Slow networks

Interesting points from http://highscalability.com/blog/2011/6/1/why-is-your-network-so-slow-your-switch-should-tell-you.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+HighScalability+%28High+Scalability%29


Network operators get calls from application guys saying the network is slow, but the problem is usually dropped packets due to congestion. It's not usually latency, it's usually packet loss. Packet loss causes TCP to back off and retransmit, which causes applications to appear slow.

Packet loss can be caused by a flakey transceiver, but the problem is usually network congestion. Somewhere on the network there's fan-in, a bottleneck develops, queues build up to a certain point, and when a queue overflows it drops packets. Often the first sign of this happening is application slowness.