Re: [tcpm] New rev ready for WGLC: draft-ietf-tcpm-generalized-ecn-15

[Mirja Kuehlewind <[e-mail]>]

Hi Bob, hi Marcelo, hi all,

I reviewed this latest version of the draft. First, thanks for all the work and this very well written document! This is important work for both AccECN and L4S and I think the draft is absolutely ready for working group last call.



I only have one comment on Section3.3.2:



This section says that for RFC3168 SYNs one needs to watch three or four packets before disabling use of ECT. However, if all packets are overwritten by the network with ECT, you might never detect that. Further there is no way to tell that the other end after the handshake negotiation. Therefore I still think it is fine and the only option to not negotiate classic ECN support if a ECT/CE marked SYN is received. This does not impact ECN++ because all SYNs need to negotiate AccECN. And as recently discussed (also basically in section 5.3) it maybe even be desirable to not use (classic) ECN if AccECN is not available on the server.



Further I have some minor editorial issues (and one tiny nit I found…):



1) In Table 1: This is the only place where “Re-XMT” is used. This seems a rather untypical abbreviation for me. I think I usually saw RXT or something…



2) In section 4.9: “MORE MEASUREMENTS NEEDED (?):” -> Is this “(?)” here still needed? What does it really mean?



3) Section 5.1 on IW10 only say “Experimentation will be needed to determine the best strategy.” -> Was it on purpose that not same highlighting style is used as for other described experiments?



4) Section 5.4: “Building on the arguments in the current draft, a QUIC sender sets ECT on all packets unless it fails the test for path support.” I don’t think the arguments of this draft actually apply to QUIC because QUIC doesn’t really have any “pure” control packets.



Nit Section 3.3.1: “Therefore, In order” -> “Therefore, in order” (lower i)





Thanks,

Mirja




From: tcpm <[e-mail]> on behalf of Bob Briscoe <ietf=[e-mail]>
Date: Saturday, 2. December 2023 at 22:27
To: "[e-mail]" <[e-mail]>, Michael Tuexen <[e-mail]>
Subject: [tcpm] New rev ready for WGLC: draft-ietf-tcpm-generalized-ecn-15

Michael (as doc shepherd and co-chair), and tcpm,

We've just posted a new rev of ECN++, which is now ready for WGLC.

These changes to ECN++ require no further changes to the AccECN draft, which stands as it was at draft-28 on 17 Nov.
Details
Links to diffs are below, but here's a summary; just 3 changes:
1.       Alternatives to the additional DupACK check for the case when SACK blocks are being stripped.
2.       Removed the description of how the latest sctpecn draft handles control packets, as you (Michael) requested, given it is only interim.
3.       Fixed a few URLs.

NealC and RIchardS have suggested useful material, for which thanks.
The alternatives to the DupACK check were compromises to (imperfectly) address Markku's concern.
I had hoped he would confirm whether they are acceptable. But instead he has started digging a different hole (which I've just pointed out is a rabbit hole to nowhere - see the list).

So we've decided to post the ECN++ draft and request WGLC, which gives Markku more time to respond.



Bob
On 02/12/2023 20:29, [e-mail]<mailto:[e-mail]> wrote:

Internet-Draft draft-ietf-tcpm-generalized-ecn-15.txt is now available. It is

a work item of the TCP Maintenance and Minor Extensions (TCPM) WG of the IETF.



   Title:   ECN++: Adding Explicit Congestion Notification (ECN) to TCP Control Packets

   Authors: Marcelo Bagnulo

            Bob Briscoe

   Name:    draft-ietf-tcpm-generalized-ecn-15.txt

   Pages:   51

   Dates:   2023-12-02



Abstract:



   This document specifies an experimental modification to ECN when used

   with TCP.  It allows the use of ECN in the IP header of the following

   TCP packets: SYNs, SYN/ACKs, pure ACKs, Window probes, FINs, RSTs and

   retransmissions.  This specification obsoletes RFC5562, which

   described a different way to use ECN on SYN/ACKs alone.



The IETF datatracker status page for this Internet-Draft is:

https://datatracker.ietf.org/doc/draft-ietf-tcpm-generalized-ecn/



There is also an HTML version available at:

https://www.ietf.org/archive/id/draft-ietf-tcpm-generalized-ecn-15.html



A diff from the previous version is available at:

https://author-tools.ietf.org/iddiff?url2=draft-ietf-tcpm-generalized-ecn-15



Internet-Drafts are also available by rsync at:

rsync.ietf.org::internet-drafts





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Bob Briscoe                               http://bobbriscoe.net/<https://protect2.fireeye.com/v1/url?k=31323334-501cfaf3-313273af-454445554331-60c0becec43f4914&q=1&e=705c3752-7ce9-4aaa-9e8f-678e39aa197b&u=http%3A%2F%2Fbobbriscoe.net%2F>