Network+ OSI Model Layers and Functions Flashcards

Which OSI layer PDU (Protocol Data Unit) is called a 'segment'?

Answer: Transport layer

The Transport layer's PDU is called a segment, which contains port numbers and sequencing information.

A network engineer is troubleshooting a connectivity issue and wants to verify physical signal integrity on the cable. Which OSI layer should they focus on?

Answer: Layer 1

The Physical layer (Layer 1) deals with the transmission of raw bits over a physical medium, including signal integrity.

Which protocol at the Application layer is used to translate domain names to IP addresses?

Answer: DNS

DNS (Domain Name System) operates at the Application layer and resolves human-readable domain names to IP addresses.

During data transmission, which OSI layer adds a trailer containing a Frame Check Sequence (FCS) for error detection?

Answer: Data Link layer

The Data Link layer adds both a header and a trailer; the trailer contains the FCS used for error detection.

A VPN concentrator terminates encrypted tunnels at which OSI layer when using IPSec in tunnel mode?

Answer: Layer 3

IPSec in tunnel mode operates at the Network layer (Layer 3), encrypting entire IP packets and encapsulating them in new IP packets.

Which of the following best describes the role of the Session layer in the OSI model?

Answer: Establishes, manages, and terminates communication sessions

The Session layer (Layer 5) is responsible for establishing, managing, and terminating sessions between applications.

An application developer is building a network program and needs to ensure data is delivered reliably with error checking. Which Transport layer protocol should they use?

Answer: TCP

TCP (Transmission Control Protocol) provides reliable, connection-oriented delivery with error checking and acknowledgments.