On Tue, Apr 04, 2023 at 06:40:55PM +0200, Havard Eidnes wrote:
> > ; ANSWER
> > ; AUTHORITY
> > example.com. IN NS ns1.provider.net.
> > example.com. IN NS ns2.provider.net.
> >
> > is a valid delegation response (and so not from this perspective a LAME
> > delegation), whether or not the target servers actualy serve the zone.
>
> I agree that this is a valid delegation response. I do however
> disagree with the latter part of this sentence; it *may* be a
> "lame delegation" depending on the response you as a recursive
> resolver get from the two delegated-to name servers when you try
> to look up a name in the example.com zone.
At the time such a delegation response is being processed by a resolver,
it looks just fine. Nothing to see here, move along (down the tree)...
> > A LAME delegation (response) happens when "ns1" or "ns2" respond to
> > queries with yet another (e.g. self) delegation that does not move the
> > resolver closer to the target:
> >
> > ; ANSWER
> > ; AUTHORITY
> > example.com. IN NS ns1.provider.net.
> > example.com. IN NS ns2.provider.net.
>
> I am having problems seeing under what normal-ish circumstances
> either ns1 or ns2 would provide this response.
I can't tell you **why** they do it, but there are many that do in fact
respond with non-productive delegations:
; .COM:
ksyunv5.com. 172800 IN NS ns1.ksyuncdn.com.
ksyunv5.com. 172800 IN NS ns2.ksyuncdn.com.
ksyunv5.com. 172800 IN NS ns3.ksyuncdn.com.
---
; .ksyunv5.com:
jshsos.ksyunv5.com. NS ns4.bpldns.com.
jshsos.ksyunv5.com. NS ns3.bpldns.com.
---
; .jshsos.ksyunv5.com:
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 12951
;; flags: qr; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;lzd.jshsos.ksyunv5.com. IN AAAA
;; AUTHORITY SECTION:
jshsos.ksyunv5.com. NS ns4.bpldns.com.
jshsos.ksyunv5.com. NS ns3.bpldns.com.
Another example, a more "normal" upward referral:
; .CO.UK:
healthwize.co.uk. 172800 IN NS ns.mainnameserver.com.
healthwize.co.uk. 172800 IN NS ns2.mainnameserver.com.
---
; healthwize.co.uk:
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42663
;; flags: qr; QUERY: 1, ANSWER: 0, AUTHORITY: 13, ADDITIONAL: 0
;; QUESTION SECTION:
;healthwize.co.uk. IN A
;; AUTHORITY SECTION:
. NS a.root-servers.net.
. NS b.root-servers.net.
. NS c.root-servers.net.
. NS d.root-servers.net.
. NS e.root-servers.net.
. NS f.root-servers.net.
. NS g.root-servers.net.
. NS h.root-servers.net.
. NS i.root-servers.net.
. NS j.root-servers.net.
. NS k.root-servers.net.
. NS l.root-servers.net.
. NS m.root-servers.net.
Non-productive (LAME) delegation responses are sadly all too common.
--
Viktor.
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