Pilz PSSnet SHL 8T MRP - Manual (Page 55)

Rapid Spanning Tree
PSSnet SHL - Redundancy Configuration
Pilz GmbH & Co. KG, Felix- Wankel Str. 2, 73760 Ostfildern
4.1 The Spanning Tree Protocol
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4.1 The Spanning Tree Protocol
Because RSTP is a further development of the STP, all the following
descriptions of the STP also apply to the RSTP.
4.1.1 The tasks of the STP
The Spanning Tree Algorithm reduces network topologies that are set up
using bridges, and that have ring structures with redundant connections, to a
tree structure. In doing this, STP divides up the ring structures on the basis
of specified rules by deactivating redundant paths. If a path is interrupted by
mistake, the STP reactivates the path just deactivated. This enables redun-
dant connections for increased data safety.
In forming the tree structure, the STP determines what is known as a root
bridge. This forms the basis of the STP tree structure.
Features of the STP algorithm:
X automatic reconfiguration of the tree structure in the case of a bridge error
or the interruption of a data path
X the tree structure is stabilized up to the maximum network size (up to
39
hops, depending on the setting for “Max. Age”)
X stabilization is effected within a brief, specified period
X topology can be specified and reproduced by the administrator
X transparency for the terminal devices
X low network load relative to the available transmission capacity due to the
tree structure created