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Subject: RE: MTU
From: "Tom Parker" <tparker,AT,netspace,DOT,net,DOT,au>
Date: Tue, 8 Apr 2003 13:26:07 +0200
In-reply-to: <200303311147.41036.dwilson@ibl.bm>

Michael,

I'm not sure what I need to build cipe-win32 (I've got both cygwin and
vs6.0, but it seems like I need something else).

To save me the hassle can you email your binary to me.  I'm having trouble
with MTU too - I'm trying to boot my NFS based mp3 player and the packets
are getting scrambled because of MTU issues (it is sending 1498 byte packets
despite the registry being set for 1442).

Thanks heaps,
Tom

----------------------------------
Tom Parker tparker,AT,netspace,DOT,net,DOT,au
http://www.wiresncode.com/projects

> -----Original Message-----
> From: owner-cipe-l,AT,inka,DOT,de [mailto:owner-cipe-l,AT,inka,DOT,de 
> Behalf Of
> Damion Wilson
> Sent: Tuesday, 1 April 2003 1:48 AM
> To: Michael Clarke
> Cc: cipe-l,AT,inka,DOT,de
> Subject: Re: MTU
>
>
> Yes, that helps a lot !
>
> DKW
>
> On Monday 31 March 2003 11:14 am, you wrote:
> > Hi Damion et al,
> >
> > I've been looking at the MTU problem myself over the past few days. The
> > way I fixed it was to modify the CIPE tap driver to advertise a lower
> > transmit MTU. Currently the driver advertises a transmit MTU of 1486, 14
> > bytes less than the 1500 bytes advertised by a normal Ethernet driver.
> > I've lowered it to 1459 (see derivation below) and now any fragmentation
> > is performed before the CIPE service sees the packets. This might be
> > superior to changing the TCP MTU using the registry fixes as it covers
> > UDP frames too - ping -l 2000 frames are now fragmented before being
> > encrypted.
> >
> > In cipdrvr/cipdrvr.c(590):
> >         case OID_GEN_MAXIMUM_FRAME_SIZE:
> >         case OID_GEN_TRANSMIT_BLOCK_SIZE:
> >         case OID_GEN_TRANSMIT_BUFFER_SPACE:
> >            l_Query.m_Long = DEFAULT_PACKET_LOOKAHEAD - // 1500
> >                             20 - // IP header
> >                             8 -  // UDP header
> >                             8 -  // IV
> >                             1 -  // 'P' byte
> >                             4;   // CIPE CRC
> >
> > Hope this helps,
> >
> > Michael.
> >
> > -----Original Message-----
> > From: owner-cipe-l,AT,inka,DOT,de [mailto:owner-cipe-l,AT,inka,DOT,de On 
> > Behalf Of
> > Mark Cooke
> > Sent: 31 March 2003 15:48
> > To: Damion Wilson
> > Cc: cipe-l,AT,inka,DOT,de
> > Subject: Re: MTU
> >
> > Hi Damion,
> >
> > In this particular case, it would have saved me a few minutes digging
> > around trying to work out how to set an MTU, so having it as an option
> > in the control panel/next generation setup program would get my vote.
> >
> > Thanks for the efforts you make with cipe on windows. It has been
> > exceedingly helpful here - avoiding the need to try to force windows and
> > freeswan to co-exist.
> >
> > Mark
> >
> > On Mon, 2003-03-31 at 15:26, Damion Wilson wrote:
> > > Would it help if there was a per adapter MTU option in the settings ?
> > >
> > > DKW
> > >
> > > On Monday 31 March 2003 08:19 am, Phil wrote:
> > > > On Mon, 2003-03-31 at 13:06, Mark Cooke wrote:
> > > > > Hi Phil,
> > > > >
> > > > > I had an issue with MTU, and I manually changed the CIPE-Win32 MTU
> >
> > to
> >
> > > > > 1442 by changing the registry, on the windows end of a linux-win32
> >
> > cipe
> >
> > > > > link.[*]
> > > > >
> > > > > This cured a problem I was having where small packets, like imap
> >
> > checks
> >
