Cache Countdown

Honesty Boundary

This is a tiny TTL countdown, not production DNS operations.

highlighted = computed this step

What this countdown shows

This toy response has one A answer and one TTL countdown table.

rows=3\text{rows}=3
DNS TTL honesty boundaryRemaining TTL is recomputed from elapsed seconds.DNS TTL countdown - www.example.com A 93.184.216.34, TTL 300 secondselapsedremainingvalidstate0300yesvalid120180yesvalid3000noexpired

Checked values

The trust boundary recomputes pointer offset 12, TTL 300, the answer address, and every remaining row.

TTL=300\text{TTL}=300
DNS TTL honesty boundaryRemaining TTL is recomputed from elapsed seconds.DNS TTL countdown - www.example.com A 93.184.216.34, TTL 300 secondselapsedremainingvalidstate0300yesvalid120180yesvalid3000noexpired

What this does not model

NOTE: toy DNS answer TTL countdown example only; not resolver cache eviction policy, authoritative refresh, DNSSEC validation, negative caching, clock skew, prefetch, serve-stale, CDN behavior, or production DNS operations.

toy answer=1\text{toy answer}=1
DNS TTL honesty boundaryRemaining TTL is recomputed from elapsed seconds.DNS TTL countdown - www.example.com A 93.184.216.34, TTL 300 secondselapsedremainingvalidstate0300yesvalid120180yesvalid3000noexpired

Summary

The answer is byte-exact, and the countdown rows are recomputed from TTL and elapsed seconds.

countdown rows=3\text{countdown rows}=3
DNS TTL honesty boundaryRemaining TTL is recomputed from elapsed seconds.DNS TTL countdown - www.example.com A 93.184.216.34, TTL 300 secondselapsedremainingvalidstate0300yesvalid120180yesvalid3000noexpired