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Glossary

NVRAM

Non-Volatile RAM: Random-access memory that keeps its con-

tents intact while power is turned off.

Optical Carrier: A series of physical protocols, designated as OC-1,

OC-2, OC-3, and so on, for SONET optical signal transmissions. OC signal
levels place STS frames on a multimode fiber-optic line at various speeds, of
which 51.84Mbps is the lowest (OC-1). Each subsequent protocol runs at a
speed divisible by 51.84. See also: SONET.

octet

Base-8 numbering system used to identify a section of a dotted dec-

imal IP address. Also referred to as a byte.

100BaseT

Based on the IEEE 802.3u standard, 100BaseT is the Fast

Ethernet specification of 100Mbps baseband that uses UTP wiring. 100BaseT
sends link pulses (containing more information than those used in
10BaseT) over the network when no traffic is present. See also: 10BaseT,
FastEthernet, and IEEE 802.3.

100BaseTX

Based on the IEEE 802.3u standard, 100BaseTX is the

100Mbps baseband FastEthernet specification that uses two pairs of UTP or
STP wiring. The first pair of wires receives data; the second pair sends data.
To ensure correct signal timing, a 100BaseTX segment cannot be longer than
100 meters.

ones density

Also known as pulse density, this is a method of signal

clocking. The CSU/DSU retrieves the clocking information from data that
passes through it. For this scheme to work, the data needs to be encoded to
contain at least one binary 1 for each eight bits transmitted. See also: CSU
and DSU.

one-time challenge tokens

Used to provide a single-use password. This

prevents replay attacks and snooping; however, it also requires the user to
have a device that provides the token. This physical component of the secu-
rity model works to prevent hackers from guessing or obtaining the user's
password.

OSI

Open Systems Interconnection: International standardization pro-

gram designed by ISO and ITU-T for the development of data networking
standards that make multivendor equipment interoperability a reality.

www.sybex.com