RUGGEDCOM RSG2488
User Guide
Chapter 5
Setup and Configuration
RSTP in Ring Backbone Configurations
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To design a structured wiring coniguration, do the following:
1.
Select the design parameters for the network.
What are the requirements for robustness and network failover/recovery times? Are there any special
requirements for diverse routing to a central host computer? Are there any special port redundancy
requirements?
2.
Identify required legacy support.
Are STP bridges used in the network? These bridges do not support rapid transitioning to forwarding. If these
bridges are present, can they be re-deployed closer to the network edge?
3.
Identify edge ports and ports with half-duplex/shared media restrictions.
Ports that connect to host computers, Intelligent Electronic Devices (IEDs) and controllers may be set to
edge ports in order to guarantee rapid transitioning to forwarding as well as to reduce the number of topology
change notifications in the network. Ports with half-duplex/shared media restrictions require special attention
in order to guarantee that they do not cause extended fail-over/recovery times.
4.
Choose the root bridge and backup root bridge carefully.
The root bridge should be selected to be at the concentration point of network traffic. Locate the backup root
bridge adjacent to the root bridge. One strategy that may be used is to tune the bridge priority to establish
the root bridge and then tune each bridge’s priority to correspond to its distance from the root bridge.
5.
Identify desired steady state topology.
Identify the desired steady state topology taking into account link speeds, offered traffic and QOS. Examine
of the effects of breaking selected links, taking into account network loading and the quality of alternate links.
6.
Decide upon a port cost calculation strategy.
Select whether fixed or auto-negotiated costs should be used? It is recommended to use the auto-negotiated
cost style, unless it is necessary for the network design to change the auto-negotiated cost style. Select
whether the STP or RSTP cost style should be used. Make sure to configure the same cost style on all
devices on the network.
7.
Enable RSTP Fast Root Failover option.
This is a proprietary feature of RuggedCom. In a mesh network with only RuggedCom devices in the core
of the network, it is recommended to enable the RSTP Fast Root Failover option to minimize the network
downtime in the event of a Root bridge failure.
8. Calculate and configure priorities and costs.
9. Implement the network and test under load.
Section 5.2.2.2
RSTP in Ring Backbone Configurations
RSTP may be used in ring backbone configurations where rapid recovery from link failure is required. In normal
operation, RSTP will block traffic on one of the links, for example, as indicated by the double bars through link H
in
Figure 86, “Example - Ring Backbone Configuration”
. In the event of a failure on link D, bridge 444 will unblock
link H. Bridge 333 will communicate with the network through link F.
