>It SHOULD be done before the request enters theDNS service interface.
To achieve interoperability, canonicalisation MUST be done at a single well-defined place in the DNS resolution process. One could imagine either doing it in the client resolver or in the server. Whichever place is selected, this must be really clearly specified for us to have global interoperability with the DNS protocol.
Your proposal appears to say it is in the DNS resolver client.
+---------------+
| Application |
+---------------+
| Application service interface
| For ex. GethostbyXXXX interface
+---------------+
| Resolver |
+---------------+
| <----- DNS service interface
+-------------------------------------------+--Paul Hoffman, Director --Internet Mail Consortium