Table of Contents




NetWare Asynchronous Communication Services. Novell software that supports Novell's AIO and NASI programming interfaces. NACS promotes the sharing of communications resources such as modems, asynchronous hosts, and X.25 network services.


North American Directory Forum. Collection of organizations that offer, or plan to offer, public directory services in North America, based on the CCITT X.500 Recommendations.


nearest active downstream neighbor. In Token Ring or IEEE 802.5 networks, the closest downstream network device from any given device that is still active.

Nagle's algorithm

Actually two separate congestion control algorithms that can be used in TCP-based networks. One algorithm reduces the sending window; the other limits small datagrams.


negative acknowledgment. Response sent from a receiving device to a sending device indicating that the information received contained errors. Compare to acknowledgment.

Name Binding Protocol


name caching

Method by which remotely discovered host names are stored by a router for use in future packet-forwarding decisions to allow quick access.

name resolution

Generally, the process of associating a name with a network location.

name server

Server connected to a network that resolves network names into network addresses.


Commonly distributed set of names in which all names are unique.


North American Network Operator's Group. Primary forum for information exchange among U.S. exchange point participants, Internet service providers, and end users.


North American Numbering Plan.


network access point. Location for interconnection of Internet service providers in the United States for the exchange of packets.


NBMA Address Resolution Protocol. Functional subset of NHRP that returns only the address mappings of nodes that are directly connected to the NBMA network. Compare with NHRP.


See baseband.

Narrowband ISDN



network access server. Cisco platform (or collection of platforms such as an AccessPath system which interfaces between the packet world (e.g. the Internet) and the circuit world (e.g. the PSTN). (See access device.)


network access server. A NASI

NetWare Asynchronous Support Interface.


Network Address Translation. Mechanism for reducing the need for globally unique IP addresses. NAT allows an organization with addresses that are not globally unique to connect to the Internet by translating those addresses into globally routable address space. Also known as Network Address Translator.

National Bureau of Standards

See NBS.

National Institute of Standards and Technology


National Research and Education Network


National Science Foundation

See NSF.

National Science Foundation Network


native client interface architecture

See NCIA in the "Cisco Systems Terms and Acronyms" section.


network addressable unit. SNA term for an addressable entity. Examples include LUs, PUs, and SSCPs. NAUs generally provide upper-level network services. Compare with path control network.


nearest active upstream neighbor. In Token Ring or IEEE 802.5 networks, the closest upstream network device from any given device that is still active.


NetBIOS Frames Control Protocol. Protocol that establishes and configures NetBIOS over PPP. See also NetBIOS and PPP.


nonbroadcast multiaccess. Term describing a multiaccess network that either does not support broadcasting (such as X.25) or in which broadcasting is not feasible (for example, an SMDS broadcast group or an extended Ethernet that is too large). See also multiaccess network.


NetBIOS Name Service.


Name Binding Protocol. AppleTalk transport-level protocol that translates a character string name into the DDP address of the corresponding socket client. NBP enables AppleTalk protocols to understand user-defined zones and device names by providing and maintaining translation tables that map names to their corresponding socket addresses.


National Bureau of Standards. Organization that was part of the U.S. Department of Commerce. Now known as NIST. See also NIST.


See NCIA (native client interface architecture) in the "Cisco Systems Terms and Acronyms" section.


1. Network Control Program. In SNA, a program that routes and controls the flow of data between a communications controller (in which it resides) and other network resources.

2. Network Control Protocol. Series of protocols for establishing and configuring different network layer protocols, such as for AppleTalk over PPP. See also

NCP/Token Ring Interconnection



National Center for Supercomputing Applications.


network driver interface specification. Microsoft specification for a generic, hardware- and protocol-independent device driver for NICs.


network element. In OSS, a single piece of telecommunications equipment used to perform a function or service integral to the underlying network.

nearest active upstream neighbor



Regional network in New England (United States) that links Boston University, Harvard University, and MIT. Now part of BBN Planet. See also BBN Planet.


Network Equipment Building Systems. In OSS, the Bellcore requirement for equipment deployed in a central office environment. Covers spatial, hardware, crafts person interface, thermal, fire resistance, handling and transportation, earthquake and vibration, airborne contaminants, grounding, acoustical noise, illumination, EMC, and ESD requirements.

negative acknowledgment

See NAK.

neighboring routers

In OSPF, two routers that have interfaces to a common network. On multiaccess networks, neighbors are dynamically discovered by the OSPF Hello protocol.


Network Element Management Server.


network entity title. Network addresses, defined by the ISO network architecture, and used in CLNS-based networks.


Short for Network.


NetBIOS Extended User Interface. Enhanced version of the NetBIOS protocol used by network operating systems such as LAN Manager, LAN Server, Windows for Workgroups, and Windows NT. NetBEUI formalizes the transport frame and adds additional functions. NetBEUI implements the OSI LLC2 protocol. See also LLC2 and OSI.


