From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262067AbVFQT1i (ORCPT ); Fri, 17 Jun 2005 15:27:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262069AbVFQT1h (ORCPT ); Fri, 17 Jun 2005 15:27:37 -0400 Received: from waste.org ([216.27.176.166]:59074 "EHLO waste.org") by vger.kernel.org with ESMTP id S262067AbVFQT1Y (ORCPT ); Fri, 17 Jun 2005 15:27:24 -0400 Date: Fri, 17 Jun 2005 12:27:15 -0700 From: Matt Mackall To: David Brownell , linux-kernel , linux-usb-devel@lists.sourceforge.net Subject: usbnet ethernet duplex issue? Message-ID: <20050617192715.GK27572@waste.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I'm experimenting with a Netgear FA-120 USB 2.0 to Ethernet device and seeing some strange behavior. If I run a 100MB transfer (TCP, via nc and dd) over out LAN, with the Netgear on the sending end, I get about 10MB/s, as expected. Receiving, I get ~5MB/s. If I do simultaneous send and receive, the throughput is a few K per second at best. If I do the same transfers between a pair of isolated laptops, with the Netgear on one end and Intel e100 or e1000 on the other, I see about 500-900K per second in either direction. There are no errors detected by the usbnet driver and ethtool reports that the device is autonegotiating, full duplex. Setting autoneg off and duplex to half lets the isolated transfers go at wirespeed. So the question is, what's up with duplex? Everything I can find about the hardware (including the ASIX datasheet) claims it's full-duplex capable but aside from the error counters, it's really behaving like a half-duplex device. -- Mathematics is the supreme nostalgia of our time.