Alan,

Thanks for your reply, but we do have the MTU sizes matching at both the
Linux
and OS/390 ends of the ctc connection. For the testing I am referring to, we
change the MTU on Linux with an IFCONFIG CTC0 MTU cmd and then do NETSTAT -I
to check.
At the OS/390 end my network colleague stop/starts the ip stack changing the
MTU to match the
Linux end in the process.

Thanks, Eric Lawler.

-----Original Message-----
From: Alan Altmark [mailto:[EMAIL PROTECTED]]
Sent: 10 December 2001 15:02
To: [EMAIL PROTECTED]
Subject: Re: Problem with Virtual CTCs between VM Linux guests and
OS/390 2.10 IP Stack.


On Monday, 12/10/2001 at 11:49 GMT, Eric Lawler
<[EMAIL PROTECTED]> wrote:

> I must say the Linux VM ctc connection to OS/390 does not seem very
robust.
> We have no problem sending data from OS/390 to Linux at any matching MTU
> value eg 1492.
>
> Any further suggestions eg Linux buffers ?

The MTU sizes on both sides of the CTC connection must match.  Make both
sides 32768 or something.  (VTAM CTC connections have the same issues!  If
the buffer sizes don't match you get truncated PIUs...)  This is the nature
of the CTC hardware (virtual or real).

Regards,
Alan

Senior Software Engineer
z/VM, TCP/IP, VIF, and Linux for zSeries Development,     Endicott, NY
Phone  607.752.6027    fax 607.752.1497     t/l 852

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