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4. Switch Operation
4.1 MAC Address Table and Learning
The switch is implemented with a MAC address table which is composed
of many entries. Each entry is used to store the address information of network
nodes on the network, including MAC address, port ID, etc. The information is
the most important base to do packet filtering and forwarding.
When one packet comes in from any port, the switch will learn the source
address, port ID, and the other related information in address table. Therefore,
the content of the MAC table will update dynamically.
4.2 Filtering and Forwarding
When one packet comes in from any port of the switch, it will check the
destination address besides the source address learning. The switch will look up
the address table for the destination address. If not found, this packet will be
forwarded to all the other ports except the port in which this packet comes. If
found, and the destination address is located at different port from this packet
comes in, the packet will be forwarded to the port where this destination
address is located according to the information of address table. But, if the
destination address is located at the same port as this packet comes in then this
packet will be filtered.
4.3 Store and Forward
Store-and-forward is one kind of packet-forwarding methodology. As a
store-and-forward switching hub, it will store the complete packet in the
internal buffer and do the complete error checking before transmitting to the
network. Therefore, no error packets will disturb the network. It is the best
choice when a network needs efficiency and stability.
