[olug] Domain name propagation - how long?

[Brian Wiese]

On Wed, 29 Oct 2003 14:59:35 -0600
Thom <id4spam at cox.net> wrote:

|I ran some tests:
|
|# host thom.homelinux.com
|Host thom.homelinux.com not found: 3(NXDOMAIN)
...
|Where's the delay?

You are not updating a "2nd level domain name" (i.e. domain.com) with the
root servers where they are responsible for the *.tld domains, but rather
you are dynamically updating a "3rd level domain name" (i.e.
3rdlvl.domain.com) where the authority for that dns->IP address mapping
usually resides with the "homelinux.com" DNS server, but actually the
dyndns.org servers in this case since it seems like homelinux.com is
something they run[1].  

By running your dyndns update, you're updating the "authoritative" name
server for those 3rd level domains (ns1.dyndns.org, etc).  Any new
requests that have to be resolved will ask that authoritative name server,
and of course hopefully get the right response since you just told them
what your new IP addy is.

I'm actually suprised that it updated the new IP address almost
"instantly".  Usually the name server you use (cox's nameservers) which
sends the request along to the ns*.dyndns.com nameservers, would keep that
resolution information in cache for a couple minutes -- incase anyone else
on the cox network wanted to know who "thom.homelinux.com" was (and its
most unlikely those shouldn't change within minutes/hours/days in most
cases).  So I would have expected for you to get your old IP back from a
resolution, for at least the next couple of minutes-- or perhaps cox NSs
are not caching.

A 2nd level domain then (.net, .com, .org, etc.. are the top level
domains, TLD), like dyndns.org, when its setup needs an authoritative NS
(the root servers responsible for the .org TLD) to tell people how to get
there.  So, you ask the root dns servers for *.tld, and you ask the
dyndns.org servers for *.dnydns.org.  Its a heirarchy. 

[1] 
bwiese at franklin:~$ dig thom.homelinux.com
<snip>
;; ANSWER SECTION:
thom.homelinux.com.     60      IN      A       68.13.170.107

;; AUTHORITY SECTION:
homelinux.com.          86400   IN      NS      ns5.dyndns.org.
homelinux.com.          86400   IN      NS      ns1.dyndns.org.
homelinux.com.          86400   IN      NS      ns2.dyndns.org.
homelinux.com.          86400   IN      NS      ns3.dyndns.org.
homelinux.com.          86400   IN      NS      ns4.dyndns.org.


 Brian Wiese | bwiese(at)cotse.com | aim: unolinuxguru
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