Lapisan Aplikasi

Summary

This video introduces the top three layers of the OSI model—Application, Presentation, and Session—and compares them with the application layer in the TCP/IP model. It explains the roles and functions of these layers in facilitating network communication, including data encoding, compression, and encryption. It also covers how protocols such as DNS, HTTP, SMTP, Telnet, and FTP enable communication across the internet. The video emphasizes the importance of these protocols in transferring data, ensuring connectivity, and maintaining communication between different hosts in a network.

Takeaways

• 😀 The top three layers of the OSI model (Application, Presentation, and Session) function similarly to the application layer in the TCP/IP model.
• 😀 The OSI model is an abstract guide for creating network protocols, dividing the process into seven logical layers with unique functions.
• 😀 Communication begins at the Application layer on the sender's host and progresses down the layers until it reaches the Physical layer.
• 😀 The data is then transmitted over a communication channel to the receiving host, where the data is processed upwards from the Physical layer back to the Application layer.
• 😀 The TCP/IP model's Application layer corresponds to the combined functions of the OSI model's Application, Presentation, and Session layers.
• 😀 The Presentation layer in OSI handles encoding, data compression, and encryption to ensure that information is understood by the receiving application.
• 😀 Data formats for multimedia (e.g., QuickTime for videos, GIF for graphics) are determined by the Presentation layer's standards.
• 😀 The Session layer ensures that communication sessions between applications are properly initiated, maintained, and terminated, especially after interruptions.
• 😀 Protocols at the Application layer, such as DNS, HTTP, SMTP, Telnet, and FTP, enable key internet functionalities like domain resolution, webpage transfer, email sending, remote access, and file transfer.
• 😀 The OSI model was developed before widespread PC and multimedia growth, so it did not initially account for modern graphical and multimedia standards.

Q & A

What is the purpose of the OSI model?

The OSI model is an abstract framework designed to guide the development of network protocols. It divides the network communication process into seven logical layers, each with distinct functions, protocols, and services.

How does the OSI model process information?

Information flows hierarchically through the layers, starting from the application layer at the sender's host. The data is then converted into digital format and passed through the lower layers, eventually being transmitted through a communication channel to the receiving host. The data is processed in reverse order at the receiving end.

What is the relationship between the OSI and TCP/IP models?

The top three layers of the OSI model (application, presentation, and session) have similar functions to the application layer of the TCP/IP model. However, the TCP/IP model was developed before the OSI model, and its application layer combines several OSI layer functions.

What does the application layer in both OSI and TCP/IP models do?

The application layer provides an interface between the applications used for communication and the underlying network, facilitating data exchange between programs running on different hosts.

What are the main functions of the presentation layer in the OSI model?

The presentation layer has three main functions: encoding (data conversion), compression (reducing data size for transmission), and encryption (encoding data for secure transmission).

What role does the session layer play in the OSI model?

The session layer establishes, maintains, and terminates dialogs between applications on different hosts. It ensures a consistent exchange of information and manages disruptions or idle periods in the communication.

Which protocols are associated with the application layer of the TCP/IP model?

Common protocols at the application layer of the TCP/IP model include DNS (Domain Name System), HTTP (Hypertext Transfer Protocol), SMTP (Simple Mail Transfer Protocol), Telnet, and FTP (File Transfer Protocol).

How does DNS work within the TCP/IP model?

DNS translates domain names into IP addresses, allowing users to access websites and other network resources using easily readable names instead of numeric IP addresses.

What is the purpose of HTTP in the context of the TCP/IP model?

HTTP is used to transfer files that form web pages over the internet. It enables communication between web browsers and servers to retrieve and display web content.

What is the role of SMTP in email communication?

SMTP is responsible for sending and receiving emails, including attachments. It ensures that email messages are routed correctly between servers and delivered to recipients.