How does DNS propagation work

Your website works fine from my end, although it’s still not available in a few countries. This is mostly due to DNS propagation. I suggest you use CouldFlare name servers if this persists.

That’s not how DNS propagation works. It’s dependent on caching and configuration, which is in no way related to geographic location.

Remember that internet packets travel at the speed of light.

So no need to worry about settings needing time to travel across the world.

I suggest to not add complexity to your website unless you need to. And changing DNS settings to fix DNS caching does more to hurt than to help.

I not quite sure, in my opinion geographic location indeed matters. Especially because of the DNS Hierarchy. for an example TLD servers, intermediate DNS servers, and local DNS resolvers are located on specific geographical locations. So if the user’s domain name is a TLD one, it’s likely to get updated first because it’s a top level. And TTL matters too.

I split the topic so we can discuss the nature of DNS propagation while keeping the MyBB plugin topic clean.

I don’t see the relation.

Of course, servers exist at geographic relation, and there is correlation between geographic location and the latency to another server at another geographic location. But that latency is typically no more than a few hundred milliseconds, so it doesn’t explain why DNS changes can take days to take effect.

I wrote an article before explaining how DNS propagation works, so I won’t cover that in detail here:

In the most basic setup, the DNS Resolvers configured in your device (usually provided by your ISP) will directly contact the authoritative nameservers of your domain to fetch the records, and cache it. The reason DNS propagation is an issue is because the DNS resolver may be caching it for a long time.

This can get worse with tiered caching. If your own device caches the DNS results it obtains from your router, your router caches the DNS results from your ISP, and your ISP caches the DNS results from the authoritative nameservers, it can take a long time for all the caches to be updated with new information.

Geographic location is meaningless. Someone living next to the datacenter may be unable to access the website for weeks because their DNS resolver obtained results in the past, and really aggressively caches it, but someone on a different continent can see the website immediately because their DNS resolver did not have any records cached, or just doesn’t cache it for very long.

That’s also irrelevant. Whether someone is trying to look up example.com or example.wuaze.com doesn’t matter.

For the custom domain, they will have to look up the authoritative nameservers of the domain with the .com nameservers, and then query those authoritative nameservers.

For the subdomains, they may have already cached which nameservers are responsible for wuaze.com, but to know where example.wuaze.com is hosted, they will have to query our nameservers first. Our nameservers will return the relevant IP for that subdomain, but they could just as well have delegated control to different nameservers entirely.

These few hundred miliseconds doesn’t matter, but you indeed said in that article that it depends on how fast your DNS resolver fetch the new records.

So it is still relevant I think, but in a way more abstract way.

It’s true people can pick a new resolver, but most people don’t even know there’s such a thing. All they know is that this website “doesn’t work”. They probably just stick to a location relevant DNS for their whole life.

Some sites just said that the sign of whether the DNS propagation is complete is that the record is avaliable in every region by the way.

If that’s how you interpret that, they I may not have worded it correctly.

Deciding factor isn’t how long it takes for the resolver to obtain new records, the deciding factor is how often the resolver decides to obtain them in the first place.

Absolutely. In an ideal world, changing DNS resolvers should not be necessary. The ISP or network administrator setup or use properly working DNS resolvers so the end user can assume that DNS resolution works well.

In reality, there are ISPs that try to do “smart things”, such as:

• Caching results for longer than the TTL specifies to reduce bandwidth cost and improve performance.
• Setup tiered caching for scalability.
• Setup security filtering to protect their users from bad things on the internet.

All of these things may result in DNS changes taking much longer to take affect, or websites being unreachable entirely.

That’s not how it works. Because again, DNS cache is determined by what DNS resolver you are using, not where in the world you are.

Sites like dnschecker.org heavily play into this with their “propagation map”, which is still not how it works. Although their actual checks aren’t that stupid, because they are actually querying public resolvers from various providers across the world. So they do give some idea as whether your site would be accessible from these providers.

But of course, dnschecker.org showing all green is no guarantee that your site works everywhere, because they only check the resolvers which they check. Other resolvers that they don’t check may still serve outdated data.

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Although I will defend the hill that DNS propagation is unrelated to geographic location, there are cases when it does matter: geo distributed DNS.

Because DNS data doesn’t change a lot, and you want it to be accessible quickly, many providers choose to setup DNS servers in multiple locations across the world. The free hosting nameservers for example have locations in east coast US, west coast US, and in Europe. When you do a DNS lookup, your queries will be routed to the nearest servers (more or less).

That’s great for performance, but it does provide the chance that different people will see different results. We have had issues in the past where DNS changes were not being pushed to one of those locations, meaning that sites were only inaccessible in some parts of the world.

The same is true for DNS resolvers. Google and Cloudflare have many datacenters from where they run their DNS, so someone in America, Europe or Asia all using Cloudflare will be connected to different datacenters, which may not share the same cache, and therefore will see different results.

So while it is possible for geographic location to be the deciding factor, I would not call this DNS propagation.

Thank you, admin, for explaining this. I thought DNS Hierarchy was the main matter. I’ve got one more doubt, though. Correct me if I am wrong. Let’s say my website, example.com, changed the DNS records a few minutes ago. Did the Authoritative DNS Servers send them to the root server first? If so, from the root server, is it getting distributed to all the other global servers? And after that, will the new changes depend on TTL and configuration? I don’t know if this is a dump question or not, but I need to get my head clean.

Never mind I found the answer

It works a bit differently than that.

The authoritative DNS servers don’t send their records anywhere. The root nameservers (or rather the .com registry nameservers) don’t know the DNS records of the domain itself, they only know that control of that domain is delegated to the domain nameservers. It’s up to the DNS resolvers to query the root nameservers, then the registry nameservers, and finally the domain nameservers to find the actual host.

The authoritative nameservers should publish their records nearly instantly, but some DNS providers take a few hours to publish the changes, but this depends on how they setup their system.

The only thing TTL does is provide a suggestion to DNS resolvers regarding how long the records should be cached.

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