THE PRESENTATION LAYER

The Presentation Layer

The presentation layer performs certain functions that are requested frequently enough to justify seeking a general solution, rather than leaving problems to each user to solve. In particular, and unlike all the lower layers that are concerned only with reliably moving bits back and forth, the presentation layer deals with the syntax and semantics of the information being transmitted.

A typical example of a presentation service is the encoding of data in an agreed standard form. Most user programs don't exchange strings of random bits, they exchange things like: names of people, dates, amounts of money, bills. These elements are represented as strings, integers, floating point quantities, and data structures made up of several simpler elements.

Different computers have different codes to represent strings, integers, and so on. In order to make communication between computers with different representations possible, the data structure to be exchanged can be defined in an abstract way, together with a standard code that is used "on the wire". The presentation layer handles these abstract data structures and converts them from the presentation you use inside the computer to the standard presentation on the network and vice versa.

Presentation Layer Operations.

The presentation layer performs the following operations:

• Translate between various data formats using a common format.
• Define the data structure to transmit.
• Define the code to use to represent a character string.
• Format information for viewing or printing.
• Compress the data if necessary.
• Apply cryptographic processes to the data.