A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ADSL Asymmetric Digital Subscriber Line. High-speed transmission technology using existing local loops to transmit POTS and data to and from customer location. Asymmetrical Data transfer where upstream and downstream data flow occurs at different speeds, usually a higher rate of speed downstream, and a slower rate upstream. Reflective of typical end-user Internet usage patterns, where more data is received than sent, and no servers (such as web server) are in operation. ATM Asynchronous Transfer Mode. High bandwidth, low-delay, connection-oriented, packet-like switching and multiplexing technique requiring 53-byte fixed-sized cells. ATU ADSL Transceiver Unit. The ADSL Forum uses terminology for DSL equipment based on the ADSL model for which the Forum was originally created. Thus, the DSL endpoint is known as the ATU-R and the CO unit is known as the ATU-C. These terms have since come to be used for other types of DSL services, like RADSL and SDSL. ATU generally represents XDSL services. ATU-C ATU - Central Office. ATU Equipment placed in carrier's central office in support of DSL-based services. ATU-R ATU - Remote. Equipment placed in customer location in support of DSL-based services. Backbone Equipment that provides connectivity for users of distributed network and includes all the network infrastructure required to provide connectivity between the edge vehicles. In the context of the Internet, this terms also refers high-volume, "primary" data carriers that make-up the long-haul capabilities of the network. CO Central Office, a building used by telecommunication carriers to connect circuits to communications equipment. Also refers to the equipment located within the Central Office. DACS Digital Access & Cross-Connect System. A digital cross-connect device for routing lines among multiple ports. The connections are typically set up in advance of the call. DDS Digital Data Service. Private line digital service with data rates of 56/64 kbps. DLCI Data Link Connection Identifier. The Frame Relay virtual circuit number used in internetworking to denote the port to which the destination LAN is attached. DNS Domain Name Services (DNS). The collection of protocols and methods for mapping human-friendly domain names (e.g., select.net) to machine-friendly IP addresses (e.g., 127.192.11.34) for the purposes of accessing Internet services. DNS Registration Domain Name Services (DNS) Registration is the process of recording domain names in an Internet domain name registry (e.g., InterNIC) so they are recognized by users of the Internet. Downstream Refers to transmission speed from the CO to the service user. DSL Digital Subscriber Line. DSL is a copper loop transmission technology enabling high-speed access in the local loop, often referred to as the last mile between the Network Service Provider and service user. DSLAM Digital Subscriber Line Access Multiplexer. Provides high-speed Internet or Intranet access over traditional twisted-pair telephone wiring through the use of xDSL technology. Provides simultaneous high-speed digital data access and POTS analog service over the same twisted-pair telephone line. Can be installed in the CO or at an Internet Service Provider adjacent to the CO. DSU Digital Service Unit. Digital loop device residing on customer premises providing interface to customer's DTE (data terminal equipment). Electronic Commerce An Internet service that supports an electronic transaction exchange between customers and vendors to privately, and securely purchase goods and services. Ethernet A baseband LAN specification invented by Xerox Corporation. Ethernet has become a series of standards referred to as IEEE 802.3. FCC Federal Communications Commission. The United States federal regulatory agency responsible for regulating interstate, Inter-LATA, and international communications. FDDI Fiber Distributed Data Interface. A LAN Token Ring standard using fiber optic cable. Firewalls A computer device and/or software that separates a Local Area Network from a Wide Area Network and prevents unauthorized access to the Local Area Network through the use of electronic security mechanisms such as IP filtering, address remapping, etc. FRAD Frame Relay Access Device. An interface between customer DTE (data terminal equipment) and a frame relay data circuit. Frame Relay A networking technology that uses a form of packet switching with variable length frames over a shared data network, and is protocol independent. FRF Frame Relay Forum. An industry organization whose focus is frame relay technology. FTP File Transfer Protocol. Internet tool for sending and/or receiving files from a server linked to the Internet. GUI Graphical User Interface. A computer environment, such as Microsoft Windows or MacOS, that graphically represents