B. Glossary
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Decryption.
Decryption is the process of converting encrypted data to its original form. See
Encryption.
De-Militarized Zone (DMZ).
A computer host or small network placed between a company’s
private network and the outside public network to prevent outside users from gaining direct
access to a server that contains company data. The term is derived from the geographic area
between two opponents where fighting is prohibited. A DMZ is an optional, more secure
approach to a firewall and effectively acts as a proxy server as well.
Direct Inward Dialling (DID).
DID is a service that allows users that are connected to a common
server (such as a media exchange or a PBX) to receive calls from sources external to the server
without the intervention of an auto attendant or operator. Under DID, each user is assigned a
unique telephone number, as opposed to the typical PBX setup that assigns extensions that are
based on a common telephone number.
Domain Name System (DNS).
Defines the manner that the Internet translates names of network
nodes into addresses. SIP uses DNS to resolve the host names of endpoints to IP addresses.
Dynamic Host Configuration Protocol (DHCP).
A communication protocol that defines a method
where network administrators manage and automate Internet Protocol (IP) address assignment
within an enterprise network. DHCP allows you to move network devices from one subnet to
another without administrative attention. If using DHCP, you can connect IP phones to the
network and become operational without having to manually assign an IP address and additional
network parameters. The ZIP 4x4 phone complies with the DHCP specifications documented in
RFC 2131 and are DHCP-enabled by default.
Advanced Encryption Standard (AES).
Also known as Rijndael, this is a block cipher adopted as an
encryption standard by the U.S. government and developed by two Belgian cryptographers, Joan
Daemen and Vincent Rijmen. It has been analyzed extensively and is now used widely
worldwide as a replacement for its predecessors the Data Encryption Standard (DES) and the
triple DES (3DES). AES was announced by the NIST on 26 November 2001 after a 5-year
standardization process and became a standard on 26 May 2002. It is one of the most popular
algorithms used in symmetric key cryptography and is acceptable by the US government for
classified information up to Top Secret.
Encryption.
The process of converting data into a form that can be read only by the intended
receiver. Decryption is the process of converting encrypted data to its original form. Traditional
encryption schemes utilize the same key to encrypt and decrypt data. Public-key encryption
schemes require two keys: a public key, which anyone may use, and a corresponding private key,
which is possessed only by the person who created it. With this method, anyone may send a
message encrypted with the owner's public key, but only the owner has the private key necessary
to decrypt it. PGP (Pretty Good Privacy) and DES (Data Encryption Standard) are two of the most
popular public-key encryption schemes.
Ethernet.
The most widely-installed local area network (LAN) technology. Originally developed
at the Xerox Corporation Palo Alto Research Center, Ethernet is specified in the IEEE 802.3
standard. Ethernet is a best-effort delivery system that uses CSMA/CD technology. Ethernet can
be run over a variety of physical media, including coaxial, twisted pair, and fiber optics.
Firewall.
A device, located at a network gateway server, that protects the resources of a private
network from external entities. Typically comprises a set of related programs or a dedicated
computer equipped with such security features as logging, reporting, alarms, and a control
mechanism.