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 full duplex link, both ends of the link must understand flow control for the mechanism to operate properly.
7.3.3 Auto-Negotiation
As discussed above, you need to 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:
1000Mbps/Full Duplex 1000Mbps/Half Duplex (never used) 100Mbps/Full Duplex 100Mbps/Half Duplex 10Mbps/Full Duplex 10Mbps/Half Duplex
With
Note: If an Ethernet device that is capable of
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