Internet Draft: Let 'localhost' be localhost
On the one hand, this isn't exactly a new idea and in the real world has been happening for years now.* dnscache from djbdns has handled "localhost." queries internally all along, since 1999.  It maps "localhost." to 127.0.0.1 and bgack again.  Various people, including me, have since added code to do the same thing with the mappings between "localhost." and ::1.  (http://jdebp.eu./Softwares/djbwares/guide/dnscache.html)  I implemented implicit localhost support in my proxy DNS servers for OS/2, as well.* It is conventional good practice to have a db.127.0.0 and a master.localhost "zone" file on BIND that do this.  This is in Chapter 4 of the book by Albitz and Liu, for example.* Unbound has built-in "local zone" defaults mapping between "localhost." and both 127.0.0.1 and ::1.On the other hand, this proposal explicitly rules out all of the aforementioned existing practice, by demanding that both proxy and content DNS servers instead return "no such domain" answers for the domain name "localhost.".  That seems like a fairly pointless deviation from what is fast approaching two decades of existing practice, for which no rationale is given and none is apparent.