The open systems interconnection model (OSI) consists of 7 layers which are as follows:
7th Layer – Application
This layer of open systems interconnection model supports the processes of end-user and applications. The partners of communication are recognized, service quality is also identified, privacy and user-authentication are also taken into consideration & constraint on the data-syntax is also recognized. All the things at 7th layer of OSI are specified by application. Services of application are provided by this OSI layer to file the e-mail, transfers and many other services of software-network. FTP and Telnet are those applications which exist totally in this application-level. Tiered-application-architecture also forms an application layer’s part.
6th Layer – Presentation
This open systems interconnection model‘s layer caters freedom from the dissimilarity in the representation of data, for example encryption, through translating to the network-format from the application & vice-versa.
This layer performs work for transforming data or information into that form which is accepted by the application-layer. Data are formatted and encrypted by this presentation layer so that it can be sent to the network, thereby providing independence from the compatibility issues. Sometimes this presentation layer is also called as Syntax-layer.
5th Layer – Session
In this type of OSI layer, establishment, termination and management of connections is done in between the applications.
This layer exchanges, coordinates, terminates and sets-up conversations & dialogues in between the applications present on every end. This layer deals particularly with connection and session coordination.
4th Layer – Transport
This type of layer caters transparent data transfer in between the hosts or end-system & is regarded responsible mainly for the end-to-end recovery of error & flow-control. Complete transfer of data is insured by this layer.
3rd Layer – Network
This open system interconnection model’s layer caters routing and switching technologies, forming logical ways called as the virtual-circuits, to transmit data or information from one node to the other. The two functions of network layers are forwarding and routing. The other functions are addressing, handling error, internetworking, controlling congestion & design sequencing.
2nd Layer – Data Link
Encoding of data-packets is done in this data-link layer into various bits. It provides transmission-protocol management and knowledge & errors are handled in the flow-control, physical-layer & frame-synchronization. This layer has been segmented into 2 sub-layers: MAC – Media-Access-Control layer and LLC – Logical-Link-Control layer. The (MAC) Media-Access-Control layer regulates how one computer on network acquires access or control to data & permission for transmitting it. The (LLC) Logical-Link-Control layer regulates synchronization of frames, error-checking and flow-control.
1st Layer – Physical
This is the first layer of the open systems interconnection model. It conveys bit-stream – signals radio or light, impulse of electricity, through network which is at mechanical and electrical level. This layer also furnishes means of hardware for receiving and sending data or information on a particular carrier, comprising defining-cables, physical-aspects and cards.