Re: [quicwg/base-drafts] Spin per peer (#1982)

[ianswett <[e-mail]>]

ianswett commented on this pull request.



> +
+The selection process SHOULD be designed such that
+on average the spin bit is disabled for at least one eighth of network paths.
+The selection process SHOULD be externally unpredictable but consistent for
+any given combination of source and destination address/port. For instance,
+the implementation might have a static key which it uses to key a pseudorandom
+function over these values and use the output to determine whether to
+send the spin bit. The selection process performed at the beginning
+of the connection SHOULD be applied for all paths used by the connection.
+
+Note that where multiple connections use the same path,
+the use of the spin bit MAY be coordinated by endpoints,
+recognizing that this might not be possible in many cases.
+
+When the spin bit is disabled, endpoints MAY set the spin bit to any value,
+and MUST accept any incoming value.
 

Thanks for the summary.

My experience with ossification is that as long as it's not fixed across all connections, the likelihood of ossification is much lower.  But past experiences may not predict the future.  The 'QUIC bit' will likely be helpful as a single thing middleboxes can latch onto, possibly preventing more nefarious ossification.

I think leaving it completely unspecified has a cost.  Namely that I think either setting it randomly or setting a fixed value are safe, and other approaches could inadvertently leak information.  Previously I was concerned that setting it randomly could leak information, but people tell me that's not a real concern.  So if we're going to leave it flexible, I think we should add a SHOULD that if you're not going to spin, you should either randomize or pick a fixed value.  Martin made some clever suggestions previously that I was immediately able to infer loss and reordering from, so I think other options are prone to information leakage.

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