Re: [quicwg/base-drafts] Revalidation for ECN (#4037)

[Gorry Fairhurst <[e-mail]>]

@gorryfair commented on this pull request.



> @@ -3892,6 +3889,7 @@ errors are detected.
 Endpoints validate ECN for packets sent on each network path independently.  An
 endpoint thus validates ECN on new connection establishment, when switching to a
 server's preferred address, and on active connection migration to a new path.
+If validation fails, an endpoint could also periodically attempt validation.

Why is this a could. Ignoring ECN is inappropriate and dangerous to the health of other flows. (If a flow received CE-marks it could reasonably assume ECN is working, if it see nothing it needs at some point to recheck this works.)

I'd expect this to be needed: Why therefore is this not a SHOULD?


> @@ -3843,11 +3843,8 @@ instead of dropping it.  Endpoints react to congestion by reducing their sending
 rate in response, as described in {{QUIC-RECOVERY}}.
 
 To use ECN, QUIC endpoints first determine whether a path supports ECN marking
-and the peer is able to access the ECN codepoint in the IP header.  A network
-path does not support ECN if ECN marked packets get dropped or ECN markings are
-rewritten on the path. An endpoint validates the use of ECN on the path, both
-during connection establishment and when migrating to a new path
-({{migration}}).
+and the peer is able to access the ECN codepoint in the IP header; see
+{{ecn-validation}}.

I think the new text is wrong. Support by the endpoint isn't sufficient. The path validation is required to use ECN, and this spec needs to say this for each new path.

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