Switch operation, 1 address table, 2 learning – PLANET GS-4210-8P2T2S User Manual

Page 325: 3 forwarding & filtering, 4 store-and-forward

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User’s Manual of GS-4210-8P2T2S

5. SWITCH OPERATION

5.1 Address Table

The Switch is implemented with an address table. This address table is composed of many entries. Each entry is used to store

the address information of some nodes on the network, including MAC address, port no, etc. This information comes from the

learning process of Ethernet Switch.

5.2 Learning

When one packet comes in from any port, the Switch will record the source address, port number and the other related

information in the address table. This information will be used to decide either forwarding or filtering for future packets.

5.3 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 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, 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 a 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 the

address table. But, if the destination address is located at the same port with this packet, then this packet will be filtered, thereby

increasing the network throughput and availability

5.4 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 and does the complete error checking before transmission. Therefore, no error packets occur. It is the

best choice when a network needs efficiency 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 existence

hubs, which nearly always improves the overall performance. An Ethernet Switching can be easily configured in any Ethernet

network environment to significantly boost bandwidth using the conventional cabling and adapters.

Due to the learning function of the Ethernet switching, the source address and corresponding port number of each incoming and

outgoing packet is stored in a routing table. This information is subsequently used to filter packets whose destination address is

on the same segment as the source address. This confines network traffic to its respective domain and reduces the overall load

on the network.

The Switch performs "Store and forward"; therefore, no error packets occur. More reliably, it reduces the re-transmission rate.

No packet loss will occur.

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