On Wed, Oct 8, 2008 at 8:14 AM, Ryan Malayter <[EMAIL PROTECTED]> wrote: > 2) Predictable routing - Almost no internet path of mroe than a few > hops is symmetric. This behavior is almost guaranteed by BGP and the > "cold-potato" routing scheme used by all major ISPs. The NTP protocol > assumes symmetric network paths, but that is a bad assumption on the > Internet, unless the servers are very close in the network sense.
Ooops. I obviously meant "hot-potato" routing, not "cold-potato". You can examine this behavior using a traceroute tool on a site such as www.dnsstuff.com. For example, when I use DNSstuff to traceroute to my network, the path is essentially Dallas/theplanet->Dallas/glbx->Dallas/xo->Chicago/xo When I traceroute in the other direction, from my network to the DNSstuff servers, the path is: Chicago/xo->Chicago/level3->Denver/level3->Dallas/level3->Dallas/theplanet. Clearly there is a systemic asymmetry in that network path. Basically, all ISPs dump traffic that is not destined for their own network to the nearest applicable peering point, which results in route asymmetry on the Internet. If two hosts exchanging traffic are close geographically, it is far more likely that the peering point chosen by both ISPs will be the same peering point. -- RPM _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
