Planet Technology SGSW-4802 - Manual (Page 77)

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5. SWITCH OPERATION
5.1 Address Table
The Managed 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 Managed Switch.
5.2 Learning
When one packet comes in from any port. The Managed 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 con-
nected. 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 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, 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 Managed 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. A 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 respective domain, reducing the overall load on
the network.
The Managed 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 SGSW-4802 switch have built-in "Auto-negotiation". This technology auto-
matically sets the best possible bandwidth when a connection is established with another network
device (usually at Power On or Reset). Detecting the modes does this and speeds at the second of
both devices are 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/1000Base-SX can only connected in
Full-duplex mode.