g both the query and the response would have to travel guarantees that this transaction will suffer from at least some degree of latency. In addition, the network access points where backbones exchange traffic might well be congested, as might CNN's file server (Kende 2000). A new technological solution known as "content delivery networks" has emerged that has the potential to mitigate these problems. 21 Content delivery net- works dynamically store content and applications at multiple locations throughout the Internet. When a last-mile network receives a query for content stored on a content delivery network, instead of blindly directing that request to the desig- nated URL, the content delivery network may redirect the request to a particular cache that is closer or less congested. In the process, it can minimize delay and congestion costs by taking into account the topological proximity of each server, the load on each server, and the relative congestion of different portions of the network. In this manner, content delivery networks can dynamically manage net- work traffic in a way that can minimize transmission costs, congestion costs, and latency. Distributing multiple copies of the content throughout the Internet also enhances network performance in other ways, by allowing content and applications providers to aggregate server capacity and by giving them added protection against denial of service attacks. Using distributed caching to bypass the backbones also weakens whatever market power is enjoyed by backbones and regional ISPs (Besen et al. 2001). Content delivery networks have proven tremendously successful. The leading content delivery network, known as Akamai, reportedly maintains more 21 For an excellent overview of content delivery networks, see Clark et al. (2006). The Regulation of Broadband Networks and the Internet than 14,000 servers and handles more than fifteen percent of the world's Web con- tent (Washington Technology 2005). Indeed, it is conceivable that content delivery networks might dis