This network is too good...

Leo Bicknell bicknell at
Thu Feb 2 02:21:35 UTC 2012

In a message written on Wed, Feb 01, 2012 at 08:51:13PM -0500, Robert E. Seastrom wrote:
> Any thoughts on products that screw up networks in deterministic (and
> realistic found-in-the-wild) ways?  I'm thinking of stuff like
> PacketStorm, Dummynet, etc.  Dial up jitter, latency, tail drop, RED,
> whatever...
> (I know someone's gonna say "Just buy a Brand Z FubarSwitch 3k, they
> will screw up your whole network and you don't even have to configure
> it to do so!")

The only good L2 solutions I've ever seen are expensive commercial
testing.  DummyNet, on a L3 aware FreeBSD box is extremely useful and
easy to configure to simulate varous loss or latency patterns.

What tool is right depends on if you want to test at L2 (simulate a
circuit/cable with a particular problem) or L3 (just a router in the
middle dropping packets), or testing an end user application.  L2,
particularly if you want to simulate things like a duplex mismatch is
hard, and not often needed.

If your goal is to test applications against network conditions, OSX has
a nifty new tool, "Network Link Conditioner".  It's basically just
dummynet with various throughput, delay, and packet loss settings but it
makes it dead simple to select from various pull downs.

I bring it up mainly because if you want to set your own DummyNet
settings for other testing it's a nice database of average case
performance for a number of link types!

       Leo Bicknell - bicknell at - CCIE 3440
        PGP keys at
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