IBM SMB: Server Message Block protocol

Server Message Block (SMB) protocol is an IBM protocol for sharing files, printers, serial ports, etc. between computers. The SMB protocol can be used over the Internet on top of the TCP/IP protocol or other network protocols such as Internetwork Packet Exchange (Novell IPX) and NetBEUI.

SMB is a client server, request-response protocol, which provides a method for client applications in a computer to read and write to files on and to request services from server programs in various types of network environment. Using the SMB protocol, an application can access files at a remote server as well as other resources, including printers, mailslots, and named pipes.

In the TCP/IP environment, clients connect to servers using NetBIOS over TCP/IP (or NetBEUI/TCP or SPX/IPX). Once they have established a connection, clients can then send SMB commands to the server that allow them to access shares, open files, read and write files, and generally do all the sort of things that you want to do with a file system.

Microsoft Windows operating systems since Windows 95 include client and server SMB protocol support. Microsoft has offered an open source version of SMB for the Internet. Called the Common Internet File System (CIFS), which provides more flexibility than existing Internet applications such as the File Transfer Protocol (FTP). For Unix systems, a shareware program, Samba, is available.

The Server Message Block (SMB) protocol defines two levels of security:

Share level. Protection is applied at the share level on a server. Each share can have a password, and a client only needs that password to access all files under that share.

User Level.Protection is applied to individual files in each share and is based on user access rights. Each user (client) must log in to the server and be authenticated by the server. When it is authenticated, the client is given a UID which it must present on all subsequent accesses to the server.

Protocol Structure - IBM SMB: Server Message Block protocolSMB has many variants to handle the complexity of the underneath network environments that it is employed. The following table display part of the SBM variants:

SMB Protocol Variant	Protocol Name	Comments
PC NETWORK PROGRAM 1.0	Core Protocol	The original version of SMB as defined in IBM's PC Network Program. Some versions were called PCLAN1.0
MICROSOFT NETWORKS 1.03	Core Plus Protocol	Included Lock&Read and Write&Unlock SMBs with different versions of raw read and raw write SMBs
MICROSOFT NETWORKS 3.0	DOS LAN Manager 1.0	The same as LANMAN1.0, but OS/2 errors must be translated to DOS errors.
LANMAN1.0	LAN Manager 1.0	The full LANMAN1.0 protocol.
DOS LM1.2X002	LAN Manager 2.0	The same as LM1.2X002, but errors must be translated to DOS errors.
LM1.2X002	LAN Manager 2.0	The full LANMAN2.0 protocol.
DOS LANMAN2.1	LAN Manager 2.1	The same as LANMAN2.1, but errors must be translated to DOS errors.
LANMAN2.1	LAN Manager 2.1	The full LANMAN2.1 protocol.
Windows for Workgroups 3.1a	LAN Manager 2.1	Windows for Workgroups 1.0?
NT LM 0.12	NT LAN Manager 1.0	Contains special SMBs for NT
Samba	NT LAN Manager 1.0	Samba's version of NT LM 0.12?
CIFS 1.0	NT LAN Manager 1.0	Really NT LM 0.12 plus a bit

Related Protocols
UDP , TCP , Ethernet , Token Ring , X.25

Sponsor Source

SMB is an IBM protocol.

Reference