Some domains don't resolve.

Danny Mayer mayer at
Mon Jun 9 03:48:32 UTC 2008

Barry Margolin wrote:
> In article <g2aeee$1bb9$1 at>, Kevin Darcy <kcd at> 
> wrote:
>> Barry Margolin wrote:
>>> But if your ISP has 100,000 users of the same caching server, it will be 
>>> cached if any of 1,000 users have accessed it recently.  For any one of 
>>> them, there's only a 0.1% chance that their lookup will be the one that 
>>> has to wait for fetching from the source.
>> And if you have 100,000 users using the same caching server, it's likely 
>> to experience big spikes of activity (e.g. several thousands of queries, 
>> within the course of less than a second), during which time some users 
>> will experience some extra delay in getting their queries resolved.
> Certainly if the nameserver is not engineered to handle the load it's a 
> bad idea to use it as a forwarder.  That's a completely different issue 
> than whether it's useful to share caches via a forwarding hierarchy.

I wonder how many people remember HTTP Caching Servers? They have fallen 
out of use in most places because there was almost no benefit to using 
them. DNS is much the same when it comes to forwarders. Don't forget 
that DNS already does caching, it's intrinsic to DNS.


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