From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.17.22]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 03A913B2BC for ; Thu, 7 Apr 2016 12:16:29 -0400 (EDT) Received: from hms-beagle.lan ([93.237.70.232]) by mail.gmx.com (mrgmx101) with ESMTPSA (Nemesis) id 0LsgvV-1bqFIA0Ycj-012L77; Thu, 07 Apr 2016 18:16:27 +0200 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2104\)) From: moeller0 In-Reply-To: <57066793.5050608@gmail.com> Date: Thu, 7 Apr 2016 18:16:25 +0200 Cc: "cerowrt-devel@lists.bufferbloat.net" Content-Transfer-Encoding: quoted-printable Message-Id: <056D9AAF-85E2-4849-A3EC-4CE77276DF24@gmx.de> References: <57066793.5050608@gmail.com> To: Richard Smith X-Mailer: Apple Mail (2.2104) X-Provags-ID: V03:K0:23G1Z9RXFbXMsGYI7nuRkggGC0cbkakOJF/H5zimWfu4MV9d3rz ostol2YwODoaAbYfw4HSjCHtt12Qsfw15g4jAJsurkknyunWyax94c4GqwHogNRJFwkZLCn kjusKtW8Zd22YXbQb/cES3/oAKyOwopHS47VMUNi+FYIrPdO9o7taWYNlF/v9aIp2dZLBCh RBgdZW7YnTRbC6M2SatSA== X-UI-Out-Filterresults: notjunk:1;V01:K0:xVM7/kgiCJg=:WwTjOhLP2q3eUIqNBYKpol vTeotlT1Ncp4T5/p09oDh/jwFei9B8RRRhKicfEgiCK+1V+4VM8b71CG/fRPwgLBmKBVQU0Pb uqTP6gzcXp6nnGi+lDsRhGLwdrh3TRNEi0DBjiSH1pM6YTixiwm1UW8vqR0FyZqmYNiOTaBOF YnXnoFQTRC1BjFBcl2JsOURiP9/70Bz3cjfBnfOF0wE3VxAKhvw+faOaXF6rQ0Aa/AmM+YFRx A8kWSG8phAQLNAfSIxgbpWMZpOZe5FpJSTysac0QjbRe/grh2ZG/b0VbqviE6YFMLB+1cTDEE 9FLECLX7zLCtUdhY61nBscUpxrf4mTZoUhJnydkf4Rk0/d7qNhWCzA3Qcfa9dXDmN9ePy4slE tNZiHEteGTjv3WyBRrPGfJ9jxaouVp/3mCfscPZOSG8FnekBzDgx6yroP3T14abklz3a9kMgo Y7o3RQk4CHltKHekRHYmvC9TQGTrvHneGBucXsZ4bb+v6iGe1ZhyLUZeUGdh70HL9U7N3sx/z mF6DLtASWLvulHrUeKwCm+HQC9NRga+72T+1bnQbLpsoRASNAOJvCjdHm9ZtYqdH1ZUU8rttL B1+/eERgCwAyfrT8pa55Tca1hf+lCMG+L+vb2/bG26gstc5oICZX7W93xlwjlcCJ90X5PIu0C cII515j8M038jmArokISpkTQ/dsPU3XfIZVJCa/NjVCL0JxXsHWI6sG+ZVYKGOAchc9gfmE5g sB+DFIUtH72pOvs7U+Q3OQ0hTTHCsQRmcvJUmpEQPc/ipGx/DAvu219HImlEAS2X/Bg1XmJrp a6PiD1Q Subject: Re: [Cerowrt-devel] Linksys wrt1900acs rrul traces X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Apr 2016 16:16:30 -0000 Hi Richard, > For these tests I had the inbound and outbound limits set to 975000 = kbps. 975000 was somewhat arbitrary. I wanted it below 1Gbps enough = that I could be sure it was the router as the limit but yet fast enough = that I would be able to see the peak transfer rates. All of the following might be old news to you, but please let me = elaborate for others on this list (well, most folks here know way more = about these things than I do).=20 I believe Gbit ethernet is trickier than one would guess, the 1 = Gbit rate contains some overhead that one typically does not account = for. Here is the equivalent on-the-wire size of a full MTU non-jumbo = ethernet frame: Layer =E2=80=9C1+": 1500 (payload pMTU) + 6 (dest MAC) + 6 (src MAC) + 2 = (ethertype) + 4 (FCS) + 7 (preamble) + 1 (start of frame delimiter) + 12 = (interframe gap)) =3D 1500+6+6+2+4+7+1+12 =3D 1538 =E2=80=9DEquivalent=E2=80=9D in that the interframe gap is not really = used, but filled with silence but it has the duration one would need for = 12 bytes. The kernel, if left to its own devices, will only account for 14 of 38 = overhead bytes. But that means that each packet will carry an additional = 24 bytes of unaccounted for size that still needs to be transferred: 975000 * (1538/1514) =3D 990455.746367 (which still is below the 1GBit = Layer1+ ceiling that GbE has). At 985000 * (1538/1514) =3D = 1000614.26684 you would already have slowly caused the NIC=E2=80=99s = buffer to fill ;) Luckily sqm-scripts will allow you to specify any additional per-packet = overhead so just set this to 24 and things should just work out I = believe. Best Regards Sebastian=