[kragen]

With DNS failover there is only added latency during the time interval between when a server goes down, causing the DNS to get updated, and when the dead IP times out everywhere, which can easily be a few minutes. If the server can anticipate that it is going to go down it can remove itself, and then only people using shitty ISPs that don't respect the TTL will ever see extra latency.

[jedberg]

> and then only people using shitty ISPs that don't respect the TTL will ever see extra latency.

In my experience running large websites, that's about 10% of the internet, if not more.

When I made a DNS change, only about 70% of the traffic dropped off in the TTL. The rest took anywhere between a few hours and a few weeks (and some never dropped off, we had to just let them fail after a while).

[kragen]

Thanks, I didn't realize it was that large. :'(

Do you think the advent of DoH will improve that situation?

[jedberg]

I don't think so. DoH deals more with streamlining the transmission of requests and responses, but I don't recall any part of the RFC dealing with TTLs.

You'll still be talking to your local DNS server with its own caching rules.

[yjftsjthsd-h]

I thought part of the big deal with DoH was precisely that you don't use your local DNS server (or more importantly, your ISP's DNS server). If DoH effectively means that more people pull DNS straight from Cloudflare, then I would expect the TTL situation to improve.

[jedberg]

Right now Cloudflare is the main provider, but it's an open standard. Anyone would be able to provide the service.

Chrome for example will only use it against your ISPs DNS servers, otherwise it will use Google's servers. So that would at least help, but if the big ISPs start supporting it, then Chrome would use that.