OSI LAYER MODELS
In this section, we would introduce you to internetworking. You will learn the basics of the Open Systems Interconnection (OSI) model the way Cisco wants you to learn it. Ethernet networking and standards are discussed in detail.
This in-depth section covers the very beginnings of the Internet Protocol stack and then goes all the way to IP addressing and understanding the difference between a network address and a broadcast address before finally ending with network troubleshooting.
In the first article, we would discuss the advantage of OSI layer. Later we would cover each layer in depth so you can understand every aspect of layer model. Pay more attention to these articles as CCNA cover several questions from this model. Before moving on next category be to assure that you didn't skip any topics from this category.
The advantage of OSI Layer model
In 1984, International Organization for Standardization (ISO) developed the seven-layer model to help vendors and network administrators in such a way that they can gain a better understanding of how data is handled and transported between networking devices, as well as to provide a guideline for the implementation of new networking standards and technologies.
What is OSI Layer model?
ISO developed OSI Reference Model that describes how information is transferred from one networking component to another, from the point when a user enters information using a keyboard and mouse to when that information is converted to electrical or light signals transferred along a piece of wire (or radio waves transferred through the air). The OSI reference model is the primary model for network communications. The early development of LANs, MANs, and WANs was confused in many ways.
Early 1980 saw great increases in the number and sizes of networks. As companies realized that they could save money and gain productivity by using networking technology, they added networks and expanded existing networks as rapidly as new network technologies and products were introduced. To assist in this process, the OSI Reference Model separates the network communication process into seven simple layers.
Dividing the network into seven layers provide these advantages:
Advantage of OSI Layer model
Reduces complexity:
It breaks the network communication process into smaller and simpler components, thus aiding component development, design, and troubleshooting.
Standardizes interfaces:
It standardizes network components to allow multiple vendor development and support.
Facilitates modular engineering:
It allows different types of network hardware and software to communicate with each other.
Interoperability between Vendors:
It allows multiple-vendor development through standardization of network components. Defines the process for connecting two layers together, promoting interoperability between vendors It Allows vendors to compartmentalize their design efforts to fit a modular design, which eases implementations and simplifies troubleshooting.
Ensures interoperable technology:
It prevents changes in one layer from affecting the other layers, allowing for quicker development.
Accelerates evolution:
It provides for effective updates and improvements to individual components without affecting other components or having to rewrite the entire protocol.
Simplifies teaching and learning:
It breaks network communication into smaller components to make learning easier. Provides a teaching tool to help network administrators understand the communication process used between network components.
OSI Reference Model
· OSI reference model consists of seven layers: physical, data-link, network, transport, session, presentation, and application.
· OSI model layers usually do not correspond exactly to the protocol stack running on an actual system.
· Data-link layer protocols often include physical layer specifications.
· Network and transport layer protocols work together to provide a cumulative end-to-end communication service.
· Functions of the session, presentation, and application layers are often combined into a single application layer protocol.
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