From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.15.18]) (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 827673BA8E for ; Thu, 7 Sep 2017 03:58:37 -0400 (EDT) Received: from [192.168.250.101] ([134.76.241.253]) by mail.gmx.com (mrgmx001 [212.227.17.190]) with ESMTPSA (Nemesis) id 0MQzUc-1e2Ou20Kfm-00UN89; Thu, 07 Sep 2017 09:58:36 +0200 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) From: Sebastian Moeller In-Reply-To: Date: Thu, 7 Sep 2017 09:58:35 +0200 Cc: Dennis Fedtke , Cake List Content-Transfer-Encoding: quoted-printable Message-Id: References: <915b0913-0ac5-c6b6-3771-752a9e41dff2@gmail.com> <0D998858-A2FD-4CE3-8B9B-07C6448C8F3B@gmx.de> <6581a265-041e-5ac0-9d1c-66067e45bfa6@gmail.com> <066e0fb5-b1a8-ab53-5a66-25fbf47d8007@gmail.com> To: Jonathan Morton X-Mailer: Apple Mail (2.3273) X-Provags-ID: V03:K0:2c27dQ2fsNOwkrKANtOFceY24pN23gPAubIVEwLuu+EKOGco3H7 tf1JT1TP4xDfMcZhpdn93jyr5iRzCBCB1xFwlWM4ivvdQiHmFLmDyJPQApEkJiMGGugSAm4 SaTWgkqleOVDvM/HpG+xMHVKsJtjdvRLOv3cgxqzAUsJ7ZqeDtFHM7IcdjwBmJAl5FiKQ7D 1bHUPmPX5kCjT8IQVslaA== X-UI-Out-Filterresults: notjunk:1;V01:K0:IabjSV+wTj4=:J0cXpLT4fZ1/44Vm3RcYbz d7U7u9tZ5g5CrXK0T+v11pNJj+/4Sb/1BkjQoIRF1AbApOz4lYaG4rD0me69lgLdMjFWUDlVN +1TDq3i9EbyBmijhKFbva9fZ2acp6M8Gr0FQlUZe9oUbTbKWYtN7z4kO/Q9foP7WIgbZLjtZK JnwhJvAGt5wzqvT+HNEwfmX3llJZSn+LqYi+rLiAkmpmrcXSXBRAhmM3u+O43javUFV473uOq 3qSN1EuMDWAcQNF+wnsGCXnf4q2Uc8fjloCkh8BDpCd+4n1/u5LKwSwWcb09gnV1UJbfjA3XE Rew0B20yZ7C+ZMEsnqb7tGfYHJqGIgsLH7fOwi9f9GIyMRK8U7Fs1AGx8wQrBHPUwBE6ERcxS PXg/eemFWlQGKHIqORTrTHpxoPTHKvz5IHwZvyGSxYAWNHlJe3Rd4myESX1h8Omk23agJ2YJO NkNWpMhZOBPwmCcSbHih2Ngcs10CF/p73jFhHPW11oSBlXMlWsOvLIObrOEmlFqH4cYzp7FVT dH8SW69suCpgqrSjjgqTjfcSKxTwtC0PdHBnUFejZUii2TfOcXyRkLnI8pIRo54pMmtnPNlg1 sw2xdHbK7sIWykUPEKi2rDGUEufhgthXxmwOMEwoO8TlPOYHgmOtBXZE/aqRLCOSp4OGTJgO+ XTBMHCaUVhRYTJ2w6PNuurO6XY90i6wCVd+LshETRHSPlbXXUFBIPR6NK8Qr7ou+cDTdBmGuC +kqpQEoNvlVCHzjWkjW08v6EC1mQUHhkFpvvqH0hZK59ROZ1guZSNT8px8rfAmYxlkVJ7q6wj +e7ErSe6jWSal7U2yYz3Xl+PCiQtp0nP1362s1WBBMuavuImiw= Subject: Re: [Cake] overhead and mpu 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: Thu, 07 Sep 2017 07:58:37 -0000 Hi Jonathan, please let me elaborate below. > On Sep 7, 2017, at 06:25, Jonathan Morton = wrote: >=20 > Because 1514 is the normal maximum size of an Ethernet frame. This might or might not be true (depending on the defnition of = ethernet frame one uses), but it certainly is not overly helpful to = novices, as e.g. https://en.wikipedia.org/wiki/Ethernet_frame will show = the FCS as being part of the layer2 ethernet frame and 1514 does not = contain the FCS nor any potential VLAN tag(s).=20 What is probably correct to say is that 1514 is the kernel's internal = view of the size of an ethernet frame (most likely the FCS will be added = by the NIC, so 1514 is the true size of the data the kernel shuttles = around at that abstraction layer, but certainly not a real complete = ethernet frame). > This can easily differ from the size actually used on the wire Not easily, but certainly with 1500 bytes payload an ethernet = packet will take at least 1518 bytes on the L2-wire and effectively = 1518+20 =3D 1538 bytes on L1 (here I account for the silent inter-frame = gap by the 12 bytes worth of data that could be transmitted in the same = time) > and from the size used by the provisioning shaper. And that is the thing that makes specifying overhead hard to = automate, instead of the actually connected interface one needs to = figure out the overhead (and bandwidth) applicable on the slowest part = of the internet connection... (Which in theory is variable, but in = practice it luckily is often the link to the ISP). Best Regards Sebastian >=20 > - Jonathan Morton > _______________________________________________ > Cake mailing list > Cake@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/cake