Tracking the QUIC spin bit on Tofino
Ike Kunze, Constantin Sander, Klaus Wehrle, Jan Rüth · 2021
QUIC offers security and privacy for modern web traffic by closely integrating encryption into its transport functionality. In this process, it hides transport layer information often used for network monitoring, thus obsoleting traditional measurement concepts. To still enable passive RTT estimations, QUIC introduces a dedicated measurement bit - the spin bit. While simple in its design, tracking the spin bit at line-rate can become challenging for software-based solutions. Dedicated hardware trackers are also unsuitable as the spin bit is not invariant and can change in the future.