Networking · interactive
The TCP and TLS handshakes
Before a single byte of the page arrives, the browser and the server trade several messages, and each one has to cross the distance between them. Count the round trips, then move the server further away.
TCP + TLS 1.2
round trip 70 ms · 35 ms elapsed
Browser → server: SYN. 35 ms so far.
Protocol
How far away is the server?
1 SYN, SYN-ACK, ACK: both sides agree to talk and pick starting sequence numbers. One full round trip before anything else.
1 round trip.
2 3 4
In production
Tools and technologies
Every HTTPS request pays these round trips; the protocols and providers below exist to cut them.
Not tied to one language — use these names when you search docs or design a system.
- TLS 1.3 (RFC 8446)Protocol
One-round-trip handshake, and 0-RTT resumption.
Official site ↗ - QUIC (RFC 9000)Protocol
Transport over UDP with the TLS handshake built in.
Official site ↗ - Chrome DevTools timingSoftware
See DNS, connection, TLS and waiting time for every request.
Documentation ↗ - curl -wSoftware
Print time_connect, time_appconnect and time_starttransfer from the terminal.
Documentation ↗