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full-flow-control

what's the difference between duplex full and duplex

full-flow-control, which has the better performance?

thanks.

1 REPLY
Cisco Employee

Re: full-flow-control

Assuming that this quesiton refers to Fast / Gigabit Ethernet - the difference between full-duplex and full-duplex flow-control is that:

Essentially, in the latter, 802.3x flow control would be enabled. This enables a device to respond to and/or iniate 'pause' frames to/from the link partner. Consequently the transmitter temporarily reduces the amount of data being sent. This is done to prevent buffer-overflow (dropped packets) on the receiver. UniverCD will provide config details and defaults for each platform/sw type - for example on the cat6000 check out the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_6_3/cmd_ref/set_po_r.htm#30647

The question of better performance depends.... If the implementation can handle it ie both end devices have enough 'horsepower' to process the tx/rx rates, then full-duplex alone is faster. However, if there is an issue wrt buffering/horsepower rates, then flow-control may help prevent packet drops and the resulting time spent in packet re-transmission.

rgds

steve

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