Re: [ippm] QUIC concerns relating to draft-ietf-ippm-explicit-flow-measurements

[Martin Thomson <[e-mail]>]

On Fri, May 12, 2023, at 01:21, Christian Huitema wrote:
> Igor is right. In fact, the "square bit" that he describes is 
> implemented in Picoquic, under an option negotiation.

It's not about whether endpoints could negotiate something that allows the use of these bits, it's about whether measurement systems are able to rely on that happening.

It's quite possible that some extension could be negotiated that creates a signal in these bits.  OK, so now you can deploy a measurement system that relies on that.  Most bits will be random, but some proportion will have the signal.  Enter statistical methods and you can recover some signal.

Well...almost.  This works until someone else decides to negotiate the use of those bits for carrying a different signal.  Now you have a harder statistical problem to solve.  Maybe you can boost your adaptation by observing connection initiation and looking for clients that advertise a certain version and set of transport parameters.

> The probability that these measurement features be turned on by default 
> is extremely low, and the draft should be very explicit about it, 
> including a description of the privacy/measurement tradeoff.

This is really the point of all this.