Glossary - 24
FORE Systems ES-2810 Ethernet Switch User's Manual
Glossary
Network Redundancy - Duplicated network equipment and/or data which can provide a
backup in case of network failures.
Network Service Access Point (NSAP) - OSI generic standard for a network address consisting
of 20 octets. ATM has specified E.164 for public network addressing and the NSAP address
structure for private network addresses.
Network-to-Network Interface or Network Node Interface (NNI) - the interface between two pub-
lic network pieces of equipment.
Node - A computer or other device when considered as part of a network.
Non Return to Zero (NRZ) - a binary encoding scheme in which ones and zeroes are represented
by opposite and alternating high and low voltages and where there is no return to a zero (ref-
erence) voltage between encoded bits.
Non Return to Zero Inverted (NRZI) - A binary encoding scheme that inverts the signal on a “1”
and leaves the signal unchanged for a “0”. (Also called transition encoding.)
Nonvolatile Storage - Memory storage that does not lose its contents when power is turned off.
NuBus - a high-speed bus used in Macintosh computers, structured so users can put a card
into any slot on the board without creating conflict over the priority between those cards.
nx64K - This refers to a circuit bandwidth or speed provided by the aggregation of nx64 kbps
channels (where n= integer > 1). The 64K or DS0 channel is the basic rate provided by the T
Carrier systems.
Nyquist Theorem - In communications theory, a formula stating that two samples per cycle is
sufficient to characterize a bandwidth limited analog signal; in other words, the sampling rate
must be twice the highest frequency component of the signal (i.e., sample 4 KHz analog voice
channels 8000 times per second).
Object Identifier (OID) - the address of a MIB variable.
Octet - a grouping of 8 bits; similar, but not identical to, a byte.
One’s Density - The requirement for digital transmission lines in the public switched telephone
network that eight consecutive “0”s cannot be in a digital data stream; exists because repeaters
and clocking devices within the network will lose timing after receiving eight “0”s in a row; a
number of techniques are used to insert a “1” after every seventh-consecutive “0” (see Bit
Stuffing).
Open Shortest Path First (OSPF) Protocol - a routing algorithm for IP that incorporates least-
cost, equal-cost, and load balancing.
Open Systems Interconnection (OSI) - the 7-layer suite of protocols designed by ISO commit-
tees to be the international standard computer network architecture.
OpenView - Hewlett-Packard's network management software.
Operation and Maintenance (OAM) Cell - a cell that contains ATM LM information. It does not
form part of the upper layer information transfer.
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