In computer networking, Server Message Block (SMB), also known as Common Internet File System operates as an application-layer network protocol mainly used for providing shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an authenticated inter-process communication mechanism. Most usage of SMB involves computers running Microsoft Windows, where it was known as "Microsoft Windows Network" before the subsequent introduction of Active Directory. Corresponding Windows services are the "Server Service" (for the server component) and "Workstation Service" (for the client component). The Server Message Block protocol can run atop the Session (and lower) network layers in several ways: Barry Feigenbaum originally designed SMB at IBM with the aim of turning DOS "Interrupt 33" (21h) local file-access into a networked file-system.
Contributions by Socrates2008, Guy Harris, and SmackBot.