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  Layer 6 Darstellungsschicht   Presentation Layer


Ver-/Entschlüsselung; Encoding

Die Darstellungsschicht (engl. Presentation Layer; auch Datendarstellungsschicht, Datenbereitstellungsebene) setzt die systemabhängige Darstellung der Daten (zum Beispiel ASCII, EBCDIC) in eine unabhängige Form um und ermöglicht somit den syntaktisch korrekten Datenaustausch zwischen unterschiedlichen Systemen. Auch Aufgaben wie die Datenkompression und die Verschlüsselung gehören zur Schicht 6. Die Darstellungsschicht gewährleistet, dass Daten, die von der Anwendungsschicht eines Systems gesendet werden, von der Anwendungsschicht eines anderen Systems gelesen werden können. Falls erforderlich, agiert die Darstellungsschicht als Übersetzer zwischen verschiedenen Datenformaten, indem sie ein für beide Systeme verständliches Datenformat, die ASN.1 (Abstract Syntax Notation One), verwendet.

OSI Layer 6 - Presentation Layer

The presentation layer is responsible for the delivery and formatting of information to the application layer for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems. An example of a presentation service would be the conversion of an EBCDIC-coded text computer file to an ASCII-coded file.

The presentation layer is the lowest layer at which application programmers consider data structure and presentation, instead of simply sending data in the form of datagrams or packets between hosts. This layer deals with issues of string representation - whether they use the Pascal method (an integer length field followed by the specified amount of bytes) or the C/C++ 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 deal with the rest.

Serialization of complex data structures into flat byte-strings (using mechanisms such as TLV or XML) can be thought of as the key functionality of the presentation layer.

Encryption is typically done at this level too, although it can be done on the application, session, transport, or network layers, each having its own advantages and disadvantages. Decryption is also handled at the presentation layer. For example, when logging on to bank account sites the presentation layer will decrypt the data as it is received.[1] Another example is representing structure, which is normally standardized at this level, often by using XML. 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, and the exact way that streaming video is transmitted.

In many widely used applications and protocols, no distinction is made between the presentation and application layers. For example, HyperText Transfer Protocol (HTTP), generally regarded as an application-layer protocol, has presentation-layer aspects such as the ability to identify character encoding for proper conversion, which is then done in the application layer.

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.

In the OSI model: the presentation layer ensures the information that the application layer of one system sends out is readable by the application layer of another system. For example, a PC program communicates with another computer, one using extended binary coded decimal interchange code (EBCDIC) and the other using ASCII to represent the same characters. If necessary, the presentation layer might be able to translate between multiple data formats by using a common format.



  • Daten manipulation
  • Text Encoding
  • Kompression
  • Ver-/Entschlüsselung


Die Darstellungsshicht wird überlicherweisse in folgende Sektoren unterteilt:

CASE common application service element

ACSEAssociation Control Service Element
ROSERemote Operation Service Element
CCRCommitment Concurrency and Recovery
RTSEReliable Transfer Service Element

SASE specific application service element

FTAMFile Transfer, Access and Manager
VTVirtual Terminal
MOTISMessage Oriented Text Interchange Standard
CMIPCommon Management Information Protocol
JTMJob Transfer and Manipulation
MMSManufacturing Messaging Service
RDARemote Database Access
DTPDistributed Transaction Processing