Accessing and Sharing Windows Resources

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Understanding the Windows Protocols: SMB and CIFS

The Simple Message Block (SMB) protocol provides the basis for Windows file and print sharing. SMB provides support for file browsing and two levels of security:

  • User A user must authenticate with the SMB server during the initial connection. The supplied username and password determine what resources the user can access.

  • Share Share-level security operates on an individual shared resource. The resource has a single password. Anyone with access to the password can access the resource.

SMB is implemented on top of a transport protocol. Think of this as similar to the way that AppleTalk exists on top of LocalTalk (serial networking) and EtherTalk (ethernet-based networks).

The SMB protocol has gone through several phases in its existence. Early in life, it used NetBEUI as its transport protocol. NetBEUI is independent of TCP/IP and, as such, was only suited for local-area networks. Today, most SMB services run on top of NetBIOS (NetBT/NBT). NetBIOS is the equivalent of NetBEUI, but running on top of TCP/IP. This creates a routable file/print serving system that can be used across the Internet as well as in LAN situations.

Unfortunately, things aren't that clean and simple. The NetBEUI protocol used a simple broadcast protocol to enable browsing of local resources. When SMB moved to NetBIOS (and thus TCP/IP), finding remote resources became a bigger problem. Machines needed a new way to locate each other, besides sending broadcast packets. This was the only way to successfully handle spanning across multiple subnets.

The Windows Internet Naming Service (WINS) protocol was created to provide a central registration point for Windows computers. When coming online, a computer can register itself with a WINS server as well as look up other machines for creating a connection.


Yes, WINS is a proprietary name resolution system that bears a resemblance to DNS (domain name service). Versions of Windows later than 98 and NT 4.0 support DNS resolution of remote computer names. Microsoft's latest attempt at a proprietary directory service is the Active Directory Service (ADS). ADS offers greater support for open standards, but continues to be based on a proprietary system.

The latest version of SMB is known as Common Internet File System (CIFS) and is backed by Microsoft as well as several third-party companies. CIFS is an open version of SMB with Internet-specific modifications. For the sake of remaining reasonably sane, you can assume that CIFS and SMB are synonymous.


The history of SMB, NetBEUI, NetBIOS, and how everything fits together is documented on the What Is SMB? page:

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    Mac OS X Tiger Unleashed
    Mac OS X Tiger Unleashed
    ISBN: 0672327465
    EAN: 2147483647
    Year: 2005
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