Introduction to Server Message Block (SMB)

IBM first created server Message Block (SMB) protocol in the 1980s. It is one of the versions of the Common Internet File System (CIFS) to transfer the files over the network. Server Message Block is a network communication transfer protocol to provide shared access to files, printers, ports between the networks.

What is Server Message Block?

SMB is a client-server interaction protocol where clients request a file, and the server provides it to the client. It is now a Windows-based network that gives users to create, modify and delete the shared files, folders, printers within the network. SMB is an application layered protocol that uses TCP Port 445 to communicate. It also provides a herborized intercommunication mechanism to transfer to share the files between the client and the server. With the upgrades of its versions, the services are much more enhanced and effective to use by the users or clients.

How does SMB work?

Server Message Block is a request-response protocol, meaning it transfers multiple messages between the client and server to accomplish the request.

The below diagram illustrates how it works. Here the client must request the server for its need and, in return, the server responses. The server makes the file systems and other services like files, folders, printers, ports, etc., to be available to the client or user on the network.

Features of Server Message Block

As the versions of SMB have increased, the performance level is also increasing. Below are the few important features of SMB:

SMB provides an authenticated intercommunication process mechanism to share the files or resources (files, folders, printers) within the server.
SMB provides the clients to edit files, delete them, share the files, browse the network, print services, etc., over the network.
SMB version 2 has decreased the usage of a number of commands and subcommands used to transfer the file over the network.
SMB2 supports symbolic links as an enhancement version to SMB version 1.

Server Message Block Version Enhancements

Given below are the SMB Version Enhancements:

1. SMB1

SMB1 is very similar to the CIFS protocol that shares the files over a network to access them among the clients in an effective way. SMB was initially introduced to run on top of NetBIOS and TCP/IP interface. SMB Version 1 Protocol was giving performance issues as it was using an ineffective way of networking resources. To reduce the networking issue, the improvised version SMB2 was introduced.

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2. SMB2.0

Microsoft then introduced version 2 to improve the incorrect usage of networking resources. SMB2 has reduced the “chattiness” of SMB1.0 Version file system protocol by reducing the number of commands and subcommands that are used to communicate the system to just nineteen commands. This Version also has a pipeline mechanism that sends an additional service request before the response to a previous request is arrived. This mechanism has improved the performance level, which was lagging in the previous SMB 1.0 version. SMB1.0 was using a 16-bit data size, whereas SMB2.0 is using a higher level of 32 or 64-bit wide storage data fields. This helps store larger file data and communicate the large files over the network in less time.

3. SMB3.0

Later SMB3.0 Version was introduced in WINDOWS 8 Server and windows server 2012. It was introduced to improve the encryption level end to end.

4. SMB3.1.1

This version of SMB was introduced with Windows 10 Server and Windows server 2016. SMB 3.1.1 version uses AES encryption Algorithm to implements pre-authenticated security checks using the SHA-512 hash key.

CIFS VS SMB

CIFS and SMB both are the same in their functionality in their earlier versions. It is also said that CIFS is a form of SMB Version 1. CIFS is generally used in larger firms where many people work on huge or larger data needed by the clients or employers in the firm. We need a set of message packets for transferring to determine a version of the protocol, which is called a dialect. It is generally said that CIFS is a dialect form of SMB.

Which one to use, CIFS or SMB?

Below are a few comparisons to determine the better usage of CIFS or SMB:

In this world, with all updated technology, CIFS is now very rarely used than SMB. With the high level of pre-authentication checks during the file transfer in the server, SMB took it over CIFS. In the world of Windows Server, SMB is much preferred. The version SMB2 is supported for Windows Vista 2006, and SMB3 supports Windows 8 and Windows Server 2012.
Commands and subcommands are used to transfer a file over the network for which the clients request. In CIFS, the number of commands used was more than a hundred to just transfer a file. But in SMB, it has been reduced to almost nineteen commands, which is an effective way of file transfer over the system.
Data storage size in SMB is more compared to CIFS Protocol. Here in SMB, we can store 32-bit data.
SMB is an application interface network protocol, while CIFS is a TCP/IP Protocol that runs on top of the server.
Initially, CIFS was a “chatty protocol” that was a bug and considered to have network issues. SMB has overcome it by using a pipeline mechanism.
Thus, with the above-considered reasons, we use SMB over CIFS.

SMB Authentication Protocol

SMB contains two levels of security checks. They are the user checks and share checks. Share is generally referred to as a file or folder that is requested by the client, directory or a printer service that is to be accessed by the clients over the server. The user is referred to as a client who requests to access the file over the network. There is a user-level authentication check that indicates that the client is accessing a server.

The client should give their username and password for this user-level authentication check. Only when this authentication is completed, the user can then access the request on the server. Share-level authentication check refers to the access that is controlled by a password that is assigned to the file or share over the network. This share-level authentication check does not require the username to access the file but requires a password that is linked to the secured, and thus no user identity is stored during the access.