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What is the conventional wisdom regarding 802.3x flow control?

I'm setting up a network at a new colo and am wondering if I should be enabling it or not. My oh-cool-a-bright-and-shiny-new-toy self wants to enable it, but this seems like one of those decisions that could blow up in my face later on.

My network:

  • An HP ProCurve 2510G-24 switch
  • A pair of Debian 5 HP DL380 G5's with built-in NC373i 2-port NIC LACP'd as one link. 9000 jumbo frames enabled. (Application)
  • A pair of hand-built Ubuntu server with 4-port Intel Pro/1000 LACP'd as one link. 9000 jumbo frames enabled. (NAS)
  • A few other servers with with single 1Gbps ports, but one with 100Mbps.

Most of this kit is 802.3x. I've been enabling it as I go along, and am about to test the network. But as my 'go live' day nears, I am worried about the 802.3x decision as I've never explicitly used it before. Also, I've read some 10-year old articles out there on the Intertubes that warn against using flow control.

Should I be enabling 802.3x hardware flow control?

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Experience here has been that 802.3x is very rarely what you want. In most circumstances you would be better served by either upgrades to the link speeds if there is congestion, or the implementation of "real" QoS/CoS (DSCP and 802.1p).

The behavior of 802.3x has also been known to interact poorly with protocols with their own flow control such as TCP.

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