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May 5, 2020

DNS Lookups Explained (With Pictures)

The other day I was wondering if the domain registrar I chose had any effect on my site’s load time. This sent me down the rabbit-hole of how DNS lookups worked.

What is a DNS Lookup, and How Does it Work?

A DNS lookup is the process used to find the IP address of a web server’s domain name. That IP address is what you will use to network with the web server.

When you visit a web page, your computer first checks if it already knows this website’s IP address.

DNS figure out IP

If your computer has already cached the IP address, it will use that. If not, it will send the request up the chain to your Internet Service Provider’s name-server.

dns does router know IP

Your ISP’s name-server will return the IP address if it knows it. If it doesn’t know it, it’ll ask the closest root-server for all the TLD name-servers associated with the .com extension.

DNS ask root servers for locations of name servers

From there, your ISP’s name-server will recursively ask the .com name-servers if they know your domain’s IP address. This goes on until one of them knows the answer, or it has asked every name-server.

DNS ask name servers for IP

Once your ISP’s name-server knows the answer, it’ll report it back to your computer, and the DNS lookup is complete.

Return IP to user

Does Your DNS Registrar Have Any Effect On Load Times?

Your domain registrar has no impact on how long it takes your domain name to resolve. So whether you choose NameCheap (who I use), Google Domains, GoDaddy, etc. your site’s load time will remain the same.

Why is that? Well, if you go back to how DNS works, your choice of registrar clearly doesn’t impact whether your computer, router, or ISP have the value cached.

DNS how they get the name

This only leaves us with root name-servers and the TLD servers that can impact load times. But, as we’ll see in a minute, your registrar has no impact on those servers as well.

Who Runs Root Name-Servers?

You can find the locations of all root name-servers and who operates them at root-servers.org. When you go to root-servers.org, you’ll see a map like the one below. You’ll also see a list of organizations that operate those root-servers. It’ll be organizations like Verisign, University of Maryland, NASA Ames Research Center, ICANN, etc.

root server locations

Root-servers aren’t run by Google, GoDaddy, NameCheap, etc. All root-servers do is return a list of TLD name-servers indiscriminately. Your registrar has no impact on the list of TLD servers that they return.

Who Runs TLD Nameservers?

IANA.org provides a list of what companies run which TLD’s name-servers. If you check the .com TLD, you’ll see VeriSign Global Registry Services run all 13 name-servers. Further, it’ll give you a list of all registrars that are signed up with Verisign to submit DNS records.

The TLD servers to find your domain aren’t organized in a way that gives preference to registrars. The ordering will be determined by load and geographic region. Meaning your registrar has no impact on DNS lookups.

There are only two registrar-related factors that impact DNS resolution times.

How Quickly Your Registrar Submits DNS Changes to the TLD Server.

If you make a change to your domain on NameCheap.com, how long will it take them to submit that to Verisign? This will affect how long it takes your domain name changes to propagate throughout the Internet.

That said, most reputable domain registrars will perform this task quickly.

Your Domain’s Time To Live(TTL) Values

When setting up your domain with your registrar, you should see a Time To Live Value next to your entry. This value specifies how long each of the computers in the chain should cache your IP address.

time to live value

A longer Time to Live will result in your ISP’s name-server caching the domain’s IP address for longer. But, increasing the TTL will cause changes to propagate the Internet more slowly.

DNS lookups will usually only take 10-100ms. So it doesn’t make sense to set an unusually large TTL value to improve load times.

Plus, many ISP’s will ignore your TTL values and use their own. This is the reason your ISP tells you to wait 24 hours for domain changes to take effect.

Shaun Poore was looking into if his DNS provider could effect his site speed (it can't), and after doing a deep dive on how DNS works, decided to write an entire blog post on the subject that explains how the entire system works in-depth.

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