CIFS

CIFS
source
Name	CIFS
Developer	Microsoft
Released	1980s
Latest release version	N/A
Programming language	C (programming language)
Operating system	Microsoft Windows, Linux (kernel), FreeBSD, macOS
Platform	x86, x86-64, ARM
Genre	Network file system protocol

CIFS Common Internet File System is a network file-sharing protocol associated with Microsoft and used for remote file and printer access. It is an evolution of earlier file-serving protocols and has been implemented across a variety of Microsoft Windows versions and by third-party projects on Linux (kernel), FreeBSD, and macOS. CIFS played a central role in interoperability efforts among vendors such as Microsoft, Novell, IBM, and open-source communities including Samba (software).

Overview

CIFS is a stateful protocol designed for file and printer sharing over IP networks and was widely deployed in enterprise environments running Windows NT, Windows Server 2003, Windows 2000, and legacy Windows 95/Windows 98 clients. It is commonly associated with the Server Message Block family originating at IBM and later extended by Microsoft. CIFS operates over transport layers provided by TCP/IP and was often integrated with name-resolution services such as NetBIOS and directory services like Active Directory. Implementations include native stacks in Microsoft Windows and open-source implementations such as Samba (software), used by organizations including Red Hat, SUSE, and Canonical.

History and Development

CIFS evolved from the Server Message Block protocol developed at IBM in the 1980s and was extended by Microsoft during the 1990s to support broader networking scenarios and Internet-oriented deployments. The protocol's development intersected with product lines including Windows NT, Windows 95, and Windows for Workgroups, and with standards and interoperability initiatives involving Novell and Apple Inc.. Major milestones include extensions for Unicode filename support relevant to Windows 2000 and integration with Active Directory in Windows Server 2003. The open-source project Samba (software)—founded by developers inspired by interoperability needs with Microsoft Windows NT domains—implemented the protocol to allow Unix-like systems to interoperate with Windows Server domains and print services.

Protocol Architecture and Operation

CIFS messages are exchanged using a request/response model built upon the RPC (remote procedure call) paradigm and packet framing compatible with NetBIOS or direct TCP/IP encapsulation. The architecture includes session management, file and record locking semantics, opportunistic file caching, and file attribute operations familiar to Windows API semantics. CIFS supports an array of operations including file create/open/read/write/close and directory enumeration consistent with expectations from Microsoft Windows Explorer and Windows API functions used by applications like Microsoft Office. Name resolution and server discovery were often performed via NetBIOS over TCP/IP, the Windows Internet Name Service, or browsing mechanisms implemented in Windows Networking.

Features and Extensions

CIFS introduced features such as byte-range locking, file oplocks, extended attributes, and support for named pipes and print queues used by services like Print Spooler (Windows) and RPC (remote procedure call). Later enhancements and successor protocols added Unicode filename support and stronger negotiation of capabilities for interoperability with POSIX semantics on systems like Linux (kernel). Extensions were formalized in documents and influenced by collaboration among Microsoft, IETF, and implementers such as Samba (software), with practical effects seen in enterprise products from Red Hat, Novell, and IBM server offerings.

Security and Authentication

Authentication mechanisms historically used by CIFS include challenge/response schemes such as NTLM and integrations with Kerberos in Active Directory environments. Implementations interacted with account stores such as Active Directory and legacy SAM (Security Account Manager), and administrators often configured encryption and signing options to mitigate man-in-the-middle attacks identified in advisories affecting Windows Server platforms. Security considerations prompted adoption of SMB (protocol) protocol versions with mandatory signing or encryption in later Windows Server releases and guidance from vendors like Microsoft and distributions such as Red Hat for securing file shares in enterprise deployments.

Implementations and Client Support

Native CIFS stacks were included in Microsoft Windows client and server releases, while open-source implementations such as Samba (software) provided client and server functionality on Linux (kernel), FreeBSD, and other Unix-like systems. Commercial NAS vendors and storage arrays from companies like EMC Corporation, NetApp, and Dell EMC offered CIFS-compatible services to integrate with Windows Server environments. Client-level support was provided in productivity suites such as Microsoft Office and by system utilities in Windows Explorer and third-party file managers. Interoperability testing and conformance efforts involved organizations such as Wireshark developers for packet analysis and engineering teams at Microsoft and Red Hat.

Performance and Limitations

CIFS exhibited limitations in high-latency and high-bandwidth scenarios due to chatty request/response semantics and locking behavior, which impacted deployments across WAN links and prompted optimization strategies like SMB multichannel and durable file handles in successor protocols. Benchmarks and performance studies by vendors including NetApp, EMC Corporation, and research groups at University of California, Berkeley and Carnegie Mellon University highlighted throughput and latency trade-offs relative to protocols such as NFS and later versions of SMB (protocol). Workarounds included caching proxies, protocol tuning in Windows Server, and adoption of more efficient protocol versions in cloud services from providers like Amazon Web Services and Microsoft Azure.

Category:Network protocols