Switch Operation; Address Table; Learning; Forwarding & Filtering - Planet Networking & Communication igs-801m User Manual

User's Manual of IGS-801M

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.
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