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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 information 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 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 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. A Ethernet Switch can be easily configured in
any Ethernet network environment to significantly boost bandwidth using conventional cabling and
adapters.