Watchguard Firebox X1000 Reference Manual page 135

Reference Guide
individual who is simply a computer enthusiast or expert;
however, WatchGuard publications use the former definition.
hash code
A unique, mathematical summary of a document that serves to
identify the document and its contents. Any change in the hash
code indicates that the document's contents have been altered.
header
A series of bytes at the beginning of a communication packet that
provide identification information about the packet such as its
computer of origin, the intended recipient, packet size, and
destination port number.
Help system
A form of online information about a software or hardware
system.
hexadecimal
A numbering system containing 16 sequential numbers as base
units before adding a new position for the next number.
Hexadecimal uses the numbers 0—9 and the letters A—F.
hierarchical trust
A graded series of entities that distribute trust in an organized
fashion, commonly used in ANSI X.509 to issue certifying
authorities.
High Availability
A WatchGuard Firebox System option that enables the installation
of two Fireboxes on one network in a failover configuration. At
any given moment, one Firebox is in active mode while the other
is in standby mode, ready to take over if the first box fails.
Historical Reports
A WatchGuard Firebox System application that creates HTML
reports displaying session types, most active hosts, most used
services, and other information useful in monitoring and
troubleshooting a network.
HMAC
A key-dependent, one-way hash function specifically intended for
use with MAC (Message Authentication Code), and based upon
IETF RFC 2104.
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