Re: [DNSOP] sentinel and timing?

Joe Abley <> Wed, 07 February 2018 16:25 UTC

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From: Joe Abley <>
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Date: Wed, 07 Feb 2018 11:25:28 -0500
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To: Paul Wouters <>
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Subject: Re: [DNSOP] sentinel and timing?
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Hi Paul,

> On Feb 7, 2018, at 10:43, Paul Wouters <> wrote:
> I think it is useful to know how long the DNS resolver process has been
> up, and/or how long the server running the DNS resolver has been up,
> when it is sending the sentinel queries.
> That would allow us to detect if we are looking at spun up server
> instances and/or provisioned containers with old software stuck to
> KSK2010, versus old software running forever on an unmaintained server.

On the authoritative server, receiving a query from a resolver, it's not possible to be certain that two queries from the same source address correspond to the same originating host. 

On the client side, receiving a response from a resolver, it's far less possible to be certain that two responses from the same source address correspond to the same originating host. In particular, there are a relatively small number of resolver sources used by a large proportion of the end-user population, all of which to my knowledge are provisioned at scale, in clusters that are often distributed geographically.

I'm not sure what practical use a host-specific "uptime" indicator would have unless we also had a way to tie it to a particular host, and we see enough people going to the trouble to obscure the responses to ID.SERVER/CH/TXT type queries that such host identification might be contentious.

[Disclosure: there is yet more snow coming down, I have not yet had coffee, I have not yet left the house today, I am quite possibly running degraded right now, so perhaps wait until the failed units have been replaced before commenting on performance.]