ABSTRACT
The International Organization for Standardization has defined a Reference Model for internetworking that has become a worldwide standard or high-level protocol for designers of network products and for network designers. The reference model in Exhibit 24.1 defines the computer communications function in terms of seven distinct layers, and is designed to enable open systems to communicate with one another. There are several significant technological developments and societal phenomena that have impacted the network designer’s world over the past few years. PCs have proliferated and local area network (LAN) have become as common and as essential as telephone networks. As a result of these changes in the requirements of businesses to communicate, frequently over considerable distances, today’s network designer is usually required to include LAN-wide area network interconnectivity in a network design.
