Skip to content

DNS System — Notes#

Functional#

  • Recursive resolution.
  • Authoritative serve.
  • Zone provisioning.
  • DNSSEC, DoH, DoT.
  • GSLB / latency-based routing.

Non-functional#

  • Hot resolution from cache < 5 ms.
  • Cold path 50–300 ms.
  • 99.99%+ availability.

Trade-offs#

  • TTL low = fast failover, high QPS to auth.
  • TTL high = traffic shedding for auth but slow updates.
  • Anycast = best ops; complex to set up.

Refs#

  • RFC 1035 (DNS), RFC 4033 (DNSSEC), RFC 8484 (DoH).
  • Cloudflare 1.1.1.1, Google Public DNS engineering posts.
  • "DNS for Rocket Scientists" book.