> On 4 Nov 2018, at 7:01 pm, Paul Vixie <p...@redbarn.org> wrote:
>
>
>
> Ray Bellis wrote:
>>
>>
>> On 04/11/2018 08:05, Ray Bellis wrote:
>>
>>> AFAIK, BIND does not currently do this. That said, MarkA has a patch
>>> that supports it, so we do know it's possible.
>>
>> Correction - BIND *does* do this, but only for address records that are
>> already in the cache. If the AAAA for the target is in the cache, but
>> the A record isn't, that's all you'll get.
>
> that's all we need. it's all we do for MX and NS additional data, too.
>
>> Mark's patch forces BIND to pre-fill the cache with the A and AAAA
>> records for the SRV target before replying.
>
> that would be a mistake. we are hitting for average here not power -- the
> behaviour to optimize for is whatever's most common. if the SRV is used, the
> AAAA or A RRsets will be fetched, and thus cached. if the SRV is only used
> once, that caching effort will be wasted. if the SRV is used many times, then
> the dominant use case will be that the additional data is found in cache
> because the client caused this to be so.
The main objection to SRV was the double RTT to the recursive server. Fetching
the address records before returning will speed up the sites that are not
talked to regularly and will not slow down the sites that are talked to
regularly as the values will already be in cache.
> --
> P Vixie
>
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Mark Andrews, ISC
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