Q99154: Ideas for Troubleshooting and Fine-tuning Throughput

Article: Q99154
Product(s): Microsoft LAN Manager
Version(s): 
Operating System(s): 
Keyword(s): kbnetwork
Last Modified: 30-JUL-2001

SUMMARY
=======

Transmission rates across a WAN can sometimes be increased by making
configuration adjustments. Before you can improve a throughput rate, though, you
need to understand why it is slow, and what you can or cannot change to fix it.
This article discusses these points using an example of a configuration with a
throughput problem.

MORE INFORMATION
================

In one reported instance, two LAN Manager 2.2 networks were connected through
remote bridges (64kbits/s), and a 380K file took more than 4 minutes to
transfer. Configuring LAN Manager didn't help, nor did adjusting T1 = 3500 or
4500.

The theoretical throughput on the WAN link was 64Kbps; that rate might not seem
slow, but there are other factors to consider. For one thing, divide by 8
bits/byte and this yields a not particularly fast 8Kbytes/sec. But there is some
overhead for headers and so on, so the true data rate is closer to 6Kbytes/sec
total between the two networks.

Also remember that the machine in question is never the only machine on the net.
Broadcasts and traffic from other stations also are being passed.

To isolate the cause of a slow transmission rate, try a file copy to a local
system. If that works much better, analyze traffic over the bridge.

The most likely culprit is high broadcast traffic. It doesn't take much to
saturate a link as small as 8Kbytes/sec. TCP/IP, NetBEUI, and IPX create a lot
of broadcast traffic over the bridges.

There are ways to reduce broadcast traffic, but be careful when trying them. Try
reducing the frequency of server announcements (LAN Manager 2.1a and later
versions default to 3 minutes, 2.1 and earlier to 1 minute). You can also shut
off NET WHO if it's not being used, by setting "netwho=no" in the netlogon
section of LANMAN.INI.

If these measures don't help, it may be necessary to study the traffic using a
network analyzer to see if more traffic reduction is possible.

Additional query words: 2.00 2.0 2.10 2.1 2.10a 2.1a 2.20 2.2

======================================================================
Keywords          : kbnetwork 

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.