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Glossary

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access list

A set of test conditions kept by routers

that determines "interesting traffic" to and from the
router for various services on the network.

access method

The manner in which network

devices approach gaining access to the network itself.

access server

Also known as a "network access

server," it is a communications process connecting
asynchronous devices to a LAN or WAN through net-
work and terminal emulation software, providing syn-
chronous or asynchronous routing of supported
protocols.

acknowledgment

Verification sent from one net-

work device to another signifying that an event has
occurred. May be abbreviated as ACK.

Contrast

with: NAK.

ACR

allowed cell rate: A designation defined by the

ATM Forum for managing ATM traffic. Dynamically
controlled using congestion control measures, the
ACR varies between the minimum cell rate (MCR)
and the peak cell rate (PCR).

See also: MCR

and

PCR.

action plan

A list of steps or procedures used to

resolve a network problem. This plan should possess
four characteristics: make one change at a time, make
non-impacting changes, do not compromise security,
and have a procedure to back out of any changes made.

active monitor

The mechanism used to manage a

Token Ring. The network node with the highest MAC
address on the ring becomes the active monitor and is
responsible for management tasks such as preventing
loops and ensuring tokens are not lost.

address learning

Used with transparent bridges to

learn the hardware addresses of all devices on an inter-
network. The switch then filters the network with the
known hardware (MAC) addresses.

address mapping

By translating network addresses

from one format to another, this methodology permits
different protocols to operate interchangeably.

address mask

A bit combination descriptor identify-

ing which portion of an address refers to the network or
subnet and which part refers to the host. Sometimes
simply called the mask.

See also: subnet mask.

address resolution

The process used for resolving

differences between computer addressing schemes.
Address resolution typically defines a method for trac-
ing Network layer (Layer 3) addresses to Data-Link
layer (Layer 2) addresses.

See also: address mapping.

adjacency

The relationship made between defined

neighboring routers and end nodes, using a common
media segment, to exchange routing information.

adjacency table

The adjacency table is a table that

contains all active/existing adjacencies of neighboring
routers.

administrative distance

A number between 0 and

225 that expresses the value of trustworthiness of a
routing information source. The lower the number,
the higher the integrity rating.

administrative weight

A value designated by a net-

work administrator to rate the preference given to a
network link. It is one of four link metrics exchanged
by PTSPs to test ATM network resource availability.

ADSU

ATM Data Service Unit: The terminal

adapter used to connect to an ATM network through
an HSSI-compatible mechanism.

See also: DSU.

advertising

The process whereby routing or service

updates are transmitted at given intervals, allowing
other routers on the network to maintain a record of
viable routes.

AEP

AppleTalk Echo Protocol: A test for connectiv-

ity between two AppleTalk nodes where one node
sends a packet to another and receives an echo, or
copy, in response.

AFI

Authority and Format Identifier: The part of an

NSAP ATM address that delineates the type and for-
mat of the IDI section of an ATM address.

AFP

AppleTalk Filing Protocol: A Presentation-layer

protocol, supporting AppleShare and Mac OS File
Sharing, that permits users to share files and applica-
tions on a server.

AIP

ATM Interface Processor: Supporting AAL3/4

and AAL5, this interface for Cisco 7000 series routers
minimizes performance bottlenecks at the UNI.

See

also: AAL3/4

and

AAL5.

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