North American Network Operators Group|
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Re: Alternative to BGP-4 for multihoming?
> >> 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. ------- Peter Van Oene Senior Systems Engineer UNIS LUMIN Inc. www.unislumin.com