Network+ OSI Model Layers and Functions Flashcards

A network technician is troubleshooting an issue where a user can access local network resources but cannot connect to any external websites. Pinging the default gateway is successful, but pinging a public DNS server by its IP address fails. At which layer of the OSI model is the problem MOST likely occurring?

Answer: Network Layer (Layer 3)

The issue is most likely at the Network Layer (Layer 3). The user can access the local network, indicating that Layers 1 and 2 are functioning correctly. However, the inability to reach external IP addresses points to a problem with routing, which is a primary function of the Network Layer. Devices like routers operate at this layer to forward packets between different networks.

Which of the following functions is primarily associated with the Data Link Layer (Layer 2) of the OSI model?

Answer: Packaging data into frames and managing access to the physical medium

The Data Link Layer (Layer 2) is responsible for packaging Network Layer packets into frames, performing error detection for the physical link, and managing how devices access the physical network medium using MAC addresses.

A web browser is preparing to send a request for a webpage. It needs to ensure the data is segmented, transmitted reliably, and reassembled in the correct order at the destination. Which OSI model layer handles these responsibilities?

Answer: Transport Layer (Layer 4)

The Transport Layer (Layer 4) is responsible for end-to-end communication, providing services like data segmentation, sequencing, flow control, and error checking. Protocols like TCP (Transmission Control Protocol) operate at this layer to ensure reliable, ordered delivery of data, which is essential for applications like web browsing.

A user is attempting to access a secure website using HTTPS. The web server sends back data that needs to be decrypted and formatted so the user's browser can render it correctly. Which layer of the OSI model is PRIMARILY responsible for this data translation, including encryption and decryption?

Answer: Presentation Layer (Layer 6)

The Presentation Layer (Layer 6) is responsible for translating data between the application layer and the network format. Its key functions include data formatting, character encoding, compression, and encryption/decryption, such as handling SSL/TLS.

Which of the following Protocol Data Units (PDUs) is associated with the Network Layer of the OSI model?

Answer: Packet

At the Network Layer (Layer 3), the Protocol Data Unit (PDU) is called a packet. Bits are used at the Physical Layer (Layer 1), Frames at the Data Link Layer (Layer 2), and Segments at the Transport Layer (Layer 4).

A network administrator is configuring a firewall to block access to a specific file-sharing application that uses a well-known protocol. This protocol provides the interface between the user's software and the network. At which OSI layer does this protocol operate?

Answer: Application Layer

The Application Layer (Layer 7) provides the interface for applications to access network services. Protocols for specific user-facing applications, such as FTP for file sharing, HTTP for web browsing, and SMTP for email, operate at this layer.