From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-x235.google.com (mail-lf0-x235.google.com [IPv6:2a00:1450:4010:c07::235]) (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 BEB273B25E for ; Fri, 6 May 2016 15:33:30 -0400 (EDT) Received: by mail-lf0-x235.google.com with SMTP id u64so142803573lff.3 for ; Fri, 06 May 2016 12:33:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=WJlt6BVMQ7HRgvWO4xW2a3RhHmjA4/rRVJnXjvPT7/k=; b=YJjw1ufxt+Fn216yWOlL0SDxakSp7UpyHTyVzLRHHQp4oTM0STWbeBJsZV5ALsiPRV CKNUGjPDkMZRt+fORzqfBpi76rGJ4mdq3kW2b3TX7HmclICZVSNJ8E2tMYWLz1QPTDVt czMS1dvZgp7clOfLHBzWXJAWrm0tA6mCUvs2Ej5LoxJu00fIBTfUyZedFsrN086NLVUS PzuHkUjbX2nLvrhHOYA3nQm5vlEGbiPlIrbPEnTzSKUTIU4yP+Q4uRiTQZ88GNFrPtng QIKPYfQV2QFAiOiunnJM+SN8vDfq8NXr/iNDt9S9DwzZBiv5x886xCmsjA7g3unFfnhT WLmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=WJlt6BVMQ7HRgvWO4xW2a3RhHmjA4/rRVJnXjvPT7/k=; b=mWVcNf0dJ//VCF88W3upUDwuKgzm+cS6B4ReTrzcs62lZwjVuvkM1ogrsK2Nb5Htwz dc0fxwznTeUpzFBKJPFWBWhm2xOuY12EhbUaOj8BK/vpsB7YA2KGCSjUapi7w5jv1RR2 tWQoJ8hK//PKw88c4Oz79zhkr2VIvJv3aC5dK4PD6fSNpHxKR1uIQP2j6N9eU2dAIBpl X4BC4yFjHbhdiPwCxKAX4KF5XBWQ22B1I/1AhapA6DGEWToo8pecBYMjEqtXyZTVhVhP xl3Y5LwRrjDTWhrGD+eu1CkZfZDZJU1gH+/xB5AGVz4BvREvPHcFqfcf6Ovg5YrgzQQe 76xA== X-Gm-Message-State: AOPr4FU2NvYNehvXoW4kwo9wfwPl5VClcEFUpTLpXOX9oLjHJAuwNlhwrIfNSKYBvLoRkg== X-Received: by 10.112.30.174 with SMTP id t14mr2737664lbh.128.1462563209611; Fri, 06 May 2016 12:33:29 -0700 (PDT) Received: from bass.home.chromatix.fi (87-93-84-153.bb.dnainternet.fi. [87.93.84.153]) by smtp.gmail.com with ESMTPSA id v4sm2750818lbv.40.2016.05.06.12.33.27 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 06 May 2016 12:33:28 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) From: Jonathan Morton In-Reply-To: Date: Fri, 6 May 2016 22:33:26 +0300 Cc: Stephen Hemminger , cake@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: <89951A22-6568-4A07-BC52-5142DADB95BC@gmail.com> References: <1462201620.5535.250.camel@edumazet-glaptop3.roam.corp.google.com> <1462205669.5535.254.camel@edumazet-glaptop3.roam.corp.google.com> <2D83E4F6-03DD-4421-AAE0-DD3C6A8AFCE0@gmail.com> <1577AB06-3C14-43D1-92AD-E37CEDCB8E11@gmail.com> <8F329CCB-038C-4EF4-A01D-DB8C093AE6B2@gmx.de> <20160506083114.0730d9f1@xeon-e3> <26BC8860-0485-4052-A8AC-574737B878E6@gmail.com> To: David Lang X-Mailer: Apple Mail (2.3124) Subject: Re: [Cake] Fwd: [Codel] fq_codel_drop vs a udp flood 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, 06 May 2016 19:33:31 -0000 > On 6 May, 2016, at 22:14, David Lang wrote: >=20 > On Fri, 6 May 2016, Jonathan Morton wrote: >=20 >>> On 6 May, 2016, at 21:50, David Lang wrote: >>>=20 >>> what IP id are you referring to? I don't remember any such field in = the packet header. >>=20 >> It=E2=80=99s the third halfword. >=20 > half a word is hardly enough to be unique across the Internet, = anything that small would lead to lots of attackes that inserted garbage = data into threads. It doesn=E2=80=99t need to be globally unique. It merely identifies, in = conjunction with src/dst address pair (so 80 bits in total), a = particular sequence of fragments to be reassembled into the original = packet. If the fourth halfword is zero (or has only the Don=E2=80=99t = Fragment bit set), the IP ID field has no meaning. Hence the entire = second word can be considered fragmentation related. I agree that it=E2=80=99s not a very robust mechanism; it breaks under = extensive packet reordering at high packet rates (circumstances which = are probably showing up in iperf tests against flow-isolating AQMs). It = would be better not to have fragmentation at the IP layer at all. But = it=E2=80=99s not as bad as you say; it does work for low packet rates, = which is all it was intended for. Here=E2=80=99s my preferred reference diagram: = https://nmap.org/book/tcpip-ref.html - Jonathan Morton