Re: [quicwg/base-drafts] Gorry's ECN rewrite (#4059)

[mirjak <[e-mail]>]

@mirjak requested changes on this pull request.



>  
-It is possible for faulty network devices to corrupt or erroneously drop packets
-with ECN markings.  To provide robust connectivity in the presence of such
-devices, each endpoint independently validates ECN counts and disables ECN if
-errors are detected.
+For example, if one each of an Initial, 0-RTT, Handshake, and 1-RTT QUIC packet
+are coalesced, the corresponding counts for the Initial and Handshake packet
+number space will be incremented by one and the counts for the application data
+packet number space will be increased by two.

Is this correct? The congestion controller will only count this as one mark and for validation the sender must then also track the sent markings on a QUIC packet base and not per IP packet.

>  
-#### Sending ECN Markings
+It is possible for faulty network devices to corrupt or erroneously drop packets
+that set an ECN codepoint.  To provide robust connectivity in the presence of
+such devices, an endpoint validates the ECN counts for each network path  and

This needs more explanation because you say first something about "drops" and the "validate ECN counts" but to check for drops you need to detect loss of ECT marked packet which is not really discussed here.

> +frame.  This is why ECN counts are permitted to be larger than the value
+corresponding to the largest acknowledged packet number.

Didn't we also discuss a check were all packets get marked as CE (including non-ECT packets)? That's actually the only check that is basically implemented today in TCP (checking if the SYN is CE which should be non-ECT).

>  
-* Set the ECT(0) codepoint in the IP header of early outgoing packets sent on a
-  new path to the peer ({{!RFC8311}}).
+* The endpoint SHOULD set the ECT(0) codepoint in the IP header of early

I don't think normative language makes sense here as we already say in the intro sentence "an endpoint SHOULD do the following"

> +To reduce the chances of misinterpreting loss of packets dropped by a faulty
+network element, an endpoint could set an ECT codepoint for only the first ten
+outgoing packets on a path, or for a period of three RTTs, whichever occurs
+first.

I think it actually not beneficial :-)

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