Siemens SCALANCE X-200 Specifications download pdf (Page 7)

SCALANCE X-300

Operating Instructions, 01, A5E01113043

Description

2.1 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 very large spans are possible with switches. The distances

achieved depend on the fiber-optic interfaces used in the devices and the FO fibers used

(see technical specifications).

• 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 IE Switches X-300 from SIMATIC NET are designed for use in high-speed plant

networks that will also meet future requirements. With the HSR redundancy function and

standby coupling of rings, high network availability can be achieved. Support of IT standards

such as VLAN, RSTP, IGMP, and GARP makes seamless integration of automation

networks in existing office networks possible.

The IE Switches X-300 are designed for use in switching cubicles and cabinets.

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Siemens SCALANCE X-200 Specifications Page 7