PLANET ISW-504PS - Manual (Page 77)

User’s Manual
5. SWITCH OPERATION
5.1 Address Table
The Switch is implemented with an address table. This address table composed of many entries. Each entry is used to
store the address information of some node in network, including MAC address, port no, etc. This information comes
from the learning process of Industrial Ethernet Switch.
5.2 Learning
When one packet comes in from any port, the Industrial Switch will record the source address, port no. And the other
related information in address table. This information will be used to decide either forwarding or filtering for future
packets.
5.3 Forwarding & Filtering
When one packet comes from some port of the Industrial Ethernet Switch, it will also check the destination address
besides the source address learning. The Industrial Ethernet Switch will lookup the address-table for the destination
address. If not found, this packet will be forwarded to all the other ports except the port which this packet comes in.
And these ports will transmit this packet to the network it connected. If found, and the destination address is located at
different port from this packet comes in, the Industrial Ethernet Switch will forward this packet to the port where this
destination address is located according to the information from address table. But, if the destination address is
located at the same port with this packet comes in, then this packet will be filtered. Thereby it will increase the network
throughput and availability.
5.4 Store-and-Forward
Store-and-Forward is one type of packet-forwarding techniques. A Store-and Forward Ethernet Switching stores the
incoming frame in an internal buffer, do the complete error checking before transmission. Therefore, no error packets
occurrence, it is the best choice when a network needs efficiency and stability.
The Industrial Ethernet Switch scans the destination address from the packet-header, searches the routing table
provided for the incoming port and forwards the packet, only if required. The fast forwarding makes the switch
attractive for connecting servers directly to the network, thereby increasing throughput and availability. However, the
switch is most commonly used to segment existing hubs, which nearly always improves overall performance. An
Industrial Ethernet Switch can be easily configured in any Ethernet network environment to significantly boost
bandwidth using conventional cabling and adapters.
Due to the learning function of the Industrial Ethernet switch, the source address and corresponding port number of
each incoming and outgoing packet are stored in a routing table. This information is subsequently used to filter
packets whose destination address is on the same segment as the source address. This confines network traffic to its
respective domain, reducing the overall load on the network.
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