700
Glossary
failure domain
The region in which a failure has occurred in a Token Ring.
When a station gains information that a serious problem, such as a cable
break, has occurred with the network, it sends a beacon frame that includes
the station reporting the failure, its NAUN, and everything between. This
defines the failure domain. Beaconing then initiates the procedure known as
autoreconfiguration. See also: autoreconfiguration and beacon.
fallback
In ATM networks, this mechanism is used for scouting a path if
it isn't possible to locate one using customary methods. The device relaxes
requirements for certain characteristics, such as delay, in an attempt to find
a path that meets a certain set of the most important requirements.
Fast Ethernet
Any Ethernet specification with a speed of 100Mbps. Fast
Ethernet is ten times faster than 10BaseT, while retaining qualities like MAC
mechanisms, MTU, and frame format. These similarities make it possible for
existing 10BaseT applications and management tools to be used on Fast
Ethernet networks. Fast Ethernet is based on an extension of IEEE 802.3
specification (IEEE 802.3U). Compare with: Ethernet. See also: 100BaseT,
100BaseTX, and IEEE.
fast switching
A Cisco feature that uses a route cache to speed packet
switching through a router. Contrast with: process switching.
fault tolerance
The extent to which a network device or a communication
link can fail without communication being interrupted. Fault tolerance can
be provided by added secondary routes to a remote network.
FDM
Frequency-Division Multiplexing: A technique that permits informa-
tion from several channels to be assigned bandwidth on one wire based on
frequency. See also: TDM, ATDM, and statistical multiplexing.
FDDI
Fiber Distributed Data Interface: A LAN standard, defined by
ANSI X3T9.5 that can run at speeds up to 200Mbps and uses token-
passing media access on fiber-optic cable. For redundancy, FDDI can use
a dual-ring architecture.
FECN
Forward Explicit Congestion Notification: A bit set by a Frame
Relay network that informs the DTE receptor that congestion was encoun-
tered along the path from source to destination. A device receiving frames
with the FECN bit set can ask higher-priority protocols to take flow-control
action as needed. See also: BECN.
Copyright ©2002 SYBEX, Inc., Alameda, CA
www.sybex.com