From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: 802.3x pause frames Date: Tue, 11 Nov 2014 12:29:39 +0000 Message-ID: <1415708979.3398.92.camel@decadent.org.uk> References: <545B70C9.7090702@fkie.fraunhofer.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-+TPJzN4a+eTNAiiDQrU4" Cc: netdev@vger.kernel.org To: Julia Niewiejska Return-path: Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33237 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752943AbaKKM3w (ORCPT ); Tue, 11 Nov 2014 07:29:52 -0500 In-Reply-To: <545B70C9.7090702@fkie.fraunhofer.de> Sender: netdev-owner@vger.kernel.org List-ID: --=-+TPJzN4a+eTNAiiDQrU4 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2014-11-06 at 13:59 +0100, Julia Niewiejska wrote: > Hello, >=20 > I indend to do some experiments with 802.3x pause frames, but I have yet= =20 > to find a setup that works. I used a tool that generates pause frames=20 > [1] in two setups. First one consists of two virtual machines on a=20 > VMWare ESXi 5.5 server connected with each other through a virtual=20 > switch. In second setup two physical machines (Desktop PCs) were=20 > connected directly by an ethernet cable. The VMs are running Debian=20 > Wheezy 32bit while Debian Testing (Jessie) 64bit is installed on both=20 > desktop PCs. Below you will find some information on the ethernet=20 > adapters and drivers used in the VM [2], the desktop PC with the more up= =20 > to date hardware [3] and the older machine [4]. I used the following=20 > command to activate flow control: >=20 > ethtool -A autoneg off rx on tx on >=20 > First of all I noticed some discrepancies between the output of=20 > mii-tools or ethtool -a and the attempt to change the flow control=20 > settings with the command above. Only the Realtek adapter actually=20 > output that it didn't support the operation, the other adapters accepted= =20 > the settings without any error message. >=20 > In both setups pause frames were generated on one machine while a ping= =20 > was sent simultaneously, as suggested in [1]. While the VM connection=20 > was set to 1 Gbps the whole time, I also tested a 10 Mbps setting on the= =20 > physical connection. Even though the pause frames were always visible in= =20 > tcpdump at the receiver, I didn't notice any influence whatsoever in the= =20 > ping results. [...] MACs that implement flow control will not pass pause frames to the host; therefore these MACs do not implement flow control. Ben. --=20 Ben Hutchings Experience is directly proportional to the value of equipment destroyed. - Carolyn Scheppne= r --=-+TPJzN4a+eTNAiiDQrU4 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIVAwUAVGIBOee/yOyVhhEJAQoNxg/9EcWZSLPhV4fq7KVhEGrSR63+eqhu2Wbi n2G3nodejtxBt7RNgy2fXApBw9LAO69NFiVoezJx8vMkx1BWHNBf4ZrB8azZm+vu qd+mWFBOeHiA3mdLcWSrQrO5h//2D4RB+zNAoHeZiRzE1iqlIQ7ZhaUIaRzeMvV6 XVEdIl3zocrOaSFXmTMlMcs95HJX5gZcsEKtoSISnGsXBdWsIYP4uhiivVTZUC5a ciyJK8RjObkh2+rwsuM8KJL8C5sWoZ6OR5h2yqbRPIkwib7YArIyE+8sCWY5SFX+ 2YRgm/+2dfEz44h+xmxLU1EKfHZxpAnEC7hh0sjc8jfAfTHCn/vk1TBgP32ZNkSc aD0oCsNW0cmXxWHkzrqsuiNE/TNie3lSzfQYiE/i8zLGWfC96xRyNZUujJf48bOv X9QJrsajCtK2tOg/V6zmjfMYhez2+Lx4Q0pWz9C5To/1aJPw0qJgJ1P88GNZ0IMY JGb9RNpJldI7vRB1+199S316AhM2kLqxE2WRgf9N8k8TezlymVneXMG9bZJBMHDn 4a0FvHMQQbzQQOJE8TCJ6tqShMEzNHX8GY+d19RC7ty/smqp9D4ibyO3wVFBuwOV SaIu9dUEu7WBbdySHTdlg1ooqMAEvhPgQJnlmN9fsiphWb0WLIJOLdf2NQK5iEOj J/P9gCi35sM= =3A8a -----END PGP SIGNATURE----- --=-+TPJzN4a+eTNAiiDQrU4--