Siemens SIMATIC ET 200SP HA, System Manual

Page: 23 / 186

Plant planning
4
4.1 Topology
An overview of various options for setting up a PROFINET network is given below.
Linear
All the communication nodes are connected in a linear bus topology.
If a connecting element (for example switch) fails, data exchange beyond the failed connecting
element is no longer possible.
For PROFINET the line topology is implemented with switches that are integrated in the IO
devices. Therefore, the linear bus topology at PROFINET is merely a special form of tree / star
topology.
Linear bus topology structures require the least wiring.
Ring
In order to increase the availability of a network, use ring structures. In principal, a linear
topology is connected to a ring through a so-called redundancy manager. Typical redundancy
managers are:
● CPU that supports the Media Redundancy Protocol (MRP)
● Communication processor that supports the Media Redundancy Protocol (MRP)
● External switch (SCALANCE X)
If there is a break in the network, the redundancy manager ensures that the data is redirected
over an intact network connection.
Star
When IO devices are connected to a switch with more than two PROFINET ports, a star
topology arises automatically.
Unlike in other structures, if an individual IO device fails, this does not necessarily result in
failure of the entire network. The failure of the switch results in the failure of the IO devices
connected to this switch.
Tree
If you interconnect multiple star structures, a tree-shaped topology arises.
Line
MRP
Star
ET 200SP HA Distributed I/O system
System Manual, 08/2019, A5E39261167-AD
23