Understanding Open Systems and the OSI Model

Open Systems Architecture

This definition refers to computer systems architecture that enables interconnection and easy distribution.

Key Features

• Not tied to a single type of proprietary hardware.
• Integrated information environment.
• Meets and/or generates standards.
• General specifications.
• High degree of software portability.
• Flexibility of programming languages.
• Management of different operating environments.

Data Packets

The data packet contains the source address, where it generates the packet, and the destination address.

Transmission Medium

A medium is the material through which data travels. It can be any of the following materials:

• Telephone cables
• UTP coaxial cable
• Fiber optic

Communication Protocols

A set of rules, or an agreement, which determines the format and data transmission.

OSI Model

Open Systems Interconnection

Advantages

• Divides interrelated aspects of network operation into less complex elements.
• Standard interfaces are defined to support plug-and-play integration of components from various manufacturers.
• Allows design engineers to specialize and promote symmetry in the different functions of modular internetworking.
• Prevents changes occurring in one area from affecting others, allowing each area to evolve more rapidly.
• Divides the complexity of internetworking operations into subsets, making learning easier.

OSI Layers

Physical Layer

This layer handles sending bits across a physical transmission medium.

Data Link Layer

In this layer, bits are received from the physical layer and grouped to form frames.

Network Layer

Responsible for reviewing the operation of the subnet.

Transport Layer

The purpose of this layer is to take data from the Session Layer and ensure it reaches its destination.

Session Layer

This layer provides the service of establishing working sessions between different nodes of a network.

Presentation Layer

It provides facilities for transmitting data using the proper syntax for node applications.

Application Layer

In this layer, network applications exploit the resources of other nodes.

Data Encapsulation

Encapsulation allows computers to communicate data.

Network Protocols

NetBIOS, TCP/IP

TCP/IP enables communication of data between two computers anywhere in the world. Its layers include: Application, Transport, and Internet.

FTP

The File Transfer Protocol is included as part of TCP/IP, providing services for file transfer.