Re: [RRG] Are we solving the wrong problem?

["Mark Handley" <M.Handley@cs.ucl.ac.uk>]

On Wed, Mar 5, 2008 at 3:42 PM, marcelo bagnulo braun
<marcelo@it.uc3m.es> wrote:
> Hi Pekka,
>
>  El 05/03/2008, a las 6:39, Pekka Nikander escribió:
>
>
>  ...
>
> >>
>  >
>  > The biggest differences between your thinking and HIP seems to be
>  > that HIP is implemented below TCP, so that it works also for UDP.  I
>  > think it matches better with the IP semantics, as a single IP
>  > address is (today) typically associated with a number of co-located
>  > TCP and UDP end-points.
>  >
>  > Then there is also work specific to TCP, e.g Christian Huitema's
>  > eTCP (or whatever it was called).
>  >
>  > I'm glad to see that more people come to the roughly same
>  > conclusions, independently.  :-)
>  >
>
>  right, but i think that what is missing in all these proposals is to
>  understand the interaction with congestion control, which may be
>  critical if they get deployed.

Absolutely.  The stable load-balancing properties come out of using
multiple links simultaneously in such a way that congestion on one
path causes more bytes to be sent the other way.  But crucially it
must not move all the traffic the other way, or the system is unstable
and can oscillate backwards and forwards between the multiple paths.
This is the reason why I think you can solve the problem at L4 without
changing the apps (or at the application layer, but only if you change
the apps), but I don't think you get the same properties if you solve
the problem below layer 4.

 - Mark

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