Presentation Layer
The Presentation Layer is concerned with the
syntax and semantics of the information exchanged between two communicating
devices.
- The presentation
layer takes care such that the data is sent to the receiver in
such a way that the receiver will understand the information (data) and
will be able to use the data.
- Syntax may be different from
the two communicating machines. In this condition, the presentation
layer plays the role of translator between them.
- It is possible for two
machines to communicate with different data representations, data
structures to be exchanged can be defined in an abstract way. These
abstract data structures will be managed by the presentation layer and
this layer allows higher-level data structures, to be defined and
exchanged.
Functions of
Presentation Layer
- Translation: Before being
transmitted, information in the form of characters and numbers should be
changed to bit streams. The presentation layer is responsible for
interoperability between encoding methods as different computers use
different encoding methods. It translates data between the formats the
network requires and the format the computer.
- Encryption: It carries out
encryption at the transmitter and decryption at the receiver.
- Compression: It carries out data
compression to reduce the bandwidth of the data to be transmitted. The
primary role of Data compression is to reduce the number of bits to be
0transmitted. It is important in transmitting multimedia such as audio,
video, text etc.
Design issues with Presentation Layer :
- Standard way of encoding
data –
The presentation layer follows a standard way to encode data when it needs to be transmitted. This encoded data is represented as character strings, integers, floating point numbers, and data structures composed of simple components. It is handled differently by different machines based on the encoding methods followed by them. - Maintaining the Syntax and
Semantics of distributed information –
The presentation layer manages and maintains the syntax as well as logic and meaning of the information that is distributed. - Standard Encoding on the
wire –
The data structures that are defined to be exchanged need to be abstract along with the standard encoding to be used “on the wire”.
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