Some domains don't resolve.

Kevin Darcy kcd at
Tue Jun 10 20:46:54 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.
It's not a different issue, since many if not most ISPs don't "engineer" 
for load, they just throw more hardware at the problem when the users 
complain about bad performance. Squeaky-wheel theory of "engineering". 
When you do your own iterative resolution you're not reliant on your 
ISP's competence or incompetence at anticipating load spikes.

                           - Kevin

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