Planet Technology SW-501 Appendix B Switch Operation, Address Table, Learning, Store-and-Forward

Appendix B SWITCH OPERATION

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 infor- mation of some node in network, including MAC address, port no, etc. The information comes from the learning process of Ethernet Switch.

Learning

When one packet comes in from any port, the Ethernet Switch will record the source address, port no. and the other related information in address table. These information will be used to decide either forwarding or filtering for future packets.

Forwarding & Filtering

When one packet comes from some port of the Ethernet Switch, it will also check the destination address besides the source address learning. The 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 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, when this packet will be filtered. Thereby increasing the network throughput and availability

Store-and-Forward

Store-and-Forward is one type of packet-forwarding techniques. A Store-and-Forward Ethernet Switch stores the incoming frame in an inter- nal 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 Switch scans the destination address from the

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