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Spanning Tree
Redundancy L2B
Release 6.0 07/2010
3.1 Sub-Ring
39
4 Spanning Tree
Note:
The Spanning Tree Protocol is a protocol for MAC bridges. For this
reason, the following description employs the term bridge for Switch.
Local networks are getting bigger and bigger. This applies to both the
geographical expansion and the number of network participants. Therefore,
it is advantageous to use multiple bridges, for example:
X
to reduce the network load in sub-areas,
X
to set up redundant connections and
X
to overcome distance limitations.
However, using multiple bridges with multiple redundant connections
between the subnetworks can lead to loops and thus the total failure of the
network. In order to avoid this, you can use Spanning Tree. Spanning Tree
enables loop-free switching through the systematic deactivation of redundant
connections. Redundancy ensures the systematic reactivation of individual
connections as needed.
RSTP is a further development of the Spanning Tree Protocol (STP) and is
compatible with it. If a connection or a bridge fails, the STP required a
maximum of 30 seconds to reconfigure. This is no longer acceptable in time-
sensitive applications. RSTP achieves average reconfiguration times of less
than a second. When you use RSTP in a ring topology with 10 to 20 devices,
you can even achieve reconfiguration times in the order of milliseconds.
Note:
RSTP reduces a layer 2 network topology with redundant paths into a
tree structure (Spanning Tree) that does not contain any more redundant
paths. One of the Switches takes over the role of the root bridge here. The
maximum number of devices permitted in a branch (from the root bridge to
the tip of the branch) is specified by the variable
Max Age
for the current root
bridge. The preset value for
Max Age
is 20, which can be increased up to 40.
If the device working as the root fails and another device takes over its
function, the
Max Age
setting of the new root bridge determines the
maximum number of devices allowed in a branch.
Содержание MACH 1040 Series
Страница 8: ...Key 8 Redundancy Release 6 0 07 2010...
Страница 12: ...Introduction 12 1 2 Overview of Redundancy Protocols Redundancy Release 6 0 07 2010...
Страница 26: ...Ring Redundancy 26 2 2 Example of an MRP Ring Redundancy Release 6 0 07 2010...
Страница 38: ...Multiple Rings 38 3 1 Sub Ring Redundancy Release 6 0 07 2010...
Страница 76: ...Index 76 4 7 Combining RSTP and MRP Redundancy Release 6 0 07 2010...
Страница 78: ......