From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-xd31.google.com (mail-io1-xd31.google.com [IPv6:2607:f8b0:4864:20::d31]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id E514C3B29D for ; Fri, 24 Jan 2020 19:46:22 -0500 (EST) Received: by mail-io1-xd31.google.com with SMTP id z8so3861284ioh.0 for ; Fri, 24 Jan 2020 16:46:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=V0xIgAIuoaJHowke9MSLdroGb9sK0O/MLx4X1pOFG/s=; b=htYv9sbw0AYfr9JwieXLUjKHTuYf9zPcDGEylqNPWf4j9GVQjiOPtvTsJuRmY7qT1T WROaMwTUeR2ITEh2rdCZS5rwjpGKgxu4ksNCfGt+0f2culLl7+9/kGLxceauhnKaKne7 FTx+0L/CxstKEiKr0SDvFmxgD6kZU9EdO+/t8dWnPue5B85AicUVrjA0NAu+G66fzm1l xppEatzBqLvW19l6ZrSa8rE8hdbUlJo0wI/w0PWPTOjn0bYZEuGiqMRXj/7ajd1eDVMJ 4ItxHuVTe/7Lt17Hp+XGuptXXKtTqTZkqwobIZAS3xVmgrF/omq1c7AujCyMTuJIxyhX 71gw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=V0xIgAIuoaJHowke9MSLdroGb9sK0O/MLx4X1pOFG/s=; b=UXr4fVWc0qPNoRRrkScCTncHqz06O4Ju00Njj64G7mxpVdwGy4fml9sMYXY4tTu+uO eP1E5qXM5ovUB77pDvRj7ATx7MfN+GecejZsqpRoK1DH4t+zsLl6ohmL0Ajr3EfS8iXk HfLwosRo93wVAH2ExGDfu/7nxPBevTVW9iLn/+g3UlAHRMImGc5T7wTDpN97hJ6jnqRq 6i5RABsrTt6Jsoh34P3oU1ErjCPbMrWOBxSrd5A7hxr7VYGpyqPh9tDxm029RwHfwkfG GFtDRNS0U2mfaR9U1vKK3xKnQmuOPNqDWLhqcWMRmiZj3k2CUPzTKvJH8q3BQ7lh1MIE ZbzA== X-Gm-Message-State: APjAAAUTubmhTmPETal+oDYlcZ6fNyJnnYbyMAp9Ag/lWAFFPMAfAXQ9 7Hd/QYlhY+sBJE+RNw0gDo/7kZdg3R9ZTwljOS9wxavl X-Google-Smtp-Source: APXvYqyk7T7BONtWEiQnxIdEd5266RLZqE8BRAG2UwfNpxEWRo/i3KV0KvR/7SoAr1ypeRS7kQKLS/l38t/chGBnsJo= X-Received: by 2002:a5d:9697:: with SMTP id m23mr4600671ion.45.1579913182076; Fri, 24 Jan 2020 16:46:22 -0800 (PST) MIME-Version: 1.0 From: Dave Taht Date: Fri, 24 Jan 2020 16:46:11 -0800 Message-ID: To: ECN-Sane Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: [Ecn-sane] ECN++ note X-BeenThere: ecn-sane@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussion of explicit congestion notification's impact on the Internet List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 25 Jan 2020 00:46:23 -0000 I'm not on the tcpm mailing list, but am trying to catch up. To quote this message message rather than reply directly: https://mailarchive.ietf.org/arch/msg/tcpm/PHhSAnkBFiBKGavsuU9T_lgQf2M "Yet another interesting observation =E2=80=93 as fbsd currently doesn=E2= =80=99t refrain from marking SACK-retransmission to be not-ECT, you can actually end up getting a CE mark on a retransmission across a ECN-enabled congestion point= . Obviously this is better than loss=E2=80=A6" Well, so far as I understand, not-ect for lets an overburdened network push back even harder on slowing a flow down. Losing retransmissions will ultimately halt the tcp flow entirely and induce a timeout. "What happens next is, that fbsd "honors" that ECE mark, since it is in loss-recovery, not congestion-recovery. It adjusts the recovery_point to the current snd_max (rightmost sent segment), and adjusts ssthresh and cwnd by multiplicative decrease factor..." Except for the cwnd floor of 2 or 4 (bbr). I would like it if reducing cwnd to 1 was on the table. Furthermore, it appears that it also resets the traversal of the SACK scoreboard (incidential a "good" thing, as a few earlier retransmissions also got dropped, not marked, and are being resent without an RTO)." "But in the context of ECN++, what would be the expected response here? I assume, that with the exception of the fresh traversal of the SACK scoreboard, the above steps seem sensible. Any thoughts on this interesting interaction between ECE (during SACK loss recovery)?" More data from the real world is needed. .... Multiplicative decrease is capped at cwnd 2 for reno and cwnd 4 for bbr. --=20 Make Music, Not War Dave T=C3=A4ht CTO, TekLibre, LLC http://www.teklibre.com Tel: 1-831-435-0729