Siemens ESM - Manual (Page 45)

Network Topologies with OSM/ESM
Industrial Ethernet OSM/ESM
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3.5 Coupling Network Segments
A network segment can be connected to each of the ports of an OSM/ESM.
The Ethernet Planning Rules:
• Sum of the delay equivalents and cable lengths in the worst-case path shorter
than 4520 m
• Sum of the variability values in the worst-case path less than 50 bit times
need only be maintained as previously in each individual segment (see also
"SIMATIC NET Industrial Twisted Pair and Fiber Optic Networks" manual).
The coupling of network segments via OSM has further advantages:
• The collision domain ends at the OSM ports and the network segments
attached to them, the permitted total network span increases.
• Only valid data packets are passed on via OSM ports. Network segments with
problems cannot influence other network segments.
• Data packets are only passed on to the ports to which the DTE with the
destination address is connected. The available transmission capacity
increases since the local data traffic of a network segment no longer puts load
on another network segment.