From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-x22d.google.com (mail-qk0-x22d.google.com [IPv6:2607:f8b0:400d:c09::22d]) (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 7F0ED3CC2F for ; Fri, 8 Apr 2016 07:51:13 -0400 (EDT) Received: by mail-qk0-x22d.google.com with SMTP id i4so42752495qkc.3 for ; Fri, 08 Apr 2016 04:51:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:to:references:cc:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding; bh=UzsFG6ilNM/r31bXVupg7DS+hiFBkglDBF8mukq39ng=; b=iUWgAjhlBOosFS8WhAq59XxS6n5PAE1ZQaUpN+qekk0Lp8QD3mLlsLCC3b3M2+lnTy nCrlYpf4JGU5litucoBdr5yp/5O7czyDQApSIl8wn2iDdKcqsKA2o416ipw5hMuIxqos hoYbcd8BFx8gVCl+8WUxm2NqJgEdcVj0m2/KYpkzkbqNFWMPrgrHFYtZ2V1oF75CBeXy JjCRpsQ3jkTQxoWq1ge4Dozik26N8xyGaTkeLRloIkqwbMzxB8fL7imqUu/eglGUk46E IQO0DVnOMVVu5wSj5ruDpzHpS+6atpLsCusqFOwdd4QNUEOKtR13eU1eVKYtE/xGhjzV NDXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:cc:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding; bh=UzsFG6ilNM/r31bXVupg7DS+hiFBkglDBF8mukq39ng=; b=EmJgh5njBas41HI0fEfCPbmp43lCMEQA+4ODmiugmMDTI2CPXq5M2VUKEJx246t5ix HEE7TgRQDyg75f0aliSZakMrx448/VEOrkCgw7kOcbVO1iaUwQW8DsQrrImwhI5xGSRb +4xhm5xj5LvDebUCKkeZQuD5xDisHFmr+qlFlKbq+GZ7QHYHpOUJgjUUOTpDcHVFS2DN f4D3tMTjWIFYf0ghs/X82fGsn7NavCHfpEB/xTHYB7cGcQkoOGS41KnftIAVVhWkOLCQ fqymzsviM7hGPf6P4dLM63EyZUkqBB0SxwSU0QN+yjZZViFUhnXHSIyqCRfHerp/Hyo/ WnQQ== X-Gm-Message-State: AD7BkJKqFLKoe6ezIRIw4C6AdasNEAilxJS/XZCXDSbvXsTOmjFezSXvN8ghhK4ztL3SJQ== X-Received: by 10.55.75.12 with SMTP id y12mr10379343qka.73.1460116273157; Fri, 08 Apr 2016 04:51:13 -0700 (PDT) Received: from [192.168.1.156] (c-24-61-11-132.hsd1.ma.comcast.net. [24.61.11.132]) by smtp.googlemail.com with ESMTPSA id l126sm5317203qhb.30.2016.04.08.04.51.12 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 08 Apr 2016 04:51:12 -0700 (PDT) To: moeller0 References: <57066793.5050608@gmail.com> <056D9AAF-85E2-4849-A3EC-4CE77276DF24@gmx.de> Cc: "cerowrt-devel@lists.bufferbloat.net" From: Richard Smith Message-ID: <57079B2F.8070607@gmail.com> Date: Fri, 8 Apr 2016 07:51:11 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <056D9AAF-85E2-4849-A3EC-4CE77276DF24@gmx.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit 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: Fri, 08 Apr 2016 11:51:13 -0000 On 04/07/2016 12:16 PM, moeller0 wrote: > 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). 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 “1+": > 1500 (payload pMTU) + 6 (dest MAC) + 6 (src MAC) + 2 (ethertype) + 4 > (FCS) + 7 (preamble) + 1 (start of frame delimiter) + 12 (interframe > gap)) = 1500+6+6+2+4+7+1+12 = 1538 ”Equivalent” in that the > interframe gap is not really used, but filled with silence but it has > the duration one would need for 12 bytes. I knew there was a bit of overhead but thanks for laying out the details and why it matters. > 975000 * (1538/1514) = 990455.746367 (which still is below the 1GBit > Layer1+ ceiling that GbE has). At 985000 * (1538/1514) = > 1000614.26684 you would already have slowly caused the NIC’s buffer > to fill ;) So by luck I just barely made it. :) > 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. I knew that there might need to be some overhead accounting and I looked at Link Layer Adaption tab in the options when I set up the SQM but the info in that menu isn't quite descriptive enough for for my setup. It has a box for "Ethernet with overhead, select for eg VSDL2". I'm using Ethernet but I don't know about VSDL2. If I select it then I get a 2nd box that asks for the per packet overhead. Even if I had tried to fill that out then I would have gotten it wrong. :) The other option is "ATM" which I know I'm not using. Not knowing what I really should select I just left it at None. Perhaps there are too many combinations to add items for everything but a few more options and more descriptions of scenarios might be helpful. So now that I have that set at 24 is it worth re-running some of the tests? -- Richard A. Smith