one service also offers case studies in each of the five types of access we have identified. A close examination reveals how each type of access can have different impact on network demand, the optimal net- work configuration, transaction costs, implementation difficulties, and dynamic efficiency. Iowa Utils. Bd., 525 U.S. at 734-76; U.S. Telecom Ass'n V. FCC, 290 F.3d 415 (D.C. Cir. 2002); U.S. Telecom Ass'n V. FCC, 359 F.3d 554 (D.C. Cir. 2004). Covad Commc'ns Co. V. FCC, 450 F.3d 528 (D.C. Cir. 2006). The Regulation of Local Telephone Networks 1. Retail Access Although the Federal Communications Commission has largely deregulated retail access for interstate services, state public utility commissions have continued to mandate retail access to local telephone networks. Although new carriers are often allowed to pick and choose among their customers, the incumbent local telephone company is typically designated the "carrier of last resort" and is unable to deny service to anyone who requests it. Because carriers could render retail access a nullity simply by charging exorbitant prices, retail access is generally accompanied by direct regulation of retail rates. Retail access interferes with a network owner's ability to manage its network. As we noted in Chapter 5, networks owners configure their network based on the predicted level of network demand to provide service that satisfies consumers' expectations about reliability at the least cost. Unanticipated increases in demand leave the network owner with the options of increasing network capacity, refusing to accept new customers, rationing demand by increasing prices, or bringing demand back into line with supply by allowing service to degrade. Although expanding network capacity remains the best long-term solution, the simple reality that net- work capacity cannot be expanded instantaneously means that that may not be a short-run option. Retail access has the effect of foreclosing the second and third solutions by preventing the network owner from refusing cus