sustain constant levels of voltage with no signal shift-
ing (no return to zero-voltage level) during a bit inter-
val. 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.
sition 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 con-
tinually inverted. NRZI signals are not self-clocking.
See also: NRZ.
use an NT2, you must use a terminal adapter (TA).
turned off.
in order to define the problem and see whether the
changes implemented were effective.
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.
as a byte.
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.
against the optimum switching cache.
for the development of data networking standards
that make multivendor equipment interoperability a
reality.
International Organization for Standardization (ISO),
describing how any combination of devices can be con-
nected for the purpose of communication. The OSI
model divides the task into seven functional layers,
forming a hierarchy with the applications at the top and
the physical medium at the bottom, and it defines the
functions each layer must provide. See also: Application
layer, Data-Link layer, Network layer, Physical layer,
Presentation layer, Session layer, and Transport layer.
version of the IS-IS protocol, whose features include
multipath routing, load balancing, and least-cost rout-
ing. OSPF is the suggested successor to RIP in the
Internet environment. See also: Enhanced IGRP, IGP,
and IP.
interface cards. The organization then puts this OUI
on each and every card they manufacture. The OUI is
3 bytes (24 bits) long. The manufacturer then adds a 3-
byte identifier to uniquely identify the host on an inter-
network. The total length of the address is 48 bits (6
bytes) and is called a hardware address or MAC
address.
a console connection not directly interfaced through
the local LAN or WAN or a dial-in modem. Compare
with: in-band management.
cies separate from those ordinarily used for data trans-
fer. For example, the initial configuration of a Cisco
Catalyst switch requires an out-of-band connection
via a console port.