Date: Mon, 06 Jan 2003 09:50:52 -0500 From: fkittred@gwi.net To: Evren Yurtesen <eyurtese@turkuamk.fi> Cc: "Wright, Michaelx L" <michaelx.l.wright@intel.com>, fkittred@gwi.net, 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: <200301061451.h06Ep9O16289@valen.gwi.net> In-Reply-To: Your message of "Fri, 03 Jan 2003 21:28:35 %2B0200." <Pine.A41.4.10.10301032125330.138484-100000@bessel.tekniikka.turkuamk.fi>
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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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