Siemens ESM - Manual (Page 29)

Functions
Industrial Ethernet OSM/ESM
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Functions
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This chapter discusses the general functions of the OSM/ESM, in particular the
properties of the switching technology.
Increased Network Performance
By filtering the data traffic based on the Ethernet (MAC) address of the DTEs,
local data traffic remains local, only data intended for nodes in another network
segment are passed on by the OSM or ESM. This reduces the data traffic in the
network segments and lowers the network load in the network segments.
Simple Network Configuration and Network Expansion
OSMs and ESMs store the data received at the ports and the direct it to the
destination address. The restriction of the network span resulting from collision
detection (CSMA/CD) ends at the OSM/ESM port. With multimode graded-index
fibers, a total network span of up to 150 km and more can be achieved without
problems. With the OSM ITP62-LD, the monomode fibers allow a network span of
up to 1300 km.
Limitation of Errors to the Network Segment Affected
OSMs and ESMs only pass on valid data. Invalid packets are discarded so that
bad packets within a network segment have no effect on any other segment
attached to the OSM/ESM.
Learning Addresses
By evaluating the source addresses in the data packets, OSMs/ESMs
automatically learn the addresses of the DTEs attached via a particular port. If an
OSM/ESM receives a data packet, it directs this packet only to the port via which
the appropriate DTE can be obtained.
An OSM/ESM can learn up to 7000 addresses.