D-Link DES-3226L, Cli Command Reference

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Glossary 123
Glossary
Numerics
802.1D. The IEEE designator for Spanning Tree Protocol
(STP). STP, a link management protocol, is part of the
802.1D standard for media access control bridges. Using
the spanning tree algorithm, STP provides path
redundancy while preventing endless loops in a network.
An endless loop is created by multiple active paths
between stations where there are alternate routes between
hosts. To establish path redundancy, STP creates a logical
tree that spans all of the switches in an extended network,
forcing redundant paths into a standby, or blocked, state.
STP allows only one active path at a time between any two
network devices (this prevents the loops) but establishes
the redundant links as a backup if the initial link should
fail. If STP costs change, or if one network segment in the
STP becomes unreachable, the spanning tree algorithm
reconfigures the spanning tree topology and reestablishes
the link by activating the standby path. Without spanning
tree in place, it is possible that both connections may be
simultaneously live, which could result in an endless loop
of traffic on the LAN.
802.1P. The IEEE protocol designator for Local Area
Network (LAN). This Layer 2 network standard improves
support of time critical traffic, and limits the extent of high
bandwidth multicast traffic within a bridged LAN. To do
this, 802.1P defines a methodology for introducing traffic
class priorities. The 802.1P standard allows priority to be
defined in all 802 MAC protocols (Ethernet, Token Bus,
Token Ring), as well as in FDDI. For protocols (such as
Ethernet) that do not contain a priority field, 802.1P
specifies a method for indicating frame priority based on
the new fields defined in the 802.1Q (VLAN) standard.
802.1Q VLAN. The IEEE protocol designator for Virtual
Local Area Network (VLAN). This standard provides
VLAN identification and quality of service (QoS) levels.
Four bytes are added to an Ethernet frame to allow eight
priority levels (QoS) and to identify up to 4096 VLANs.
See “VLAN” on page 127 for more information.
A
Address Resolution Protocol. An Internet Protocol that
dynamically maps Internet addresses to physical
(hardware) addresses on a LAN.
Aging. When an entry for a node is added to the lookup
table of a switch, it is given a timestamp. Each time a
packet is received from a node, the timestamp is updated.
The switch has a user-configurable timer that erases the
entry after a certain length of time with no activity from
that node.
B
BPDU. See “Bridge Protocol Data Unit” on page 123.
BootP. See “Bootstrap Protocol.” on page 123.
Bootstrap Protocol. An Internet protocol that enables a
diskless workstation to discover its own IP address, the IP
address of a BootP server on the network, and a file to be
loaded into memory to boot the machine. This enables the
workstation to boot without requiring a hard or floppy disk
drive.
Bridge Protocol Data Unit. BPDU is the IEEE 802.1D
MAC Bridge Management protocol that is the standard
implementation of STP (Spanning Tree Protocol). It uses
the STP algorithm to insure that physical loops in the
network topology do not result in logical looping of
network traffic. Using one bridge configured as root for
reference, the BPDU switches one of two bridges forming
a network loop into standby mode, so that only one side of
a potential loop passes traffic. By examining frequent
802.1d configuration updates, a bridge in the standby
mode can switch automatically into the forward mode if
the other bridge forming the loop fails.
C
Checksum. A simple error-detection scheme in which
each transmitted message is identified with a numerical
value based on the number of set bits in the message. The
receiving station then applies a formula to the message and
checks to make sure the accompanying numerical value is
the same. If not, the receiver can assume that the message
has been corrupted.
CLI. See “Command Line Interface” on page 123.
Command Line Interface. CLI is a line-item interface
for configuring systems. (In the case of D-Link, it is one of
the user interfaces they have programmed for allowing
programmers to configure their system).
D
DHCP. See “Dynamic Host Configuration Protocol.” on
page 123.
Dynamic Host Configuration Protocol. DHCP is a
protocol for assigning dynamic IP addresses to devices on
a network. With dynamic addressing, a device can have a
different IP address every time it connects to the network.