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From YouTube: HotRFC IETF 112 - The Hidden Delay Bit: How to Mask Connection RTT

Description

The latency Spin Bit has been adopted by the QUIC transport protocol but is rarely implemented for privacy concerns (the RTT may roughly reveal the distance between client and server). The algorithm of the Delay Bit (or even the Spin Bit) can be slightly modified to mask the RTT of the connection to an intermediate observer. This result can be achieved using a simple expedient which consists in delaying the client-side reflection of the delay sample (or the spin edge) by a pre-determined time value. This leads an observer to measure a wrong RTT greater than the real one. Nonetheless, the observer-server component of the delay remains valid and can be used to measure network performance.