Date: Fri, 3 Jan 2003 21:28:35 +0200 (WET) From: Evren Yurtesen <eyurtese@turkuamk.fi> To: "Wright, Michaelx L" <michaelx.l.wright@intel.com> Cc: 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: <Pine.A41.4.10.10301032125330.138484-100000@bessel.tekniikka.turkuamk.fi> In-Reply-To: <B5677069E3D9994D9EE1C7295072EA960D7291@orsmsx402.jf.intel.com>
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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. Evren On Fri, 3 Jan 2003, Wright, Michaelx L wrote: > Good Afternoon All, > > I am curious to know if you are taking into account MTU limitations > imposed by link-partners i.e. switches, hubs, routers and the like. Some > if not most ( for Unix) require end-nodes to be approximately 22 bytes > less than the link-partner device's maximum supported MTU. I am not sure > if, but would somewhat expect, a wireless access point to have some > impact on the sizing and/transfer at above the 1500 MTU setting. > > > > > Cheers > > M. L. Wright > Intel UNIX-NQL > 503.264.8300 > > -----Original Message----- > From: Evren Yurtesen [mailto:eyurtese@turkuamk.fi] > Sent: Friday, January 03, 2003 10:07 AM > To: fkittred@gwi.net > Cc: Michael Sierchio; dmagda@ee.ryerson.ca; freebsd-stable@FreeBSD.ORG; > wpaul@ctr.columbia.edu > Subject: Re: wi0 and mtu setting [bad idea] > > You are definetely right, setting the MTU might be really bad thing, but > why dont you let the person setting it decide it for himself? > Thus FreeBSD wi driver can support setting this value higher than 1500 > in > your own risk. Its a functionality request only. I dont suggest that you > set the default mtu for wi driver something higher than 1500! > > Evren > > On Fri, 3 Jan 2003 fkittred@gwi.net wrote: > > > On Fri, 3 Jan 2003 02:22:34 +0200 (WET) Evren Yurtesen wrote: > > > I definetely agree and obviously since mikrotikos supports this then > linux > > > should do since mikrotikos is built on linux. Why shouldnt FreeBSD > support > > > setting mtu of wireless interfaces higher than 1500 > > > > Setting a "wireless interface" to a MTU of higher than 1500 octets is > > ill-advised unless you are in very specific, unusual conditions. > > > > The subject header talks about "wi0", which implies IEEE Ethernet > > 802.11b standard interface. > > > > The IEEE maintains the Ethernet standards. Start with: > > > > http://www.ieee.org > > > > or > > > > http://www.ieee802.org > > > > >From a quick glance at the standard: > > > > "IEEE Std 802.11b-1999 (Supplement to ANSI/IEEE Std 802.11, 1999 > Edition) > > Supplement to IEEE Standard for Information technology > > Telecommunications and information exchange between systems Local > > and metropolitan area networks Specific requirements Part 11: > > Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) > > specifications: Higher-Speed Physical Layer Extension in the 2.4 > GHz > > Band" > > > > it is not clear to me that MTU > 1500 octets are legal with 802.11b. > > > > If your system is connected to the Internet, setting the MTU on your > > FreeBSD system, which is probably not a core router, to anything above > > 1500 is a stupid idea. If you don't already know this, and don't > > understand the reasons why, you would be best advised not to mess with > > the MTU at all. > > > > Stick with the default until you gain more experience. You might want > > to read up on "packet fragmentation" and "MTU discovery" for > > explanations why this is a good idea. > > > > good luck, > > fletcher > > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-stable" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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