Date: Sat, 4 Jan 2003 02:13:56 +0100 From: =?iso-8859-1?Q?Sten_Daniel_S=F8rsdal?= <sten.daniel.sorsdal@wan.no> To: "Wright, Michaelx L" <michaelx.l.wright@intel.com>, "Evren Yurtesen" <eyurtese@turkuamk.fi>, <fkittred@gwi.net> Cc: "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: <0AF1BBDF1218F14E9B4CCE414744E70F07DE29@exchange.wanglobal.net>
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How about a configuration of two Ad-hoc cards pointing towards = eachother between two buildings and an IPSec tunnel is applied. Wouldn't it be great if (unencrypted) = packets destined to go through=20 that IPSec tunnel could go through in full ethernet size, without = fragmentation, pr host tcp stack adjustments or resending because of DF flag? What about transporting VLANs over wireless? There is a lot of equipment out there, especially wireless but also = wired (ATM?) that allows larger MTUs for special circumstances. It's like buying a car with all the extra features - but only a = handful of the features work. Just my 2 nkr=20 ----------- Med vennlig hilsen / Best regards=20 Sten Daniel S=F8rsdal=20 Wireless Manager WAN Norway AS=20 ----------- -----Original Message----- From: Wright, Michaelx L [mailto:michaelx.l.wright@intel.com]=20 Sent: 3. januar 2003 19:28 To: Evren Yurtesen; 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] 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]=20 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 >=20 > Setting a "wireless interface" to a MTU of higher than 1500 octets is=20 > ill-advised unless you are in very specific, unusual conditions. >=20 > The subject header talks about "wi0", which implies IEEE Ethernet=20 > 802.11b standard interface. >=20 > The IEEE maintains the Ethernet standards. Start with: >=20 > http://www.ieee.org >=20 > or >=20 > http://www.ieee802.org >=20 > >From a quick glance at the standard: >=20 > "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" >=20 > it is not clear to me that MTU > 1500 octets are legal with 802.11b. >=20 > If your system is connected to the Internet, setting the MTU on your=20 > 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=20 > understand the reasons why, you would be best advised not to mess with = > the MTU at all. >=20 > Stick with the default until you gain more experience. You might want = > to read up on "packet fragmentation" and "MTU discovery" for=20 > explanations why this is a good idea. >=20 > good luck, > fletcher >=20 >=20 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 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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