Watchguard Firebox X1000, Справочное руководство

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CHAPTER 9: Glossary
146 WatchGuard Firebox System
allowed, often stated as “That which is not explicitly allowed is
denied.”
star topology
A networking setup used with 10BASE-T cabling and a hub in
which each node on the network is connected to the hub like
points of a star.
static NAT
Network address translation in which incoming packets destined
for a public address on an external network are remapped to an
address behind the firewall.
stream cypher
A class of symmetric key encryption where transformation can be
changed for each symbol of plain text being encrypted; useful for
equipment with little memory to buffer data.
subnet
A network segment connected by hubs or repeaters. For example,
one could take a class C network with 256 available addresses and
create two additional netmasks under it that separate the first 128
and last 128 addresses into separate identifiable networks.
Subnetting enables a client with a single network to create
multiple networks; the advanced or multiple network
configurations can then be used when setting up the Firebox.
subnet mask
A 32-bit number used to identify which port of an IP address is
masked.
substitution cypher
A method in which the characters of the plain text are substituted
with other characters to form the cipher text.
switch
A device that filters and forwards packets between LAN
segments.
symmetric algorithm
Also called conventional, secret key, and single key algorithms;
the encryption and decryption key are either the same or can be
calculated from one another.