[e2e] TCP Local Area Normal behaviour? any references?

[Jonathan M. Smith]

Why not do it on WiFi?
-JMS


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Jonathan M. Smith
Olga and Alberico Pompa Professor of Engineering and Applied Science
Professor of Computer and Information Science, University of Pennsylvania
Levine Hall, 3330 Walnut Street, Philadelphia, PA 19104

On Fri, 21 Jan 2005, Craig Partridge wrote:

>
> In message <Pine.LNX.4.58.0501211436140.11281 at tesla.psc.edu>, Matt Mathis write
> s:
>
> >I think capture effect does not become a problem unless the end-system and
> >routers/switches can send true back-to-back packets for a large portion of the
> >window.  Just a small amount of idle makes the channel arbitration much more
> >fair.  It might be kind of interesting to try to reconstruct the Boggs result
> >with modern PC's.....
>
> Sounds like great fun.  Let's see, what would the experiments be (always
> fun to do experimental science on the fly)....
>
> Van tested a single TCP connection over cable (in the old days when you
> actually tapped into a cable!) with just two hosts.  He used two different
> Ethernet adapters (and showed that one couldn't go full line rate, and
> the other could).  It seems to me that in today's world you'd do this
> experiment four ways:
>
>     * single cable, two hosts (which I think you can do with a crossover
>       cable), one TCP connect.
>
> 	    This is about as close as we can get to Van's original
> 	    experiment.  Note that the length of the cable may matter
> 	    (and should be tested)
>
>     * same experiment but with a switch in between
>
> 	    Probably try multiple switches.
>
>     Notes: probably worth doing at various TCP window sizes, to eliminate/
>      identify window effects -- e.g., the delay bandwidth product is probably
>      small, but worth computing, especially through the switch.
>
>      If one is feeling ambitious, one could also do 802.11 (both direct
>        and through a hub).
>
> Boggs and Mogul tested an Ethernet by using 1 to 25 hosts that
> concurrently each tried to send 20 seconds of fixed length packets
> as fast as possible.  During the middle 10 seconds it measured a bunch
> of stats (which may or may not be accessible from current adapters).
> They also experimented with cable length effects.  I think you can't
> quite replicate it now, but you can certainly load up a single switch
> (probably want an 8-port) and also try networks with more than one
> switch.  There's also a question of what the max capacity of the network
> is, if the switch is full duplex on all ports (you may end up measuring
> the switch backplane if you're not careful).
>
> My gut says the Jacobson experiment is the easier one to replicate and may
> reveal a lot on its own.  I don't have time to do this experiment, but happy
> to help if someone else wants to take it on.
>
> Craig
>