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Glossary

FQDN

fully qualified domain name: Used within the DNS domain struc-

ture to provide name to IP address resolution on the Internet. An example of
an FQDN is bob.acme.com.

FRAD

Frame Relay access device: Any device affording a connection

between a LAN and a Frame Relay WAN. See also: Cisco FRAD and FRAS.

fragment

Any portion of a larger packet that has been intentionally seg-

mented into smaller pieces. A packet fragment does not necessarily indicate
an error and can be intentional. See also: fragmentation.

fragmentation

The process of intentionally segmenting a packet into

smaller pieces when sending data over an intermediate network medium that
cannot support the larger packet size.

FragmentFree

LAN switch type that reads into the data section of a

frame to make sure fragmentation did not occur. Sometimes called modi-
fied cut-through.

frame

A logical unit of information sent by the Data Link layer over

a transmission medium. The term often refers to the header and trailer,
employed for synchronization and error control, that surround the data
contained in the unit.

frame filtering

Frame filtering is used on a layer-2 switch to provide more

bandwidth. A switch reads the destination hardware address of a frame and
then looks for this address in the filter table, built by the switch. It then only
sends the frame out the port where the hardware address is located, and the
other ports do not see the frame.

frame identification (frame tagging)

VLANs can span multiple con-

nected switches, which Cisco calls a switch-fabric. Switches within this
switch-fabric must keep track of frames as they are received on the switch
ports, and they must keep track of the VLAN they belong to as the frames
traverse this switch-fabric. Frame tagging performs this function. Switches
can then direct frames to the appropriate port.

Frame Relay

A more efficient replacement of the X.25 protocol (an unre-

lated packet relay technology that guarantees data delivery). Frame Relay is
an industry-standard, shared-access, best-effort, switched Data Link layer
encapsulation that services multiple virtual circuits and protocols between
connected mechanisms.

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