North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: How common is lack of DNS server diversity?
And what happens if the 4.0.0.0/8 route is flapped from the routing table? No more DNS. So you still want route diversity that isn't in the same block or aggregated block. Then I guess you try and get a bunch of /24's for your name servers but they might get filtered elsewhere by someone else. Thomas Sean Donelan wrote: > > Mice and Men found that 38% of the .COM domains surveyed > had all their name servers on the same subnet. And 75% > had one or more configuration errors. > > http://www.menandmice.com/dnsplace/healthsurvey.html > > DNS, like most databases, suffers from information entropy. > > In other words, it takes a lot of energy to keep information > correctly updated while it is being changed. Anyone who has > been Hostmaster for even a moderately sized ISP knows there > is an amazing number of ways for people to mess up any of the > pieces of data required to make the whole thing work. > > As several people pointed out, you can't really assume close > IP addresses are in fact topologically close on the network. > > For example, if you look at the name severs for GENUITY.NET > > Domain servers in listed order: > > DNSAUTH1.SYS.GTEI.NET 4.2.49.2 > DNSAUTH2.SYS.GTEI.NET 4.2.49.3 > DNSAUTH3.SYS.GTEI.NET 4.2.49.4 > > They appear to be closely related. However, the addresses are > in fact routed to very diverse locations on Genuity's network. > > You will find the same thing if you look at the name servers > for UU.NET > > Domain servers in listed order: > > AUTH00.NS.UU.NET 198.6.1.65 > AUTH60.NS.UU.NET 198.6.1.181 > > These servers are also geographically diverse. > > So I'm not sure if the 38% number is a true indication of how > much diversity DNS servers have.
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