> > > > > for new mail, would make it over the encrypted link, but bulk
> >
> > transfers
> >
> > > > > such as actually grabbing the new messages, would fail.
> > > > >
> > > > > This was on XP.
> > > > >
> > > > > Note, I also set the service to manual, because even with the
> >
> > latest
> >
> > > > > dependancy registry mods, on (my install of) XP, the machine still
> > > > > pauses for ~ 2 minutes during startup, logging DWK failed to
> >
> > start, and
> >
> > > > > then a terminated unexpectedly, before finally starting up.  I
> >
> > just
> >
> > > > > added a key to the 'Run' part of the registry, so the service is
> >
> > started
> >
> > > > > on login.[#]  It means I have to login before the CIPE link comes
> >
> > up,
> >
> > > > > but that isn't too big a deal in my situation.
> > > > >
> > > > > With both the above, CIPE runs very well over my 802.11b link, so
> >
> > I was
> >
> > > > > able to switch off WEP (which isn't secure anyway).  I should just
> >
> > note
> >
> > > > > I've had a couple of blue screens since installing CIPE.
> > > > >
> > > > > YMMV,
> > > > >
> > > > > Mark
> > > > >
> > > > > [*]  I added an MTU dword key to the right interface in
> >
> > HKLM\System\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{}
> >
> > > > > [#] HKLM\Software\Microsoft\Windows\CurrentVersion\Run, added a
> >
> > string,
> >
> > > > > "C:\windows\system32\cipsrvr.exe" -start
> > > > >
> > > > > On Mon, 2003-03-31 at 09:55, Phil wrote:
> > > > > > hi,
> > > > > >
> > > > > > I'd like to konwo if it is ok that my cipcb0's MTU is 1442 ? if
> >
> > I use a
> >
> > > > > > windows 2000 client and a cipe linux server, can I have a
> >
> > problem with
> >
> > > > > > MTU?
> > > > > >
> > > > > > Best regards,
> > > > > >
> > > > > > Phil
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Message sent by the cipe-l,AT,inka,DOT,de mailing list.
> > > > > > Unsubscribe: mail majordomo,AT,inka,DOT,de, "unsubscribe cipe-l" 
> > > > > > in
> >
> > body
> >
> > > > > > Other commands available with "help" in body to the same
> >
> > address.
> >
> > > > > > CIPE info and list archive:
> > > > > > <URL:http://sites.inka.de/~bigred/devel/cipe.html>
> > > > >
> > > > > --
> > > > > Mark Cooke <mpc,AT,star,DOT,sr,DOT,bham,DOT,ac,DOT,uk>
> > > > >
> > > > >
> > > > > --
> > > > > Message sent by the cipe-l,AT,inka,DOT,de mailing list.
> > > > > Unsubscribe: mail majordomo,AT,inka,DOT,de, "unsubscribe cipe-l" in 
> > > > > body
> > > > > Other commands available with "help" in body to the same address.
> > > > > CIPE info and list archive:
> > > > > <URL:http://sites.inka.de/~bigred/devel/cipe.html>
> > > >
> > > > thx for your answer Mark. My VPN is ok with 2 Linux (yeaaahhhh!
> >
> > Linux's
> >
> > > > POWER) but It doesn't work with Linux <-> windows 200 Cipe-Win32.
> >
> > I'll
> >
> > > > try to modify Windows's MTU.
> > > > thx for your help.
> > >
> > > --
> > > Message sent by the cipe-l,AT,inka,DOT,de mailing list.
> > > Unsubscribe: mail majordomo,AT,inka,DOT,de, "unsubscribe cipe-l" in body
> > > Other commands available with "help" in body to the same address.
> > > CIPE info and list archive:
> >
> > <URL:http://sites.inka.de/~bigred/devel/cipe.html>
>
>
> --
> Message sent by the cipe-l,AT,inka,DOT,de mailing list.
> Unsubscribe: mail majordomo,AT,inka,DOT,de, "unsubscribe cipe-l" in body
> Other commands available with "help" in body to the same address.
> CIPE info and list archive:
> <URL:http://sites.inka.de/~bigred/devel/cipe.html>
>





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