OSI Model

Open System Interconnection —Introduction

This model been developed by ISO: “International Organization for Standardization” in the year 1984. It is a 7 layer architecture with each layer having different functionalities to perform. There is collaboration between each of the 7 layers to transmit the data .

1. Layer 1: Physical Layer

The Lowest layer of the OSI model.All the information in this layer is in the form of bits. Basic Functionality is for transmitting individual bits from one node to next. The signals received to this layer will be in binary format 0s and 1s and sends to the Data link layer .

2. Layer 2 : Data link layer

Node-to-node delivery takes place in this layer. The main function of this layer is to make sure data transfer is error-free from one node to another, over the physical layer. When a packet arrives in a network, it is the responsibility of DLL(Data link Layer) to transmit it to the Host using its MAC address.

3. Layer 3 : Network Layer

Transfer of data from one host to another host located at different locations. Packet routing i.e. Shortest path to route the packets. The sender & receiver’s IP addresses are placed in the header by the network layer.

4. Layer 4: Transport Layer

The transport layer provides services to the application layer and takes services from the network layer. The data in the transport layer is referred to as Segments. It is responsible for the End to End Delivery of the complete message.

5. Layer 5: Session Layer

Responsible for maintaining sessions, authorization and also ensures security. Enables to establish connection and terminate connection.

6. Layer 6 : Presentation Layer

The presentation layer is also called the Translation layer. The data from the application layer is extracted here and manipulated as per the required format to transmit over the network.

7. Layer 7 : Application Layer

The topmost layer of OSI model , we find the Application layer which is implemented by the network applications. These applications produce the data, which has to be transferred over the network.