[ntp:questions] http://www.ntp.org/ => a blank page?

Danny Mayer mayer at ntp.org
Tue Mar 10 12:09:20 UTC 2009


Martin Burnicki wrote:
> David,
> 
> David J Taylor wrote:
>> Richard B. Gilbert wrote:
>> []
>>> I've been using Comcast for five or six years now without a problem!
>>> YMMV.
>> There have been a few problems with my ISP, hence I moved to a 3rd party.
> 
> We did't ever have any problems using the DNS servers of our ISPs.
>  
> [...]
>> I used to have my own DNS server.  You do /not/ have to get the rest of
>> the world from Comcast.  DNS is /not/ like NTP, and you talk directly to
>> the root servers to start with, which then pass you down gradually to the
>> correct server for the domain (e.g. for microsoft.com) and in future you
>> query the relevant domain server directly.  All seems to work very
>> smoothly and automatically.
> 
> IMHO DNS is not like NTP in the sense that is just *starts* sending queries
> for domains which have not yet been resolved to the root DNS servers and
> then are redirected/go on down to the authoritative DNS for that domain,
> whereas NTP would stuck with the top level servers if they have been
> configured.
> 
> However, if several local subnets needed to resolve "microsoft.com" then
> each one would have to ask the root servers the first time.
> 
> If you send DNS queries to your ISP's servers then this would save bandwidth
> since they are normally closer to your network than the root DNS servers,
> and there is a chance that other customers of your ISP has already sent
> queries for "microsoft.com" so this has already been cached by the ISP's
> DNS servers and no request has to be made to the root servers.
> 
> IMHO in this sense it's similar to NTP so the load is distributed and not
> concentrated on the root servers.
> 
> Martin

It is nothing like NTP. You cannot make that comparison. You are not
really saving anything in the way of bandwidth or speed and almost no
query from different groups of people is going to have an answer already
cached at the ISP's DNS. It's a lot like using an HTTP Caching Proxy:
people thought it would be beneficial but it was quickly shown that less
than 10% of the pages were already cached and that number was decreasing
rapidly. Jeff Mogul wrote a paper on that a number of years ago.

Danny


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