existed on a given LAN, but those islands couldn't communicate with other departments, clus- ters, or divisions located elsewhere in the enterprise. LAN internetworking there- fore took place throughout the late 1980s and early to mid-1990s, bringing with it the evolution, introduction, and rapid penetration of interconnection devices such as hubs, bridges, routers, and brouters, whose purpose is to internetwork between separate networks. Internet Commercialization In the mid-1990s, yet another alternative for data networking came about with the commercialization of the Internet. Before about 1995, the Internet was mainly available to the academic, research, and government communities. Because it pre- sented a very cost-effective means for data networking, particularly with text- based, bursty data flows, it held a significant appeal for the academic and research community. However, until the introduction of the World Wide Web, the Internet remained largely an academic platform. The intuitive graphical interfaces and nav- igational controls of the WWW made it of interest to those without UNIX skills- that is, anyone with a PC running some version of Windows-and hastened the demise of just about every other form of Internet communications, including Archie, Gopher, WAIS, and Veronica. The Internet was particularly useful for appli- cations such as e-mail, for which there was finally one standard that was open enough to enable messaging exchanges between various businesses that used dif- ferent systems. Application-Driven Networks The mid- to late 1990s began to see the development of advanced, bandwidth-hungry applications, such as videoconferencing, collaboration, multimedia, and media conferencing. This caused another shift in how people thought about deploying networks. In the days of hierarchical networks, decisions about network resources were based on the number of devices and their distance from one another. But when advanced applications-which had great capacity demands and could not tolerate delays or con