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by lxgr 334 days ago
> DoH hosts can resolve to multiple IPs (and even different IPs for different clients)?

Yes, but not from a different organization. That was GPs point with

> So if you want to use DNS over HTTPS on Android, it is not possible to provide a fallback.

A cross-organizational fallback is not possible with DoH in many clients, but it is with plain old DNS.

> It's worth noting that DoH (DNS-over-HTTPS) traffic remained relatively stable as most DoH users use the domain cloudflare-dns.com

Yes, but that has nothing to do with failovers to an infrastructurally/operationally separate secondary server.
1 comments
ignoramous 334 days ago
> A cross-organizational fallback is not possible with DoH in many clients, but it is with plain old DNS.

That's client implementation lacking, not some issue inherent to DoH?

   The DoH client is configured with a URI Template, which describes how to construct the URL to use for resolution. Configuration, discovery, and updating of the URI Template is done out of band from this protocol.

  Note that configuration might be manual (such as a user typing URI Templates in a user interface for "options") or automatic (such as URI Templates being supplied in responses from DHCP or similar protocols). DoH servers MAY support more than one URI Template. This allows the different endpoints to have different properties, such as different authentication requirements or service-level guarantees.
https://datatracker.ietf.org/doc/html/rfc8484#section-3
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lxgr 334 days ago
Yes, but this restriction of only a single DoH URL seems to be the norm for many popular implementations. The protocol theoretically allowing better behavior doesn't really help people using these.
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