The Old Pain
A TCP connection is identified by the four values of source address, source port, destination address, and destination port. When a phone moves from wifi to cellular, its address changes and the connection breaks. QUIC avoids this.
Connection Identifiers
QUIC names a session with a connection identifier rather than the address tuple. The identifier travels in the packet, so the session is recognized even when the underlying address shifts.
- The client can keep talking after a network change.
- No new handshake is needed to continue.
- Downloads and calls survive a switch between networks.
Validating The New Path
A changed address could be an attacker spoofing packets, so QUIC validates the new path. The server sends a random challenge to the new address and waits for the matching response before fully trusting it.
- This path validation stops traffic from being redirected to a victim.
- It confirms the peer truly receives data at the new address.
Privacy Touches
QUIC can rotate connection identifiers over time so observers cannot easily link a moving device across networks by a stable identifier.
Key idea
QUIC identifies sessions by a connection identifier rather than an address tuple, so a session survives network changes after a quick path validation confirms the new address.