Yes, actually this is why I asked first about MTU settings in wi. I use
PPPoE and it has 8bytes overhead. It could be nice to set MTU to 1508 so
1500 byte ethernet frames can be encapsualted in PPPoE without
fragmentation.
I just dont understand why FreeBSD people have to make this wi driver so
tight in standarts even though there are wireless cards which support
non-standard(and sometimes nice) things which can be useful. I definetely
disagree that something should be in standard so you will allow setting of
it!
For example in /etc/defaults/rc.conf it says
-----------------------------------------------
tcp_drop_synfin="NO" # Set to YES to drop TCP packets with SYN+FIN
# NOTE: this violates the TCP specification
-----------------------------------------------
So why do you let this to violate TCP specifications but you cant let user
to violate ethernet specifications?
Evren
On Sat, 4 Jan 2003, Sten Daniel S�rsdal wrote:
>
> 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
> 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
>
> -----------
> Med vennlig hilsen / Best regards
>
> Sten Daniel S�rsdal
> Wireless Manager
> WAN Norway AS
> -----------
>
>
> -----Original Message-----
> From: Wright, Michaelx L [mailto:[EMAIL PROTECTED]]
> Sent: 3. januar 2003 19:28
> To: Evren Yurtesen; [EMAIL PROTECTED]
> Cc: Michael Sierchio; [EMAIL PROTECTED]; [EMAIL PROTECTED];
>[EMAIL PROTECTED]
> 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:[EMAIL PROTECTED]]
> Sent: Friday, January 03, 2003 10:07 AM
> To: [EMAIL PROTECTED]
> Cc: Michael Sierchio; [EMAIL PROTECTED]; [EMAIL PROTECTED];
>[EMAIL PROTECTED]
> 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 [EMAIL PROTECTED] 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
> >
> >
>
>
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