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McDATA® Sphereon 3032 and 3232 Fabric Switches Installation and Service Manual
Glossary
Underwriters
Laboratories
UL. A laboratory organization accredited by the Occupational Safety
and Health Administration and authorized to certify products for use
in the home and workplace (D).
unicast Communication between a single sender and a single receiver over a
network.
uninterruptable power
supply
UPS. A buffer between public utility power or another power source,
and a system that requires precise, uninterrupted power (D).
UNIX A popular multi-user, multitasking operating system originally
designed to be a small, flexible system used exclusively by program-
mers. UNIX was one of the first operating systems to be written in a
high-level programming language, namely C. This meant that it
could be installed on virtually any computer for which a C compiler
existed. Due to its portability, flexibility, and power, UNIX has
become the leading operating system for workstations. Historically, it
has been less popular in the personal computer market, but the emer-
gence of a new version called Linux is revitalizing UNIX across all
platforms.
upper level protocol ULP. Protocols that map to and run on top of the Fibre Channel FC-4
layer. ULPs include Internet protocol (IP) and small computer system
interface (SCSI).
UPS See uninterruptable power supply.
user datagram
protocol
UDP. A connectionless protocol that runs on top of Internet protocol
(IP) networks. User datagram protocol/Internet protocol (UDP/IP)
offers very few error recovery services, instead providing a direct
way to send and receive datagrams over an IP network. UDP/IP is
primarily used for broadcasting messages over an entire network.
Contrast with transmission control protocol/Internet protocol.
V
VAC See volts alternating current.
VDC See volts direct current.
virtual machine VM®. (1) A virtual data processing system that appears to be at the
exclusive disposal of a single user, but whose functions are accom-