viders of bandwidth-intensive applications waiting in the wings to soak up any increases in capacity. Relying on capacity expansion to solve problems related to congestion also ignores the problems associated with the inherent impossibility of perfect forecast- ing of demand and the inability to expand capacity instantaneously. Unless network owners are able to anticipate changes in demographic patterns, improvements in networking technology, and the development of complementary products that drive demand for network services, situations will exist in which network owners under- estimate the growth in network demand. When that occurs, some form of network management may prove to be the only viable short-run solution. Stated more gener- ally, capacity expansion and network management represent alternative approaches to dealing with the problems of congestion. Because the relative costs of each solu- tion are likely to be different and likely to vary over time, there appears to be no rea- son to erect what would amount to a systematic preference for one solution over the other. These problems are well illustrated by the impact of the emergence of per- sonal computers on the NSFNET during the 1980s, introduced in Chapter 11. The increased functionality provided by the PC enabled users to run increasingly bandwidth-intensive applications on the network, most notably file transfer pro- grams. As a result, terminal-based NSFNET sessions began to run unacceptably slowly. Because capacity cannot be added instantaneously, NSFNET adopted the interim solution of reprogramming its routers to give terminal sessions priority over file transfer sessions. This emergence of the PC represents an exogenous shock caused by a technological development in a related technology that is inevitable in the broadband industry and that makes anticipating the future demand for capacity difficult. This example also shows how discrimination on the basis of the application can be the preferred (and perhaps the only feasible) solution to prob- le