In the seven-layer

OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...

computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...

ing, the presentation layer is layer 6 and serves as the data translator for the

network Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

.Microsoft TechNet
/ref> It is sometimes called the syntax layer.

Description

Within the service layering semantics of the OSI network architecture, the presentation layer responds to service requests from the application layer and issues service requests to the session layer through a unique presentation service access point (PSAP). The presentation layer ensures the information that the application layer of one system sends out is readable by the application layer of another system. On the sending system it is responsible for conversion to standard, transmittable formats. On the receiving system it is responsible for the translation, formatting, and delivery of information for processing or display. http://www.linfo.org/presentation_layer.html Linux Information Project In theory, it relieves application layer protocols of concern regarding syntactical differences in

data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted ...

representation within the

end-user In product development, an end user (sometimes end-user) is a person who ultimately uses or is intended to ultimately use a product. The end user stands in contrast to users who support or maintain the product, such as sysops, system administrat ...

systems. An example of a presentation service would be the conversion of an extended binary coded decimal interchange code (

EBCDIC Extended Binary Coded Decimal Interchange Code (EBCDIC; ) is an eight-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems. It descended from the code used with punched cards and the corresponding six- ...

-coded) text

computer file A computer file is a computer resource for recording data in a computer storage device, primarily identified by its file name. Just as words can be written to paper, so can data be written to a computer file. Files can be shared with and transfe ...

to an

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...

-coded file. If necessary, the presentation layer might be able to translate between multiple data formats using a common format. In many widely used applications and protocols no distinction is actually made between the presentation and application layers. For example,

HyperText Transfer Protocol The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...

(HTTP), generally regarded as an application-layer protocol, has presentation-layer aspects such as the ability to identify

character encoding Character encoding is the process of assigning numbers to Graphics, graphical character (computing), characters, especially the written characters of Language, human language, allowing them to be Data storage, stored, Data communication, transmi ...

for proper conversion, which is then done in the application layer. The presentation layer is the lowest layer at which application programmers consider

data structure In computer science, a data structure is a data organization, management, and storage format that is usually chosen for efficient access to data. More precisely, a data structure is a collection of data values, the relationships among them, a ...

and presentation, instead of simply sending data in the form of

datagrams A datagram is a basic transfer unit associated with a packet-switched network. Datagrams are typically structured in header and payload sections. Datagrams provide a connectionless communication service across a packet-switched network. The deliv ...

or packets between hosts. This layer deals with issues of string representation - whether they use the

Pascal Pascal, Pascal's or PASCAL may refer to: People and fictional characters * Pascal (given name), including a list of people with the name * Pascal (surname), including a list of people and fictional characters with the name ** Blaise Pascal, Fren ...

method (an integer length field followed by the specified amount of bytes) or the C/

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

method (null-terminated strings, e.g. "thisisastring\0"). The idea is that the application layer should be able to point at the data to be moved, and the presentation layer will translate this to commands able to be understood by other applications and processes.

Serialization In computing, serialization (or serialisation) is the process of translating a data structure or object state into a format that can be stored (e.g. files in secondary storage devices, data buffers in primary storage devices) or transmitted (e ...

of complex data structures into flat byte-strings (using mechanisms such as TLV,

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable ...

JSON JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other ser ...

) can be thought of as the key functionality of the presentation layer. Structure representation is normally standardized at this level, often by using

. As well as simple pieces of data, like strings, more complicated things are standardized in this layer. Two common examples are 'objects' in

object-oriented programming Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pr ...

, and the exact way that streaming

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...

is transmitted.

Encryption In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decip ...

and

Decryption In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decip ...

are typically done at this level too, although it can be done on the application, session,

transport Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land (rail and road), water, cable, pipeline, an ...

, or

network layer In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers. Functions The network layer provides the means of transfe ...

s, each having its own advantages and disadvantages. For example, when logging on to bank account sites the presentation layer will decrypt the data as it is received.

Services

Data conversion Data conversion is the conversion of computer data from one format to another. Throughout a computer environment, data is encoded in a variety of ways. For example, computer hardware is built on the basis of certain standards, which requires tha ...

* Character code translation *

Compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression * Gas compression *Compression ratio, of a ...

* Encryption and Decryption *

Protocols

Protocols sometimes considered at this level (though perhaps not strictly adhering to the OSI model) include: *

Apple Filing Protocol The Apple Filing Protocol (AFP), formerly AppleTalk Filing Protocol, is a proprietary network protocol, and part of the Apple File Service (AFS), that offers file services for macOS and the classic Mac OS. In Mac OS 9 and earlier, AFP was the ...

(AFP) *

Independent Computing Architecture Independent Computing Architecture (ICA) is a proprietary protocol for an application server system, designed by Citrix Systems. The protocol lays down a specification for passing data between server and clients, but is not bound to any one platfo ...

(ICA), the Citrix system core protocol *

Lightweight Presentation Protocol Lightweight Presentation Protocol (LPP) is a protocol used to provide ISO presentation services on top of TCP/IP based protocol stacks. It is defined in RFC 1085. The Lightweight Presentation Protocol describes an approach for providing "stream-lin ...

(LPP) *

NetWare Core Protocol The NetWare Core Protocol (NCP) is a network protocol used in some products from Novell, Inc. It is usually associated with the client-server operating system Novell NetWare which originally supported primarily MS-DOS client stations, but later su ...

(NCP) * Network Data Representation (NDR) *

Tox Tox or TOX may refer to: Science and technology * TOX, a protein encoded by the TOX gene * Tox screen, medical diagnostic screening for toxic substances Computing * Tox (protocol), peer-to-peer instant messaging software * tox (Python testing ...

, The Tox protocol is sometimes regarded as part of both the presentation and application layer * eXternal Data Representation (XDR) * X.25 Packet Assembler/Disassembler Protocol (PAD)

References

{{Reflist OSI model

Description

Services

Protocols

See also

References