Jan 8, 2023 2 min read

The OSI Model

The OSI Model

The Open Systems Interconnection Model or OSI Model is logical structure for understanding computer networking designed by the International Organization for Standardization (ISO). The OSI Model is separated into 7 layers which are 1) Physical Layer, 2) Data Link Layer, 3) Network Layer, 4) Transport Layer, 5) Session Layer, 6) Presentation Layer and 7) Application Layer.

Layer 1: Physical Layer

The physical layer is designed to establish a connection between physical devices. The information found at this layer is in the form of bits, 1’s and 0’s.

The data link layer is responsible for error free communication between nodes on the physical layer. The data here is found in the form of frames and it is transferred using MAC addresses.

Layer 3: Network Layer

The network layer allows information to be communicated between multiple hosts on different networks. The network layer is responsible for routing traffic and for logical addressing. Logical addressing is how routers distinguish between multiple devices.

Layer 4: Transport Layer

The transport layer transfers data in the form of segments and is responsible for end to end delivery of a message. This layer confirms receipt of information and helps with error handling if a malfunction occurs. This layer ensures successful communication through segmentation, flow and error controls from upper and lower layers.

Layer 5: Session Layer

This layer of the OSI model establishes and maintains continuity of network connections. Features of the session layer include authentication, session maintenance and security. The session layer helps to synchronize data in transit and help to mitigate errors during communication. Once a session has carried out its purposes the session layer is then responsible for terminating the session.

Layer 6: Presentation Layer

The next layer of the OSI model is the presentation which is responsible for data translation between nodes. Data here is extracted and translated into the necessary form to transmit over the network. This layer is responsible for encryption and for the formate of data being transmitted over the network. Without the presentation layer the receiver would not be able to interpret the data bring transmitted.

Layer 7: Application Layer

The Application layer is the seventh layer of the OSI model and it is responsible for adjusting data so that users can access the network and access the data being transmitted over it. This allows users to leverage services such as accessing remote files, sending emails and using common web applications.

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