NODATA type 3 with CNAME

[James Ponder]

Hi

Can someone clarify for me the section in RFC 2308 on type 3 NODATA
responses when there is a CNAME?

The RFC shows an example where the response is a NOERROR with 0 answers,
0 authorities and 0 additionals, indicating that this is a type 3 NODATA
response, and then goes on to say that a CNAME could also be included,
"in which case it would be the value of the last CNAME for which NODATA
would be concluded."

The reason for my question is that all 4 of the authoritative
nameservers for news.bbc.co.uk respond with what looks to me like a type
3 NODATA response, but clearly news.bbc.co.uk is very popular and works
well.

$ dig news.bbc.co.uk @212.58.224.21                                         
; <<>> DiG 9.3.4-P1.1 <<>> news.bbc.co.uk @212.58.224.21
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 12148
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;news.bbc.co.uk.                        IN      A

;; ANSWER SECTION:
news.bbc.co.uk.         3600    IN      CNAME   newswww.bbc.net.uk.

;; Query time: 25 msec
;; SERVER: 212.58.224.21#53(212.58.224.21)
;; WHEN: Sat Aug  2 01:11:13 2008
;; MSG SIZE  rcvd: 62

Thanks

James