programs, activities and services, and is typically manipulated through both keyboard and mouse. High-speed Concentrators A multi-protocol computer device that aggregates lower speed connections into broadband circuits. HDSL High-bit-rate Digital Subscriber Line. A technology to put two-way Tl/El service on normal unshielded twisted pair without repeaters up to 20,000 feet. HTU-C HDSL Transceiver Unit - Central Office. HTU-R HDSL Transceiver Unit - Remote. IDSL ISDN DSL using 2BlQ line code. IETF Internet Engineering Task Force. The primary working body developing new TCP/IP standards for the Internet. ILEC Incumbent Local Exchange Carrier. Refers to the primary existing carrier, as distinguished from new competitive carriers with the advent of telecom deregulation. Internet Access The provisioning of connectivity to the Internet. Interoperability The ability of equipment from multiple vendors to communicate using standardized protocols. IP Internet Protocol. A standard describing software that keeps track of the Internetwork addresses for different nodes, routes outgoing messages, and recognizes incoming messages. IPX Internetwork Packet Exchange. LAN communications protocol used to move data between server and/or workstation programs running on different network nodes. ISDN Integrated Services Digital Network. Provides circuit-switched access to the public network of speeds of 64 kbps or Nx64 for voice, data, and video transmission. Basic Rate ISDN (BRI) and Primary Rate ISDN (PRI) are the two types of ISDN service. ISP Internet Service Provider. A vendor who provides access to the Internet and usually related services such as e-mail and web hosting. IXC InterExchange Carrier. All long distance carriers; also known as Common Carriers. kbps Kilobits per second. 1,000 bits per second. L2TP Layer Two Tunneling Protocol. LAN Local Area Network. Privately owned and administered network for data communications. Usually a high bandwidth over a limited geographical area for communication between attached devices. Last mile Refers to the local loop and is the difference between a local telephone company office and the service user; a distance of about 2-3 miles or 3-4 kilometers. LEC Local Exchange Carrier. LECs provide local transmission services. Legacy Network A service that allows customers to continue to use their existing network along with network services based on more advanced technology. Mbps Megabit per second. 1,000,000 bits per second. MDF Main Distribution Frame. Central point where all local loops terminate in the CO. MIB Management Information Base. MSO Multiple System Operator. A cable industry term that describes a company that operates more than one cable TV system. MTBF Mean time between failure. A measure of hardware reliability. Multimedia Solutions A combination of networking, computing devices, and software to improve business productivity by integrating voice, data, and video communication services. Multiplexer A device that enables several data streams to be sent over a single physical line or a device for combining several channels to be carried by one line or fiber. NAP Network Access Provider. The NAP provides a transit network service permitting connection of service subscribers to NSPS. The NAP is typically the network provider that has access to the copper twisted pairs over which the DSL-based service operates. NDIS Network Design Interface Specification. Used for all communication with network adapters. Works primarily with LAN manager and allows multiple protocol stacks to share a single NIC. NEBS Network Equipment Building Standards. A set of requirements for the reliability and usability of equipment, established by Bellcore. Newsgroups Also Usenet news. Shared message conferences on the Internet, arranged hierarchically by subject matter. NIC Network Interface Card. The circuit board or other hardware that provides the interface between a communicating DTE and the network. NID Network Interface Device. An electronic device that connects the telephone line and the POTS splitter to the local loop. NMS Network Management System. The system that is responsible for managing a network and is typically run on a workstation that presents a GUI to the network manager. Provides access to a wide variety of information regarding network configuration, performance, and status. Exchanges information via a network management protocol, such as SN MP NOC Network Operations Center. A centralized point of network management within a large scale data network. Node A node on a network is usually formed by the presence of a router and user access equipment. Often, several leased lines are joined together at a network node. NSN Network Service Node. NSP Network Service Provider. Can include a local telephone company, ISP, or Competitive Local Exchange Carrier. NTU