Planet FSD-2405 [11/18] 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.

The 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 Ethernet

Switching can be easily congured in any Ethernet network environment to

signicantly boost bandwidth using conventional cabling and adapters.