Digitus DN-80233, User Manual

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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 302 for
more information.
A
ABR.
See “Area Border Router” on page 294.
Access Control List.
An ACL is a database that an Operating System uses to track each user’s access
rights to system objects (such as file directories and/or files).
ACL.
See “Access Control List” on page 294.
Address Resolution Protocol.
An Internet Protocol that dynamically maps Internet addresses to
physical (hardware) addresses on a LAN.
Advanced Network Device Layer/Software.
Our devise’s term for the Device Driver level.
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.
API.
See “Application Programming Interface” on page 294.
Application Programming Interface.
An API is an interface used by an programmer to interface
with functions provided by an application.
Area Border Router.
A router located on the border of one or more OSPF areas that connects those
areas to the backbone network. ABRs are considered members of both the OSPF backbone and the
attached areas. They therefore maintain routing tables describing both the backbone topology and the
topology of the other areas.
ARP.
See “Address Resolution Protocol” on page 294.
ASAM.
See “ATM Subscriber Access Multiplexer” on page 294.