Trace an HTTPS request through the OSI model with curl

Mon, 09 Nov 2026 12:00:00 +0100

After more than 20 years in networking, I still use the seven-layer OSI model to structure a simple troubleshooting question: at which layer does the connection stop?

curl -v --http1.1 https://example.com/

Verbose output exposes several stages of an HTTPS request: hostname resolution, the TCP connection, TLS negotiation and certificate verification, followed by the HTTP request and response headers. Forcing HTTP/1.1 keeps the application exchange easy to recognise instead of negotiating HTTP/2.

TLS on Ivan Versluis — Networknet

Trace an HTTPS request through the OSI model with curl