From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ey0-f171.google.com (mail-ey0-f171.google.com [209.85.215.171]) (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 135182020B8 for ; Fri, 22 Jun 2012 13:41:43 -0700 (PDT) Received: by eaaa12 with SMTP id a12so1255263eaa.16 for ; Fri, 22 Jun 2012 13:41:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type:content-transfer-encoding; bh=losU27Giq9+xZ7tSPzDsGic8Ze318le/comyzUbPukg=; b=Fh2I0BtaQvZkodS2pBvBL22/W6uvezlGB8t+SdFQ1DJIGhCd+gE+iLlPWgKOOo0+EB RCPbMyLRoHLFxlgVHEA1kbIapxQg4VHJ6pexEOZXz5UwUgvGI3V3HyRH5Q4f0WkUOirm 3h0NuDkdni/9eWS1ExrKyLQpKOjR4y22inJzc2kZHjhL848UrRrAKDxuyVA0lLCu1W9R Mdh7V2eDXRRPOwTa6A44q0W5Vje1iQSCUfoaupZMeph9B1Y8D1yEuPVXhiUOodSltZxB ccbtKqu20H28SlmgrQmkvAPokYyQtcVhnZkIMwRPOjloOfmy3mD+nWV60c8ifH5jXzSf qv0w== Received: by 10.14.99.132 with SMTP id x4mr756672eef.1.1340397701428; Fri, 22 Jun 2012 13:41:41 -0700 (PDT) Received: from ?IPv6:2001:5c0:1400:a::6a1? ([2001:5c0:1400:a::6a1]) by mx.google.com with ESMTPS id t3sm115984463eeb.15.2012.06.22.13.41.39 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 22 Jun 2012 13:41:40 -0700 (PDT) Message-ID: <4FE4D882.50308@gmail.com> Date: Fri, 22 Jun 2012 21:41:38 +0100 From: Robert Bradley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: cerowrt-devel@lists.bufferbloat.net References: <1340395875.353911244@apps.rackspace.com> In-Reply-To: <1340395875.353911244@apps.rackspace.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Cerowrt-devel] Fwd: [PATCH] ag71xx: Added support for baby-jumbo packets. 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: Fri, 22 Jun 2012 20:41:45 -0000 On 22/06/12 21:11, dpreed@reed.com wrote: > Good step. Why not allow 9K byte jumbos when one's packets traverse a path that is internal to the local area, and all the 1 GigE links support 9K? > All the posts I could see claim that the System-on-Chip NIC (Atheros AR7161) cannot handle packets greater than 1540 octets, so routing 9k packets from wired->wireless or wired->WAN would not be an option. If I understood Dave's previous post correctly, though, the built-in switch allows jumbo packets, so wired->wired internal traffic should work fine with 9K packets already. The only issue with that setup is that with mismatched MTUs, it might be impossible to communicate with the router and the 9k-friendly nodes at the same time. Thankfully, on Linux at least, you can set per-route MTUs (http://lartc.org/howto/lartc.cookbook.mtu-discovery.html), so it might be possible to exploit that to do what you want. Maybe something like this would work? ip route add default via 172.30.42.1 mtu 1500 ip route add 172.30.42.1/32 dev eth0 mtu 1500 ip route add 172.30.42.1/27 dev eth0 mtu 9000 -- Robert Bradley