Black Box Advanced Console Server User Manual page 378

Glossary
TTY
UDP
U Rack Height Unit
VPN
Watchdog Timer
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terminal servers are sometimes used as console access
servers.
1. In Unix, refers to any terminal; sometimes used to refer to
the particular terminal controlling a given job (it is also the
name of a Unix command which outputs the name of the
current controlling terminal). 2. Also in Unix, any serial port,
whether or not the device connected to it is a terminal; so
called because under Unix such devices have names of the
form tty.
User Datagram Protocol uses a special type of packet called
a datagram. Datagrams do not require a response; they are
one way only (connectionless). Datagrams are usually used
for streaming media because an occasional packet loss will
not affect the final product of the transmission.
A standard computer rack has an internal width of 17 inches.
Rack space on a standard rack is measured in units of height
(U). One U is 1.75 inches. A device that has a height of 3.5
inches takes 2U of rack space.
Virtual Private Networking allows local area networks to
communicate across wide area networks, typically over an
encrypted channel. See also: IPsec.
A watchdog timer (WDT) is a device or electronic card that
performs a specific operation after a certain period of time if
something goes wrong with an electronic system and the
system does not recover on its own.
A common problem is for a machine or operating system to
lock up if two parts or programs conflict, or, in an operating
system, if memory management trouble occurs. In some
cases, the system will eventually recover on its own, but this
may take an unknown and perhaps extended length of time.
A watchdog timer can be programmed to perform a warm
boot (restarting the system) after a certain number of seconds
during which a program or computer fails to respond
following the most recent mouse click or keyboard action.