In Windows 95, the key to access of disk and redirected devices is the Installable File System (IFS) Manager. The IFS Manager arbitrates access to file system devices, and other file system device components.
Under MS-DOS and Windows 3.1, INT 21 provided access to the file system to manipulate file information on a disk device. To support redirected disk devices (for example, a network drive or a CD-ROM drive), other system components such as the network redirector would hook the INT 21 function so that it could examine the file system request to determine whether it should handle the file I/O request or let the base file system handle it. Although this mechanism provided the ability to add more device drivers, some add-on components ran improperly and interfered with other installed drivers.
Another problem with the MS-DOS – based file system was the difficulty in loading multiple network redirectors to provide concurrent access to different network types. Windows for Workgroups provided support for running the Microsoft Windows Network redirector at the same time as an additional network redirector such as Novell® NetWare® or Banyan® VINES®; however, support for running more than two network redirectors at the same time was not supported. In Windows 95, the network redirectors are implemented as file systems under IFS Manager, so an unlimited number of 32-bit redirectors can be used.