• Summary:
• Contents:

What is DNS?

Ref: https://learn.cantrill.io/courses/2022818/lectures/45637095

YouTube: https://www.youtube.com/watch?v=zEmUuNFBgN8

• 🔧 Domain Name System (DNS) = “the phone book of the internet”
  • Can be thought of as a huge DB that maps URLs and website names to their corresponding IP addresses
    • URLs, website names and domain names are easy to remember for humans
    • Machines use IP addresses to connect to the correct servers
  • DNS uses a L7 Protocol designed to get the IP address of a given DNS domain name
    • 💡 DNS protocol runs on TCP port 53 → Reason why the AWS product for DNS is called Amazon Route53 (R53)
  • Critical infrastructure
    • 💡 Many large scale failures on the Internet can be caused by failed DNS or poorly implemented DNS structure
• Domain name = string of text that maps to an IP address via DNS
  • e.g. Google's domain name = google.com
  • A domain can have subdomains → e.g. mail.google.com, drive.google.com…
  • 💡 A uniform resource locator (URL), sometimes called a web address, contains the domain name of a site as well as other information, including the protocol and the path.
    • e.g: for the URL https://cloudflare.com/learning/:
      • cloudflare.com - domain name
      • https - protocol
      • /learning/ - path to a specific page on the website
• DNS High Level Diagram

DNS Architecture and Infrastructure

Ref: https://learn.cantrill.io/courses/2022818/lectures/45637097

YouTube: https://www.youtube.com/watch?v=QTu7yDnR_58

Why not one DNS server or cluster of servers?

1. Risk: bad actors could take down DNS if it were a small cluster of servers
2. Scaling: everyone in the Internet uses DNS → would lead to huge NW bottlenecks
3. Data volume: ~341 million domains currently → huge DB
4. Delegation: ideally DNS domains should be administered locally (.uk in UK, .it in Italy…)

• 🔧 Conclusion: DNS requires a large, distributed & complex infrastructure