Hi!
On Sun, 4 Feb 2001, Haim Gelfenbeyn wrote:
> At least on my Windows 2000 MTU of 1536 was used after connection was
> opened using the Bezeq dialer... Did you compute the MTU yourself or
> used some reference? If I understand well, you need to substract from
> 1500 the size of all headers added by PPTP, corect?
The 1452 value was found by trial and error. Theoreticaly there shouldn't
be a problem with larger values, as the ip stack should create fragments.
The pptp is a tcp session, and thus should be able to handle fragments.
Note that the payload of the pptp is ppp packets , that may or may not be
compressed. so it is hard to calculate the exact mtu size.
Dani
>
> Thanks,
> Haim.
>
> > -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED]]On Behalf Of Dani Arbel
> > Sent: Sunday, February 04, 2001 10:13 AM
> > To: Eran Tromer
> > Cc: linux-il
> > Subject: Re: IP masquerading and ADSL
> >
> >
> > Eran,
> > use mru 1542 and mtu 1542 in your pptp command to reduce
> > the packet size
> > received from the peer.
> > This is updated in the new HOWTO
> > Dani
> >
> > On Sun, 4 Feb 2001, Eran Tromer wrote:
> >
> > > Hello,
> > >
> > > I tried reducing the MTU on the client box, and it
> > doesn't help. I can't
> > > see why it should -- the problem occurs when the *remote* host is
> > > sending a large packet *into* the LAN.
> > >
> > > Looking at captured network traffic both between the
> > masquerading box
> > > and the ADL modem and between the masquerading box and
> > the client box, I
> > > see no packet larger than 500 bytes. This means that the
> > large packets
> > > are eaten by the ADSL modem, or earlier somewhere out there.
> > >
> > > Eran
> > >
> > >
> > > Dani Arbel wrote:
> > > >
> > > > reduce the maxmtu of the win boxes to 1452 and they
> > will work fine.
> > > > Dani
> > > >
> > > > On Sat, 3 Feb 2001, Eran Tromer wrote:
> > > >
> > > > > Howdy list,
> > > > >
> > > > > Thanks to mulix, my Linux ADSL connection is up and
> > running. Next, I set
> > > > > up IP masquerading, and encountered the following odd problem.
> > > > >
> > > > > When conneting from some host on the LAN, every time
> > the remote host
> > > > > tries to send "a lot of data at once" (a large TCP
> > packet, perhaps?),
> > > > > the masqueraded TCP connection is lost. So, for instance, when
> > > > > telnetting to a POP server I can download short
> > e-mails -- any number of
> > > > > them, in fact -- but if I try to RETR a long e-mail
> > the connection is
> > > > > immediately broken (I don't even get the header). The
> > same happens on
> > > > > other ports (e.g, HTTP only retrieves short pages,
> > telnet breaks on long
> > > > > 'ls' outputs).
> > > > >
> > > > > >From the masquerading box (the one talking to the
> > ADSL modem), all works
> > > > > fine.
> > > > >
> > > > > Notably, the same happens with Windows2000
> > masquerading using ADSL,
> > > > > while ISDN masquerading worked fine on the same
> > Windows2000 box. I would
> > > > > have suspected a fault in the modem (Orckit ATUR3) or
> > ISP (Internet
> > > > > Gold), but they're not supposed to be able to
> > distinguish masqueraded
> > > > > sessions, at least not nonmaliciously.
> > > > >
> > > > > On the Linux box which runs kernel 2.4.1, I set up
> > masquerading using
> > > > > # insmod ipchains
> > > > > # ipfwadm-wrapper -F -a m -S 192.168.0.0/16 -D 0.0.0.0/0
> > > > > (yes, compatibility layer upon compatibility layer,
> > but may Murphy curse
> > > > > me if I relearn those arcane command line options yet again!)
> > > > >
> > > > > I would have tried a 2.2 kernel, but since the same
> > problem occurs with
> > > > > Windows2000 this probably won't change anything.
> > > > >
> > > > > Any ideas? Did anyone else encounter this?
> > > > >
> > > > > Regards,
> > > > > Eran Tromer
> > > > >
> > > > >
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