Appendix C:
Glossary
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(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 Remote ID sub-option was
designed to carry information relating to the remote host end of the circuit.
The definition of Circuit ID in the switch is 4 bytes in length and the format is "vlan_id"
"module_id" "port_no". The parameter of "vlan_id" is the first two bytes represent the VLAN
ID. The parameter of "module_id" is the third byte for the module ID (in standalone switch it
always equal 0, in stackable switch it means switch ID). The parameter of "port_no" is the
fourth byte and it means the port number.
The Remote ID is 6 bytes in length, and the value is equal the DHCP relay agents MAC
address.
DHCP Snooping
DHCP Snooping is used to block intruder on the untrusted ports of the switch device when it
tries to intervene by injecting a bogus DHCP reply packet to a legitimate conversation
between the DHCP client and server.
DNS
DNS is an acronym for
D
omain
N
ame
S
ystem. It stores and associates many types of
information with domain names. Most importantly, DNS translates human-friendly domain
names and computer hostnames into computer-friendly IP addresses. For example, the
domain name www.example.com might translate to 192.168.0.1.
Dotted Decimal Notation
Dotted Decimal Notation refers to a method of writing IP addresses using decimal numbers
and dots as separators between octets.
An IPv4 dotted decimal address has the form x.y.z.w, where x, y, z, and w are decimal
numbers between 0 and 255.
Drop Precedence Level
Every incoming frame is classified to a Drop Precedence Level (DP level), which is used
throughout the device for providing congestion control guarantees to the frame according to
what was configured for that specific DP level. A DP level of 0 (zero) corresponds to
'Committed' (Green) frames and a DP level of 1 or higher corresponds to 'Discard Eligible'
(Yellow) frames.
DSCP
DSCP is an acronym for
D
ifferentiated
S
ervices
C
ode
P
oint. It is a field in the header
of IP packets for packet classification purposes.