N


NAK

Negative acknowledgment: A response sent from a receiver, telling the sender that the information it received contained errors. Compare with: acknowledgment.

NAT

Network Address Translation: An algorithm instrumental in minimizing the requirement for globally unique IP addresses, permitting an organization whose addresses are not all globally unique to connect to the Internet, regardless, by translating those addresses into globally routable address space.

native VLAN

An access link is part of one VLAN, and that VLAN is referred to as the native VLAN of the port. Any device attached to an access link is unaware of a VLAN membership—the device just assumes it’s part of a broadcast domain, but it has no understanding of the physical network.

NBP

Name Binding Protocol: In AppleTalk, the transport-level protocol that interprets a socket client’s name, entered as a character string, into the corresponding DDP address. NBP gives AppleTalk protocols the capacity to discern user-defined zones and names of mechanisms by showing and keeping translation tables that map names to their corresponding socket addresses.

NCP

NetWare Core Protocol. In Novell NetWare, a presentation-layer procedure used by a server when responding to workstation requests. It includes routines for manipulating directories and files, opening semaphores, printing, and creating and destroying service connections.

neighboring routers

Two routers in OSPF that have interfaces to a common network. On networks with multiaccess, these neighboring routers are dynamically discovered using the Hello protocol of OSPF.

NetBEUI

NetBIOS Extended User Interface: An improved version of the NetBIOS protocol used in a number of network operating systems including LAN Manager, Windows NT, LAN Server, and Windows for Workgroups, implementing the OSI LLC2 protocol. NetBEUI formalizes the transport frame—not standardized in NetBIOS—and adds more functions. See also: OSI.

NetBIOS

Network Basic Input/Output System: The API employed by applications residing on an IBM LAN to ask for services, such as session termination or information transfer, from lower-level network processes.

NetFlow Switching

A feature of some routers that allows them to categorize incoming packets into flows. Because packets in a flow often can be treated in the same way, this classification can be used to bypass some of the work of the router and accelerate its switching operation.

NetView

A mainframe network product from IBM, used for monitoring SNA (Systems Network Architecture) networks. It runs as a VTAM (Virtual Telecommunications Access Method) application.

NetWare

A widely used NOS created by Novell, providing a number of distributed network services and remote file access.

Network Campus

One of the many modules that make up the Cisco ECNM. The network campus module includes private clients, servers, and network devices.

Network Edge

One of the many modules that make up the Cisco ECNM. The Network Edge module includes proxy services, firewalls, VPN servers, and publicly accessible servers.

Network IDS

(NIDS) looking over the whole network for a complete intrusion detection system, a NIDS is better at preventing general network attacks than a host-based IDS.

Network layer

In the OSI reference model, it is Layer 3—the layer in which routing is implemented, enabling connections and path selection between two end-systems. See also: Application layer, Data Link layer, Physical layer, Presentation layer, Session layer, and Transport layer.

network management

When designing networks, network management is one of the key factors to the network’s overall success. Industry standards allow network management of many different types of networking devices, including routers, bridges, and switches.

network operations center

(NOC) Usually a central hub of network engineers and administrators who manage enterprise networks.

Network Time Protocol

(NTP) provides a way to ensure that accurate time is kept on all devices. When dealing with attacks, seconds matter because it is important to identify the order in which a specified attack occurred.

Network topology

The map of a network. Physical topology describes where the cables are run and where the workstations, nodes, routers, and gateways are located. Networks are usually configured in bus, ring, star, or mesh topologies. Logical topology refers to the paths that messages take to get from one user on the network to another.

NFS

Network File System: One of the protocols in Sun Microsystems’ widely used file system protocol suite, allowing remote file access across a network. The name is loosely used to refer to the entire Sun protocol suite, which also includes RPC, XDR (External Data Representation), and other protocols.

NHRP

Next Hop Resolution Protocol: In a nonbroadcast multiaccess (NBMA) network, the protocol employed by routers in order to dynamically locate MAC addresses of various hosts and routers. It enables systems to communicate directly without requiring an intermediate hop, thus facilitating increased performance in ATM, Frame Relay, X.25, and SMDS systems.

NHS

Next Hop Server: Defined by the NHRP protocol, this server maintains the next-hop resolution cache tables, listing IP-to-ATM address maps of related nodes and nodes that can be reached through routers served by the NHS.

NIC

Network Interface Card: An electronic circuit board placed in a computer. The NIC provides network communication to a LAN.

NLSP

NetWare Link Services Protocol: Novell’s link-state routing protocol, based on the IS-IS model.

NMP

Network Management Processor: A Catalyst 5000 switch processor module used to control and monitor the switch.

node

Any device attached to the network capable of communicating with other network devices. In Novell NetWare documentation, a workstation is often called a node.

non-stub area

In OSPF, a resource-consuming area carrying a default route, intra-area routes, interarea routes, static routes, and external routes. Non-stub areas are the only areas that can have virtual links configured across them and exclusively contain an anonymous system boundary router (ASBR). Compare with: stub area. See also: ASBR and OSPF.

NRZ

Nonreturn to Zero: One of several encoding schemes for transmitting digital data. NRZ signals sustain constant levels of voltage with no signal shifting (no return to zero-voltage level) during a bit interval. If there is a series of bits with the same value (1 or 0), there will be no state change. The signal is not self-clocking. See also: NRZI.

NRZI

Nonreturn to Zero Inverted: One of several encoding schemes for transmitting digital data. A transition in voltage level (either from high to low or vice versa) at the beginning of a bit interval is interpreted as a value of 1; the absence of a transition is interpreted as a 0. Thus, the voltage assigned to each value is continually inverted. NRZI signals are not self-clocking. See also: NRZ.

NVRAM

Non-Volatile RAM: Random-access memory that keeps its contents intact while power is turned off.




CCDA. Cisco Certified Design Associate Study Guide
CCDA: Cisco Certified Design Associate Study Guide, 2nd Edition (640-861)
ISBN: 0782142001
EAN: 2147483647
Year: 2002
Pages: 201

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