North American Network Operators Group|
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How common is lack of DNS server diversity?
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 18.104.22.168 DNSAUTH2.SYS.GTEI.NET 22.214.171.124 DNSAUTH3.SYS.GTEI.NET 126.96.36.199 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 188.8.131.52 AUTH60.NS.UU.NET 184.108.40.206 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.