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Re: [LUG] OT: openDNS

 

> I don't understand this?! How does it abuse the technology? Why is it no
> good for email?

The whole point of the DNS is to delegate control to an appropriate
authority, not for 3rd parties to stick their finger in an say "no we
think cia.gov email should go here....". Or this address isn't as it
should be.

The DNS lookup doesn't say what the purpose of the lookup is. So if one
was checking email addresses for validity say, have example.iy returned
as example.it, might not be the action you wanted.

The fundamental problems with OpenDNS arise from this blindness to
purpose, and trying to poke in areas that they are not the delegated
authority for (like the root zone).

Which is why mistyped domains are probably best corrected by the
browser, or browser plugin, as they can be application aware (know you
just typed a URL in). Most browsers already do this for you anyway, as
you'd have discovered if you mistyped URLs before. If you hadn't noticed
this feature of most browsers, one probably didn't need OpenDNS in the
first place.

And yes, larger caches will produce faster DNS lookups, but in most
cases the saving per novel domain is less than 1/3rd of a second last
time I tested this. It really isn't a big issue for most people except
people running huge mailing lists (or other mechanical reasons for
multiple DNS lookups), when a local cache is usually recommended.  This
1/3 of a second was measured against Demon Internet's caching DNS
servers, if your DNS cache is geographically further away than your ISPs
caching servers the benefits will be correspondingly less.

One could of course provide large caches, without messing with the data
in any arbitrary way, which would give performance benefits without
creating any of the other issues.

Usually DNS lookup time is only an issue if it isn't being cached
locally, most browsers are over aggressive in caching DNS lookup
results, in that they cache the result for longer than it is supposedly
valid.

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