SCALANCE X-400
Operating Instructions, 06/2015, C79000-G8976-C186-12
13
Description
3
3.1
Basic information on Ethernet switching
Ethernet switching
Ethernet switches forward data packets directly from the input port to the appropriate output
port during data exchange based on the address information. Ethernet switches operate on a
direct delivery basis.
Essentially, switches have the following functions:
●
Connection of collision domains / subnets
Since repeaters and star couplers (hubs) operate at the physical level, their use is
restricted to the span of a collision domain. Switches connect collision domains. Their use
is therefore not restricted to the maximum span of a repeater network. On the contrary,
extremely large networks with large spans are possible with switches.
●
Containing load
By filtering the data traffic based on the Ethernet (MAC) addresses, local data traffic
remains local. In contrast to repeaters or hubs, which distribute data unfiltered to all ports
/ network nodes, switches operate selectively. Only data intended for nodes in other
subnets is switched from the input port to the appropriate output port of the switch. To
make this possible, a table assigning Ethernet (MAC) addresses to output ports is
created by the switch in a "teach-in" mode.
●
Limiting errors to the affected subnet.
By checking the validity of a data packet on the basis of the checksum which each data
packet contains, the switch ensures that bad data packets are not transported further.
Collisions in one network segment are not passed on to other segments.
The need for Industrial Ethernet switches
With over 95% of LANs based on Ethernet, this is the most commonly used technology. The
use of switches is particularly important. They allow extensive networks with large numbers
of nodes to be set up, increase the data throughput, and simplify network expansion.
The modular IE Switches X-400 from SIMATIC NET are designed for use in high-speed plant
networks that will also meet future requirements. Thanks to their modular design, the
IE Switches X-400 can be adapted to the task in hand in terms of number of ports and
transmission medium. Due to support of IT standards such as VLAN, RSTP, IGMP, and
GARP makes seamless integration of automation networks in existing office networks
possible.
The devices are designed for use in switching cubicles and cabinets.
