The Free On-line Dictionary of Computing (30 December 2018):

Server Message Block

    (SMB) A client/server protocol that provides
   file and printer sharing between computers.  In addition SMB
   can share serial ports and communications abstractions such
   as named pipes and mail slots.  SMB is similar to remote
   procedure call (RPC) specialised for file system access.

   SMB was developed by Intel, Microsoft, and IBM in the
   early 1980s.  It has also had input from Xerox and 3Com.
   It is the native method of file and print sharing for
   Microsoft operating systems; where it is called Microsoft
   Networking.  Windows for Workgroups, Windows 95, and
   Windows NT all include SMB clients and servers.  SMB is also
   used by OS/2, Lan Manager and Banyan Vines.  There are
   SMB servers and clients for Unix, for example Samba and
   smbclient.

   SMB is a presentation layer protocol structured as a large
   set of commands (Server Message Blocks).  There are commands
   to support file sharing, printer sharing, user
   authentication, resource browsing, and other miscellaneous
   functions.  As clients and servers may implement different
   versions ("dialects") of the protocol they negotiate before
   starting a session.

   The redirector packages SMB requests into a network control
   block (NBC) structure that can be sent across the network to
   a remote device.

   SMB originally ran on top of the lower level protocols
   NetBEUI and NetBIOS, but now typically runs over TCP/IP.

   Microsoft have developed an extended version of SMB for the
   Internet, the Common Internet File System (CIFS), which in
   most cases replaces SMB.  CIFS runs only runs over TCP/IP.

   Just what is SMB?
   (http://samba.anu.edu.au/cifs/docs/what-is-smb.html).

   IBM protocols
   (http://protocols.com/pbook/ibm.htm).

   Microsoft SMB/CIFS documents
   (ftp://ftp.microsoft.com/developr/drg/CIFS/).

   (1999-08-08)