SMB - Server Message Block

What is SMB?

SMB stands for Server Message Block. It is a network file sharing protocol that allows applications and users to read, write, and manage files, printers, and other resources on a remote server.

Why is SMB useful?

  • Enables seamless file and printer sharing over a network.

  • Supports access control, file locking, and network browsing.

  • Integrates tightly with Windows environments for authentication and resource sharing.

  • Used by network-attached storage (NAS) devices and enterprise file servers.

How it works?

  • A client sends SMB requests to a server to access shared resources (files, printers).

  • The server authenticates the client and grants or denies access based on permissions.

  • The client then performs operations like open, read, write, or delete files remotely.

  • SMB can also be used over the NetBIOS protocol or directly over TCP/IP (modern versions).

Where is SMB used?

  • In Windows-based networks for file and printer sharing.

  • In NAS devices to provide shared network drives.

  • In Linux and macOS systems via implementations like Samba.

  • In mixed-platform environments where interoperability is required.

Which OSI layer does this protocol belong to?

  • SMB operates at the Application Layer (Layer 7) of the OSI model.

  • It uses lower layers like TCP/IP for data transmission.

IS SMB Windows specific?

  • No, SMB is not Windows-specific.

  • While it was developed by Microsoft and is native to Windows, it is supported on other platforms using implementations like Samba.

IS SMB Linux Specific?

  • No, SMB is not Linux-specific.

  • Linux systems can use SMB through Samba to access or provide file shares, but SMB itself is a cross-platform protocol.

Which Transport Protocol is used by SMB?

  • Modern SMB versions (SMB 2.0 and above) use TCP as the transport protocol.

  • Older versions of SMB could operate over NetBIOS, which in turn could run over TCP or UDP.

Which Port is used by SMB?

  • SMB over NetBIOS uses ports 137-139.

  • SMB over TCP (direct host) uses port 445, which is the default in modern SMB implementations.

Is SMB using Client server model?

  • Yes, SMB follows the client-server model.

  • Clients request access to shared resources, and servers respond by granting or denying access and performing requested operations.

Topics in this section,

  • In this section, you are going to learn

  • Terminology

  • Version Info

  • rfc details

  • setup

  • setup

  • packet details

  • usecases

  • features

  • Reference links