.Which layer in the Open Systems Interconnection (OSI) model enables coding and conversion functions for application layer data?
A. Presentation layer
B. Session layer
C. Application layer
D. Physical layer
Correct Answer: A
The Presentation layer in the OSI model enables coding and conversion functions for application layer data. Data formatting and encryption is done at this layer. The Presentation layer converts data into a format that can be accepted by the application layer. The Presentation layer is also known as the syntax layer, which provides translation between different data formats by using a common format.
The Session layer in the OSI model does not enable coding and conversion functions for the application layer data. It is used to create, manage, and terminate sessions between communicating nodes. The session layer handles the service requests and service responses that take place between different applications.
The Application layer in the OSI model does not enable coding and conversion functions for the application layer data. The application layer is responsible for interacting directly with the application, and provides application services, such as e-mail and File Transfer Protocol (FTP).
The Physical layer in the OSI model does not enable coding and conversion functions. The Physical layer consists of the hardware that sends and receives data on a carrier. The protocols that work at the Physical layer include Fast Ethernet, RS-232, and Asynchronous Transfer Mode (ATM). The Physical layer is the base layer in the OSI model.
The three remaining layers in the OSI model are the Transport, Network, and Data Link layers. The Transport layer is responsible for error-free and sequential delivery of data. This layer is used to manage data transmission between devices, a process known as flow control. The Transport layer protocols are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
The Network layer is used to define the network address or the Internet Protocol (IP) address that is then used by the routers to forward the packets. The Data Link layer ensures reliable transmission of data across a network.
The seven layers of the OSI model are sequentially interconnected to each other. From the top to the bottom, the seven layers are:
Layer 7: Application
Layer 6: Presentation
Layer 5: Session
Layer 4: Transport
Layer 3: Network
Layer 2: Data Link
Layer 1: Physical
Compare and contrast OSI and TCP/IP models
Internetworking Technology Handbook > Internetworking Basics > OSI Model and Communication Between Systems