Planet SW-504 [12/16] Switch operation

3. SWITCH OPERATION

3.1 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 Ethernet

Switch.

3.2 Learning

When one packet comes in from any port, the 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

ltering for future packets.

3.3 Forwarding & Filtering

When one packet comes from some port of the Ethernet Switching,

it will also check the destination address besides the source address

learning. The Ethernet Switching 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 Switching 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 ltered.

Thereby increase the network throughput and availability.

3.4 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 efciency and stability.