Network emulation with Bering-uClibc - Advice on adding "netem" support to iproute2

[davidMbrooke]

Hi,

I want to test how a client-server application responds to high latency,
packet loss etc. - i.e. typical WAN characteristics - within a lab
environment, so what I need is a WAN emulator. Ideally I'd like to
extend LEAF (Bering-uClibc) to do this.

Initially I tried using NIST Net (http://snad.ncsl.nist.gov/nistnet/)
since this seems well-regarded and will run on a Linux 2.4 kernel. I got
this mostly working on Bering-uClibc 3.1.1-Beta1 but the big problem for
me is that NIST Net only operates as a Router, not as a Bridge. I'd much
prefer to have a machine that I can "transparently" insert between a
client and a server, and that needs to be an Ethernet Bridge.

Then I came across Netem (http://www.linuxfoundation.org/en/Net:Netem)
which can be used with a Bridge as well as a Router. I was delighted to
find that the "netem" kernel module is already included in Bering-uClibc
so the only extra component required is a netem-aware version of "tc",
from iproute2.

Right now the main iproute source file for Bering-uClibc is
iproute_20010824.orig.tar.gz which does not contain the netem code that
I need. Judging by the style of the filename this is a Debian source
package, the latest equivalent of which seems to be
iproute_20080725.orig.tar.gz (from
http://ftp.debian.org/debian/pool/main/i/iproute/) and this does include
the netem code; there's also a iproute_20080725-2.diff.gz patch.

Is this a sensible approach? In particular is it sensible to use the
Debian source package rather than the upstream source code from
http://www.linuxfoundation.org/en/Net:Iproute2 ?


Thanks,

david M brooke


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[KP Kirchdoerfer-2]

Am Sonntag, 15. Februar 2009 19:01:53 schrieb davidMbrooke:

> Hi,
>
> I want to test how a client-server application responds to high latency,
> packet loss etc. - i.e. typical WAN characteristics - within a lab
> environment, so what I need is a WAN emulator. Ideally I'd like to
> extend LEAF (Bering-uClibc) to do this.
>
> Initially I tried using NIST Net (http://snad.ncsl.nist.gov/nistnet/)
> since this seems well-regarded and will run on a Linux 2.4 kernel. I got
> this mostly working on Bering-uClibc 3.1.1-Beta1 but the big problem for
> me is that NIST Net only operates as a Router, not as a Bridge. I'd much
> prefer to have a machine that I can "transparently" insert between a
> client and a server, and that needs to be an Ethernet Bridge.
>
> Then I came across Netem (http://www.linuxfoundation.org/en/Net:Netem)
> which can be used with a Bridge as well as a Router. I was delighted to
> find that the "netem" kernel module is already included in Bering-uClibc
> so the only extra component required is a netem-aware version of "tc",
> from iproute2.
>
> Right now the main iproute source file for Bering-uClibc is
> iproute_20010824.orig.tar.gz which does not contain the netem code that
> I need. Judging by the style of the filename this is a Debian source
> package, the latest equivalent of which seems to be
> iproute_20080725.orig.tar.gz (from
> http://ftp.debian.org/debian/pool/main/i/iproute/) and this does include
> the netem code; there's also a iproute_20080725-2.diff.gz patch.
>
> Is this a sensible approach? In particular is it sensible to use the
> Debian source package rather than the upstream source code from
> http://www.linuxfoundation.org/en/Net:Iproute2 ?

You're right, we've used the source from debian plus a few patches.
So using a newer debian source is no worse than the upstream source as long as
it works with Bering-uClibc.
Let us know if you can compile and if it works for you. Maybe we can update
for a future version...

kp

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[davidMbrooke]

On Mon, 2009-02-23 at 10:56 +0100, KP Kirchdoerfer wrote:

> Am Montag, 16. Februar 2009 21:52:51 schrieben Sie:
>
> Hi;
> just back from visting my relatives (to explain slow response time :))
>
> I appreciate your plan to write a chapter for the User's Guide - and you're
> right, there is no specific documentation for Bering-uClibc and traffic
> shaping. You may be "misleaded" because the shorewall stuff has originally
> written by Arne Bernin who worked also a lot on Bering-uClibc.
>
> If you find in your testing, that the new iproute version works as expected
> pls send me the buildtool.cfg and .mk so I can add it to my testing
> environment and probably later into next version.
>
> thx kp
>

Hi KP,

No need to explain - we all have other things to do than LEAF...
I remembered to send my reply to the list rather than just you this
time :-)

Bering-uClibc-3.1.1-beta2 is now working well for me (minor issues with
the i2c modules as per my mail just now to leaf-users) so at the weekend
I will replace tc.lrp, etc.lrp and root.lrp with my new iproute2
versions and start testing. If it works OK I will certainly send you my
buildtool files.

dMb




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