Re: Alternative to BGP-4 for multihoming?

[adrian () creative net au]

On Mon, Mar 13, 2000, Peter A. van Oene wrote:
> > > Its these cases I'm concerned with.  In my mind, irrespective of the
> > > comments on the functionality of DNS for this purpose, I see little
> other
> > > choice.
> >
> > DNS is not the droid you're looking for.
> >
> > Using DNS response times to predict likely TCP performance is silly for at
> > least as many reasons as using BGP aspath lengths to predict likely TCP
> > performance is silly.
> >
> > > That being said, if anyone has better ideas on how to provide for high
> > > availability to millions of web sites worldwide, please let me know.
> >
> > TCP performance is affected by congestion symmetry, since TCP uses the
> > spacing of ACK packets to control the spacing of data packets.  While
> > there's no way to guarantee congestion symmetry, one of the leading
> > indicators of whether you will have congestion symmetry is "whether you
> > have path symmetry."  Furthermore, the leading indicator of whether you
> > have path symmetry is "whether the outbound flow's first hop is the same
> > as the incoming flow's last hop."
>
> Just a quick note in clarification, I am less interested in intelligently
> directing the traffic to the closest or most optimal server farm that I am
> in purely ensuring that the traffic can be balance between sites that sit
> within different AS's.  


How do you propose to do this? It is a non trivial solution - if you
don't believe me, go ask someone trying to do it (eg Akami). 

People forget the magic tenant things are built on here - "The less the
control you have on a network, the harder you have to work to
deliver a given quality of service", where quality of service is
something other than 'terrible' .





Adrian