ZyXEL Communications XGS3600 Series Manual page 332

C
CC
CC is an acronym for Continuity Check. It is a MEP functionality that is able to detect loss
of continuity in a network by transmitting CCM frames to a peer MEP.
CCM
CCM is an acronym for Continuity Check Message. It is a OAM frame transmitted from a
MEP to it's peer MEP and used to implement CC functionality.
CDP
CDP is an acronym for Cisco Discovery Protocol.
D
DEI
DEI is an acronym for Drop Eligible Indicator. It is a 1-bit field in the VLAN tag.
DES
DES is an acronym for Data Encryption Standard. It provides a complete description of a
mathematical algorithm for encrypting (enciphering) and decrypting (deciphering) binary
coded information.
Encrypting data converts it to an unintelligible form called cipher. Decrypting cipher
converts the data back to its original form called plaintext. The algorithm described in this
standard specifies both enciphering and deciphering operations which are based on a
binary number called a key.
DHCP
DHCP is an acronym for Dynamic Host Configuration Protocol. It is a protocol used for
assigning dynamic IP addresses to devices on a network.
DHCP used by networked computers (clients) to obtain IP addresses and other
parameters such as the default gateway, subnet mask, and IP addresses of DNS servers
from a DHCP server.
The DHCP server ensures that all IP addresses are unique, for example, no IP address is
assigned to a second client while the first client's assignment is valid (its lease has not
expired). Therefore, IP address pool management is done by the server and not by a
human network administrator.
Dynamic addressing simplifies network administration because the software keeps track
of IP addresses rather than requiring an administrator to manage the task. This means
that a new computer can be added to a network without the hassle of manually assigning
it a unique IP address.
DHCP Relay
DHCP Relay is used to forward and to transfer DHCP messages between the clients and
the server when they are not on the same subnet domain.
The DHCP option 82 enables a DHCP relay agent to insert specific information into a
DHCP request packets when forwarding client DHCP packets to a DHCP server and
remove the specific information from a DHCP reply packets when forwarding server
DHCP packets to a DHCP client. The DHCP server can use this information to implement
IP address or other assignment policies. Specifically the option works by setting two sub-
options: Circuit ID (option 1) and Remote ID (option2). The Circuit ID sub-option is
supposed to include information specific to which circuit the request came in on. The
XGS3600 Series User's Guide
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