[c-nsp] cheap core switch for a "hacker space" (nonprofit association)

[Phil Mayers]

On 09/12/13 14:47, Markus H wrote:

> I don't think microbursts are that much of a problem for us. I at least
> don't see them impacting the VM host sending a backup to the file server,

That's *exactly* the sort of thing that microbursts tend to impact.

The basic problem is:

  port A sends to port B at 1Gbit/sec
  port C sends a burst of 10 packets to port B every X seconds
  port A TCP flow drops, and recovers relatively slowly
  repeat
  A->B bulk throughput is a small fraction of the link rate

> or even several of us pushing photos/videos from an event we attended onto
> the owncloud instance. (If anyone however has some nice article that I
> should read on microbursts feel free to send a link my way.)

There's extensive discussion on this in the list archives, but the basic 
idea is simple; tiny bursts of traffic, often back-to-back / linerate 
(e.g. as a result of 10kb of data being send via TSO NIC offload) cause 
other TCP flows to sawtooth.

They may not be a problem for you - we used the 3750s for years without 
problems - but don't underestimate how annoying they can be.