Bridge Protocol Data Units - D-Link DGS-3224TG User Manual

DGS-3224TG Gigabit Ethernet Switch User's Guide
The following are the user-configurable STP parameters for the port or port group level:

Bridge Protocol Data Units

For STP to arrive at a stable network topology, the following information is used:
•
The unique switch identifier
•
The path cost to the root associated with each switch port
•
The port identifier
STP communicates between switches on the network using Bridge Protocol Data Units (BPDUs). Each
BPDU contains the following information:
•
The unique identifier of the switch that the transmitting switch currently believes is the root
switch
address. The Bridge Identifier
(Not user-
consists of two parts: a 16-bit
configurable except
priority and a 48-bit Ethernet MAC
by setting priority
address
below)
Priority A relative priority for each switch –
lower
priority and a greater chance of a
given switch being elected as the
root bridge
Hello Time The
broadcasts of the hello message by
the switch
Maximum Age Timer Measures the age of a received
BPDU for a port and ensures that
the BPDU is discarded when its
age exceeds the value of the
maximum age timer.
Forward Delay Timer The amount time spent by a port
in the learning and listening states
waiting for a BPDU that may
return the port to the blocking
state.
Table 5-1. STP Parameters – Switch Level
Variable Description
Port Priority A relative priority for each port –
lower
priority and a greater chance of a
given port being elected as the root
port
Port Cost A value used by STP to evaluate
paths.
Table 5-2. STP Parameters – Port Group Level
numbers give a higher
length of time between
numbers give a higher
17
32768
2 seconds
20 seconds
15 seconds
Default
Value
32768
19