Open Systems Interconnection (OSI) model

The Internet Protocols are based on protocol specifications supported by work­ing prototypes. If a prototype does not exist, a suggested protocol is not on track for becoming an Internet protocol. The Open Systems Interconnection (OSI) model was a top-down approach generally dominated by abstract system design with the thought that it could be implemented if specified properly. Further complicating the OSI protocol was the necessity for it to be unanimously and internationally accepted in its abstract specification making very weighty specifications or specifications with a very large number of options that frustrated interoperability.

However, the Open Systems Interconnection (OSI) model provides a means for discussing protocols. Because of the excellent academic work, concentrating on a top-down design, it encapsulates and explains the functions of networking very well.

As networking of computer systems became more popular in the world, a structured well organized logical framework for connecting networks and developing applications was needed. In the late 1970s, the ISO (Interna­tional Standards Organization) developed the OSI networking reference model.

The OSI reference model is a seven-layered logical approach to network communications that includes specifications for the actual hardware connection to the network at the bottom layers of the model, and rules for applications and more complicated functions at the higher layers.

Networking rules for communication, also known as protocols, exist at almost every layer of the Open Systems Interconnection (OSI) model. The more complicated the protocol, the higher up on the model it resides. Important security-related protocols will be discussed in detail later in this chapter. Network transmission, se­curity, session connection information, and hardware are all associated with particular layers.

Picture yourself sitting at your computer working on a Microsoft Word document. You are actually utilizing functions that reside at the top layer of the OSI reference model known as the Application layer or layer 7.

Questionnaire:

• Explain about the Open Systems Interconnection (OSI) model.