Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264667AbTF0SsA (ORCPT ); Fri, 27 Jun 2003 14:48:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264682AbTF0SsA (ORCPT ); Fri, 27 Jun 2003 14:48:00 -0400 Received: from cs180094.pp.htv.fi ([213.243.180.94]:6272 "EHLO hades.pp.htv.fi") by vger.kernel.org with ESMTP id S264667AbTF0Srx (ORCPT ); Fri, 27 Jun 2003 14:47:53 -0400 Subject: Re: TCP send behaviour leads to cable modem woes From: Mika Liljeberg To: Svein Ove Aas Cc: linux-kernel@vger.kernel.org In-Reply-To: <200306272020.57502.svein.ove@aas.no> References: <200306272020.57502.svein.ove@aas.no> Content-Type: text/plain Content-Transfer-Encoding: 7bit Message-Id: <1056740526.645.2.camel@hades> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.0 Date: 27 Jun 2003 22:02:06 +0300 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3349 Lines: 79 Try enabling tcp_frto on your Linux box to see if that helps the uploads. MikaL On Fri, 2003-06-27 at 21:20, Svein Ove Aas wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > My internet connection is via a cable modem, and thereon from Telenor. (A > Norwegian ISP.) > > In general, when I download something I can get up to 1400-1500 Kb/s, which is > pretty good for a 1024/256 account. (They don't appear to oversubscribe their > lines (yahoo!), but mine is also uncapped when there is spare capacity. Think > traffic-control.) > > So far, so good. > > My account includes 4 IP addresses, and when I actually have four computers > directly connected I can easily get 7-8Kb/s upload from each of them. > Oddly, when one of them is acting as a firewall/bridge for the others or I'm > just uploading from one, I get 7-8Kb/s for *all* of them. (Or the one.) > > This is, dare I say, *not* expected behaviour. > I've been in contact with telenor about it, and have garnered the following > information. > > (A) Although the line appear to be straight Ethernet attached to a > packet-filtering switch (just ARP-filtering, actually), it's *actually* an > ATM-based line. This should come as no surprise. > > (B) Whatever they have allocating the ATM cells for transfer is doing it in > bursts of about 16KB. Or possibly 32KB. Well, the tech I talked to was pretty > sure it was a power of two, at least. > > (C) This means that while I get 8 bursts (or more) of 16KB per second on > download (empirically confirmed, but the cable modem will tend to space it > out when the line is at capacity), giving me a latency of 128-256 ms and so > on and so forth (which I have), I get only *two* bursts per second to upload > things. I think. You may want to apply a multiplier somewhere. > > And, finally, (D): > > This thoroughly screws up TCP/IP for uploading purposes. It *completely* > breaks Realtek cards, screws up uploading speeds in Linux and Windows XP (I > assume they think there is a lot of intermittent packet loss because of the > delay), and has no apparent effect on Windows 9x/2000. > > The cable modem in question is manufactured by Coresma and is marked NeMo. > It's also supposed to have a pretty large send buffer, so if I could just > force Linux to send at some user-defined speed without being so paranoid > about overloading the line, I could get a lot more use out of it. > > For the curious, if I do just that with UDP, I can indeed send at up to 30KB/s > without losing packets. They *do* come in bursts, though. > > > Please, save me before I lose my mind! > > - - Svein Ove Aas > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.2.2 (GNU/Linux) > > iD8DBQE+/IsG9OlFkai3rMARAmZ4AKCeGIXGhREfh0kcA4Dr8FJs9fNuFgCg1sTb > 1bk3+ipUs9tS35oZidxcY4I= > =Zz5P > -----END PGP SIGNATURE----- > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/