From owner-freebsd-net@FreeBSD.ORG Thu Feb 10 22:05:23 2011 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C9B4C1065670 for ; Thu, 10 Feb 2011 22:05:23 +0000 (UTC) (envelope-from jayb@zoe.braeburn.org) Received: from mail119.messagelabs.com (mail119.messagelabs.com [216.82.241.195]) by mx1.freebsd.org (Postfix) with ESMTP id 670C68FC0A for ; Thu, 10 Feb 2011 22:05:23 +0000 (UTC) X-VirusChecked: Checked X-Env-Sender: jayb@zoe.braeburn.org X-Msg-Ref: server-10.tower-119.messagelabs.com!1297375522!4828014!1 X-StarScan-Version: 6.2.9; banners=-,-,- X-Originating-IP: [144.160.20.145] Received: (qmail 22064 invoked from network); 10 Feb 2011 22:05:22 -0000 Received: from sbcsmtp6.sbc.com (HELO mlpd192.enaf.sfdc.sbc.com) (144.160.20.145) by server-10.tower-119.messagelabs.com with DHE-RSA-AES256-SHA encrypted SMTP; 10 Feb 2011 22:05:22 -0000 Received: from enaf.sfdc.sbc.com (localhost.localdomain [127.0.0.1]) by mlpd192.enaf.sfdc.sbc.com (8.14.4/8.14.4) with ESMTP id p1AM5jO4025834 for ; Thu, 10 Feb 2011 17:05:45 -0500 Received: from alpd052.aldc.att.com (alpd052.aldc.att.com [130.8.42.31]) by mlpd192.enaf.sfdc.sbc.com (8.14.4/8.14.4) with ESMTP id p1AM5dBo025748 for ; Thu, 10 Feb 2011 17:05:40 -0500 Received: from aldc.att.com (localhost.localdomain [127.0.0.1]) by alpd052.aldc.att.com (8.14.4/8.14.4) with ESMTP id p1AM5Gmq021960 for ; Thu, 10 Feb 2011 17:05:16 -0500 Received: from oz.mt.att.com (oz.mt.att.com [135.16.165.23]) by alpd052.aldc.att.com (8.14.4/8.14.4) with ESMTP id p1AM5DDa021849 for ; Thu, 10 Feb 2011 17:05:13 -0500 Received: by oz.mt.att.com (Postfix, from userid 500) id B051F2BF2C; Thu, 10 Feb 2011 17:05:00 -0500 (EST) X-Mailer: emacs 21.2.1 (via feedmail 8 I); VM 7.18 under Emacs 21.2.1 Message-ID: <19796.24842.872566.716691@oz.mt.att.com> Date: Thu, 10 Feb 2011 17:04:58 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable From: Jay Borkenhagen To: Jack Vogel In-Reply-To: References: <19796.13124.805432.342309@oz.mt.att.com> X-GPG-Fingerprint: DDDB 542E D988 94D0 82D3 D198 7DED 6648 2308 D3C0 Sender: jayb@zoe.braeburn.org Cc: freebsd-net@freebsd.org, Sergey Kandaurov Subject: Re: cannot set mtu > 1500 on em0 optical Gig-E X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: Jay Borkenhagen List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 Feb 2011 22:05:23 -0000 Jack Vogel writes: > Thanks Sergey :) >=20 [...] > > > > Hmm.. Did jumbo frames really work on these cards for you=3F Intel= > > claims: "Adapters based on the Intel=AE 82542 and 82573V/E > > controller do not support Jumbo Frames. These correspond to the > > following product names: > > > > * Intel=AE PRO/1000 Gigabit Server Adapter > > * Intel=AE PRO/1000 PM Network Connection " > > > > As seen from code, the behavior was changed to match the > > description ("keep old 82542 from using jumbo frames") and merged > > to 6-STABLE before 6.3. > > Well, I've got tcpdumps showing DF-bit-set pings succeeding to and from such a NIC with MTU >> 1500, on a box running 6.2-RELEASE. (pciconf data below.) In this particular case I have MTU=3D4470, which= is really good enough for what I need, and DF pings succeed up to 'ping -s 4442' Maybe Intel thought they couldn't handle MTUs approaching 9k, or maybe they had problems approaching linerate -- neither of which are concerns in my application... em0@pci0:2:0: class=3D0x020000 card=3D0x10008086 chip=3D0x10008086 re= v=3D0x03 hdr=3D0x00 vendor =3D 'Intel Corporation' device =3D '82542 Gigabit Ethernet Controller' class =3D network subclass =3D ethernet