SMB

The Server Message Block (SMB) is a client/server file sharing protocol. IBM developed Server Message Block (SMB) in the late 1980s to describe the structure of shared network resources, such as directories, files, printers, and serial ports. It is a request-response protocol. Unlike the file sharing supported by FTP, clients establish a long term connection to servers. Once the connection is established, the user of the client can access the resources on the server as if the resource is local to the client host. SMB file-sharing and print services have become the mainstay of Microsoft networking. With the introduction of the Windows 2000 series of software, Microsoft changed the underlying structure for using SMB. In previous versions of Microsoft products, the SMB services used a non-TCP/IP protocol to implement name resolution. Beginning with Windows 2000, all subsequent Microsoft products use DNS naming. This allows TCP/IP protocols to directly support SMB resource sharing, as shown in the figure. The LINUX and UNIX operating systems also provide a method of sharing resources with Microsoft networks using a version of SMB called SAMBA. The Apple Macintosh operating systems also support resource sharing using the SMB protocol.

The SMB protocol describes file system access and how clients can make requests for files. It also describes the SMB protocol inter-process communication. All SMB messages share a common format. This format uses a fixed-sized header followed by a variable-sized parameter and data component. SMB messages can: