From owner-freebsd-net@FreeBSD.ORG Mon Mar 26 14:16:51 2012 Return-Path: Delivered-To: net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 619671065672 for ; Mon, 26 Mar 2012 14:16:51 +0000 (UTC) (envelope-from kudzu@tenebras.com) Received: from mail-yx0-f182.google.com (mail-yx0-f182.google.com [209.85.213.182]) by mx1.freebsd.org (Postfix) with ESMTP id 17AF98FC14 for ; Mon, 26 Mar 2012 14:16:50 +0000 (UTC) Received: by yenl9 with SMTP id l9so4628278yen.13 for ; Mon, 26 Mar 2012 07:16:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:x-gm-message-state; bh=/J1SM8/nc0mEUVUQaHPI3xd9LMBOAHAkNw5Hrac5biA=; b=I8lLU0OdyOauXomOY6e7PBYS0Y8XV4g6iOI+4zl0W84DEJWErDnIR4OgmLJyEpVYka ULPAmLuAedzznZHPMK5P+12F93ltRhfJJV3crCr0T52liqb57gdkBPjPCWEEqBvkCWoH 1ZJvqpDxozEdxlFb1MeObY+TzEbWaxV2RUt/wmZ64BYs3ev/mYQ5EQfQAp3+QKOr1pmv O7o06lEAEhP9c3WNYCPMrac6ikQpbFpz+EdIfhisOHu7dwwLGSHpnxA/+bhb4z0/miu4 iPVpV0Vnq0DI+6MRq7XTLt28RLHTjm2wzTtXo8edCbXLpW9HPO6oD8tFHISiRtFycSzo +liA== MIME-Version: 1.0 Received: by 10.60.4.134 with SMTP id k6mr27601055oek.19.1332771410198; Mon, 26 Mar 2012 07:16:50 -0700 (PDT) Received: by 10.60.119.105 with HTTP; Mon, 26 Mar 2012 07:16:50 -0700 (PDT) In-Reply-To: <8904.1332769428.5720084203749900288@ffe15.ukr.net> References: <8904.1332769428.5720084203749900288@ffe15.ukr.net> Date: Mon, 26 Mar 2012 07:16:50 -0700 Message-ID: From: Michael Sierchio To: =?UTF-8?B?0JLQu9Cw0LTQuNGB0LvQsNCyINCf0YDQvtC00LDQvQ==?= X-Gm-Message-State: ALoCoQkiVeH1c9NdwbumIO+KRUsPTdnd+wXAQZ17Ol23lvlJP+JG1leHiLpnunl8zRK8LVqS0agj Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: net@freebsd.org Subject: Re: The problem with MTU <1500 X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 26 Mar 2012 14:16:51 -0000 2012/3/26 =D0=92=D0=BB=D0=B0=D0=B4=D0=B8=D1=81=D0=BB=D0=B0=D0=B2 =D0=9F=D1= =80=D0=BE=D0=B4=D0=B0=D0=BD > > Dear all! > I have two different values of uplink MTU - 1440 and 1492. > And in a local network - 1500. > In Cisco routers can be set 'set ip df 0', but I have no such router :( > What options are there for FreeBSD? > man ifconfig - not the 'mtu' option. You should set the MTU size on the interface to match the uplink MTU. And you should make sure you handle ICMP need-frag error messages, otherwise Path MTU discovery will be broken. Only use the net/tcpmssd? That's a workaround for not properly handling ICMP error messages, and just for TCP ;-) > Will it be possible to process both two channels of 1Gb? > > Never. ;-) Not in practice. What is the bandwidth - delay product? That's a fraction of the 1Gbps you'll never get. - M