Date: Mon, 6 Jan 2003 17:22:14 +0200 (WET) From: Evren Yurtesen <eyurtese@turkuamk.fi> To: fkittred@gwi.net Cc: "Wright, Michaelx L" <michaelx.l.wright@intel.com>, Michael Sierchio <kudzu@tenebras.com>, dmagda@ee.ryerson.ca, freebsd-stable@FreeBSD.ORG, wpaul@ctr.columbia.edu Subject: Re: wi0 and mtu setting [bad idea] Message-ID: <Pine.A41.4.10.10301061716300.116252-100000@bessel.tekniikka.turkuamk.fi> In-Reply-To: <200301061451.h06Ep9O16289@valen.gwi.net>
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I think something is called broken when it doesnt work as you expect it to work or it doesnt comply with standards. Also I think something is called an 'extra feature' if it is not in the standard which defines it but you have access to it. Can you please show me the 802.11b document where it says the MTU shouldnt be more than 1500bytes? Maybe it doesnt say that the MTU can be more than 1500 bytes but I think the standards also doesnt say if it must be smaller than 1500 bytes. Also by lettin user to be able to set MTU higher than 1500 you do not break the wi driver. You give an extra feature to it. It is the user who breaks the standards(if it says in 802.11b standards that the MTU cant be bigger than 1500) if he/she sets MTU higher than 1500 Evren On Mon, 6 Jan 2003 fkittred@gwi.net wrote: > On Fri, 3 Jan 2003 21:28:35 +0200 (WET) Evren Yurtesen wrote: > > Isnt it also the responsibility of the person who sets the MTU that he > > should be sure everything will work right? in my access points setting MTU > > to higher than 1500 works for example. I am using linux based access > > points. > > For these last 20 years or so, I have been an IP Network engineer. I > assure you that it ends up not being the responsibility of the end > user, it is the responsibility of the network staff at the few dozen > ISPs a given connection traverses. Bad MTUs combined with broken MTU > detection leads to mysterious failures. > > The Internet has few governing laws. It is an extraordinary example > of international cooperation on an unprecidented scale. There is no > law stopping you from using an illegal MTU setting, just convention > and engineering good manners. > > I posted the links to the wi (802.llb) standards. In a brief scan of > the document, I did not see anything in there allowing MTUs greater > than 1500 octets. In the networking world, it is considered very bad > to justify a configuration/feature because a given implementation > allows the configuration. This leads to networks that don't work. > > If the wi standard requires interfaces to allow MTUs greater than 1500 > octets, and the FreeBSD wi driver doesn't allow them, then wi is > broken. If the wi standard optionally allows MTUs > 1500 octets, then > the wi driver may be uncompetitive. If the wi standard doesn't allow > MTUs > 1500 octets, and the Linux driver does, then the Linux driver > is majorly broken. > > So, I don't know the answer to whether MTUs greater than 1500 octets > are legal under the standard. The standard is the only valid source > of information. Supply this information and we can move forward. > > regards, > fletcher > > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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