Data Communication Lecture#4 Abdullah Tayyab email@example.com
Presentation Layer • The Presentation Layer is Layer 6 of the seven-layer OSI model of computer networking. • It responds to service requests from the application layer and issues service request to the session layer. • Receives message from application layer, formats it, and passes it to the session layer.
Functions of Presentation Layer Here are some of the specific types of data handling issues that the presentation layer handles • Data Format or Translation • Data Security • Data Compression
Syntax • The presentation layer is concerned with the syntax and semantics of the information transmitted. • The presentation layer sometimes called the syntax layer in the (OSI) is basically used to address and resolve data communication across the 7 layers
Syntax Cont.. • The presentation layer of the OSI model at the receiving computer is also responsible for the conversion of “the external format” with which data is received from the sending computer to one accepted by the other layers in the host computer
Data Security • Another function of the presentation layer is found in the encryption or protection of data offered to transmissions/sessions within the layers • This can be achieved by cryptography. • Cryptography is a data security science achieved by hiding information/data in transit.
Data Compression • The goal of data compression is to represent an information source (e.g. a data file, a speech signal, an image, or a video signal) as accurately as possible using the fewest number of bits.
Presention Layer in TCP/IP model • In TCP/IP, this function is provided by the Application Layer. e.g. • External Data Representation Standard (XDR) • Multipurpose Internet Mail Extensions (MIME)
Session Layer • The fifth layer in the OSI Reference Model is the session layer. • To allow devices to establish and manage session • Establishes, maintains, and synchronized the interaction among communicating systems. • occurs.
Cont.. • Synchronization • allows a process to add checkpoints, or synchronization points, to a stream of data. • Responsible for enforcing the rules of dialog (e.g., Does a connection permit half-duplex or full-duplex communication?), synchronizing the flow of data, and reestablishing a connection in the event a failure
Session Layer in TCP/IP model • In TCP/IP, its characteristics are provided by the TCP protocol. (Transport Layer