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 37B7F3B29E for ; Sun, 3 Feb 2019 20:49:44 -0500 (EST) Received: by mail-lf1-x134.google.com with SMTP id l10so9096462lfh.9 for ; Sun, 03 Feb 2019 17:49:44 -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=IyLRgtldJZnMO532SRxv7gx73or6LZlsOP3E8tjBQag=; b=Seck/JRAN5Xc4MMSNQ9H4CSDkU6rgp9R+R8+/fEDtK/mV5xEkti6D0Z7ZNWJbZRj71 zc3FjjClhuBn37Dk6amPFYJ+4acBzyHjw9My3kQT0bnn4w0A/WlzeVaj1Jg+dQ5K/vOK yRPsxgVPX2UXy+2gUJfMJ1pCD/P0fqnbnjqG9IFF5ut19XP7ORtcBDhYHm90hvdfT0s5 D6otkEndJ0RWSdVqhZuNwWT7+WkrdaDfPrr3URXxRFMO8BEnLeZab28MiqiaZ0nasqP9 fMCrDLTAbD4HAICJwfXuqhjRJrBUt8+pzS4dZeN+p3LviZy6hj9uswQRj2dUWe8A9qrd XydA== 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=IyLRgtldJZnMO532SRxv7gx73or6LZlsOP3E8tjBQag=; b=An49lgu7QfXPG3nUkUahtZNUyyYt2AVrzozulapPO/IYbwkkrHVrQCZR4+g3kWlHeg cWTHG9McD3eYKRWUr97CYBfRe1q0dqqvhrNHZzAK91aeAOjiRuBawyKrkj/wi6VIdlA0 lx3L0zcTmGc4JHedXGQOhkw/t33pYJMmsa3yYaOHp9RNBAKOsv+8vN+TIpTell6D7nQq r3UzrsGcbyjEsx2AP5WMPbKzNJTgHvv84clvx3NdvyHgLGzdSPc+ONoHua7CPvFjMHG5 LJj1Pf4x/F0Jx/tQg9X0i2HwlBgEZVHvgGiXF5IJgy2IXiRFQmUXY6f6fYVZ1Fu/gsg4 tnKg== X-Gm-Message-State: AHQUAuYrhTQM6h7gKcS1Uw8yF6H7nk2ABJNbAtJ8O50rO6jyKZceCLgC NnKebO2dfvGcik2ZYF26/Xc= X-Google-Smtp-Source: AHgI3IYusE8rbXTxv8e/+ljTNr0zNi4ftU0sT/ulRf7WK+AFK+H9lqwQbLIcrxntZ6FjAaEq6Vv1qQ== X-Received: by 2002:ac2:5329:: with SMTP id f9mr8046954lfh.88.1549244983005; Sun, 03 Feb 2019 17:49:43 -0800 (PST) Received: from jonathartonsmbp.lan (83-245-233-163-nat-p.elisa-mobile.fi. [83.245.233.163]) by smtp.gmail.com with ESMTPSA id v9sm2778232lfg.15.2019.02.03.17.49.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 03 Feb 2019 17:49:42 -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: Mon, 4 Feb 2019 03:49:40 +0200 Cc: Bloat@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: <35629581-F09C-4E5A-B1D2-83836B43E0C9@gmail.com> References: To: Evuraan X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Bloat] question about ack-filter X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 04 Feb 2019 01:49:44 -0000 > On 4 Feb, 2019, at 3:26 am, Evuraan wrote: >=20 > What is ack-filtering? How is it important? What's the difference > between ack-filter-aggressive and ack-filter? Simply put, we sometimes found that downstream throughput was limited by = acks on the reverse path, on highly asymmetric links (such as ADSL) = loaded in both directions simultaneously. Because acks are themselves = very small, AQM activity by itself wasn't enough to clear the backlog. Ack-filtering looks for consecutive acks accumulating in a flow queue, = and deletes the ones which are not needed, improving throughput and = efficiency. The "aggressive" version deletes more acks, but I think we = found it hit too many under certain conditions. It's harmless to leave it switched on in the non-aggressive mode. If = you're a purist who doesn't like dropping packets, then you can switch = it off. - Jonathan Morton