From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f175.google.com (mail-wi0-f175.google.com [209.85.212.175]) (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 87F5A202224 for ; Sat, 23 Jun 2012 13:10:55 -0700 (PDT) Received: by wibhn6 with SMTP id hn6so1403769wib.10 for ; Sat, 23 Jun 2012 13:10:53 -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=480GMeNpxCScfQzrEqM49Qz+Y87Tz+aO5KmiZQZdpIQ=; b=ozWJgEddVpYd6l+cLf8DMefAkz46CkWu5BNeCmBZpPi9sya/Bbt0mu7QLejy/VVxq6 5KUdqsM8B0dgsy94Ex4Idu8Ecv57LbLO1VYZBsnVL/dEePZdzSVfWJ68KOaDf7bnTYe+ UhP38UfM+pOg4r+87pPzJDQ5vJgoEfiXgLKQkwz+t87C16ys13FNbTXuvYZhCiIaIPiF CyPygHAAA1Qd1dZmvHCM9meQDPyvtvopUq9oSIb/UBvLTrJDnX3GcDgtCAUqbQN/LT1Y Xfq1/HuzZ8O0ddjbRij9isnSr4hH+7uMcXvk/ZkRqmY5Joo4gaPzT+6ueqclcK33dquf SVLw== MIME-Version: 1.0 Received: by 10.216.198.14 with SMTP id u14mr3391559wen.12.1340482252786; Sat, 23 Jun 2012 13:10:52 -0700 (PDT) Received: by 10.223.103.199 with HTTP; Sat, 23 Jun 2012 13:10:52 -0700 (PDT) In-Reply-To: <1340479742.390625935@apps.rackspace.com> References: <1340395875.353911244@apps.rackspace.com> <4FE4D882.50308@gmail.com> <1340479742.390625935@apps.rackspace.com> Date: Sat, 23 Jun 2012 16:10:52 -0400 Message-ID: From: Dave Taht To: dpreed@reed.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: cerowrt-devel@lists.bufferbloat.net 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: Sat, 23 Jun 2012 20:10:56 -0000 On Sat, Jun 23, 2012 at 3:29 PM, wrote: > I find it curious that packet aggregation is done in 802.11n standards, b= ut that the packets are limited to 1540. =A0 I bet that limit may not be th= ere in all Atheros NICs, and maybe not in this one. =A0Will investigate now= that I'm curious. We are talking about two different interfaces here. The switch in cerowrt is capable of 9K packets (maybe more, actually, I'd have to look at the data sheet again) The ag71xx is the ethernet driver, with the 1540-ish limitation The ath9k is the wireless driver. The MTU for 802.11 is 2304 bytes. I think there is a successor standard which can do a little under 8k. Neither of which are used used a lot. Interestingly in my previous project to this one (wisp6), what I'd done was build a pure ipv6 wireless backbone and tunneled ipv4 over it - encrypted - using larger MTUs on the wifi to do so to ensure 1500MTU for the ipv4 stack. This was in part due to Nicaragua already being behind at least 2 layers of NAT in the general case, so I fiddled with things like AFTR to move the NAT closer to the gateway to the internet, and trying really hard to lift things like otherwise disconnected schools into the ipv6 world instead. I ran into zillions of problems with this, while I sort of made it work with the original hardware I used (which was an embedded arm (pocobelle project) which has a max mtu of 2048), as I tried other things like olpc, openrd (now dreamplug or smileplug), and the current ar71xx/ath9k (nanostation M5s and 2HPs), I kept hitting walls in the device drivers, in the encapsulation standards for things like diffserv bits, in crypto in general, in the MTUs and PMTU, and oh, yea, bufferbloat. Big time. I abandoned the MTU changes along the way as too hard, and later on had to shut down that project for other reasons. And at the time (2009), the entire country had like 4 ipv6 prefixes in use, and no ipv6 transit to speak of, with the pan-american fiber internet 2 line basically cut between Honduras and costa rica, due to lack of funds and attention, so almost all all US ipv4 traffic ended up being routed through Florida, and I had to use hurricane electric tunnels to even prototype the last hop. The nearest F-root server was 80+ms away from where I was. Redwood city, california, about 136ms. > > -----Original Message----- > From: "Robert Bradley" > Sent: Friday, June 22, 2012 4:41pm > To: cerowrt-devel@lists.bufferbloat.net > Subject: Re: [Cerowrt-devel] Fwd: [PATCH] ag71xx: Added support for baby-= jumbo packets. > > On 22/06/12 21:11, dpreed@reed.com wrote: >> Good step. =A0Why 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. =A0If = 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. =A0Thankfully, 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. =A0Maybe 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 > _______________________________________________ > Cerowrt-devel mailing list > Cerowrt-devel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/cerowrt-devel > > > _______________________________________________ > 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!"