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5. SWITCH OPERATION
5.1 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.
5.2 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 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 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 filtered. Thereby increasing the network throughput and avail-
ability.
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, do the complete error checking before transmission. Therefore, no error
packets occurrence, 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 existing hubs, which nearly always improves overall performance. An Ethernet
Switching can be easily configured in any Ethernet network environment to significantly boost bandwidth using
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 are 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 re-
spective domain, reducing 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.
5.5 Auto-Negotiation
The STP ports on the Switch have built-in "Auto-negotiation". This technology automatically sets the best possible
bandwidth when a connection is established with another network device (usually at Power On or Reset). This is
done by detect the modes and speeds at the second of both device is connected and capable of, both 10Base-T and
100Base-TX devices can connect with the port in either Half- or Full-Duplex mode. 1000Base-T can be only con-
nected in Full-duplex mode.