It's probably question to Microsoft, but it seems that
even Windows requests MTU from a NIC driver, it does *not*
care about the response from adapters of *WAN* type.
Thus, MTU is set always 1500 on SLIP/PPP.
However, altering the Registry possibly will help
because it is matter of static configuration of MSFT TCP/IP.
--Alexei
-----Original Message-----
From: Hu Jian <[EMAIL PROTECTED]>
To: Joe Provino - Sun BOS Software <[EMAIL PROTECTED]>
Cc: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Date: 26 ���� 1998 �. 12:29
Subject: Re: MTU problem with Dial-up on NT
:Hi, folks,
:
:The following is not the only solution to MTU on Windows NT. Actually,
:in Windows (no matter NT or 95) IP askes for MTU value during its
:initialization phase. If your SKIP is loaded and initialized before IP
:is loaded, the SKIP should be able to intercept the request for MTU from
:IP and respond accordingly.
:
:Just for your information.
:
:Hu Jian
:Uibiquity Lab
:Kent Ridge Digital Labs
:(65)874-6642
:
:Joe Provino - Sun BOS Software wrote:
:>
:> There appears to be a problem with Dial-up Networking on NT 4.0 with the
:> maximum size of a packet that can be transmitted (called MTU).
:>
:> The problem is that the Microsoft software fails to ask for the MTU and
:> must therefore be assuming a constant. This works without SKIP encryption
but
:> fails when encryption is enabled because SKIP adds some headers increasing
:> the size of the packet beyond the Adapter's MTU.
:>
:> What is supposed to happen is that when IP asks for the MTU, SKIP intercepts
:> the reply and subtracts the size of the additional headers from the MTU
:> returned to IP.
:>
:> Since IP doesn't appear to be asking for the MTU, SKIP does not get a chance
:> to reduce the MTU.
:>
:> There is a workaround that requires setting the MTU in the registry.
:>
:> I've found some information in the April '98 MSDN library.
:>
:> The Title is "TCP/IP and NBT Configuration Parameters for Windows NT".
:>
:> The registry value that needs to be set to specify the MTU is called "MTU" in
:>
:>
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\NdisWan<n>\Paramters\Tcpip
:>
:> MTU DWORD <value>
:>
:> <n> is a number, e.g. NdisWan7
:>
:> <value> is the Adapter's MTU - 134, e.g. 1500 - 134 = 1366.
:>
:> This _should_ fix the problem.
:>
:> jp
:
