{"id":52365,"date":"2020-12-23T11:13:48","date_gmt":"2020-12-23T05:43:48","guid":{"rendered":"https:\/\/ye1o34zhk8.onrocket.site\/?p=52365"},"modified":"2022-09-28T14:38:41","modified_gmt":"2022-09-28T09:08:41","slug":"open-systems-interconnection","status":"publish","type":"post","link":"https:\/\/instrumentationtools.com\/open-systems-interconnection\/","title":{"rendered":"What is Open Systems Interconnection?"},"content":{"rendered":"

The purpose of Open Systems Interconnection (OSI) is to standardize network architecture and encourage vendors to develop network equipment that would avoid proprietary design.<\/strong><\/p>\n

International Standards organization (ISO) in 1974 produced an open system interconnection reference model.<\/p>\n

It allows any computer system anywhere in the world to communicate with any other, as long as both obey OSI<\/a> protocol standards.<\/p>\n

OSI has codified in the reference model referred to as the OSI\/RM. It is an abstract description of inter-process communications.<\/p>\n

It defines types of objects that are used to describe an open system, the general relations among these types of objects, and general constraints on these types of object relations.<\/p>\n

A seven-layer OSI model is used to represent the OSI\/RM, its overall architecture, the services provided, the functions necessary to be performed, and peer protocols needed for achieving inter-process communication.<\/p>\n

Open Systems Interconnection<\/h2>\n

\"Open<\/p>\n

Image Courtesy: Wikimedia Commons<\/a><\/p>\n

To assure an end to end systems interoperability, adherence to the OSI\/RM is not sufficient. It is only achieved when full compliance with the OSI peer protocol is satisfied.<\/p>\n

The services provided by the seven layers of the OSI\/RM can be divided into three main regions, as shown below.<\/p>\n

Network Utilities-layers 7,6, and 5.<\/p>\n

Host to host transport and internet working – Layers 4, and 3.<\/p>\n

Sub-network transmission (Local area and wide area networks) – Layers 3,2,1 and Media 0. Layers 3,2,1 and Media 0.<\/p>\n

Functions of each OSI Layer<\/h2>\n

Application Layer<\/h3>\n

Layer 7 provides interfaces for applications to access network services such as file sharing, message handling, and data access.<\/p>\n

It also handles error recovery for applications, as desired.<\/p>\n

Presentation Layer<\/h3>\n

The presentation layer at level 6, handles data formatting and translation. For outgoing messages, the presentation layer converts data into a format specified by the Application layer, if necessary; for incoming messages, it reverses the conversion if required by the receiving application.<\/p>\n

In short, Layer 6 presents the data in a suitable to the application layer.<\/p>\n

The presentation layer engages protocol conversion, data encryption, decryption, data compression, decompression, data representation incompatibilities between OSI, and graphic commands.<\/p>\n

Session Layer<\/h3>\n

Layer 5, the session layer permits two computers to hold ongoing communications-called a session – across a network so applications on either end of the session can swap or exchange data as long as the session lasts.<\/p>\n

Transport Layer<\/h3>\n

The transport layer is (Layer 4) manages data transfer from one application to another across a network.<\/p>\n

It breaks long data streams into smaller blocks called \u201cSegments\u201d.<\/p>\n

Network Layer<\/h3>\n

The network layer, below the Transport layer, is responsible for routing the packet based on its logical address.<\/p>\n

It moves packets of data from the source to the destination and across the networks if necessary.<\/p>\n

Data Link Layer<\/h3>\n

Layer 2 the data link layer, works with frames and is the mediator between the Network layer and Physical layer.<\/p>\n

It defines how computers access the network medium – also called Media Access Control (MAC), which is why the MAC address is defined at this layer.<\/p>\n

Physical Layer<\/h3>\n

The activity of Layer 1 is to convert bits into signals for outgoing messages and signals into bits for incoming messages.<\/p>\n

The type of signal generated depends upon the medium.<\/p>\n

For example, wire media, such as twisted pair cable, use electrical pulses, fiber optic media use pulses of light, and wireless media uses radio waves.<\/p>\n

Advantages<\/h2>\n