DOCUMENT:Q103878  30-JUL-2001  [crossnet]
TITLE   :Overview: Network I/O Redirection
PRODUCT :Windows for Workgroups and Windows NT Networking Issues
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NETWORK I/O REDIRECTION

When a device identifier (for example: f:, p:, lpt1:) is redirected to a
remote resource in a network command such as

   NET USE F: \\SERVER\SHARENAME

the network software that carries out the redirection sets flags in
the operating system's internal device table indicating that the
device is remote. File handles for files that are subsequently created
or opened on these remote devices are likewise flagged as remote.

When the operating system receives an I/O request--by way of an MS-DOS
interrupt x21 or OS/2 API call--directed to a remote device or file,
it passes the request to the network redirector instead of calling a
local device driver. The redirector formats the I/O request so that it
can be understood by the owner of the remote device, the server, and
sends it on its way through the network.

The network services provided by the operating system and the
redirector generally map to the OSI application layer.

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