
Active Components and Topologies
6-19
SIMATIC NET Tw isted-Pair and Fiber-Optic Networks
C79000-G8976-C125-02
6.2.6 Linking Subnets Using the OSM/ESM
Subnets
Using the OSM/ESM, it is possible to link several different Ethernet networks
together. The collision domain of a subnet ends at the port of the OSM/ESM.
OSMs/ESMs are ideal for structuring larger networks. Large networks are first
divided into smaller units (subnets). These subnets are then connected to the
OSM/ESM that not only interconnects them but also separates them in terms of
load. The time and effort required for network configuration and expansion is
considerably reduced.
Network Expansion
Selectively forwarding data to the addressed nodes contains the load in the
subnets/segments. Discarding bad data also brings about a further improvement in
network performance.
These properties make the OSM/ESM the ideal tool for expanding conventional
Ethernet networks that have otherwise reached their limits.
OLM
OLMOLM
ELM ELM
1 ITP standard cable 9/15
2 ITP XP standard cable 9/9
2
2
2
1
3 Fiber-optic cable (FO)
3
4
4
5
4 727-1 drop cable
5 Triaxial cable
ELM ELM
4
4
5
ESM ITP 80
Figure 6-11 Linking Several Collision Domains/Subnets Using an ESM
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