Looking back over the arc of my career in pseudoacademia, especially over the last three years of digging into transport stack evolution with the MAMI project, there are a few bits of work I’m especially happy to have been a part of. One of these is the inclusion of the spin bit into the QUIC transport protocol. The spin bit was conceived as the minimum useful explicit signal one could add to a transport protocol to improve measurability, the benefit for the overhead is IMO quite worth it. Though it exposes “just” RTT, latency (together with data rate, which is available simply by counting packets and bytes on the wire in any transport protocol that is not hardened against traffic analysis to the point of uselessness) is the most important metric for understanding transport layer performance diagnosing all matter of transport-relevant network problems, and the spin signal itself can also be observed to infer loss and other issues with network treatment of a packet stream. The definition and deployment of the spin bit will therefore make network protocols more measurable while preserving privacy gains from encryption, and is a clear win for network operations and management.
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