Practical deployment.
WHAT IS REQUIRED
A server supporting the protocol Encryption, which both newer versions effectively require Correct advertisement so clients know it is available
WHAT ADVERTISEMENT MEANS
A header indicating an alternative service is available on another protocol.
WHAT CLIENTS DO
Use the previous version first, then upgrade on subsequent connections.
WHAT THAT MEANS
The first visit does not benefit.
WHAT TO VERIFY
Which protocol is actually negotiated, from several networks.
HOW
Browser developer tools, which display the protocol per request.
WHAT COMMONLY PREVENTS IT
A proxy or load balancer terminating connections without support Intermediate equipment blocking the newer transport Misconfiguration of advertisement
WHAT TO CHECK IN A LAYERED SETUP
Which component actually terminates the client connection.
WHY
That component determines the protocol, not the origin behind it.
WHAT TO MEASURE
Whether the change improved real user timings.
WHY
The benefit is largest on high-latency, lossy connections and small on fast ones.
WHAT THAT MEANS HERE
The benefit is likely to be substantial.
