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Redundant LAN (RSTP operation)
11.2.3
Rapid Spanning Tree Protocol (RSTP), defined in the IEEE 802.1D, is ready to operate in the
IED, when the user set RSTP for scheme switch [RedundantMode].
Overview
(i)
'Rapid Spanning Tree Protocol (RSTP)' is designed to achieve LAN bridge connections in stable.
The RSTP choose one of bridges as the root and BPDU data (called 'Bridge Protocol Data Unit)
is exchanged periodically over RPST network. Each bridge can listen and learn the BPDU data
so that all bridges in the network can find the shortest path for the root location (we call it
"Path-cost"). Consequently, the RTSP operation clear and recover the network failure if
occurred; no temporary loop will not occur in the network (that is, all terminals can have loop-
free LAN).
Parameters
(ii)
When RSTP is set for the [RedundantMode], the user should enter several PSTP parameters
so that the IED is able to enjoy the Spanning Tree topology by the RSTP:
Setting [BridgeHelloTime]: is used to set a BPDU transferring cycle for other terminals
(i.e., BPDU sending interval; they are sent for IEDs, Network bridges, etc.)
Setting [BridgeMaxAge]: instructs the terminal (IED) to listen to a BPDU cyclically. When
a terminal (IED) cannot listen to BPDUs within the setting, the terminal (IED) starts the
computation to make new spanning tree.
Setting [BridgePrioriy]: is allowed for the user to make priority tables in the IEDs. When
a terminal has the smallest number, the terminal can become the root bridge with high
possibility Note that a number can be set in 4096 steps.
Setting [BridgeFedDelay]: is the time to wait for Listening and Learning.
Note: the user shall take the above settings based on the IEEE 802.1w equations below:
2× [
BridgeMaxAge
[
BridgeFwdDelay
] − 1.0������. ≥ [
BridgeHellowTime
] ≥ 2 × ( [
- 870 -
BridgeMaxAge
]
] + 1.0������.
6F2T0207 (0.01)
(11.2-1)
(11.2-2)
GRE200 (5,6)
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