How do you actually find out what IP Address is at google.com? The DNS protocol. It’s application-layer. Similar to Domain, it’s the many-to-many mapping. The Name Server are the thing that actually hold the information.
It’s actually a distributed database that stores all of the relevant records’
- Addresses (A Record)
- Mail Exchange
- Name Server
- TTL
Example:
google.com → 216.58.213.11 and many more
Quickly, the distributed DNS Tree:
- Every computer knows the top root node (it’s hardcoded in).
- That Name Server knows the location of all of the
.com,.edu,.orgetc. name servers. Each one of their respective ones knows all of the domains within their name servers. - Eventually, you’ll get a name server (eg.
dns0.ed.ac.uk) that will know the exact IP of a domain. That’s the authoritative name server.
How does Iterative Name Resolution Work?
- Your computer wants to find out where
google.comis. It asks the nearest name server (likely your ISPs). If (for some weird reason), your ISP doesn’t have it, it will ask the DNS tree. Each request has a unique ID (cos these name servers also have to serve many other people - not just you).- The Root Server (root node on the tree) is likely hardcoded in your computer - there’s only about 20. One’s run by ICANN, another by NASA lol.
- Your ISP asks the Root Server of the DNS tree where
.comis. - It will respond. You then ask that server where’s
Google.com. It says “No idea, but here’sns0.google.com”. - You then ask
ns0.google.comwheregoogle.comis, and it’ll tell you!- In this case,
ns0.google.comis the authoritative name server forgoogle.com dns0.ed.ac.ukis the authoritative name server fored.ac.uk
- In this case,
- In all of this, the ISP caches the records it received.
Recursive Name Resolution:
Similar vibe, except the servers do the searching for you. Notice that this way, all of the name servers learn about the full domain on the way. TODO: NEEDS CLARIFICATION
Distribution of Responsibility
So in reality, ICANN manages the root of the tree. They give specific registrars the responsibility to manage the .com or .edu or .uk. Then they (.com registrars for example) will be in charge of giving out the google.com. This helps avoid name collisions.
