Allied Telesis XS910/8, Manual

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Chapter 1: Product Description
23
Ethernet Switching Basics
An Ethernet switch interconnects network devices, such as workstations,
printers, routers, and other Ethernet switches, so that they can
communicate with each other by sending and receiving Ethernet frames.
Duplex Mode
The AT-XS910/8 switch operates in the full-duplex mode.
Store-and-
Forward
The AT-XS910/8 switch uses store-and-forward as the method for
receiving and transmitting frames. When an Ethernet frame is received on
a switch port, the switch does not retransmit the frame out the destination
port until it has received the entire frame and stored the frame in a port
buffer. It then examines the frame to determine if it is a valid frame. Invalid
frames, such as fragments or runts, are discarded by the switch. This
insures that only valid frames are transmitted out the switch ports and that
damaged frames are not propagated on your network.
Flow Control
Flow Control is a mechanism to manage the rate of data transmission
between two nodes and prevent a faster sender from overwhelming a
slower receiver. An Ethernet switch may periodically need to signal an
end-node to stop sending data. When two end-nodes are operating at
different speeds, the switch, while transferring data between the
end-nodes, might need to instruct the faster end-node to stop transmitting
data to allow the slower end-node to catch up. An example of this would
be when a server operating at 10Gbps is sending data to a workstation
operating at only 1Gbps.
The ports on the AT-XS910/8 switch use PAUSE frames, as specified in
the IEEE 802.3x standard, to stop the transmission of data from an
end-node. Whenever the switch wants an end-node to stop transmitting
data, it issues this frame. The frame instructs the end-node to cease
transmission for a period of time specified within the frame. The switch
continues to issue PAUSE frames until it is ready again to receive data
from the end-node.