Re: [dnsext] WGLC ENDS0-bis

[Joao Damas <[e-mail]>]

On 23 May 2011, at 23:08, Edward Lewis wrote:

> At 23:00 +0200 5/23/11, Florian Weimer wrote:
>> * Olafur Gudmundsson:
>> 
>>> This document obsoletes RFC2671.  The big changes from RFC2671 are:
>>>   - explicit usage of RFC2119 terms and labeling EDNS0 support as MUST;
>>>   - discussion on payload sizes and selection;
>>>   - closing of the extended label types registry and classifying
>>>        bit-labels as Historic;
>>>   - cleanup of IANA actions (that did not take place when RFC2671
>>>       was issued).
>> 
>> I would like to see guidance to implementors how they can actually
>> detect EDNS0 support or the lack thereof.  Alternatively, a minimum
>> level of support could be made mandatory, eventually making the
>> existing detection logic obsolete.
> 
> As far as declaring "a minimum level of support": an RFC cannot say "you must implement me, even if you were implemented last year." That just doesn't work.
> 

Yep.

> For backwards compatibility, we are stuck with probing for functionality.  This is a weakness of the DNS architecture.
> -- 

DNS transactions are meant to take a minimum of resources on either side. That is kind of contrary to a feature negotiation handshake ahead of the query (though one could cache a server's characteristics after the first exchange if the two messages, query and response, are able to transport that information. I think that's all that could be said here

Joao