s user nect to other switches and routers rather than equipment to telephone lines. Examples to customers. High-speed core routers are include modems for analog lines and CSUs located in core networks. for digital lines. CPE (Customer Premises Equipment) dedicated line Telephone systems, modems, terminals, and A telephone line between two or more sites of other equipment installed at customer sites. a private network. Dedicated lines are always available for the exclusive use of the private CSU/DSU (Channel Service Unit/Data Service Unit) network at a fixed, monthly fee. A digital interface device that connects cus- tomer computers, video equipment, multi- de-duplication plexers, and terminals to T1/E1 and T3/E3 A method of compression that removes lines. changes in files sent between two sites where each site has a copy of the file as it was origi- CTI (Computer Telephony nally sent. De-duplication sends only changes Integration) each time after the original transmission. The CTI software translates signals between receiving end adds the changes and puts the telephone systems and computers SO that file back together. Glossary DID (Direct-Inward Dialing) DNSSEC (Domain Name Service Secu- A feature of local telephone service whereby rity Extensions) each person in an organization has his own An Internet security standard for preventing ten-digit telephone number. Calls to DID tele- users from using other organizations' domain phone numbers do not have to be answered names, which is also known as spoofing. Dis- by onsite operators. They go directly to the guising domain names makes it more diffi- person assigned to the ten-digit DID tele- cult to track the origin of traffic. phone number. domain name DiffServ (Differentiated Services) Everything after the @ sign in an e-mail Used in routers to tag frames. The tags address. It includes the host computer, the request a particular level of service on the Internet and other IP-based networks. organization's name, and the type of organi- zation (for example, .com for co