 a higher charge or by barring the use of file-sharing programs altogether. On other occasions, network owners discriminate against particular applications on the server side, rather than the end user side, of the network. Specifically, some networks are considering deploying devices known as "policy-based routers" that will give a higher priority to traffic based on the application with which they are associated. The defensibility of end user restrictions on certain applications again turns on whether the applications being restricted are correlated with more intensive consumption of network resources. If so, it is reasonable to ask those who make greater use of network resources and who impose greater congestion costs on other users either to forego such behavior or to internalize the costs they impose on others. The problems of network management can also justify the use of policy-based routers on the server side as well. As discussed in Chapter 11, one natural response to capacity constraints is to give traffic associated with bandwidth-intensive, time- sensitive applications, such as streaming media or virtual worlds, a higher priority than traffic associated with less time-sensitive applications, such as e-mail and Web browsing, in which delays of a third of a second are essentially unnoticeable. Discriminating among applications may thus represent nothing more than the natural response of network owners attempting to manage congestion and latency in a world in which capacity is constrained and in which end user demands are increasingly heterogeneous and intense. 6. Discrimination against Particular Content The development that concerns network neutrality proponents the most is the possibility that network owners will discriminate against particular content. The original concern was that network owners would completely block access to dis- preferred Web sites, although FCC Commissioners have repeatedly noted the lack of evidence that network owners have widely adopted such practices, and even network neutra