North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Looking for geo-directional DNS service
On Jan 15, 2008, at 3:03 PM, Joe Greco wrote: Except Hank is asking for true topological distance (latency / throughput / packetloss). You are not disagreeing with me. I was responding to Woody who said: On Jan 15, 2008, at 12:00 PM, Bill Woodcock wrote: [...]Yes, and that's how anycast works: it directs traffic to the _topologically nearest_ server. If you're doing things on the Internet, instead of the physical world, Unless you define "topologically nearest" as "what BGP picks", that is incorrect. And even if you do define topology to be equivalent to BGP, that is not what is of the greatest interest. "Goodput" (latency, packet loss, throughput) is far more important. IMHO. If you don't like my example, then ignore Ashburn and take a random, medium-sized network. Now assume an anycast node which is topologically (i.e. latency, bit-miles, throughput, whatever your definition) closer through transit, compared to a node topologically farther away through peering. Which is chosen? And this is not even close to an unusual situation. This in no way means anycast sux. It just means anycast is not, by a long shot, guaranteed to give you the "closest" node by any reasonable definition. (Sorry, I don't think "node BGP picks" is "reasonable". You are welcome to disagree, but the point still stands that other definitions of "reasonable" are not satisfied.) In general, anycast is better than not-anycast, and can be optimized to be better than non-anycast for nearly all user by someone with enough clue + money + time. This is not in question. It is essentially impossible to guarantee anycast is better than any other solution for all applications and all end users, especially over time as the Internet changes. This is not in question either. -- TTFN, patrick Anycast by itself probably isn't entirely desirable in any case, and could
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