Overview

Wide area networks (WANs) have been traditionally very easy to distinguish from LANs, but this differentiation is becoming increasingly fuzzy, with the emergence of technologies such as ATM and Gigabit Ethernet. Historically WANs tended to be built with one or more orders of magnitude less bandwidth than LANs (see Table 7.1). This is partly because of the high cost per bandwidth incurred and also due to the different techniques required in order to propagate traffic over much greater distances. Wide area networks connect cities or continents rather than buildings, and central to wide area networking are the issues of cost and ownership. While some large organizations have built their own private networks, this not the norm. Wide area networks are typically leased from PTTs and telcos for one or more years, since they require a huge investment and infrastructure to install and maintain. Wide area billing is, therefore, much more mature for wide area applications; until recently LANs have been seen as effectively free access, and only now are companies starting to examine the potential for billing users for local area network time and possibly outsourcing the local infrastructure to service providers. All of this would be impractical without the convergence toward a common protocol, IP, and a new breed of high-performance data collection products.