RCODE: Not Implemented

[Mark]

When querying my name servers for a resource record type that I am sure they
don't implement ( SRV, SIG  ) named ummmm........ works.  That is it tells
me that there aren't any such records.
I thought that named would respond with the RCODE in the response packet set
to  "NOT IMPLEMENTED" at least for the older name servers.
I get this behavior from BIND 4.9.7, 8.1.2 & 8.2.2 name servers. Is dig
altering the query somehow?
I notice that nslookup won't even let you send such a query if it doesn't
recognize the RR type.
If this is so then when does named reply with "NOT IMPLEMENTED"??

Regards,

Mark

$ dig  SIG cookie.com

; <<>> DiG 8.1 <<>> SIG cookie.com
; (1 server found)
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 2
;; QUERY SECTION:
;;      cookie.com, type = SIG, class = IN

;; AUTHORITY SECTION:
cookie.com.             2D IN NS        ADMIRAL.INTERPAGE.NET.
cookie.com.             2D IN NS        INTERPAGE.NET.

;; ADDITIONAL SECTION:
ADMIRAL.INTERPAGE.NET.  2D IN A         204.75.164.2
INTERPAGE.NET.          2D IN A         204.75.164.1

;; Total query time: 2 msec
;; FROM: ValleyForge to SERVER:
;; WHEN: Wed Aug  9 10:56:45 2000
;; MSG SIZE  sent: 28  rcvd: 109