[Dnssec-deployment] who's cache is it anyway?

[Doug Barton]

On 08/08/2011 18:09, Joe Abley wrote:
> 
> On 2011-08-08, at 20:27, Doug Barton wrote:
> 
>> On 08/08/2011 05:56, Joe Abley wrote:
>>> 
>>> On 2011-08-07, at 15:05, Jim Reid wrote:
>>> 
>>>> A cache on your local device is likely to be much richer and
>>>> quicker and more useful than a possibly even bigger cache
>>>> operated elsewhere by someone else. It would be good to get
>>>> some actual numbers though.
>>> 
>>> For what it's worth, my experience is quite the opposite. A cache
>>> used by many people has a much better hit rate than a cache used
>>> by few people, at least in an ISP context.
>> 
>> If you consider the map of all possible DNS queries, sure.
> 
> Any cache which is hit with all possible DNS queries without
> repetition is going to have a hit rate of zero.
> 
>> In practice going from a cold start users will tend to populate a
>> local cache pretty quickly with the queries that they care about.
>> For records with reasonable TTLs the cache will then stay
>> populated. For those with unreasonably short TTLs it won't matter.
> 
> What you've just described is the operation of a cache, any cache.

Ya think? :)

> A cache shared by users that have something in common (same company,
> same country, also a residential user, users making use of the same
> ISP services) has the advantage that there's a greater probability of
> a cache hit due to a miss by someone else. A local, single-user cache
> will never provide such a hit, and everything else is the same.

I'm not arguing that you're wrong about how caches work. I'm saying that
the incremental increase in traffic and/or complexity for any individual
client on that network is negligible, and worth the cost.


Doug

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