Networking & Firewall (Ss/Netstat/Iptables/Curl)

Pinpointing Network Bottlenecks with Curl HTTP Timing

🧩 The Challenge

Identifying whether latency is caused by DNS resolution, TCP handshake speed, or slow server-side response times.

💡 The Fix

Use a custom curl format string to break down the total execution time into specific networking lifecycle phases.

curl -so /dev/null -w "DNS: %{time_namelookup}s\nTCP: %{time_connect}s\nTLS: %{time_appconnect}s\nTTFB: %{time_starttransfer}s\nTotal: %{time_total}s\n" https://google.com

⚙️ Why It Works

This command maps individual time variables provided by curl to visualize exactly which stage of the HTTP request is consuming the most wall-clock time.

🚀 Pro-Tip: Save this format string to a file as ~/.curlrc using the -w option to generate timing metrics automatically on every request.

Linux Tips & Tricks | © ngelinux.com | 7/7/2026