In this type of situation, I generally run my own.
Ron, thanks very much for this. I'll install it. If you don't mind one
more question...
From what I've read at the TreeWalk site I can't determine what it does
if, after it is freshly installed and goes on line while my ISP's DNS is
down. Does it use some other DNS to get started? How does it initially get
the IP-address list?
--David
It does not use your ISP's server at all.
It does the full lookup from the ground up by itself.
It does what all caching name-servers do.
On a cold-start, the cache is empty, it essentially knows nothing.
So it as a built-in 'cheat sheet' to get it started.
This cheat-sheet is called the 'Root Hints'.
It has a hard-coded list of the 13 Internet root nameservers as an initial
starting point.
http://en.wikipedia.org/wiki/Root_nameserver
If you query
www.google.com, here's what happens...
Treewalk will query one of the 13 root nameservers and ask for the
A-record ( host IP address) of
www.google.com, and it will get the reply:
"I don't know. I have delegated all .com names to the .com servers,
go ask them, here's their addresses."
So treewalk will then go ask one of the .com nameservers instead, which will
reply with:
"I don't know. I have delegated all google.com names to the google.com
servers,
go ask them, here's their addresses."
Finally, treewalk will go to the google.com nameservers, and ask for the
A-record ( host IP address) of
www.google.com, which will reply with:
Here's the IP address of
www.google.com.
To see this in action, go here:
http://www.dnsstuff.com/ and enter a website
in the top right box, DNS lookup, and hit the 'Lookup' button. You will
see the queries being re-directed down all the way from the root.
Now, Treewalk has cached the whole path, including the IP addresses of all
the nameservers which were queried right down the path. So if we now look
up
www.microsoft.com, then ot no longer needs to query the root nameservers,
it already knows about the .com branch, and can query it directly.
The more a DNS server is used, the greater the chance of a cache hit, so it
gets quicker and has to hit the root and Top-Level-Domain nameservers less.
