connects user equipment to telephone lines. Examples include modems for analog lines and CSUs for digital lines. dedicated line A telephone line between two or more sites of a private network. Dedicated lines are always available for the exclusive use of the private network at a fixed, monthly de-duplication A method of compression that removes changes in files sent between two sites where each site has a copy of the file as it was originally sent. De-duplication sends only changes each time after the original transmission. The receiving end adds the changes and puts the file back together. DID (Direct-Inward Dialing) www.TechnicalPDF.com A feature of local telephone service whereby each person in an organization has his own ten-digit telephone number. Calls to DID telephone numbers do not have to be answered by onsite operators. They go directly to the person assigned to the ten-digit DID telephone number. DiffServ (Differentiated Services) Used in routers to tag frames. The tags request a particular level of service on the Internet and other IP- based networks. disk mirroring The process of simultaneously writing data to backup and primary servers. divestiture In January 1984, divestiture deregulated long-distance service in the United States. It separated the former AT&T from its 22 local Bell telephone companies. Agreement on divestiture was reached by the Justice Department, which negotiated an antitrust settlement with the former AT&T, called the Modified Final Judgment. DLC (Digital Loop Carrier) Used to economically bring fiber closer to customers. Carriers run fiber cabling from central offices to DLCs and they lay twisted-pair copper cabling from DLCs to customers. DNIS (Dialed-Number Identification Service) The service used to identify and route toll-free and 900 numbers to particular agents or devices within a customer site. For example, if a customer has multiple 800 numbers, the network provider routes each toll-free number to a different four-digit number at the customer's telephone system. The ons