nk Chapter Data Communications Basics This chapter explores some of the basics of data communications. It starts with a discussion of the evolution of data communication and then discusses the termi- nology used to describe different aspects of data networking. It's important to have a good grasp of these basics before wading into deeper waters. The Evolution of Data Communications Data communication, or data networking, is the exchange of digital information between computers and other digital devices via telecommunications nodes and wired or wireless links. To understand the evolution of networking services, it is important to first understand the general computing architectures and traffic types, both of which have changed over time. Data Communications Architectures In the rather brief history of data networking, a variety of architectures have arisen, and each has had unique impacts on network characteristics. Table 5.1 shows a basic time line of the architectures that have prevailed during different periods. Each archi- tecture has slightly different traffic characteristics and requirements in terms of secu- rity and access control, and each has presented a different volume and consistency of traffic to the network. As described in the following sections, each new computing architecture has created a demand for new generations of network services. Chapter 5 Data Communications Basics Table 5.1 Time Line of Data Networking Architectures Architecture 1970s Standalone mainframes Early 1980s Networked mainframes Early 1980s Standalone workstations Early to late 1980s Local area networking Mid-1980s to mid-1990s LAN internetworking Mid-1990s Internet commercialization Mid- to late 1990s Application-driven networks Late 1990s Remote-access workers Early 2000s Home area networking Mid-2000s Personal area networks and the Internet as corporate backbone Standalone Mainframes The 1970s was the era of standalone mainframes. These were very hierarchical net- works, where certain paths needed to be taken. It was a time 