Chris Adams writes:
Do you see g.root-servers.net listed? Then why are you asking it about com?
Because it is a root server. Note its appearance in the set of NS records below for ',', for example. If you ask g about 'com', and instead of giving an answer like the one a.ROOT-SERVERS.NET gave you, it says it *does not exist*, you will, correctly, assume that means it doesn't exist and neither do any subdomains. Hence, if you randomly query the one server that is returning NXDOMAIN for com, all com lookups will fail. Servers must be able to follow the delegation chain, which starts at the root. The fact that a.ROOT-SERVERS.NET thinks g.root-servers.net is not authoritative doesn't matter much if you ask g and it does think it is authoritative. jmalcolm@nodens [~] [main] 2-875> dig ns @a.ROOT-SERVERS.NET . ; <<>> DiG 8.2 <<>> ns @a.ROOT-SERVERS.NET . ; (1 server found) ;; res options: init recurs defnam dnsrch ;; got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6 ;; flags: qr aa rd; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 13 ;; QUERY SECTION: ;; ., type = NS, class = IN ;; ANSWER SECTION: . 6D IN NS A.ROOT-SERVERS.NET. . 6D IN NS H.ROOT-SERVERS.NET. . 6D IN NS C.ROOT-SERVERS.NET. . 6D IN NS G.ROOT-SERVERS.NET. . 6D IN NS F.ROOT-SERVERS.NET. . 6D IN NS B.ROOT-SERVERS.NET. . 6D IN NS J.ROOT-SERVERS.NET. . 6D IN NS K.ROOT-SERVERS.NET. . 6D IN NS L.ROOT-SERVERS.NET. . 6D IN NS M.ROOT-SERVERS.NET. . 6D IN NS I.ROOT-SERVERS.NET. . 6D IN NS E.ROOT-SERVERS.NET. . 6D IN NS D.ROOT-SERVERS.NET. ;; ADDITIONAL SECTION: A.ROOT-SERVERS.NET. 6D IN A 198.41.0.4 H.ROOT-SERVERS.NET. 6D IN A 128.63.2.53 C.ROOT-SERVERS.NET. 6D IN A 192.33.4.12 G.ROOT-SERVERS.NET. 6D IN A 192.112.36.4 F.ROOT-SERVERS.NET. 6D IN A 192.5.5.241 B.ROOT-SERVERS.NET. 6D IN A 128.9.0.107 J.ROOT-SERVERS.NET. 5w6d16h IN A 198.41.0.10 K.ROOT-SERVERS.NET. 5w6d16h IN A 193.0.14.129 L.ROOT-SERVERS.NET. 5w6d16h IN A 198.32.64.12 M.ROOT-SERVERS.NET. 5w6d16h IN A 202.12.27.33 I.ROOT-SERVERS.NET. 6D IN A 192.36.148.17 E.ROOT-SERVERS.NET. 6D IN A 192.203.230.10 D.ROOT-SERVERS.NET. 6D IN A 128.8.10.90 ;; Total query time: 313 msec ;; FROM: nodens.uraeus.com to SERVER: a.ROOT-SERVERS.NET 198.41.0.4 ;; WHEN: Fri Aug 4 10:06:31 2000 ;; MSG SIZE sent: 17 rcvd: 436