I like this draft. I think the penultimate paragraph of section 2 is a bit confusing. I suggest (starting with the existing text, for context)...
To do such minimisation, the resolver needs to know the zone cut [RFC2181]. Zone cuts do not necessarily exist at every label boundary. If we take the name www.foo.bar.example, it is possible that there is a zone cut between "foo" and "bar" but not between "bar" and "example". So, assuming the resolver already knows the name servers of .example, when it receives the query "What is the AAAA record of www.foo.bar.example", (new text) it does not know how many labels it needs to append before it will find the zone cut. If it uses QNAME minimization, it will guess there is a cut between "bar" and "example" so it will query the .example name servers for the NS records for bar.example. It will get a NODATA response, indicating there is no cut at that point, so it has to to query the .example name servers again with a longer name. Without QNAME minimization, it would send the .example nameservers a query for www.foo.bar.example and immediately get a referral for foo.bar.example, without the need for more queries to probe for the zone cut. Section 6 discusses this performance discrepancy further. (end) (I can't see anything that describes a way to find a zone cut in RFC 2181 - just, "The existence of a zone cut is indicated in the parent zone by the existence of NS records specifying the origin of the child zone" which is less than a suggestion, merely a vague hint that only the clueful will grok.) Regarding the last paragraph of section 6, I think the IPv6 reverse DNS is the best place to find names with lots of labels but few zone cuts. (But your current example is just like where I work...) Tony. -- f.anthony.n.finch <d...@dotat.at> http://dotat.at/ Shannon: North or northeast 4 or 5, increasing 6 at times. Slight or moderate. Occasional thundery rain. Moderate or good. _______________________________________________ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
