facilities do not vary directly with output in the short term. Moreover, like other capital investments, the configuration of the network's physical assets cannot be changed in the short term. Given sufficient time, however, the network's capital equipment is variable and can be adjusted to create different capacity levels. Networks in Telecommunications The operation of a network's facilities often requires variable inputs as well, such as the labor used to maintain its facilities and to monitor its operations. In combination, the productive inputs that constitute the network are used to create a stream of services, such as the transmission and distribution of communi- cations, that are the outputs of the network. Just as natural gas transmission does not consume the physical pipeline, usage of a telecommunications network does not consume the network itself, but instead only temporarily precludes the provi- sion of services to some other user. Of course, network use does impose some wear and tear on the network's physical production facilities. The measures of depreci- ation employed under generally accepted accounting principles do not accurately indicate the value of the services provided by the equipment, however. As a result, the applicable depreciation rules typically do not properly reflect the equipment's economic life. E. A Coasian Theory of Networks The five types of access refer to a network's external connections. The five-part classification scheme for access to networks provides the basis for a Coasian theory of networks. The communications sector is composed of many networks. These networks often are interconnected to form a very large network of networks. This extends beyond the Internet, which itself is a network of networks, to encom- pass traditional telephone networks, cable television transmission networks, data networks, and mobile telecommunications. This raises the critical question: what determines the boundaries of a network? The size and structure of individual networks are closely rel