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

[David Williamson <dlw+rrg@tellme.com>]

On Tue, Feb 19, 2008 at 05:35:09AM +0000, Mark Handley wrote:
> So, what happens if we stop trying to hide the multihoming.  Take a
> server at this multi-homed site and give it two IP addresses, one from
> each provider's aggregated prefix.  Now we modify TCP to use both
> addresses *simultaneously* - this isn't the same as SCTP, which
> switches between the two.  The client sets up a connection to one
> address, but in the handshake learns about the other address too.  Now
> it runs two congestion control loops, one with each of the server's IP
> addresses.  Packets are shared between the two addresses by the two
> congestion control loops - if one congestion-controlled path goes
> twice as fast as the other, twice as many packets go that way.

Interesting idea, but not all critical traffic is TCP.  My site, for
example, depends on UDP based applications.  My customers (generally
Fortune 100 companies) aren't really interested in routing scale
problems, but just want the service I offer to work.  That requires me,
in the current world, to multihome a whole pile of PI allocations.
While my announcements are pretty efficient, I'm clearly one of the
problem sites you try to address, yet your solution is inapplicable for
the vast majority of traffic.

A simple approach might be to try to stripe UDP traffic across all
available paths.  I hope it is obvious why this is a bad idea with
real-time traffic.

For me, at least, your solution is only a half-solution.  Interesting,
but I think I agree with Geoff that this needs to get fixed in the
network layer. 

-David

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