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Q237443: MultinetGetConnectionPerformance() May Not Give Expected Results

Article: Q237443
Product(s): Microsoft Windows NT
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): kbnetwork kbprogramming kbdocfix
Last Modified: 13-NOV-1999

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Workstation version 4.0 
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SUMMARY
=======

The MultinetGetConnectionPerformance() function contained in the Win32
Application Programming Interface (API) is designed to return an estimate of
throughput, when using a Universal Naming Convention (UNC) or redirected driver
letter as a parameter.

The MultinetGetConnectionPerformance() function relies on the transport provider
to provide this metric. The specific implementation of the measurement algorithm
is protocol specific.

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

This API returns a more reliable measurement for all protocols after data is
transmitted through the connection. To assure realistic measurements of the
connection's throughput, approximately 64 KB of data is passed before
measurement. However, the measurement is only an approximation of the current
throughput. The measurement is dependent on the transport provider, which is
dependent on the network adapter card driver, so the accuracy of the metric
varies with the installed protocols and network cards.

TCP/IP uses a method of calculating the throughput based on the number of bytes
transmitted on the connection. If the total number of bytes transmitted is
relatively small when compared to the elapsed time of the established
connection, it returns the default speed of the media, which is obtained from
the network adapter card driver. In the case of Ethernet, this value is usually
10,000,000 bytes, but it is driver specific. This behavior can cause unexpected
results returned from measuring an inactive connection over TCP/IP. By passing
about 64 KB of data across the connection, the measurement is generally within
the expected range, rather than the default media speed.

REFERENCES
==========

For additional information about the use of the
MultinetGetConnectionPerformance() function, please see the following Microsoft
Web sites:

  http://msdn.microsoft.com/

  http://msdn.microsoft.com/library/psdk/network/networks_96p1.htm

  http://msdn.microsoft.com/library/ddkdoc/win95ddk/network_0851.htm

  http://msdn.microsoft.com/library/psdk/network/networks_70tu.htm


Additional query words: TDI_CONNECTION_INFO OID_GEN_LINK_SPEED GetConnectionPerformance

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Keywords          : kbnetwork kbprogramming kbdocfix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400xsearch kbWinNTSsearch kbWinNTS400xsearch kbWinNTS400
Version           : winnt:4.0
Issue type        : kbinfo

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