Owner's Manual

942 | Appendix E. Glossary
NETGEAR 8800 User Manual
STP Spanning Tree Protocol. STP is a protocol, defined in IEEE 802.1d, used to
eliminate redundant data paths and to increase network efficiency. STP allows a
network to have a topology that contains physical loops; it operates in bridges
and switches. STP opens certain paths to create a tree topology, thereby
preventing packets from looping endlessly on the network. To establish path
redundancy, STP creates a 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 STP topology and
re-establishes the link by activating the standby path.
STPD Spanning Tree Domain. An STPD is an STP instance that contains one or more
VLANs. The switch can run multiple STPDs, and each STPD has its own root
bridge and active path. In the NETGEAR implementation of STPD, each domain
has a carrier VLAN (for carrying STP information) and one or more protected
VLANs (for carrying the data).
STPD mode The mode of operation for the STPD. The two modes of operation are:
• 802.1d—Compatible with legacy STP and other devices using the IEEE
802.1d standard.
• 802.1w—Compatible with Rapid Spanning Tree (RSTP).
stub areas In OSPF, a stub area is connected to only one other area (which can be the
backbone area). External route information is not distributed to stub areas.
system health check The primary responsibility of the system health checker is to monitor and poll
error registers. In addition, the system health checker can be enabled to
periodically send diagnostic packets. System health check errors are reported to
the syslog.
T
TACACS+ Terminal Access Controller Access Control System. Often run on UNIX systems,
the TACAS+ protocol provides access control for routers, network access
servers, and other networked computing devices via one or more centralized
servers. TACACS+ provides separate authentication, authorization, and
accounting services. User passwords are administered in a central database
rather than in individual routers, providing easily scalable network security
solutions.
tagged VLAN You identify packets as belonging to the same tagged VLAN by putting a value
into the 12-bit (4 octet) VLAN ID field that is part of the IEEE 802.1Q field of the
header. Using this 12-bit field, you can configure up to 4096 individual VLAN
addresses (usually some are reserved for system VLANs such as management
and default VLANs); these tagged VLANs can exist across multiple devices. The
tagged VLAN can be associated with both tagged and untagged ports.
TCN Topology change notification. The TCN is a timer used in RSTP that signals a
change in the topology of the network.
S (Continued)