Presentation Layer

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Introduction

In a computer network, different computers have different codes for representing character strings (e.g., ASCII, EBCDIC, Unicode, etc), integers (e.g., one’s complement and two’s complement), and so on. In order to make it possible for computers with different representations to communicate, the data structure to be exchanged can be defined in an abstract way, along with a standard encoding to be used. The presentation layer manages these abstract data structures and converts from the representation used inside the computer to the network standard representation and back.
In other words, when data are transmitted through different computer systems, the presentation layer negotiates and manages the way data are represented and encoded. Sun’s XDR and OSI’s ASN.1 are two protocols used for this purpose.

Code/Format Conversions:
- It is the translator of the network i.e. it makes sure the data is in the correct form for the receiving application.
- The presentation layer is mainly concerned with the syntax and semantics of the information transmitted.
- This layer supports encoding of data in a standard agreed format i.e. the presentation layer performs code conversion(ASCII and EBCDIC) and data reformatting (syntax translation).
Encryption & Decryption:
- This layer also performs encryption and decryption on transmitting data hence increasing security.
Data Compression:
- The presentation layer compress the data without any loose of data quality for fast and smooth running of data in a network with security.