3Com WX2200 3CRWX220095A, WXR100 3CRWXR10095A, WX4400 3CRWX440095A manual Fdb, Fhss, Gbic

GLOSSARY 683

FDB	See forwarding database (FDB).
Federal	See FCC.
Communications
Commission
FHSS	Frequency-hopping spread-spectrum. One of two types of
	spread-spectrum radio technology used in wireless LAN (WLAN)
	transmissions. The FHSS technique modulates the data signal with a
	narrowband carrier signal that “hops” in a predictable sequence from
	frequency to frequency as a function of time over a wide band of
	frequencies. Interference is reduced, because a narrowband interferer
	affects the spread-spectrum signal only if both are transmitting at the
	same frequency at the same time. The transmission frequencies are
	determined by a spreading (hopping) code. The receiver must be set to
	the same hopping code and must listen to the incoming signal at the
	proper time and frequency to receive the signal. Compare DSSS.
forwarding database	A database maintained on a Wireless Switch (WX) for the purpose of
(FDB)	making Layer 2 forwarding and filtering decisions. Each entry consists
	of the media access control (MAC) address of a source or destination
	device, an identifier for the port on which the source or destination
	station is located, and an identifier for the virtual LAN (VLAN) to which
	the device belongs. FDB entries are either permanent (never deleted),
	static (not aged, but deleted when the WX is restarted or loses power),
	or dynamic (learned dynamically and removed through aging or when
	the WX is restarted or loses power).
frequency-hopping	See FHSS.
spread-spectrum
GBIC	Gigabit interface converter. A hot-swappable input/output device that
	plugs into a gigabit Ethernet port, to link the port with a fiber-optic or
	copper network. The data transfer rate is 1 gigabit per second (Gbps)
	or more. Typically employed as high-speed interfaces, GBICs allow you
	to easily configure and upgrade communications networks.
gigabit interface	See GBIC.
converter
glob	See MAC address glob; user glob; VLAN glob.