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G L O S S A R Y

User Guide

B-1

LOSSARY

1000Base-T: The specification that describes the use of Gigabit Ethernet over copper Cat-5 wire.

It defines data rates of 1 Gigabit per second Gb/s over a distance not to exceed 100 meters.
Advanced Encryption Standard (AES): An emerging encryption standard that can use a 128-

, 192-, or 256-bit encryption key. This new standard supports easier interoperability with other

security appliances as it becomes widely adapted.
Address Resolution Protocol (ARP): A protocol used to map an internal IP address to physical

machines that a local network recognizes. A table called an ARP Cache stores and correlates the

IP address and physical address assigned for a specific host. ARP provides the protocol rules for

making this correlation and provides address communication in both directions.
Advertisement: A method used by routers to send information to other network devices. This

could include an IP address, network mask or other data.
Authentication Header (AH): A method that provides integrity and authentication, but not

privacy, as IP data is not encrypted. AH contains an authentication value based on a symmetric-

key hash function.
Bridge: A device that enables the connection of multiple network segments while using the same

network and mask.
Data Encryption Standard (DES): A standard that uses either a 40 or 56 bit encryption

algorithm developed by the National Institute of Standards and Technology (NIST). DES uses a

block encryption method that was originally developed by IBM in the 1970s. The U. S.

Government has since certified it to transmit data that has not been as classified “top secret.”

DES uses a 64-bit key to encrypt and decrypt data into 64-bit block enabling it fixed output for

variable length input.
Data Encryption Standard-Cipher Block Chaining (DES-CBC): Standard that enables the

use of Triple DES (or 3DES). By enabling CBC, the DES encryption occurs three times, enabling

generation of the 56-bit key three times. The 3DES standard uses a key length of 168-bits.
Datagram: A self contained data packet sent over an IP network.
Default Route: A standard entry in a routing table that enables traffic to be forwarded for

destination networks that are not explicitly defined on a specific network device. The normal rep-

resentation of the default route is 0.0.0.0/0.
Demilitarized Zone (DMZ): Usually a small network that sits between the trusted local area

network (LAN) and the public Internet. DMZ enables administrators to apply different polices to

traffic that might need to be accessed from the public Internet.
Domain Name: A name that can identify one or more IP addresses. URLs normally use domain

names to identify particular web pages.
Domain Name System (DNS): An Internet system that translates domain names into IP

addresses.
Dynamic host configuration protocol (DHCP): Protocol that automatically assigns IP

addresses to computers on a local area network (LAN). Typically, a system administrator

designates a range of IP addresses that DHCP assigns. Each client computer on the LAN has its

TCP/IP software configured to request an IP address from the DHCP server. This protocol reduces

the work necessary to administer a large IP network.
Encryption: The ability for a network device to translate data into a secret code. Encryption is

an effective way to protect data so that only the intended recipient can decode it. All encryption

uses a public/private key pairing so that a user can encrypt and decrypt the specific data. A device

allows encryption using the private key, and only users with the public key can decrypt that in-

formation.
Encapsulating Security Payload (ESP/AH): Protocol that defines the IP security used for the

protocol, IP Security (IPsec). IPsec defines the keys, algorithms and networks that are encrypted.

ESP provides both authentication and encryption, while AH or Authentication provides only au-