What Happens When You Type a Domain

What Happens When You Type a Domain A sequence diagram generated by Archify. open brewedops.com what is this domain's IP? cached answer if TTL is alive who handles .com? these nameservers do read the A record 203.0.113.10 IP address HTTPS request on port 443 HTML, CSS, images page appears Ask for the address Follow the chain Fetch the site You · type brewedops.com · Sequence participant You type brewedops.com Browser · Chrome / Safari · Sequence participant Browser Chrome / Safari Resolver · ISP or 1.1.1.1 · Sequence participant Resolver ISP or 1.1.1.1 Root + .com · directory servers · Sequence participant Root + .com directory servers Nameservers · the domain's DNS zone · Sequence participant Nameservers the domain's DNS zone Web Host · server at 203.0.113.10 · Sequence participant Web Host server at 203.0.113.10 Legend request return security async trace default message

The Lookup

  • • A domain name is not an address, it is a lookup key
  • • The resolver walks root, then .com, then the domain's own nameservers
  • • Most lookups never get this far because the answer is cached

The Delivery

  • • Only after the IP is known does the browser talk to the host
  • • The host is the machine that actually stores the site files
  • • HTTPS means the connection is encrypted by a certificate

Why It Feels Slow To Change

  • • Every layer keeps the old answer until its TTL expires
  • • That waiting period is what people call propagation