[RFCI-Discuss] Interesting Question

[Derek J. Balling]

OK, I'm not going to claim to understand the DNS RFCs nearly as well  
as others.

Ponder the output of something like, a.root-servers.net:

$ dig @a.root-servers.net megacity.org ns

; <<>> DiG 9.2.4 <<>> @a.root-servers.net megacity.org ns
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44736
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 6, ADDITIONAL: 6

;; QUESTION SECTION:
;megacity.org.                  IN      NS

;; AUTHORITY SECTION:
org.                    172800  IN      NS      TLD1.ULTRADNS.NET.
org.                    172800  IN      NS      TLD2.ULTRADNS.NET.
org.                    172800  IN      NS      TLD3.ULTRADNS.org.
org.                    172800  IN      NS      TLD4.ULTRADNS.org.
org.                    172800  IN      NS      TLD5.ULTRADNS.INFO.
org.                    172800  IN      NS      TLD6.ULTRADNS.CO.UK.

;; ADDITIONAL SECTION:
TLD1.ULTRADNS.NET.      172800  IN      A       204.74.112.1
TLD2.ULTRADNS.NET.      172800  IN      A       204.74.113.1
TLD3.ULTRADNS.org.      172800  IN      A       199.7.66.1
TLD4.ULTRADNS.org.      172800  IN      A       199.7.67.1
TLD5.ULTRADNS.INFO.     172800  IN      A       192.100.59.11
TLD6.ULTRADNS.CO.UK.    172800  IN      A       198.133.199.11

;; Query time: 16 msec
;; SERVER: 198.41.0.4#53(a.root-servers.net)
;; WHEN: Sun Dec  4 16:34:43 2005
;; MSG SIZE  rcvd: 288

.... there is no ANSWER section, only an AUTHORITY section, telling  
me that "Hey, I'm not really sure the answer, the authoritative  
answer is down that-away."

Similarly, if I was to query ultradns:

$ dig @tld1.ultradns.net megacity.org ns

; <<>> DiG 9.2.4 <<>> @tld1.ultradns.net megacity.org ns
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23445
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 3

;; QUESTION SECTION:
;megacity.org.                  IN      NS

;; AUTHORITY SECTION:
megacity.org.           86400   IN      NS      ns3.megacity.org.
megacity.org.           86400   IN      NS      ns2.megacity.org.
megacity.org.           86400   IN      NS      ns1.megacity.org.

;; ADDITIONAL SECTION:
ns3.megacity.org.       86400   IN      A       65.221.104.162
ns2.megacity.org.       86400   IN      A       64.142.22.245
ns1.megacity.org.       86400   IN      A       65.221.104.161

;; Query time: 44 msec
;; SERVER: 204.74.112.1#53(tld1.ultradns.net)
;; WHEN: Sun Dec  4 16:35:41 2005
;; MSG SIZE  rcvd: 132

... it tells me "nope, the authoritative answer is thataway, but  
here's some glue in case you need it."

Why is it, then, that if I was to query gtld-servers.net servers,  
looking for a .com domain, I get something completely different?

$ dig @a.gtld-servers.net yahoo.com ns

; <<>> DiG 9.2.4 <<>> @a.gtld-servers.net yahoo.com ns
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43866
;; flags: qr rd; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 5

;; QUESTION SECTION:
;yahoo.com.                     IN      NS

;; ANSWER SECTION:
yahoo.com.              172800  IN      NS      ns1.yahoo.com.
yahoo.com.              172800  IN      NS      ns2.yahoo.com.
yahoo.com.              172800  IN      NS      ns3.yahoo.com.
yahoo.com.              172800  IN      NS      ns4.yahoo.com.
yahoo.com.              172800  IN      NS      ns5.yahoo.com.

;; ADDITIONAL SECTION:
ns1.yahoo.com.          172800  IN      A       66.218.71.63
ns2.yahoo.com.          172800  IN      A       66.163.169.170
ns3.yahoo.com.          172800  IN      A       217.12.4.104
ns4.yahoo.com.          172800  IN      A       63.250.206.138
ns5.yahoo.com.          172800  IN      A       216.109.116.17

;; Query time: 17 msec
;; SERVER: 192.5.6.30#53(a.gtld-servers.net)
;; WHEN: Sun Dec  4 16:36:47 2005
;; MSG SIZE  rcvd: 197

.... as near as I can tell this is the absolute *worst* condition  
possible, or should be from my understanding of the DNS results:

(a) the "aa" flag is not set. The answer is not considered  
authoritative.
(b) there are "0" authority records sent. No direction is given as to  
where one might find an authoritative answer

So, if you were only paying attention to "the authority path", you  
could never track down a domain through the gtld-servers.net responses.

Clearly the world hasn't ended, so what am I missing? Does the world  
just work around an archaic/broken configuration on the existing .COM  
servers? Is there some voodoo that I'm missing?

And, bonus points to anyone except Ralf or Phil Kizer who can guess  
why I noticed this discrepancy....

Cheers,
D