Network Termination Unit. Equipment at the customer premises which terminates a network access interface. Nx64 Describes a contiguous bit stream at the Nx64 kbps rate to an application. Examples are LAN interconnect and point-to-point videoconferencing. OCn Optical carrier level n signal. The fundamental transmission rate for SONET. For example, OC3 operates at 155 Mbps. OSI Open Systems Interconnection. OSI Reference Model is the seven-layer network architecture model of data communication protocols developed by ISO and ITU. PBX Private Branch Exchange. A term generally used to refer to a corporate telephone system. PSTN Public Switched Telephone Network. Refers to the country's telephone systems and networks collectively and in total. RADSL Rate Adaptive Digital Subscriber Line. Transmission technology that supports both asymmetric and symmetric applications on a single twisted-pair telephone line and allows adaptive data rates. Remote Call Center A service concept where the traditional call center workstation is moved from a central office site to a teleworker's home or small office. Router A device that interconnects LANs that can dynamically route data at Layer 3, the network layer, based on destination and routes available. RSVP Resource Reservation Setup Protocol. A reservation setup protocol for the Internet. RT Remote Terminal. Local loop terminates at Remote Terminal intermediate points closer to the service user to improve service reliability RTF Rich Text Format. A word processing document format designed for compatibility with a wide range of computing platforms and software packages. RTU Remote Termination Unit. A device installed at the service user site that connects to the local loop to provide high-speed connectivity. Also referred to as the ATU-R. SDSL Symmetric Digital Subscriber Line. Single-pair symmetric DSL. Secure Intranets A network based on the Internet Protocol that supports intra-company communications between end-users and employs security mechanisms such as firewalls, encryption, and authentication. Secure Extranets A network based on the Internet Protocol that supports inter-company communications between end-users and employs security mechanisms such as firewalls, encryption, and authentication. SNA Systems Network Architecture. IBM's vendor specific connection-oriented, virtual circuit network architecture for terminal/host communication. SNMP Simple Network Management Protocol. The network management protocol used with TCP/IP-based Internets. SOHO Small Office/Home Office. SONET Synchronous Optical Network. A set of standards for transmitting digital information over optical networks. Uses fiber optic ring technology. SWC Service Wire Center. Symmetrical Data transfer where both upstream and downstream data flow occurs at the same speed. Beneficial in cases where servers (such as web servers) will be operated, and for which asymmetrical data transfer would be undesirable. T1 A type of data circuit that provides 1.544 Mbps of bandwidth between two points. Can be provided through dedicated circuits, or frame relay. TCP/IP Transmission Control Protocol/Internet Protocol. A suite of communication protocols used by host computers to exchange information. TCP is Layer 4, the transport layer, of the OSI reference model. IP is Layer 3, the network layer, of the OSI reference model and provides connectionless datagram service. TDM Time Division Multiplexing. Technique where data from multiple channels may be allocated bandwidth on a single wite pair based on time slot assignment. Telework A service concept that will allow customers to work productively and effectively using the same business tool environment from either work or home. Telnet A program that lets you connect to other computers on the Internet. Upstream Refers typically to the transmission speed from the user to the data network. URL Uniform Resource Locator. Used with the World Wide Web as an address, e.g., http://www.select.net. Usenet A term used to describe the collection of newsgroups offered over the Internet. UTP Unshielded twisted pair cabling. VC Virtual Circuit. A logical connection or packet-switching mechanism established between two devices at the start of transmission. VDSL Very-high-bit rate DSL. Generally refers to 25 to 50+ Mbps transmission over very short distances. VLAN Virtual LAN. Workstations connected to an intelligent device which provides capabilities to define LAN membership. VPN Virtual Private Network, a networking service that is provided over a public network that allows the customer to utilize the service as if it was a private network. WAN Wide Area Network. A computer or communication network that covers a geographic area which is larger than a city. xDSL Another way of referring generically to any of the DSL variants: ADSL, HDSL, SDSL, RADSL, IDSL, VDSL.