Type of Service Field Cannot Be Set in Windows 2000 (258978)

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256986 Description of the Microsoft Windows Registry

SUMMARY

The Winsock call to set IP Type of Service (IPTOS) options on a socket generates an error on Microsoft Windows 2000-based computers. This is because of the industry standard Quality of Service (QoS) feature that is being implemented industry wide for the allocation of bandwidth to on-demand programs, such as video and audio types of programs. A program can no longer set Type of Service (ToS) as this could be a violation of policy, and as of the implementation of TCP/IP for Windows 2000, the six bits that made up the vastly unused ToS field have been renamed and given a new function under QoS. They are now called DiffServ. Microsoft has added a registry value which, when set, tells Winsock to fail attempts to set TOS.

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In Interix, this causes an error message to be generated. This behavior can be corrected by editing the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TcpIp\Parameters\DisableUserTOSSetting

This value defaults to 1 (to turn on the disabling) for Windows 2000.