Versioning (Re: [idn] The layers and character handling in DNS)

[Harald Alvestrand <Harald@Alvestrand.no>]

At 11:16 18/02/2001 -0500, John C Klensin wrote:
>(ii) We have a really good versioning model so that someone
>applying Nameprep can know what rules to use.  If
>NamePrep2001(string) != NamePrep2002(string) and one can't tell
>which one should be applied, I think that, long-term, the whole
>thing deteriorates badly.   Given an obvious variation of the F1
>!= F2 argument, I suspect (but haven't worked through the cases
>to my satisfaction yet) that means that the relevant version
>information needs to be encoded in the names themselves.  I.e.,
>the real test is whether
>   NamePrepN(F1(X,Z))=NamePrepM(F2(X,Z))   and whether
>   M and N can be determined in all places in which it is relevant
>(which would be especially important if the equality doesn't
>apply --it won't, or one wouldn't need NamePrep versions-- and
>one needs to know which version to apply.

actually versioning nameprep does not work, for any case but the one where 
a string illegal in NameprepM is now legal in NameprepN (M < N).

for this case, one can assume that 1) the name is installed using NameprepN 
(since M would disallow it) and that 2) the owner doesn't care that he is 
not reachable under NameprepM (or he would have chosen another).

For the case of NameprepM <> NameprepN, we can store the info on which name
to use:
- in the human-readable string. Will be pelted with rotten bananas.
- in the DNS entry for the name. But since we can't get to the DNS-stored 
entry before we have done nameprep, the chicken-and-egg conundrum strikes 
again.
- in the global /hosts.txt file?????

For any existing name, Nameprep can't change.


--
Harald Tveit Alvestrand, alvestrand@cisco.com
+47 41 44 29 94
Personal email: Harald@Alvestrand.no