Open Systems Interconnections

Overview

The Open Systems Interconnection (OSI) model is a layering model standardized by the ISO. It describes the implementation of network protocol suites by roughly delegating responsibilities across seven layers.

Layers

The OSI model has seven layers.

Physical

Specifies methods for moving digital information across a communication medium.

Link

Specifies methods for establishing connectivity to a neighbor sharing the same medium and, in general, for communication across a single link.

Network

Specifies methods for communicating in a multihop fashion across potentially different types of link networks.

This layer also includes addressing schemes for hosts and routing algorithms that choose where packets go when sent from one machine to another.

Transport

Specifies methods for end-to-end communication between applications on a network.

Session

Specifies methods for multiple connections constituting a communication session.

Presentation

Specifies methods for preparing data for transmission and reception between different systems.

Application

Specifies methods for accomplishing some user-initiated task.