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Glossary

Flash

Electronically Erasable Programmable Read-Only Memory

(EEPROM). Used to hold the Cisco IOS in a router by default.

flash memory

Developed by Intel and licensed to other semiconductor

manufacturers, it is nonvolatile storage that can be erased electronically and
reprogrammed, physically located on an EEPROM chip. Flash memory per-
mits software images to be stored, booted, and rewritten as needed. Cisco
routers and switches use flash memory to hold the IOS by default. See also:
EPROM, EEPROM.

flat network

Network that is one large collision domain and one large

broadcast domain.

flooding

When traffic is received on an interface, it is then transmitted to

every interface connected to that device with the exception of the interface
from which the traffic originated. This technique can be used for traffic
transfer by bridges and switches throughout the network.

flow

A shortcut or MLS cache entry that is defined by the packet properties.

Packets with identical properties belong to the same flow. See also: MLS.

flow control

A methodology used to ensure that receiving units are not

overwhelmed with data from sending devices. Pacing, as it is called in IBM
networks, means that when buffers at a receiving unit are full, a message is
transmitted to the sending unit to temporarily halt transmissions until all the
data in the receiving buffer has been processed and the buffer is again ready
for action.

FRAD

Frame Relay Access Device: Any device affording a connection

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

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