Re: FTP benchmark proposal

Malcolm Beattie (mbeattie@sable.ox.ac.uk)
Mon, 28 Jun 1999 10:13:09 +0100 (BST)


Oliver Xymoron writes:
> On 27 Jun 1999, Andi Kleen wrote:
>
> > lm@bitmover.com (Larry McVoy) writes:
> > >
> > > with each of the "c" machines masquerading as a pile of clients. The
> > > reason for that is that we want to generate the real pcb lookup load
> > > on the server so it has to think that it is talking to 6000 clients.
> >
> > The hard thing will be to simulate slow/timing out connections that occur over
> > the internet. Just low-latency local networking with no lost packets is easy.
> >
> > So perhaps something like a NISTNET box is needed inbetween?
>
> How about hacks to the traffic shaper on the client machines?

That's what I was thinking about too. Although I don't know if it
needs hacks. It may work as is.

> Choose some
> distribution function for bandwidth and latency for clients and randomly
> generate pipes that accommodate said parameters. Right now, of course,
> shaper only does bandwidth, since no one in RL wants to add latency, but
> it should be doable without too much pain. We can also make shaper do a
> more realistic simulation of congestion to generate stalls, etc.

If Alexey's 2.2 "tc" is anything like Alan's 2.0 "shaper" then I
thought it did the best and only decent way of shaping: dropping
packets on the floor so that TCP treats it like congestion. The other
part of the plan was to use Alexey's new routing stuff to simulate
lots of separate bandwidth-limited clients on one box. Allocate the
whole box a good chunk of the 10/8 network, and use
route-by-source-address to route each one via a separate tc qdisc.
Then the client side of the benchmark consists of forking a lot, each
child creates and binds a socket to its own 10.x.y.z address and the
magic of iproute2+tc will make each one into its own low bandwidth
connection. There's so much that's tweakable in the new routing engine
that I'd guess we could simulate plenty of slow clients fairly
realistically.

--Malcolm

-- 
Malcolm Beattie <mbeattie@sable.ox.ac.uk>
Unix Systems Programmer
Oxford University Computing Services

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