RTT-0 (Zero Round-Trip Time)

0-RTT (Zero Round-Trip Time Resumption) is a high-performance feature of modern network protocols like TLS 1.3 and HTTP/3. It allows a browser that has recently connected to a server to send application data in its very first message on a subsequent visit, without waiting for the security handshake to complete. This effectively eliminates one full Round Trip Time (RTT) from the connection setup, significantly speeding up the Time To First Byte (TTFB), especially on mobile networks.