From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-x134.google.com (mail-lf1-x134.google.com [IPv6:2a00:1450:4864:20::134]) (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 5C6A83CB3B for ; Fri, 23 Nov 2018 12:14:00 -0500 (EST) Received: by mail-lf1-x134.google.com with SMTP id i26so9179710lfc.0 for ; Fri, 23 Nov 2018 09:14:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=Cm8Viz4Vn9mPTVSZnax89gpOAPAwI8ezDu+lZQJ7e3c=; b=AzIxrHutCT1a/Gpol8z8Gc14yKePFuCv7XU/ZkTebveXpPs0qYSRqCRkJB5qobm/N5 wCLaqhzSpNlVWHZmzuP6F/ww/lTT1yjG67L8DjiuVQbvg8M0HMMtQ/nkxfF+Qt3Za/Wm xkt4IxslB48gKnqbz+AvPszXJVCgD36ZA8GupE0GG+sTrbtTO1v9rBm4yjUs3It6rkAt dOlsStg5gPsDPApyiNe+uKGpvJiTAxXg03Y3wansEGm6Ui/MQBYR3Pg68Jh8OYC3Jxue IDhVAmAYkCg885PCzXtqAN18RcwxtHtNlJDXCmao6K80qHBZSXY0E8hLPgmy9BndLsYb Iaiw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=Cm8Viz4Vn9mPTVSZnax89gpOAPAwI8ezDu+lZQJ7e3c=; b=n90IDuOyyhapWIxWM+FL7ccOlbvPdF0MrdOUG/z4VMefbcAYgfRRGSt2kfQ6ZkRpcf sUAVYGPOFYuE/ecbi+NISrvbYm21iOBy05ZrzSrZL3JFPmzXhMMhZaGLJ3cD6CRiPMVq J19D6vFEzpMzNpuQbM3n/pMzjSTxKdCKwecgwUMlIy282fWRFn5bR7HrMp3NUWpLXZm1 U0SJrJL1IkQYjtIBJTbi3ViaPlyvdear2LLG3t6ITgvFv6U0aPpBme6DtoZl3CtfVi9U dcaam/yAByfja3a12af+h7CzISZ0nOXrOTzc2RfoQVtv2HhBV2b1+72TDblLi/OvHlrK QAqg== X-Gm-Message-State: AGRZ1gIQ5XnsApxiSDHQ19rfEKH4E+V5xgTL6t0R9zv7MEQk33x5vkl6 WcQJmLU0ff7vLGB2vUcfHSA= X-Google-Smtp-Source: AJdET5ck8KWRLBDdZR3QLWYMeEx39uQI6Pndqc04LNxdnE8STO2MKvpRaj9wVBQkfIVd6eiDj3l1eQ== X-Received: by 2002:a19:4f0c:: with SMTP id d12mr9487109lfb.121.1542993239239; Fri, 23 Nov 2018 09:13:59 -0800 (PST) Received: from jonathartonsmbp.lan (83-245-236-220-nat-p.elisa-mobile.fi. [83.245.236.220]) by smtp.gmail.com with ESMTPSA id u79-v6sm3040683lje.36.2018.11.23.09.13.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 23 Nov 2018 09:13:58 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) From: Jonathan Morton In-Reply-To: Date: Fri, 23 Nov 2018 19:13:52 +0200 Cc: =?utf-8?Q?Dave_T=C3=A4ht?= , Cake List , Jendaipou Palmei Content-Transfer-Encoding: quoted-printable Message-Id: References: <87va4nzsn4.fsf@taht.net> To: Dave Taht X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Cake] COBALT implementation in ns-3 with results under different traffic scenarios X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 23 Nov 2018 17:14:00 -0000 > On 23 Nov, 2018, at 6:43 pm, Dave Taht wrote: >=20 > This is possibly a correct result in your simulation!! - the periodic > throughput drop you are showing in cobalt at this bandwidth and rtt. > I'm happy to see cobalt kick in early on slow start but not happy to > see the periodic drop. Jon, do you have time for a code review? I looked at it briefly, but the code structure is different enough that = I need to sit down and study it carefully to figure out whether there = are any relevant differences. The throughput drops most likely occur because the TCPs become = synchronised and remain so under AQM action. You can see that the = frequency of the system is lower in the later part of the COBALT run = than in the Codel run, but the same as Codel in the earlier part where = throughput drops don't occur. But this shouldn't really occur with a = Codel-based AQM (as COBALT is), because a single mark is sufficient to = tell TCP to back off over one RTT. An explanation might be if this = implementation of COBALT isn't running down correctly when deactivated, = so the mark frequency only rises while being turned on and off. The = run-down behaviour is a major intentional difference between COBALT and = reference Codel. I'll look at the code more closely with that in mind. - Jonathan Morton