So CloudFlare announced the 184.108.40.206 DNS resolver service the other day. Funny, coz I had been looking into various DNS options for my home network recently. What I had noticed at home was that when I use the Google DNS or OpenDNS resolvers I get a different (and much closer!) result for google.com while with other DNS servers (e.g. Quad9, Yandex) I get a server that’s farther away.
I was aware that using 3rd party DNS resolvers like this could result in me getting not ideal results, because the name server of the service I am querying would see my queries coming from this 3rd party resolver and hence give me a result from the region of this resolver (e.g. if Google.com has servers in UAE and US, and I am based in UAE, Google.com’s name servers will see that the request from www.google.com is coming from a server in the US and hence give me a result from the US thinking that’s where I am located). But that didn’t explain why Google DNS and OpenDNS were actually giving me good results.
Reading about that I came across this performance page from the Google DNS team and learnt about the edns-client-subnet (ECS) option (also see this FAQ entry). This is an option that name servers can support wherein the client can send over its IP/ subnet along with the query and the name server will look at that and modify its response accordingly. And if the DNS resolver support this, then it can send along this info to the name servers being queried and thus get better results. Turns out only Google DNS and OpenDNS support this and Google actually queries the name servers it knows with ECS queries and caches the results to keep track of which name servers support ECS. This way it can send those servers the ECS option. That’s pretty cool, and a good reason to stick with Google DNS! (I don’t think CloudFlare DNS currently does this, because I get non-ideal results with it too).
From this “how it works” page:
Today, if you’re using OpenDNS or Google Public DNS and visiting a website or using a service provided by one of the participating networks or CDNs in the Global Internet Speedup then a truncated version of your IP address will be added into the DNS request. The Internet service or CDN will use this truncated IP address to make a more informed decision in how it responds so that you can be connected to the most optimal server. With this more intelligent routing, customers will have a better Internet experience with lower latency and faster speeds. Best of all, this integration is being done using an open standard that is available for any company to integrate into their own platform.
Lastly, I came across Pi-Hole recently and that’s what I use at home nowadays. It’s an advertisement black hole. Got a good UI and all. It uses DNS (all clients point to the local Pi-Hole install for DNS) and is able to block advertisements and malware this way.