network protocols handbook.pdf

319Protocols GuideOther ProtocolsProtocol NameMicrosoft CIFS: Common InternetFile SystemProtocol DescriptionThe Common Internet File System (CIFS), an enhanced versionof Microsoft Server Message Block (SMB), is the standard waythat computer users share files across intranets and the Internet.CIFS enables collaboration on the Internet by defining a remotefile-access protocol that is compatible with the way applicationsalready share data on local disks and network file servers. CIFSruns over TCP/IP, utilizes the Internet’s global Domain NamingService (DNS) for scalability and is optimized to support slowerspeed dial-up connections common on the Internet. CIFS canbe sent over a network to remote devices using the redirectorpackages. The redirector also uses CIFS to make requests tothe protocol stack of the local computer.Key features that CIFS offers are:• File Access with integrity: CIFS supports the usual set offile operations; open, close, read, write and seek. CIFSalso supports file and record lock and unlocking. CIFSallows multiple clients to access and update the samefile while preventing conflicts by providing file sharingand file locking.• Optimization for Slow Links: The CIFS protocol hasbeen tuned to run well over slow-speed dial-up lines.The effect is improved performance for users who accessthe Internet using a modem.• Security: CIFS servers support both anonymous transfersand secure, authenticated access to named files.File and directory security policies are easy to administer.• Performance and Scalability: CIFS servers are highlyintegrated with the operating system, and are tunedfor maximum system performance. CIFS supports allMicrosoft platforms after Windows 95. It also supportsother popular operation systems such as UNIX, VMS,Macintosh, IBM LAN server etc.• Unicode File Names: File names can be in any characterset, not just character sets designed for English orWestern European languages.• Global File Names: Users do not have to mount remotefile systems, but can refer to them directly with globallysignificant names, instead of ones that have only localsignificance.• CIFS complements Hypertext Transfer Protocol (HTTP)while providing more sophisticated file sharing and filetransfer than older protocols, such as FTP.Protocol StructureThe CIFS and SMB defines many client and server type of commandsand messages. The commands and messages can bebroadly classified as follows:• Connection establishment messages consist of commandsthat start and end a redirector connection to ashared resource at the server.• Namespace and File Manipulation messages are usedby the redirector to gain access to files at the server andto read and write them.• Printer messages are used by the redirector to senddata to a print queue at a server and to get status informationabout the print queue.• Miscellaneous messages are used by the redirector towrite to mailslots and named pipes.The typical process and architecture of the CIFS message flowis shown as follows:User ModeKernel ModeNWLinkIPXUser RequestI/O ManagerRedirectorTDI LayerNet BTTCP / IPNDISFigure 2-31: Microsoft CIFS Flow ChartRelated protocolsSMB, HTTP, FTP, DNSSponsor SourceCIFS is a Microsoft protocol.Net BIOSNetworkNWLinkServerTDI LayerNet BTNDISReferencehttp://www.microsoft.com/mind/1196/cifs.aspCIFS: A Common Internet File Systemhttp://www.snia.org/tech_activities/CIFS/CIFS-TR-1p00_FI-NAL.pdfCommon Internet file System (CIFS) Technical ReferenceIPXTCP / IPNet BIOS