Multiple UNC Provider

MUP is a resource locator responsible for selecting a network provider to service UNC connections. A network provider is a service that can use network hardware to access resources—such as files and printers—located on a remote computer. MUP uses a network provider to form communications on all UNC name-based I/O requests for files and printers. We will discuss the details of a network provider later in this chapter.

Windows NT, Windows 2000, Windows 95, and Windows 98 are all capable of having multiple network providers installed. For example, Windows platforms provide a network provider named Client for Microsoft Networks. It is also possible to install other third-party network providers, such as Novell's Novell Client v3.01 for Windows 95/98. Thus, more than one network provider might be able to service a single UNC request at a time. On the other hand, Windows CE can have only one network provider: Client for Microsoft Networks.

The primary role of MUP is to decide which network provider should service a UNC request. MUP makes this decision by sending the UNC names in the request to each installed provider (in parallel). If a network provider indicates that it can service a request involving the UNC names, MUP sends the rest of the request to the provider. If more than one provider is capable of servicing a UNC request, MUP chooses the network provider with the most priority. Network provider priority is determined by the order in which providers are installed on your system. In Windows NT, Windows 2000, Windows 95, and Windows 98 the priority can be managed by modifying the registry key ProviderOrder in the following directory in the Windows registry:

 \HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Control \NetworkProvider \Order 

The installed providers are listed first to last in order of priority. Since Windows CE can have only one provider, it does not use MUP to resolve UNC names. Instead, the UNC requests go directly to its single provider.