OSI - Open Systems Interconnection Overview

Open Systems Interconnection

Introduction

Imagine how computers are organized in a network. Its physical infrastructure and the digital aspects of a network all play an important role in how it functions. Once we combine the physical and digital how do they interconnect network communication?

Your focus in this module will be to expand on the knowledge of computer organization and networking discussed previously. You will start by developing an understanding of the physical and digital aspects of a computer network. Then you will learn how the OSI model plays a role in a computer network.

Module Lessons Preview

In this module, we will study the following topics:

Physical/Digital Aspects of Computing Network Lesson

Discuss computer architecture which outlines how computers are organized in the network and task assigned to computer

 OSI Model Lesson

Learn about the purpose of the Open Systems Interconnection model (OSI) & Introduced to the 7 layers of the OSI model

 Trace the Data Lesson

Dig deeper into the OSI Model, understanding the interconnection of the 7 layers.

Key Terms

Protocol- a set of instructions written by a programmer to perform a function or group of functions.

Application Layer (7)- protocols enable software programs to negotiate formatting, procedural, security, synchronization, and other requirements with the network.

Data Link Layer (2)- bridges the networking media with the Network layer. Its primary function is to divide the data it receives from the Network layer into frames that can then be transmitted by the Physical layer.

Frame-  A package for data that includes not only the raw data, or “payload,” but also the sender’s and recipient’s addressing and control information.

HTTP (Hypertext Transfer Protocol)- An Application layer protocol that formulates and interprets requests between Web clients and servers.

ISO (International Organization for Standardization)- A collection of standards organizations representing 162 countries with headquarters located in Geneva, Switzerland; Its goal is to establish international technological standards to facilitate the global exchange of information and barrier-free trade.

Network Address- A unique identifying number for a network node that follows a hierarchical addressing scheme and can be assigned through operating system software; Network addresses are added to data packets and interpreted by protocols at the Network layer of the OSI model.

Network Layer- Protocols in the Network layer translate network addresses into their physical counterparts and decide how to route data from the sender to the receiver.

Node- a point of intersection/connection within a data communication network; create, receive and communicate information and store it or relay it to other nodes.

OSI (Open Systems Interconnection) model- A model for understanding and developing computer-to-computer communication developed in the 1980s by ISO. It divides networking functions among seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

Physical Layer (1)- generate and detect signals so as to transmit and receive data over a network medium. These protocols also set the data transmission rate and monitor data error rates, but do not provide error correction.

Presentation Layer (6)- translate between the application and the network. Here, data are formatted in a schema that the network can understand, with the format varying according to the type of network used; it also manages data encryption and decryption, such as the scrambling of system passwords.

Route- direct data between networks based on addressing, patterns of usage, and availability of network segments.

Router- A device that connects network segments and directs data based on information contained in the data packet.

Sequencing- The process of assigning a placeholder to each piece of a data block to allow the receiving node’s Transport layer to reassemble the data in the correct order.

Session-  A connection for data exchange between two parties. The term session may be used in the context of Web, remote access, or terminal and mainframe communications, for example.

Session Layer (5)- Establishes and maintains communication between two nodes on the network. It can be considered the “traffic cop” for communications, such as videoconferencing, that require precisely coordinated data exchange.

Standard- A documented agreement containing technical specifications or other precise criteria that are used as guidelines to ensure that materials, products, processes, and services suit their intended purpose.

Transport Layer (4)-  protocols ensure that data are transferred from point A to point B reliably and without errors; flow control, acknowledgment, error correction, segmentation, reassembly, and sequencing.

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