Re: Quic: the elephant in the room

Viktor Dukhovni <> Mon, 12 April 2021 15:54 UTC

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Date: Mon, 12 Apr 2021 11:54:10 -0400
From: Viktor Dukhovni <>
Subject: Re: Quic: the elephant in the room
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On Mon, Apr 12, 2021 at 12:57:21PM +0000, Salz, Rich wrote:

> >    one may as well delegate the TLSA record management to the CDN:
> Sure, if you're never going to switch CDN's.

No, to *each* CDN.  Each one can publish the appropriate TLSA RRs for
its service.

> There is a whole industry and providers around switching CDN's in real
> time.  Web-search "Cdn switch" will find them, for example.

What do you mean by "in real-time"?

> >    But any sort of TLSA RR on the customer side, while the cert rollover
>     are managed by the CDN is too fragile.  The TLSA RRs should properly
>     be published by the CDN as above.
> Sure, if there's one CDN.

It also works for multiple CDNs, provided they don't keep switching back
and forth, or proving some modest set of trust-anchors is known to cover
them all.

> >    If indeed sub-minute migration from one CDN to another is required, then
>     the TTL for the _443._tcp.[...] CNAME would need to be sub-minute.  Is
>     such a short cutover time really a requirement?
> If millions of dollars of commerce are happening per minute, then yes.
> Or the head of state dies and the official news source is overloaded.

And do they keep switching back and forth, or is a one time switch
stable for some days or longer?