Final Sigma (was: RE: Esszett, Final Sigma, ZWJ and ZWNJ)

[Patrik Fältström]

27 feb 2009 kl. 23.51 skrev Mark Andrews <Mark_Andrews at isc.org>:

>
> In message <C9732258727F2347EB29508B at PST.JCK.COM>, John C Klensin  
> writes:
>>
>>
>> --On Thursday, February 26, 2009 22:03 -0800 Erik van der Poel
>> <erikv at google.com> wrote:
>>
>>> Just an afterthought, but if it really is impossible to add a
>>> new field to DNS, one might imagine a new HTTP response header
>>> that contains the hint. Of course, one would have to come up
>>> with other ideas for protocols other than HTTP, but I hope you
>>> get the gist.
>>
>> I should let one of the DNS experts who follow the list respond
>> to this, but...
>>
>> Nothing is impossible, but this comes close.
>>
>> It is far more complex than this because of rules about caching,
>> additional information, and RR set integrity, but looking data
>> up separately for two separate RRs (if that is what you mean by
>> "field" causes the DNS overhead for IDNs to double (probably not
>> acceptable) and introduces race conditions and vulnerabilities
>> to attack (certainly not acceptable if we care anything about
>> conditions).
>
>    A quick think would have a record that contains a directionality
>    indicator.  It would also have a raw domainname containing
>    the UTF8 encoded name.  One would want it to be able to
>    exist along side CNAMEs (this would be another exception
>    like RRSIG and requires changes to both caches and authoritative
>    servers).  One would want the ttl to be the longest of all
>    the other ttls at the name.

It is much worse. You might have multiple rr's in the same or  
different rrset's (2 cases) with the same owner that want different  
behaviour.

   Patrik

>
>
>    For a cache/application to accept it the UTF8 name MUST map
>    back to the owner name.
>
>    Do we neeed to support multiple UTF8 names and if so how do
>    we tell the application which one to display in which context?
>
>    The next question is which queries need it added to the
>    additional section?  All of them?  Specific types?  How
>    does it interact with SRV records where the name of interest
>    is several label shorter?  I would also be adjusting the
>    TTL on transmission to be the minumum of the record's ttl
>    and the maximum of the other ttls with the same owner names.
>    Additional section processing requires changes to authoritative
>    servers and caches to be completely effective.
>
>    Mark
>
> -- 
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org
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