Counting round trips (a latency budget)

What you take away

• A first page load is a handful of round trips: DNS, TCP, TLS, then the request itself.
• Multiply the round trips by the user's RTT before blaming the server — setup usually dominates a first visit.
• There are only three moves: remove trips, shorten trips, or overlap them.
• A repeat visit skips almost all of it, which is why first-visit numbers are the ones worth budgeting.

How the class is laid out

1. The problem
2. The simple version
3. Where a first visit's time goes
4. The only three moves
5. TCP vs UDP
6. TLS 1.3
7. HTTP versions
8. Latency budget
9. Check your understanding