1.1 Glossary

This document uses the following terms:

@GMT token: A special token that can be present as part of a file path to indicate a request to see a previous version of the file or directory. The format is "@GMT-YYYY.MM.DD-HH.MM.SS". This 16-bit Unicode string represents a time and date in Coordinated Universal Time (UTC), with YYYY representing the year, MM the month, DD the day, HH the hour, MM the minute, and SS the seconds.

8.3 name: A file name string restricted in length to 12 characters that includes a base name of up to eight characters, one character for a period, and up to three characters for a file name extension. For more information on 8.3 file names, see [MS-CIFS] section 2.2.1.1.1.

byte mode: One of two kinds of named pipe, the other of which is message mode. In byte mode, the data sent or received on the named pipe does not have message boundaries but is treated as a continuous stream. [XOPEN-SMB] uses the term stream mode instead of byte mode, and [SMB-LM1X] refers to byte mode as byte stream mode.

Common Internet File System (CIFS): The "NT LM 0.12" / NT LAN Manager dialect of the Server Message Block (SMB) Protocol, as implemented in Windows NT. The CIFS name originated in the 1990's as part of an attempt to create an Internet standard for SMB, based upon the then-current Windows NT implementation.

Coordinated Universal Time (UTC): A high-precision atomic time standard that approximately tracks Universal Time (UT). It is the basis for legal, civil time all over the Earth. Time zones around the world are expressed as positive and negative offsets from UTC. In this role, it is also referred to as Zulu time (Z) and Greenwich Mean Time (GMT). In these specifications, all references to UTC refer to the time at UTC-0 (or GMT).

Copychunk Resume Key: A 24-byte value generated by a Server Message Block (SMB) server in response to a request by an SMB client that uniquely identifies an open file on the SMB server. A Copychunk Resume Key is used by SMB server-side data movement operations between files without requiring the data to be read by the client and then written back to the server. Note that this is different from the resume key specified in [MS-CIFS] section 2.2.6.2 that is returned by the server in response to a TRANS2_FIND_FIRST2 subcommand of an SMB_COM_TRANSACTION2 client request.

deprecated: A deprecated feature is one that has been superseded in the protocol by a newer feature. Use of deprecated features is discouraged. Server implementations might need to implement deprecated features to support clients that negotiate earlier SMB dialects.

discretionary access control list (DACL): An access control list (ACL) that is controlled by the owner of an object and that specifies the access particular users or groups can have to the object.

Distributed File System (DFS): A file system that logically groups physical shared folders located on different servers by transparently connecting them to one or more hierarchical namespaces. DFS also provides fault-tolerance and load-sharing capabilities. DFS refers to the Microsoft DFS available in Windows Server operating system platforms.

domain: A set of users and computers sharing a common namespace and management infrastructure. At least one computer member of the set must act as a domain controller (DC) and host a member list that identifies all members of the domain, as well as optionally hosting the Active Directory service. The domain controller provides authentication (2) of members, creating a unit of trust for its members. Each domain has an identifier that is shared among its members. For more information, see [MS-AUTHSOD] section 1.1.1.5 and [MS-ADTS].

Fid: A 16-bit value that the Server Message Block (SMB) server uses to represent an opened file, named pipe, printer, or device. A Fid is returned by an SMB server in response to a client request to open or create a file, named pipe, printer, or device. The SMB server guarantees that the Fid value returned is unique for a given SMB connection until the SMB connection is closed, at which time the Fid value can be reused. The Fid is used by the SMB client in subsequent SMB commands to identify the opened file, named pipe, printer, or device.

file allocation table (FAT): A data structure that the operating system creates when a volume is formatted by using FAT or FAT32 file systems. The operating system stores information about each file in the FAT so that it can retrieve the file later.

file system control (FSCTL): A command issued to a file system to alter or query the behavior of the file system and/or set or query metadata that is associated with a particular file or with the file system itself.

FileId: A 64-bit value that is used to represent a file. The value of a FileId is unique on a single volume of a local file system or a remote file server. A FileId is not guaranteed to be unique across volumes, but the file system on the server must guarantee that it is unique within a given volume if FileIds are supported. FileIds are not supported by all local file systems. On Windows, NTFS supports FileIds, but the file allocation table (FAT) file system does not support them.

guest account: A security account available to users who do not have an account on the computer.

I/O control (IOCTL): A command that is issued to a target file system or target device in order to query or alter the behavior of the target; or to query or alter the data and attributes that are associated with the target or the objects that are exposed by the target.

information level: A number used to identify the volume, file, or device information being requested by a client. Corresponding to each information level, the server returns a specific structure to the client that contains different information in the response.

