From owner-freebsd-firewire@FreeBSD.ORG Tue Aug 10 09:13:00 2004 Return-Path: Delivered-To: freebsd-firewire@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C401116A4CF for ; Tue, 10 Aug 2004 09:13:00 +0000 (GMT) Received: from smtp4.jp.viruscheck.net (smtp4.jp.viruscheck.net [154.33.69.55]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5AAAB43D48 for ; Tue, 10 Aug 2004 09:13:00 +0000 (GMT) (envelope-from bland@freebsd.org) Received: from scan3.jp.viruscheck.net ([154.33.69.38] helo=mail5.jp.viruscheck.net) by smtp4.jp.viruscheck.net with esmtp (Exim 3.36 #1) id 1BuSgk-0003EK-00; Tue, 10 Aug 2004 18:12:58 +0900 Received: from [220.221.2.219] (helo=noc.orchid) by mail5.jp.viruscheck.net with esmtp (Exim 3.36 #2) id 1BuSgk-00013I-00; Tue, 10 Aug 2004 18:12:58 +0900 Received: from [89.60.10.11] (horse.orchid [89.60.10.11]) by noc.orchid (8.12.11/8.12.11) with ESMTP id i7A9CvoY080388; Tue, 10 Aug 2004 18:12:57 +0900 (JST) (envelope-from bland@FreeBSD.org) Message-ID: <41189199.5020201@FreeBSD.org> Date: Tue, 10 Aug 2004 18:12:57 +0900 From: Alexander Nedotsukov User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8a2) Gecko/20040714 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Doug Rabson References: <4116EA33.8040405@FreeBSD.org> <200408090859.34574.dfr@nlsystems.com> <411843FD.4090201@FreeBSD.org> <200408100851.32087.dfr@nlsystems.com> In-Reply-To: <200408100851.32087.dfr@nlsystems.com> Content-Type: text/plain; charset=KOI8-R; format=flowed Content-Transfer-Encoding: 7bit cc: freebsd-firewire@FreeBSD.org Subject: Re: max MTU for fwip device. X-BeenThere: freebsd-firewire@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Firewire support in FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Aug 2004 09:13:00 -0000 Doug Rabson wrote: >On Tuesday 10 August 2004 04:41, Alexander Nedotsukov wrote: > > >>Doug Rabson wrote: >> >> >>>On Monday 09 August 2004 04:06, Alexander Nedotsukov wrote: >>> >>> >>>>Hi again, >>>>Is there any reason why we do not support MTUs higher than 1500 >>>>bytes on firewire links? >>>> >>>> >>>Basically, we are limited by the specification. The rfc states that >>>the default MTU should be 1500 bytes. From the spec: "NOTE: >>>IP-capable nodes may operate with an MTU size larger than the >>>default, but the means by which a larger MTU is configured are >>>beyond the scope of this document." >>> >>> >>Well standards are good. But I don't see any restriction here. In >>fact I belive that effective MTU should be evaluated from maximum >>payload table (RFC2734 Table 1) and ieee1394 header size. Anyway this >>1500 which comes from 10Mbit ethernet land may be good for default >>but manual configuration should not be prohibited. >> >>Btw default MTU size on MacOSX for fw? interface is 2030 which is 10 >>bytes less that theoretical maximum for S400 async stream. >> >> >> > >Interesting. The specification for IPv6 on firewire is clearer: > > The default MTU size for IPv6 packets on an IEEE1394 network is 1500 > octets. This size may be reduced by a Router Advertisement [DISC] > containing an MTU option which specifies a smaller MTU, or by manual > configuration of each node. If a Router Advertisement received on an > IEEE1394 interface has an MTU option specifying an MTU larger than > 1500, or larger than a manually configured value, that MTU option may > be logged to system management but MUST be otherwise ignored. The > mechanism to extend MTU size between particular two nodes is for > further study. > > Mmm. I still do not see any prohibition of MTU size > 1500. What I see here is definition of automatic MTU adjustment. It's stated that ATM MTU size may be only reduced by such mechanism. Am I right? So manual configuration of interface for MTU size > 1500 violates nothing. All the best, Alexander.