switch 03...

transparent bridge
a transparent bridge is the idea of a layer 2 device which segments a network and passes frames between    
these segments to nodes by learning  information about the nodes addresses, and without the nodes
knowledge of their existence (hence, the bridges are seemingly transparent to the nodes)

bridging loop
a bridging loop is a condition which can occur if more than one layer 2 path exists in a network between
two endpoints.  layer 2 is helpless to stop such occurrences for lack of a mechanism such as ttl

Spanning Tree Protocol
spanning tree is such a mechanism, designed solely to shut down a redundant path that might cause a
loop

BPDU
the unit of communication between switches to establish the rules for the effective topology of the tree, sent
every 2 seconds

root bridge
a root bridge is determined after a topology election in the tree; this is effectively the hub of the layer 2    
network. the ports of the root bridge are always designated

root port
every switch in the network determines a root port; the port with the least cost path to the root switch

root path cost
the cost determined by bandwidth to the root switch.  this cost is often cumulative

designated port
a non-root port on the switch that is the least cost path to the root connecting to another segment

Hello Time
the time between each transmission of a bpdu; default 2 seconds

Forward Delay
the cumulative time for a port to transition to the forwarding state

Max Age time
the time for the prior information learned from a bpdu to expire because a new bpdu has not been received

TCN
a topology change notification bpdu will be initiated by a switch upon port transitioning

Common Spanning Tree
a single instance (common) tree for the network

PVST
a tree instance for every vlan

PVST+
the same as pvst but ieee open standard (without isl)