7.3.2 Flow Control
With a link operating at a high data rate, a switch may experience occasional limitations in the buffer space used to store Ethernet frames before forwarding them. In this situation, if the sending station continues to send frames, the switch will have no option but to discard the frames. This may quickly lead to unacceptable delays in
In order to avoid unnecessarily dropping frames, a switch may implement Flow Control. Flow control is a feature that allows the switch to recognize when the buffer space is limited, and to send an Ethernet PAUSE frame to its link partner to cease transmission for a specified period. As with a
7.3.3 Auto-Negotiation
As discussed previously, make sure that both ends of a link agree about the duplex and flow control settings to be used (as well as the speed of the connection). In even a
To make configuration as automatic as possible, the IEEE has defined standards so that most connections can be automatically configured by the hardware, without manual intervention. Devices can agree on the speed, duplex mode, and flow control settings for each individual connection. The possible links states are ranked:
1000 Mbps/Full Duplex
1000 Mbps/Half Duplex
100 Mbps/Full Duplex
100 Mbps/Half Duplex
10 Mbps/Full Duplex
10 Mbps/Half Duplex
With
Note: If an Ethernet device that is capable of
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