Index - 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 A-Z
NACK/NAK - "Negative Acknowledge" character in many data codes; typically used to indicate receipt of a corrupted message, ordering retransmission; compare to "REJect" character in IBM data systems.
NETWORK - A collection of terminals, computers, peripheral devices, and/or switches connected to one another for a defined purpose by transmission facilities.
NETWORK ARCHITECTURE - The philosophy and organizational concept for enabling communications between multiple locations and multiple organizational units. Network architecture is a structured statement of the terminal devices, switching elements and the protocols and procedures to be used for the establishment and maintenance of effective telecommunications.
NETWORK INTERFACE - 1.) The point of interconnection between the Public Switched Telephone Network (PSTN) and privately-owned terminal equipment; 2.) The point of interconnection between one network and another. Compare: Gateway.
NETWORK LAYER - 1.) Generically, any of several strata of functions in a communications network, such as Terminal, Switching an Transmission; 2.) Specifically in the OSI Reference Model, the third layer, servicing the Transport Layer, ensuring that information is properly routed throughout the network.
NETWORK MANAGEMENT/NETWORK MANAGEMENT SYSTEM (NMS)/NETWORK MANAGEMENT CENTER (NMC) - Treating of the functions of operational control of a network. Functions may include, but not be restricted to: Traffic Analysis; Configuration Control; Transmission Quality; Reliability/Availability; Maintenance Control; Fault Detection or Call Detail Recording. Definitions and strong opinions about what constitutes "Network Management" abound.
NETWORK NUMBERING EXCHANGE - See "NNX Codes." NETWORK TOPOLOGY - Descriptive of the physical and logical relations of nodes in a network; the schematic arrangement of the links and nodes; often classed as star, ring, tree or bus topology; detail variations and hybrid combinations abound.
NETWORK TRUNKS - Circuits connecting switching centers.
NETWORK VIRTUAL TERMINAL - A data communications concept in which a variety of DTE's with different data rates, codes, speeds, formats and protocols are accommodated on a single network. In such networks, Network Processors convert all into a common format for exchange between processors, then reconvert as needed to output data elsewhere.
NNX CODES - The 3-digit code used historically for local telephone exchange prefixes. In the electromechanical era, limitations applied to the range of numbers usable in each position of the prefix. The current numbering plan allows for more variation in assigning Exchange Codes, and under it Exchange Codes are commonly referred to as "NXXs."
NODE/NETWORK NODE - A termination point for communications links; in the sense of data communications, a DTE or processor point, while in the telephony sense, usually limited to a switching machine.
NOISE - Unplanned energy introduced into a communications channel, resulting in transmission errors.
NON-BLOCKING - A switching network with sufficient paths such that a caller can always reach any idle subscriber without encountering a busy; always claimed by vendors, but not always achieved.
NON-VOLATILE (NONVOLATILE) STORAGE - A storage medium that does not lose its contents when power is removed.
NUMBERING PLAN AREA (NPA)/NPA CODE - A geographical division in the North American numbering plan within which no two telephones will have the same 7 digit number. "N" originally was any number between "2" and "9"; "P" was always "1" or "0"; and "A" was any number excluding "0" in the electromechanical era of switching machines. Colloquial synonym: "area code." Internationally equivalent to "City Codes" or "Routing Codes" in other nations, where various number sequences may be used.
NXX CODES - The current general configuration for Exchange Codes within each Area Code. See also: "NNX Codes."