Key Distribution Center (KDC): The Kerberos service that implements the authentication (2) and ticket granting services specified in the Kerberos protocol. The service runs on computers selected by the administrator of the realm or domain; it is not present on every machine on the network. It must have access to an account database for the realm that it serves. Windows KDCs are integrated into the domain controller role of a Windows Server acting as a Domain Controller. It is a network service that supplies tickets to clients for use in authenticating to services.

little-endian: Multiple-byte values that are byte-ordered with the least significant byte stored in the memory location with the lowest address.

message mode: A named pipe can be of two types: byte mode or message mode. In byte mode, the data sent or received on the named pipe does not have message boundaries but is treated as a continuous Stream. In message mode, message boundaries are enforced.

named pipe: A named, one-way, or duplex pipe for communication between a pipe server and one or more pipe clients.

network byte order: The order in which the bytes of a multiple-byte number are transmitted on a network, most significant byte first (in big-endian storage). This may or may not match the order in which numbers are normally stored in memory for a particular processor.

NT file system (NTFS): A proprietary Microsoft file system. For more information, see [MSFT-NTFS].

object store: A system that provides the ability to create, query, modify, or apply policy to a local resource on behalf of a remote client. The object store is backed by a file system, a named pipe, or a print job that is accessed as a file.

Obsolescent: A feature that has no replacement but is becoming obsolete. Although the use of obsolescent features is discouraged, server implementations might need to implement them to support clients that negotiate earlier SMB dialects.

open: A runtime object that corresponds to a currently established access to a specific file or a named pipe from a specific client to a specific server, using a specific user security context. Both clients and servers maintain opens that represent active accesses.

oplock break: An unsolicited request sent by a Server Message Block (SMB) server to an SMB client to inform the client to change the oplock level for a file.

opportunistic lock (oplock): A mechanism designed to allow clients to dynamically alter their buffering strategy in a consistent manner to increase performance and reduce network use. The network performance for remote file operations may be increased if a client can locally buffer file data, which reduces or eliminates the need to send and receive network packets. For example, a client may not have to write information into a file on a remote server if the client knows that no other process is accessing the data. Likewise, the client may buffer read-ahead data from the remote file if the client knows that no other process is writing data to the remote file.  There are three types of oplocks: Exclusive oplock allows a client to open a file for exclusive access and allows the client to perform arbitrary buffering. Batch oplock allows a client to keep a file open on the server even though the local accessor on the client machine has closed the file.  Level II oplock indicates that there are multiple readers of a file and no writers. Level II Oplocks are supported if the negotiated SMB Dialect is NT LM 0.12 or later. When a client opens a file, it requests the server to grant it a particular type of oplock on the file. The response from the server indicates the type of oplock granted to the client. The client uses the granted oplock type to adjust its buffering policy.

original equipment manufacturer (OEM) character: An 8-bit encoding used in MS-DOS and Windows operating systems to associate a sequence of bits with specific characters. The ASCII character set maps the letters, numerals, and specified punctuation and control characters to the numbers from 0 to 127. The term "code page" is used to refer to extensions of the ASCII character set that map specified characters and symbols to the numbers from 128 to 255. These code pages are referred to as OEM character sets. For more information, see [MSCHARSET].

process identifier (PID): A nonzero integer used by some operating systems (for example, Windows and UNIX) to uniquely identify a process. For more information, see [PROCESS].

raw read (on a named pipe): The act of reading data from a named pipe that ignores message boundaries even if the pipe was set up as a message mode pipe.

reparse point: An attribute that can be added to a file to store a collection of user-defined data that is opaque to NTFS or ReFS. If a file that has a reparse point is opened, the open will normally fail with STATUS_REPARSE, so that the relevant file system filter driver can detect the open of a file associated with (owned by) this reparse point. At that point, each installed filter driver can check to see if it is the owner of the reparse point, and, if so, perform any special processing required for a file with that reparse point. The format of this data is understood by the application that stores the data and the file system filter that interprets the data and processes the file. For example, an encryption filter that is marked as the owner of a file's reparse point could look up the encryption key for that file. A file can have (at most) 1 reparse point associated with it. For more information, see [MS-FSCC].

security context: An abstract data structure that contains authorization information for a particular security principal in the form of a Token/Authorization Context (see [MS-DTYP] section 2.5.2). A server uses the authorization information in a security context to check access to requested resources. A security context also contains a key identifier that associates mutually established cryptographic keys, along with other information needed to perform secure communication with another security principal.

security descriptor: A data structure containing the security information associated with a securable object. A security descriptor identifies an object's owner by its security identifier (SID). If access control is configured for the object, its security descriptor contains a discretionary access control list (DACL) with SIDs for the security principals who are allowed or denied access. Applications use this structure to set and query an object's security status. The security descriptor is used to guard access to an object as well as to control which type of auditing takes place when the object is accessed. The security descriptor format is specified in [MS-DTYP] section 2.4.6; a string representation of security descriptors, called SDDL, is specified in [MS-DTYP] section 2.5.1.

security identifier (SID): An identifier for security principals in Windows that is used to identify an account or a group. Conceptually, the SID is composed of an account authority portion (typically a domain) and a smaller integer representing an identity relative to the account authority, termed the relative identifier (RID). The SID format is specified in [MS-DTYP] section 2.4.2; a string representation of SIDs is specified in [MS-DTYP] section 2.4.2 and [MS-AZOD] section 1.1.1.2.

security principal name (SPN): The name that identifies a security principal (for example, machinename$@domainname for a machine joined to a domain or username@domainname for a user). Domainname is resolved using the Domain Name System (DNS).

