1.4 Relationship to Other Protocols
The Encrypting File System Remote Protocol is built on the Microsoft Remote Procedure Call (RPC) interface (as specified in [C706] and [MS-RPCE]). EFSRPC uses the Server Message Block (SMB) Protocol[MS-SMB][MS-SMB2] as its RPC transport. Specifically, it uses named pipes over SMB (that is, RPC protocol sequence ncacn_np) as its transport mechanism. Either version 1 or version 2 of SMB may be used. The client has to connect to the server over SMB and negotiate a version of SMB before it can access the named pipe that is the RPC endpoint on the server.
Windows also supports the storage of encrypted files via WebDAV [MS-WDV]. However, this feature does not use EFSRPC. This feature does not alter the WebDAV Protocol. Windows clients store encrypted files on WebDAV servers in the EFSRPC Raw Data Format, but the Windows WebDAV client performs all encryption and decryption operations locally. It also performs the local operations necessary to transform the file to and from the EFSRPC Raw Data Format during upload and download respectively. For more information, see [MSFT-XPUEFS].
Figure 4: Protocol relationships