It's not. The proof is that CDNs existed long before edns-client-subnet was introduced. All it does is allow the CDN's DNS servers to return the most optimal A/AAAA records for the client. But the worst that should happen without it is you get sent to a more distant CDN server, and the content loads more slowly.
The fact that archive.is somehow suffers without this feature (which, btw, wasn't standardized until 2016) suggests they're doing something really, really odd. If I were them, I'd focus on making my system more robust, rather than demanding the rest of the Internet adopt a relatively young, optional DNS extension.
Here's an interesting thought — if it's so bad for privacy and isn't necessary for a CDN, does Cloudflare the CDN simply disregard ECS when receiving requests from DNS.Google, or do they take it into account?
If archive.is thinks that Internet standards should be adopted so quickly, it's weird that they don't support IPv6 considering it's been a standard since 1998!
Obviously I'm kidding, but only kind of. When it comes to insisting on adopting new standards, edns-client-subnet is a weird hill to die on, especially considering it was always meant to be optional.
> does Cloudflare the CDN simply disregard ECS when receiving requests from DNS.Google, or do they take it into account?
I don't think they have a reason to use it because they use TCP anycast. Looking at https://cachecheck.opendns.com/ they seem to return the same IPs regardless of geography.
I don't understand that for various reasons.
1) Privacy is already lost here. If I shout my mobile number on a train with you that's full of people, everyone knows my phone number. If you choose to keep it / use it to call me tomorrow doesn't matter.
2) If Cloudflare can make _better_ decisions based on the information shared by Google, why shouldn't they? As long as it is optional and they don't take their ball and go home^W^W^W^W^W^Wreply with 127.0.0.3 in cases where you don't provide it..
* Yes, if you're running a local resolver for your LAN, or have a website on a single server, of course ECS should be optional.
* If you're running a CDN (and archive.today does), or if you're running a public resolver at 100+ POPs, then, no, ECS is not meant to be optional.
i.e it's not "(...CDN...) then ECS should not be optional"
It's not because it can be bad for privacy that you can't use it for good. The feature exist for a good reason, it's valid, it doesn't change anything to the fact though that it can be use for bad reasons too, which is why you want to remove it. In the means time, there's no reasons not to use it for good reason while it's still there.