Server Message Block (SMB): A protocol that is used to request file and print services from server systems over a network. The SMB protocol extends the CIFS protocol with additional security, file, and disk management support. For more information, see [CIFS] and [MS-SMB].

service principal name (SPN): The name a client uses to identify a service for mutual authentication. (For more information, see [RFC1964] section 2.1.1.) An SPN consists of either two parts or three parts, each separated by a forward slash ('/'). The first part is the service class, the second part is the instance name, and the third part (if present) is the service name. For example, "ldap/dc-01.fabrikam.com/fabrikam.com" is a three-part SPN where "ldap" is the service class name, "dc-01.fabrikam.com" is the instance name, and "fabrikam.com" is the service name. See [SPNNAMES] for more information about SPN format and composing a unique SPN.

session: In Server Message Block (SMB), a persistent-state association between an SMB client and SMB server. A session is tied to the lifetime of the underlying NetBIOS or TCP connection.

shadow copy: A duplicate of data held on a volume at a well-defined instant in time.

share: A resource offered by a Common Internet File System (CIFS) server for access by CIFS clients over the network. A share typically represents a directory tree and its included files (referred to commonly as a "disk share" or "file share") or a printer (a "print share"). If the information about the share is saved in persistent store (for example, Windows registry) and reloaded when a file server is restarted, then the share is referred to as a "sticky share". Some share names are reserved for specific functions and are referred to as special shares: IPC$, reserved for interprocess communication, ADMIN$, reserved for remote administration, and A$, B$, C$ (and other local disk names followed by a dollar sign), assigned to local disk devices.

share connect: The act of establishing authentication and shared state between a Common Internet File System (CIFS) server and client that allows a CIFS client to access a share offered by the CIFS server.

SMB command: A set of SMB messages that are exchanged in order to perform an operation. An SMB command is typically identified by a unique command code in the message headers, although some SMB commands require the use of secondary commands. Within [MS-CIFS], the term command means an SMB command unless otherwise stated.

SMB connection: A transport connection between a Server Message Block (SMB) client and an SMB server. The SMB connection is assumed to provide reliable in-order message delivery semantics. An SMB connection can be established over any available SMB transport that is supported by both the SMB client and the SMB server, as specified in [MS-CIFS].

SMB dialect: There are several different versions and subversions of the Server Message Block (SMB) protocol. A particular version of the SMB protocol is referred to as an SMB dialect. Different SMB dialects can include both new SMB messages as well as changes to the fields and semantics of existing SMB messages used in other SMB dialects. When an SMB client connects to an SMB server, the client and server negotiate the SMB dialect to be used.

SMB message: A protocol data unit. SMB messages are comprised of a header, a parameter section, and a data section. The latter two can be zero length. An SMB message is sometimes referred to simply as an SMB. Within [MS-CIFS], the term command means an SMB command unless otherwise stated.

SMB session: An authenticated user connection established between an SMB client and an SMB server over an SMB connection. There can be multiple active SMB sessions over a single SMB connection. The Uid field in the SMB packet header distinguishes the various sessions.

snapshot: The point in time at which a shadow copy of a volume is made.

stream: A sequence of bytes written to a file on the NTFS file system. Every file stored on a volume that uses the NTFS file system contains at least one stream, which is normally used to store the primary contents of the file. Additional streams within the file can be used to store file attributes, application parameters, or other information specific to that file. Every file has a default data stream, which is unnamed by default. That data stream, and any other data stream associated with a file, can optionally be named.

system access control list (SACL): An access control list (ACL) that controls the generation of audit messages for attempts to access a securable object. The ability to get or set an object's SACL is controlled by a privilege typically held only by system administrators.

Transmission Control Protocol (TCP): A protocol used with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. TCP handles keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.

tree connect: A connection between a CIFS client and a share on a remote CIFS server.

Unicode: A character encoding standard developed by the Unicode Consortium that represents almost all of the written languages of the world. The Unicode standard [UNICODE5.0.0/2007] provides three forms (UTF-8, UTF-16, and UTF-32) and seven schemes (UTF-8, UTF-16, UTF-16 BE, UTF-16 LE, UTF-32, UTF-32 LE, and UTF-32 BE).

Unicode string: A Unicode 8-bit string is an ordered sequence of 8-bit units, a Unicode 16-bit string is an ordered sequence of 16-bit code units, and a Unicode 32-bit string is an ordered sequence of 32-bit code units. In some cases, it could be acceptable not to terminate with a terminating null character. Unless otherwise specified, all Unicode strings follow the UTF-16LE encoding scheme with no Byte Order Mark (BOM).

volume identifier (VolumeId): A 128-bit value used to represent a volume. The value of a VolumeId is unique on a single computer (the local file system or a remote file server).

MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as defined in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.

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