[nflug] DNS

[Mike Richardson]

eric wrote:
> Does anyone know how long it would take to download all the nameservers
> .com .net etc.... for root ...a couple of days right??

Dunno, it's probably huge.

But I have to ask: what benefit one would receive personally mirroring a
root DNS server? Yeah, the entries would all be good for a day or so.
But as soon as something changes, your local DNS entries will become old
- FAST.

DNS is designed to be an authoritative system. If one level has no idea
what the answer is, it asks someone higher up, who asks someone higher
up (if necessary), for the answer (or advise on where to find out).


A simple way to track a DNS request:

1) Joe at domain.com makes a request for google.com

2) Joe's DNS servers in his domain do not know what IP address
google.com resolves to (in fact, there are a few)

3) So Joe's DNS server contacts the next level up (most likely, his ISP
DNS server dns.isp.com) and asks, "who is google.com?"

Two possible responses:
- His ISP DNS server knows the answer, it will respond with the ip
address - end of line

- His ISP DNS does not know the answer, so it asks the next level up

Steps 2 and 3 repeat until (at worst case scenario) a Root DNS server is
contacted. Either the root DNS server knows the information, or can
redirect the request back down to another server that may know (e.g.
google.com's DNS server)

Of course, if Joe's DNS servers cache previously retrieved results (or
anyone up the chain does), the requests will result in a result much
earlier.


-- 
Michael Richardson
Web Programmer, ePharmacotherapy Networks
School of Pharmacy and Pharmaceutical Sciences
State Univ. of New York at Buffalo
Hochstetter Hall Room 329
(716)645-2828 ext. 266

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