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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Alternative to BGP-4 for multihoming?
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
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