalities in the same place because there are other problems. Like among them, they can be dependent. In that case, groups are to perform and share the responsibilities. To perform the particular function divided into the given responsibility. Suppose in a real-world example, you build seven groups, and each group have 10 responsibilities. It creates an independent system and helps to sort the issues smoothly.

To make stable systems through national and worldwide systems must be generated which are compatible to interact with each other, there is an organization named ISO (International organization of Standardization) has built Open System Interconnection (OSI), and it is generally known as OSI model

The ISO-OSI model is a seven-layer architecture. It describes seven layers or levels in a perfect communication system.

ISO-OSI 7 layer network architecture:
Layer No.Layer’s Name
1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

1. Physical Layer:

As its name indicates, it contains things which we can touch like your broadband cable. You can call it the source of Internet. The layer which has the medium to connect to the Internet like your router, dial-up modem, broadband cables, etc.

2. Data Link Layer:

This layer is the home of MAC Addresses (Media Access Control) and Logical Link Control (LLC). Logical Link Control identifies the protocols and helps in the transmission of data as the rules of the protocol in use. It plays a significant role in the LAN.

3. Network Layer:

Network Layer is where an IP Address reside. Everything which happens with TCP/UDP protocols occurs in this layer. So basically Network Layer moves packets from source to destination.

4. Transport Layer:

I call it Rulebook Of Packets, and this is what it means. As we have previously discussed in How Data Travels Over Network? That when we have to upload/download a file, it is first broken down into smaller parts called Data Packets. So this layer decides what should be the size of packets, how much should we wait before sending another packet, etc.

Deals with the “Transport Of Data.”

5. Session Layer:

When two computers are connected, they form a “Session.” The session may represent continuity like when you are talking on the phone its a session. It’s the reason you and the other person are interacting. This layer manages sessions; it starts sessions and terminates sessions. When you go to a website then you open a session with their server, you send and receive data, and all this happens in Session Layer.

6. Presentation Layer:

This layer represents tasks of Operating System. Network drivers reside here; this layer deals with the encryption/decryption and compression of the data as well as character encoding.

If you are using a VPN, the data gets encrypted/decrypted here.

7. Application Layer:

Application Layer is the closest layer to the user. This layer contains the program which is using the Internet. For example, your internet browser comes into layer seven, but it doesn’t connect to the Internet itself. Other six layers help it to send and receive data over the Internet.


Tips:

When I was a beginner in this field I used to memorise those layers seven like.

Please do not throw sausage pizza away.

Means : P – 1, D – 2, N – 3, T – 4, S – 5, P – 6, A – 7.

For further reading, read this Wikipedia article


About the author

Orvill

Hi, I'm Orvill Samanta, an aspiring blogger with an obsession for all things tech. This blog is dedicated to helping peoples learn about technology.

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