[RFC] simulating network properties for benchmarks
Carl Friedrich Bolz
cfbolz at gmx.de
Thu Jul 20 22:00:52 BST 2006
This mail is trying to start a discussion about various approaches on
how to test different network properties (latency, bandwidth, dns
latency, etc). The test should be repeatable, somewhat easily doable
(e.g. not involving a huge setup) and realistic.
During the performance-sync meeting we discussed briefly two general
approaches for this:
* Using a proxy/decorator for a transport that adds some sort of
artificial overhead to every operation, like time.sleep or similar.
This has the advantage of being relatively easy to implement but the
disadvantage of being quite unrealistic, since the operations on the
transport don't really map in a straightforward manner to what is
going on at packet level.
* Simulating network properties on a lower level. If done right, this
would be quite realistic. It may be harder to implement (but Robert
hinted that he might have some ideas how to do it easily). The
only somewhat simple idea I have currently is using netem
(see http://linux-net.osdl.org/index.php/Netem) to slow down network
operations. Works only under Linux and some care has to be taken to
get it right.
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