Re: [DNSOP] Minimum viable ANAME

Paul Vixie <> Mon, 05 November 2018 17:05 UTC

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From: Paul Vixie <>
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Subject: Re: [DNSOP] Minimum viable ANAME
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Mark Andrews wrote:
>> if the stub who asked the SRV question does not receive the
>> addresses it needs in additional data, it will query for them. that
>> will put those addresses in cache, so that on subsequent same-SRV
>> questions, it will be present.
> And that requires 2 RTT’s from the client which, despite being only a
> few ms normally, has been enough for the HTTP folks to refuses to
> deploy anything other than CNAME for ~2 decades now.

i don't think we've made it clear to them that this only happens once.

>> if the SRV is never fetched again, then there's no win to be had.
> The win is loosing the extra RTT from the stub to the recursive
> server.

i know that. but the second RTT stub-rdns only happens once per unique 
SRV or AAAA/A. after they are both cached, they are returned in a single 

> And then we get back to the complaints from the HTTP side saying the
> SRV takes longer than CNAME, which is valid for the first lookup if
> you don’t fetch the additional records before returning.

i don't think they are objecting to something that only happens on the 
first time a unique SRV or AAAA/A is needed. someone should explain to 
them that we built this with the expectation that popular data would be 
fast, and unpopular data wouldn't make a difference in the long run.

P Vixie