From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-xd2e.google.com (mail-io1-xd2e.google.com [IPv6:2607:f8b0:4864:20::d2e]) (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 801EA3B29E for ; Fri, 19 Mar 2021 10:08:22 -0400 (EDT) Received: by mail-io1-xd2e.google.com with SMTP id n198so6207404iod.0 for ; Fri, 19 Mar 2021 07:08:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=JtPpgVM9T+CfWHzzAOo6S6hbIGBfsg4B7/fT58gNgXM=; b=vgyqJhQUAHVfYCufJVyBQlEzjBdSmq8cFqBwqWAFiPmRPXsdakdxfgrLdD77ClOlzI +4T8h+goVNmBbwuUyI3PnPRAhCnrOxSObxLdy9jLEMZebMvpe3OsSQ1/Y/5JC5hzi2Ei TpBU4FRvfyJ3g+zCyJKuhnGFpXr5MGhXrvuvus1IzbQRreUeO5tS9+Vpx7fjGJFLGb73 ++9nGioxBbZzH4MRturKMlD3BqXDfmFB5yvarPab0WK5Hd7elgG3kO3DCue15X0rQBjD 9EDAmLHRpiA5wvMN1tUPRmXTMkPKXfbU8YtVBgzzLzr9i6FfL0pNx7L9A5MYuGMtaFa9 PjsQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=JtPpgVM9T+CfWHzzAOo6S6hbIGBfsg4B7/fT58gNgXM=; b=KZgK4Fsc3zAgwH1R9M87XC3Gdo0aDzyDka75awxbPM//Fr4CI7qfDSqmW0mooXNLy1 f04pyHo4rjubCbHIpCCE621DurrYMhCHF4GxKp85sgQqKY0Vtk0Zdwolkqp0o8hLJheF CMxKyCwiQsk9yjsgpRlBSGqW7VzmxTtbTRZip9pa2bVZdDHma0PDRXWNdVenD37+vugF YQwPgLhlBWW5wK6+eN2tLfMXpPpZsM2uHnU1H2YGlSfFsU6mY4mFVZ++7no1etYtdvG6 qK0rjtlsAXoT3a+o6xqpc4tkaBAVlU4Jhk5twdHbR1SVGI+0B7+uzjiQiW+08dRUJB/x Ap4A== X-Gm-Message-State: AOAM533mTs7ZclimCMsesTgdXWuTlLS4uRM5znubc3nJhgOW0dZcclXe w5e31X8pa32cCD+gti3jq5bGJ5EzzOe7eqpEpPE= X-Google-Smtp-Source: ABdhPJxQStV+qT35u8aelr/6rFx3wZRieCenNX4pi6FLPPna/EcGFxU0VtexvLZE652jropRf5JYlbnx4Lbh6SigdYM= X-Received: by 2002:a5d:9250:: with SMTP id e16mr2952734iol.27.1616162901859; Fri, 19 Mar 2021 07:08:21 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Dave Taht Date: Fri, 19 Mar 2021 07:08:10 -0700 Message-ID: To: Pete Heist Cc: ECN-Sane Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: Re: [Ecn-sane] mosh ecn bits washed out 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: Fri, 19 Mar 2021 14:08:22 -0000 On Fri, Mar 19, 2021 at 1:25 AM Pete Heist wrote: > > Meaning, the negotiation succeeds and ECT(0) is set going up, but > zeroed on packets by the time they come down? There has never been any "negotiation" for setting the ect(0) bit in mosh. It's been set since 2012 on all udp packets. I reasoned at the time, that since mosh is the tool of desparate sysadmins everywhere coping with excessive latency and jitter on everything (the loca= l echo of keystrokes is a godsend), that turning further enabling CE would help, or, if stuff with that bit set was dropped, be the focus of outrage by sysadmins everywhere and ecn support quickly reverted. Nothing went wrong. :) mosh has an extremely robust response to marks, reducing the rate to 2 fram= es per second from as much as 60 fps on receipt of a single CE. Not going any further is analogous to the "subpacket window" problem ecn enabled tcps have, and attempting to sustain that low frame rate essential for mosh's operation. Ironically, since I last bothered to look, mosh gained ipv6 support, but th= e parsing of cmsg and the setsockopt for ecn capability were not updated for = that. Also ironically, mosh packets were originally marked AF42 but it stopped wo= rking on one of MITs networks, so the dscp setting was removed, but ecn kept. https://github.com/mobile-shell/mosh/blob/master/src/network/network.cc#L16= 6 It would be trivial to sce enable mosh. > > The negotiation can also be blocked with iptables --ecn-tcp-remove, > which just zeroes out ECE and CWR, preventing negotiation > (https://git.netfilter.org/iptables/tree/extensions/libipt_ECN.c), but > I doubt that's very commonly done. > > On Thu, 2021-03-18 at 13:00 -0700, Dave Taht wrote: > > mosh, which has long had excellent support for ecn, appears to be > > getting the > > ecn bit washed out along my path from california to england. > > > > ecn survives up that way, but not down. > > > > Just a single data point thus far. > > > > --=20 "For a successful technology, reality must take precedence over public relations, for Mother Nature cannot be fooled" - Richard Feynman dave@taht.net CTO, TekLibre, LLC Tel: 1-831-435-0729