Network Basic Input/Output System. API used by applications on an IBM LAN to request services from lower-level network processes. These services might include session establishment and termination, and information transfer.


A pun on "etiquette" referring to proper behavior on a network.


See NETscout in the "Cisco Systems Terms and Acronyms" section.


IBM network management architecture and related applications. NetView is a VTAM application used for managing mainframes in SNA networks. See also VTAM.


Popular distributed NOS developed by Novell. Provides transparent remote file access and numerous other distributed network services.

NetWare Link Services Protocol


NetWare Loadable Module

See NLM.


The highest level of your signaling controller system. You have only one network, within which you create your sites.


Collection of computers, printers, routers, switches, and other devices that are able to communicate with each other over some transmission medium.

network access point

See NAP.

network access server

See access server and NAS.

network address

Network layer address referring to a logical, rather than a physical, network device. Also called a protocol address. Compare with MAC address.

Network Address Translation

See NAT.

Network Address Translator

See NAT.

network addressable unit

See NAU.

network administrator

Person responsible for the operation, maintenance, and management of a network. See also network operator.

network analyzer

Hardware or software device offering various network troubleshooting features, including protocol-specific packet decodes, specific preprogrammed troubleshooting tests, packet filtering, and packet transmission.

Network Basic Input/Output System

See NetBIOS.

network byte order

Internet-standard ordering of the bytes corresponding to numeric values.

Network Control Program

See NCP.

network driver interface specification


network entity title

See NET.

Network File System

See NFS.

Network Indicator

Determines the type of call that is being placed: 0 = international, 1 = reserved, 2= national, and 3 = national spare.

Network Information Center

See InterNIC.

Network Information Service

See NIS.

network interface

Boundary between a carrier network and a privately-owned installation.

network interface card

See NIC.

network layer

Layer 3 of the OSI reference model. This layer provides connectivity and path selection between two end systems. The network layer is the layer at which routing occurs. Corresponds roughly with the path control layer of the SNA model. See also application layer, data-link layer, physical layer, PQ, session layer, and transport layer.

network management

Generic term used to describe systems or actions that help maintain, characterize, or troubleshoot a network.

Network Management Processor

See NMP.

network management system

See NMS.

network management vector transport


Network-to-Network Interface

See NNI.

network node

See NN.

network node interface

See NNI.

Network Node Server

SNA NN that provides resource location and route selection services for ENs, LEN nodes, and LUs that are in its domain.

network number

Part of an IP address that specifies the network to which the host belongs.

network operating system

See NOS.

Network Operations Center

See NOC.

network operator

Person who routinely monitors and controls a network, performing such tasks as reviewing and responding to traps, monitoring throughput, configuring new circuits, and resolving problems. See also network administrator.

network service access point


network termination device 1

See NT-1.

Network Time Protocol

See NTP.

network-visible entity

See NVE.

Next Hop Resolution Protocol



Network File System. As commonly used, a distributed file system protocol suite developed by Sun Microsystems that allows remote file access across a network. In actuality, NFS is simply one protocol in the suite. NFS protocols include NFS, RPC, XDR, and others. These protocols are part of a larger architecture that Sun refers to as ONC. See also ONC.


Next Hop Resolution Protocol. Protocol used by routers to dynamically discover the MAC address of other routers and hosts connected to a NBMA network. These systems can then directly communicate without requiring traffic to use an intermediate hop, increasing performance in ATM, Frame Relay, SMDS, and X.25 environments.


Next Hop Server. Server defined by the NHRP protocol that maintains next-hop resolution cache tables containing the IP-to-ATM address mappings of associated nodes and nodes that are reachable through routers served by the NHS.


1. network interface card. Board that provides network communication capabilities to and from a computer system. Also called an adapter. See also AUI.

2. Network Information Center. Organization whose functions have been assumed by the InterNIC. See InterNIC.


Network Information Service. Protocol developed by Sun Microsystems for the administration of network-wide databases. The service essentially uses two programs: one for finding a NIS server and one for accessing the NIS databases.


Narrowband ISDN. Communication standards developed by the ITU-T for baseband networks. Based on 64-kbps B channels and 16- or 64-kbps D channels. Contrast with BISDN. See also BRI, ISDN, and PRI.


National Institute of Standards and Technology. U.S. government organization that supports and catalogs a variety of standards. Formerly the NBS. See also NBS.


NetWare Loadable Module. Individual program that can be loaded into memory and function as part of the NetWare NOS.


NetWare Link Services Protocol. Link-state routing protocol based on IS-IS. See also IS-IS.


Network Management and Analysis. Bellcore OSS providing alarm surveillance and performance monitoring of intelligent network elements.


