Microsoft CIFS: Common Internet File System protocol

The Common Internet File System (CIFS), an enhanced version of Microsoft Server Message Block (SMB), is the standard way that computer users share files across intranets and the Internet. CIFS enables collaboration on the Internet by defining a remote file-access protocol that is compatible with the way applications already share data on local disks and network file servers. CIFS runs over TCP/IP and utilizes the Internet's global Domain Naming Service (DNS) for scalability, and is optimized to support slower speed dial-up connections common on the Internet. CIFS can be sent over a network to remote devices using the redirector packages. The redirector also uses CIFS to make requests to the protocol stack of the local computer.

Key features that CIFS offers are:

• File Access with integraty:  CIFS supports the usual set of file operations; open, close, read, write and seek. CIFS also supports file and record lock and unlocking. CIFS allows multiple clients to access and update the same file while preventing conflicts by providing file sharing and file locking.
•  Optimization for Slow Links:  The CIFS protocol has been tuned to run well over slow-speed dial-up lines. The effect is improved performance for users who access the Internet using a modem.
•  Security:  CIFS servers support both anonymous transfers and secure, authenticated access to named files. File and directory security policies are easy to administer.
• Performance and Scalability:  CIFS servers are highly integrated with the operating system, and are tuned for maximum system performance. CIFS supports all Microsoft platmforms after Windows 95. It also supports other popular operation systems such as Unix, VMS, Macintosh, IBM LAN server etc.

•  Unicode File Names:  File names can be in any character set, not just character sets designed for English or Western European languages.
• Global File Names:  Users do not have to mount remote file systems, but can refer to them directly with globally significant names, instead of ones that have only local significance.
• CIFS complements Hypertext Transfer Protocol (HTTP) while providing more sophisticated file sharing and file transfer than older protocols, such as FTP.

Protocol Structure - Microsoft CIFS: Common Internet File System protocol

The CIFS and SMB defined many client and server type of commands and messages. The commands and messages can be broadly classified as follows:

• Connection establishment messages consist of commands that start and end a redirector connection to a shared resource at the server.
• Namespace and File Manipulation messages are used by the redirector to gain access to files at the server and to read and write them.
• Printer messages are used by the redirector to send data to a print queue at a server and to get status information about the print queue.
•  Miscellaneous messages are used by the redirector to write to mailslots and named pipes.

The typical process and architecture of the CIFS message flow is shown as follows:

CIFS is defined by Microsoft.

http://www.microsoft.com/mind/1196/cifs.asp : CIFS: A Common Internet File System
http://www.snia.org/tech_activities/CIFS/CIFS-TR-1p00_FINAL.pdf : Common Internet file System (CIFS) Technical Reference