Question on ADDITIONAL SECTION

[pyh at mail.nsbeta.info]

$ dig www.cnn.com @202.96.128.166 

; <<>> DiG 9.4.2-P2 <<>> www.cnn.com @202.96.128.166
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 65353
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 0 

;; QUESTION SECTION:
;www.cnn.com.                   IN      A 

;; ANSWER SECTION:
www.cnn.com.            133     IN      A       157.166.226.25
www.cnn.com.            133     IN      A       157.166.226.26
www.cnn.com.            133     IN      A       157.166.255.18
www.cnn.com.            133     IN      A       157.166.255.19
www.cnn.com.            133     IN      A       157.166.224.25
www.cnn.com.            133     IN      A       157.166.224.26 

;; Query time: 5 msec
;; SERVER: 202.96.128.166#53(202.96.128.166)
;; WHEN: Thu Dec 30 19:07:17 2010
;; MSG SIZE  rcvd: 125 


$ dig www.cnn.com @61.144.56.100 

; <<>> DiG 9.4.2-P2 <<>> www.cnn.com @61.144.56.100
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10034
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 3, ADDITIONAL: 3 

;; QUESTION SECTION:
;www.cnn.com.                   IN      A 

;; ANSWER SECTION:
www.cnn.com.            150     IN      A       157.166.255.18
www.cnn.com.            150     IN      A       157.166.255.19
www.cnn.com.            150     IN      A       157.166.224.25
www.cnn.com.            150     IN      A       157.166.224.26
www.cnn.com.            150     IN      A       157.166.226.25
www.cnn.com.            150     IN      A       157.166.226.26 

;; AUTHORITY SECTION:
www.cnn.com.            86400   IN      NS      dmtns07.turner.com.
www.cnn.com.            86400   IN      NS      dmtns01.turner.com.
www.cnn.com.            86400   IN      NS      dmtns02.turner.com. 

;; ADDITIONAL SECTION:
dmtns01.turner.com.     3608    IN      A       157.166.226.169
dmtns02.turner.com.     3608    IN      A       157.166.224.169
dmtns07.turner.com.     3608    IN      A       157.166.255.15 

;; Query time: 541 msec
;; SERVER: 61.144.56.100#53(61.144.56.100)
;; WHEN: Thu Dec 30 19:06:58 2010
;; MSG SIZE  rcvd: 246 


For the two queries above, why the second response has a "ADDITIONAL 
SECTION" included, but the first doesn't? 

Thanks in advance. 

Regards.