See NMP (Network Management Processor) in the "Cisco Systems Terms and Acronyms" section.


network management system. System responsible for managing at least part of a network. An NMS is generally a reasonably powerful and well-equipped computer such as an engineering workstation. NMSs communicate with agents to help keep track of network statistics and resources.


network management vector transport. SNA message consisting of a series of vectors conveying network management specific information.


network node. SNA intermediate node that provides connectivity, directory services, route selection, intermediate session routing, data transport, and network management services to LEN nodes and ENs. The NN contains a CP that manages the resources of both the NN itself and those of the ENs and LEN nodes in its domain. NNs provide intermediate routing services by implementing the APPN PU 2.1 extensions. Compare with EN. See also CP.


1. Network-to-Network Interface. ATM Forum standard that defines the interface between two ATM switches that are both located in a private network or are both located in a public network. The interface between a public switch and private one is defined by the UNI standard. Also, the standard interface between two Frame Relay switches meeting the same criteria. Compare with UNI.

2. network node interface.


nature of address.


network operations center. Organization responsible for maintaining a network.


1. Endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be processors, controllers, or workstations. Nodes, which vary in routing and other functional capabilities, can be interconnected by links, and serve as control points in the network. Node is sometimes used generically to refer to any entity that can access a network, and is frequently used interchangeably with device. See also host.

2. H.323 entity that uses RAS to communicate with the gatekeeper (for example, an endpoint such as a terminal, proxy, or gateway).

3. In SNA, the basic component of a network and the point at which one or more functional units connect channels or data circuits.



Undesirable communications channel signals.

nonbroadcast multiaccess


nonextended network

AppleTalk Phase 2 network that supports addressing of up to 253 nodes and only 1 zone.

nonreturn to zero

See NRZ.

nonreturn to zero inverted


nonseed router

In AppleTalk, a router that must first obtain, and then verify, its configuration with a seed router before it can begin operation. See also seed router.

non-stub area

Resource-intensive OSPF area that carries a default route, static routes, intra-area routes, interarea routes, and external routes. Nonstub areas are the only OSPF areas that can have virtual links configured across them, and are the only areas that can contain an ASBR. Compare with stub area. See also ASAM and OSPF.

nonvolatile random-access memory


normal response mode

See NRM.

Northwest Net

NSF-funded regional network serving the Northwestern United States, Alaska, Montana, and North Dakota. Northwest Net connects all major universities in the region as well as many leading industrial concerns.


network operating system. Generic term used to refer to what are really distributed file systems. Examples of NOSs include LAN Manager, NetWare, NFS, and VINES.

Novell IPX

See IPX.


number plan identification.


National Research and Education Network. Component of the HPCC program designed to ensure U.S. technical leadership in computer communications through research and development efforts in state-of-the-art telecommunications and networking technologies. See also HPCC.


normal response mode. HDLC mode for use on links with one primary station and one or more secondary stations. In this mode, secondary stations can transmit only if they first receive a poll from the primary station.


nonreturn to zero. Signals that maintain constant voltage levels with no signal transitions (no return to a zero-voltage level) during a bit interval. Compare with NRZI.


nonreturn to zero inverted. Signals that maintain constant voltage levels with no signal transitions (no return to a zero-voltage level), but interpret the presence of data at the beginning of a bit interval as a signal transition and the absence of data as no transition. Compare with NRZ.


network service access point. Network addresses, as specified by ISO. An NSAP is the point at which OSI Network Service is made available to a transport layer (Layer 4) entity.


National Science Foundation. U.S. government agency that funds scientific research in the United States. The now-defunct NSFNET was funded by the NSF. See also NSFNET.


National Science Foundation Network. Large network that was controlled by the NSF and provided networking services in support of education and research in the United States, from 1986 to 1995. NSFNET is no longer in service.


network termination 1. In ISDN, a device that provides the interface between customer premises equipment and central office switching equipment.


Network Time Protocol. Protocol built on top of TCP that assures accurate local time-keeping with reference to radio and atomic clocks located on the Internet. This protocol is capable of synchronizing distributed clocks within milliseconds over long time periods.


NCP/Token Ring Interconnection. Function used by ACF/NCP to support Token Ring-attached SNA devices. NTRI also provides translation from Token Ring-attached SNA devices (PUs) to switched (dial-up) devices.

null modem

Small box or cable used to join computing devices directly, rather than over a network.


network-visible entity. Resource that is addressable through a network. Typically, an NVE is a socket client for a service available in a node.


nonvolatile RAM. RAM that retains its contents when a unit is powered off.


Network in New York (United States) with a T1 backbone connecting NSF, many universities, and several commercial concerns.

Posted: Tue Sep 21 15:19:49 PDT 1999
Copyright 1989-1999©Cisco Systems Inc.