WinSock Traffic Is Slow Over High Speed, High Latency Links (311084)


The information in this article applies to:

  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Professional
  • Microsoft Windows NT Server 4.0
  • Microsoft Windows NT Workstation 4.0
This article was previously published under Q311084

SYMPTOMS

When you transfer data by using WinSock (for example, by using FTP) over a high speed, high latency link (such as a satellite link), performance is slower than expected.

CAUSE

This behavior can occur because of the way that the Ancillary Function driver for WinSock (used by FTP and others) manages its buffers.

The Ancillary Function driver for WinSock tries to intelligently decide on a I/O Transmit Length based on how much memory is in the computer. When there is 64 megabytes (MB) or less, it arbitrarily sets the I/O Length to either 4 kilobytes (KB) or 8 KB, depending on how much memory there is. When the computer has more than 64 MB, the I/O Length is increased to 64 KB and the problem disappears.

NOTE: This only applies to the server product. A workstation always uses the 4 KB I/O Length.

RESOLUTION

To work around this behavior, increase the available physical memory in the server to more than 64 MB.

STATUS

This behavior is by design.

MORE INFORMATION

For additional information about related topics, click the article number below to view the article in the Microsoft Knowledge Base:

129593 Windows NT Workstation and Server Optimized For Different Roles

Modification Type:MajorLast Reviewed:5/28/2003
Keywords:kbenv kbnetwork kbprb KB311084
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