Multiple UNC Provider | Network Programming for Microsoft Windows (Microsoft Professional Series)

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 discuss the details of a network provider later in this chapter.

Windows 95, Windows 98, and Windows NT platforms 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 version 3.01 for Windows. 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 95, Windows 98, and Windows NT, 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. Because 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.