Siemens X-400 - Manual (Page 141)

Glossary
Operating Instructions for SCALANCE X-400 Industrial Ethernet Switches
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MDI Medium Dependent Interface, - straight
On an MDI port or MDI cable, the receive (Rx) and the send (Tx) leads
are not crossed.
MDI-X Medium Dependent Interface – crossover,
On an MDI-X port or MDI-X cable, the receive (Rx) and the send (Tx)
leads are crossed.
MIB Management Information Base. The MIB is a formal description of net-
work objects in the form of a tree structure that contains all the relevant
information for network management in SNMP.
Mirroring A port (mirror port) with its specific data traffic can be mirrored to an-
other port (monitor port) for test purposes. Protocol analysis devices
can be connected to the monitor port, in other words, the monitor port
is not available for data exchange. Mirroring has no effect on the mirror
port.
Modes Modes are discrete waves used to transmit data within a fiber-optic
cable. With single mode fibers, only one wave propagates, whereas in
multimode fibers several waves propagate. Modes are patterns of elec-
tromagnetic fields in FOCs.
Multimode In multimode transmission, the pulse is transferred using many modes
(waves) that travel along curved paths or are reflected within the core.
Attenuation is mainly caused by physical absorption and dispersion as
well as by mechanical bending. The amount of attenuation depends
among other things on the wavelength of the input light. Multimode
fiber-optic cables have an outer diameter of 125 µm and 50 or 62.5 µm
core diameter. Due to the larger core diameter the pulse edges de-
grade more than in single mode transmission resulting in shorter
transmission distances.
OSM Optical Switching Module – SIMATIC NET Ethernet switch with optical
ports.
Rapid spanning tree The Rapid Spanning Tree protocol (RSTP) allows redundant transmis-
sion paths. This prevents circulating frames and, if a fault develops,
provides an alternative path within one second (reconfiguration time).
Reconfiguration time The time required to restore a functional configuration if a device fails
or a network cable is interrupted.