01Overview

Before DNS, host names and addresses lived in a single hosts file maintained by hand at SRI. That could not scale. In 1983 Mockapetris designed DNS: a distributed, hierarchical naming system delegating from the root through top-level domains to authoritative servers.

Queries usually go over UDP port 53, with caches and TTLs trading speed against freshness. DNS also became the first arena of governance: who runs the root zone, how top-level domains are granted, where ICANN’s legitimacy comes from. In 2016 the US Department of Commerce handed over the IANA functions, and DNS entered multistakeholder governance.

02History

  1. 1983

    The DNS specification

    Mockapetris designs hierarchical naming.

  2. 1984

    Root servers deployed

    Thirteen root server addresses.

  3. 1998

    ICANN is founded

    The body for names and addresses.

  4. 2016

    The IANA transition

    Root-zone management becomes multistakeholder.

03Core concepts

Hierarchical naming

A tree from the root to top-level domains to authoritative servers.

Recursive and iterative queries

The resolver does the work, or each server points to the next.

TTL caching

Time to live trades speed against how quickly records update.

04Hands-on

Do it once — it beats reading it ten times

Trace a full resolution with dig +trace for one domain and draw the delegation chain from root to authoritative

05Self-check

Say it in your own words first, then open the answer. Whatever you cannot explain is what to review next.

Can you explain "Hierarchical naming"?

A tree from the root to top-level domains to authoritative servers.

Can you explain "Recursive and iterative queries"?

The resolver does the work, or each server points to the next.

Can you explain "TTL caching"?

Time to live trades speed against how quickly records update.

What problem did it solve, and why was there nothing better at the time?

Go back to the history section: how was this done before, and what did it cost?

If you had to build it today, how would you break it down?

Use the hands-on task above: write a plan of at most three steps before you start.

06Key people

P

Paul Mockapetris

1953 –

Designer of DNS.

J

Jon Postel

1943 – 1998

Founder of IANA and a driver of Internet standardisation.

07Further reading

  • RFC 1034 / 1035Mockapetris · 1987
  • Networks and StatesLaura DeNardis · 2014