INFLUENCE OF FEATURES ON DESIGN AND ARCHITECTURE                           Back To Home

Achieving Transparency with Proxy Pattern:

The transparency of the NFS is achieved with the help of RPC and XDR. These protocols are used for the client\server communication and as a language for describing the interface of the client\server.

As Shown in the figure, the client and server are interacting indirectly through stubs, i.e. client procedures have a client stub and server procedures have a server stub. The service procedure of the server is wrapped with another function to provide an interface to the server stub. The client and server stub autonomously exploit the XDR protocol to establish communication and the XDR functions are utilized to encode and decode the parameters or results at either ends of communication channel.

So NFS uses Proxy Patten to make objects appear local in the systems. The client stub, which initiates a RPC is a Proxy for the server function. This is shown better in the following figure:

NFS using the proxy pattern to achieve transparency

Sources:

http://www.auug.org.au/auugn/vol116no1/sunPaper.html

htttp://www-white.media.mit.edu/~tpminka/patterns/Proxy.html