Hi,
[EMAIL PROTECTED] said:
> Are there any public DNS services that might "know" more names than
> one's ISP?
that isn't how DNS works.
The only name server that "knows" a fully qualified domain name is the one
that is authoritative for that domain.
Any other name server that is asked for the name will need to first ask the
root name servers who is authoritative, and then ask this machine for the IP.
(There may be more than one server that is authoritative for a domain,
typically there are two although there can be more).
e.g.:
[owen@bass owen]$ nslookup
Answer crypto-validated by server:
Default Server: localhost
Address: 127.0.0.1
> set q=ns
> microsoft.com
Server: localhost
Address: 127.0.0.1
Answer crypto-validated by server:
Non-authoritative answer:
microsoft.com nameserver = ATBD.microsoft.com
microsoft.com nameserver = DNS4.CP.MSFT.NET
microsoft.com nameserver = DNS5.CP.MSFT.NET
microsoft.com nameserver = DNS1.microsoft.com
Hence microsoft.com has 4 name servers, and any one of them will be able to
give you the IP for www.microsoft.com, for example, without asking any other
servers, but the server you query (your ISPs DNS server) will need to go and
ask one of them for it, as it does not "know" the answer itself.
Most ISPs public facing name servers are what is known as caching name
servers, i.e. they do not hold any real data themselves, but when a user
performs a lookup, they cache that data for the Time To Live (ttl) period of
the domain before they discard it and would need to ask for it again if
queried.
An extremely good book on how DNS works is "DNS & Bind" by Cricket Liu, Paul
Albitz and Mike Loukides, published by O'Reilly.
Owen
--
U-NET Ltd, a Via Net.Works Company
Local Touch Global Reach
Owen McShane Web hosting/domains Team Leader
http://www.u-net.net Tel +44 (0)1925 484444
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