How to interpret "additional section" in DIG?

I'm tryıng to understand how to interpret "additional section" in my dig query.

Here is the additional section for my specific query:

;; ADDITIONAL SECTION:
janus.radore.com.   831 IN  A   109.235.251.213
mimas.rh.com.tr.    458 IN  A   77.75.34.2
titan.radore.com.   586 IN  A   95.211.70.4

What do the figures mean? What is 831?

Here is the same section from a dig for google.com:

;; ADDITIONAL SECTION:
ns1.google.com.     74569   IN  A   216.239.32.10
ns2.google.com.     45794   IN  A   216.239.34.10
ns3.google.com.     74569   IN  A   216.239.36.10
ns4.google.com.     45794   IN  A   216.239.38.10

My ultimate goal is to find the performance of the nameservers my domain uses. But still I would like to learn how to interpret "additional section" too.

Thanks, Haluk

Solution 1:

I don't have an official answer (yet), but running dig multiple times in a row shows that number decrementing -- about once a second.

To me that would indicate that's the remaining TTL on the specific entry listed. So,in your example ns4.google.com has 45794 seconds remaining before it is checked again for updates.

Edit: I actually just found this which would corroborate my initial findings:

http://www.madboa.com/geek/dig/#ttl

Solution 2:

"Additional section" means: other information that is relevant to your question but not actually the answer to it. For example:

;; QUESTION SECTION:
;google.com.            IN  A

We asked for the address (A) of google.com.

;; ANSWER SECTION:
google.com.     165 IN  A   66.102.11.104

This is its IP address.

;; AUTHORITY SECTION:
google.com.     21770   IN  NS  ns4.google.com.
google.com.     21770   IN  NS  ns3.google.com.
google.com.     21770   IN  NS  ns2.google.com.
google.com.     21770   IN  NS  ns1.google.com.

These are the authorities for that question.

;; ADDITIONAL SECTION:
ns1.google.com.     19431   IN  A   216.239.32.10
ns2.google.com.     19542   IN  A   216.239.34.10
ns3.google.com.     19368   IN  A   216.239.36.10
ns4.google.com.     19543   IN  A   216.239.38.10

These are the addresses of the nameservers.

The additional section information is actually present in the DNS answer packet as a way to avoid additional roundtrips.

The numbers you see in each line is the number of seconds for which the record can be cached.