N

NACS

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

NADN

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.

NAK

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

See NBP.

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.

NAP

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

NARP

NBMA Address Resolution Protocol. A functional subset of NHRP that returns only the address mappings of nodes that are directly connection the NBMA network. Compare with NHRP.

narrowband

See baseband.

Narrowband ISDN

See N-ISDN.

NAT

Network Address Translation. A 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

See NIST.

National Research and Education Network

See NREN.

National Science Foundation

See NSF.

National Science Foundation Network

See NSFNET.

native client interface architecture

See NCIA in the Cisco Systems Terms and Acronyms section.

NAU

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.

NAUN

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.

NBFCP

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

NBMA

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.

NBP

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.

NBS

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

NCIA

See NCIA in the Cisco Systems Terms and Acronyms section.

NCP

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. A series of protocols for establishing and configuring different network layer protocols, such as for AppleTalk, over PPP. See also PPP.

NCP/Token Ring Interconnection

See NTRI.

NDIS

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

NE

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

NEBS

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.

nearest active upstream neighbor

See NAUN.

NEARNET

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

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.

NET

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

net

Short for network.

NetBEUI

NetBIOS Extended User Interface. An 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.

NetBIOS

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.

NETscout

See NETscout in the Cisco Systems Terms and Acronyms section.

NetView

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

NetWare

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

NetWare Link Services Protocol

See NLSP.

NetWare Loadable Module

See NLM.

network

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.

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 Control Program

See NCP.

network driver interface specification

See NDIS.

network entity title

See NET.

Network File System

See NFS.

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, presentation layer, 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

See NMVT.

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

See NSAP.

network termination device 1

See NT-1.

network-visible entity

See NVE.

Next Hop Resolution Protocol

See NHRP.

NFS

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 (External Data Representation), and others. These protocols are part of a larger architecture that Sun refers to as ONC. See also ONC.

NHRP

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.

NHS

Next Hop Server. A 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.

NIC

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.

NIS

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.

N-ISDN

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.

NIST

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

NLM

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

NLSP

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

NMA

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

NMP

See NMP in the Cisco Systems Terms and Acronyms section.

NMS

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.

NMVT

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

NN

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.

NNI

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.

NOC

Network Operations Center. Organization responsible for maintaining a network.

node

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

noise

Undesirable communications channel signals.

nonbroadcast multiaccess

See NBMA.

nonextended network

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

nonreturn to zero

See NRZ.

nonreturn to zero inverted

See NRZI.

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 ASBR and OSPF.

nonvolatile random-access memory

See NVRAM.

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.

NOS

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.

NREN

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.

NRM

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.

NRZ

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

NRZI

nonreturn to zero inverted. NRZI signals 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.

NSAP

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.

NSF

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.

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.

NT-1

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

NTRI

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.

NVE

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

NVRAM

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

NYSERNet

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