When preparing for your CCNA or CCDA, concepts that relate to network models will appear again and again. While these might not seem like the most fascinating topics, I can guarantee a solid understanding of the models and how they relate to network communication and design is critical – both on the exams and in real life. Models exist to help illustrate concepts. A fundamental understanding of their goals and responsibilities will ultimately lead to a better appreciation of why networks work the way they do.
In this chapter we’ll take a look at three different network models, relating them to network communication and design. These include:
- The Open Systems Interconnect (OSI) Model. Developed by the International Organization for Standardization (ISO), this model is the foundation upon which most network communication protocols are designed.
- The TCP/IP model. The TCP/IP protocol suite is a culmination of the work of many different companies, individuals, and organizations that took place over many years. While the protocols that make up the suite can be loosely mapped to the OSI model, they are more commonly referenced using the 4-layer TCP/IP model.
- The Cisco hierarchical network design model. This model is concerned with the design of networks to meet performance, security, capacity and scalability requirements.
The key to appreciating the various models is in relating them to real-life networking concepts and scenarios. Be sure to take the time to understand the functions of each model’s layers, as well as the protocols and equipment found at each.