This network is too good...

Jensen Tyler JTyler at
Fri Feb 3 03:20:08 UTC 2012

netem - 

"netem provides Network Emulation functionality for testing protocols by emulating the properties of wide area networks. The current version emulates variable delay, loss, duplication and re-ordering." 

I have used this in the lab, works OK. You can use it with the bridge util to stay layer 2.

-----Original Message-----
From: Juuso Lehtinen [mailto:juuso.lehtinen at] 
Sent: Thursday, February 02, 2012 9:02 PM
To: Robert E. Seastrom
Cc: nanog at
Subject: Re: This network is too good...

You have pretty much two approaches:
-Special built hardware network emulators
-Network emulator software running on generic PC

Special built HW:
If you need extreme accuracy, i.e., delay generation to micro/nanosecond
accuracy, you need to go with special purpose boxes. Special built HW also
usually provides line rate throughput, regardless of impairments you are

I have experience using Anue Systems GEM/XGEM and Calnex Paragon-X network
emulators. Both tools are special built hardware platforms that allow
generating various network impairments (delay, jitter, packet reordering,
packet loss, CRC errors, etc.).

In my opinion Anue is easier to use. It provides Web GUI where you can
configure different impairment profiles. Calnex on the other hand requires
you to install a Client software on your Windows PC. In the end, both
products support pretty much the same features. There are some differences
if you are doing specific testing with network synchronization protocols,
like SyncE or 1588v2 (PTPv2).

Network emulator SW on generic PC:
I have very little experience on running SW based network emulators. I used
to play with one that was running on Linux box - unfortunately I cannot
remember the software name. The linux software was ok for introducing
packet loss, but way inaccurate when it comes to delay insertion. If
accuracy of tens of milliseconds is good enough for you, the software based
approach might be good for you.

On Wed, Feb 1, 2012 at 5:51 PM, Robert E. Seastrom <rs at> wrote:

> Hi all,
> 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!")
> I'm all-ears like Ross Perot.
> Thanks,
> -r

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