From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f171.google.com (mail-lb0-f171.google.com [209.85.217.171]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 7299B21F0C9 for ; Wed, 20 Jun 2012 17:58:48 -0700 (PDT) Received: by lbom4 with SMTP id m4so3054637lbo.16 for ; Wed, 20 Jun 2012 17:58:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=rt72GYjbpYXj9skkL6QZdSCAMKM5uDZTo07T29e4Zc8=; b=A8HbArAaeRA3cfX8wU0Hc3HW0+EaX/GTIsNnPtTAH2YLgOEDeiRzv5XNHFHtEauZu/ cptllw3TztMTKU8Ais8zoB3SnykbcS3nbXmyaeuuetp90zVMMaurFR2bQ02bk3/tFYAz xHeILm9Y1+tWYGdFnfV2spjL8ZGpmSvvkhut9Cxm68w+WOdbOekNQE8cBX3VjecEvmPQ au7e97AkLH4oZAcHIbg5xwd7yMauP8PbX+dbplnllSNLf+i5ZQtLYBzcFVKrIK5jzGOB QC+ElmmXd01JSpS5HsSA4itay1YBKydkB10MkO1/IeIqdYMLUNz8HeJ07Hnu9+ycOSfJ VoGg== MIME-Version: 1.0 Received: by 10.152.111.200 with SMTP id ik8mr8522340lab.15.1340240325797; Wed, 20 Jun 2012 17:58:45 -0700 (PDT) Received: by 10.112.85.71 with HTTP; Wed, 20 Jun 2012 17:58:45 -0700 (PDT) In-Reply-To: References: Date: Wed, 20 Jun 2012 20:58:45 -0400 Message-ID: From: Dave Taht To: Alexander Hulse Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: cerowrt-devel@lists.bufferbloat.net Subject: Re: [Cerowrt-devel] Baby jumbo frames support? X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 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, 21 Jun 2012 00:58:49 -0000 On Sat, Jun 16, 2012 at 5:53 AM, Alexander Hulse wrote: > I've done some basic research and some (unsuccessful) hacking the on the = driver source for the ag71xx driver and was wondering about baby jumbo fram= e support? > > I know that the WNDR37/800's built in switch supports passing jumbo frame= s, but the underlying router interfaces do not support large MTU frames. > > However, this: > > http://wiki.mikrotik.com/wiki/Manual:Maximum_Transmission_Unit_on_RouterB= oards > > seems to imply that the built-in interfaces ought to support baby jumbo f= rames, unless I'm misunderstanding what they are saying. > > As to the "Why?", in the UK, the fibre offering by BT using FTTC uses a P= PPoE modem that can understand PPPoE packets with an MTU 1508, as described= in RFC 4638. > > It was possible using a Netgear WNR834T with the application of some patc= hes from the pppd git: > > http://git.ozlabs.org/?p=3Dppp.git;a=3Dcommit;h=3Dfd1dcdf758418f040da3ed8= 01ab001b5e46854e7 > http://wiki.aa.net.uk/index.php/FTTC_Modem > > Would this be a useful feature to add (if possible) to CeroWrt so that fu= ll sized frames can be used if the ISP / connection supports it? I don't quite understand what you want here. The internal ethernet connections on the netgear 3800 are both connected to the switch. The switch is capable of jumbo packets, the ar71xx driver appears to have vlan support only. I'm told it does not have jumbo packet capability, but as to what it's upper limit is, is unknown. As for PPoE with a size 1508... um... one or the other device is going to get in your way here. I presume that 1500 works? You would do better to contact the author of the driver (juhosg) to get your question answered as I'm under the impression he is under the right NDAs. I note that in cerowrt the switch has been configured for jumbo frames even tho the ethernet chip can't do that - because it cuts latency down by a lot to pre-allocate for jumbo frames as the on board buffering on the switch is quite large - in fact, I regard it as too large, even now... > > Alex > _______________________________________________ > Cerowrt-devel mailing list > Cerowrt-devel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/cerowrt-devel --=20 Dave T=E4ht http://www.bufferbloat.net/projects/cerowrt/wiki - "3.3.8-6 is out with fq_codel!"