Re: artificial latency for a network interface

[Burkhard Daniel]

I had a similiar problem once, and wrote a module that overwrote the
loopback net device. Since it's loopback, the kernel won't care about
headers.

Yeah, I know: Quick & Dirty.

I made the new loopback put its packets in a queue and then deliver them
after a (adjustable) delay.

If I can still find the source for this, I'll post it here.

Burk.

On Fri, 29 Jun 2001, Andrew Morton wrote:

> Andreas Schuldei wrote:
> > 
> > to simulate a sattelite link, I need to add a latency to a
> > network connection.
> > 
> > What is the easiest and best way to do that?
> > 
> > I wanted to do that using two tun devices.
> > I had hoped to have a routing like this:
> > 
> >  <-> eth0 <-> tun0 <-> userspace, waiting queue <-> tun1 <-> eth1
> 
> yes, that works very well.  A userspace app sits on top of the
> tun/tap device and pulls out packets, delays them and reinjects
> them.
> 
> The problem is routing: when you send the packet back to the
> kernel, it sends it straight back to you.  You need to rewrite
> the headers, which is a pain.
> 
> A simpler approach is to use policy routing - use the source
> and destination devices to override the IP addresses.  Works
> well.  The code is at
> 
> 	http://www.uow.edu.au/~andrewm/packet-delay.tar.gz
> 
> It has its own variable bandwidth management as well
> as variable latency.  It's for simulating narrowband, high
> latency connections.
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