WGU D317 Networking Foundations
Exam Prep Document 2026/2027 |
Network Fundamentals,
Infrastructure
EXAM
Questions 1–15: OSI Model (Layers, Functions, and PDUs)
1. At which layer of the OSI model does a router primarily
operate?
A) Layer 1 – Physical
B) Layer 2 – Data Link
C) Layer 3 – Network
D) Layer 4 – Transport
Answer: C) Layer 3 – Network
Rationale: Routers use logical IP addresses to forward packets
between different networks. This is a Network layer (Layer 3)
function. Hubs operate at Layer 1, switches/bridges at Layer 2, and
TCP/UDP operate at Layer 4.
,2. Which OSI layer is responsible for data formatting,
encryption, and compression?
A) Application
B) Session
C) Presentation
D) Transport
Answer: C) Presentation
Rationale: The Presentation layer (Layer 6) translates data
between the application and the network, handling formatting
(e.g., JPEG, MPEG), encryption (SSL/TLS), and compression. The
Application layer interfaces with user programs; the Session layer
manages dialogues.
3. The TCP protocol operates at which layer of the OSI model?
A) Layer 2
B) Layer 3
C) Layer 4
D) Layer 5
Answer: C) Layer 4
Rationale: TCP (Transmission Control Protocol) is a Transport
layer protocol responsible for reliable, connection-oriented data
delivery, segmentation, and retransmission of lost packets.
,4. Which layer of the OSI model is responsible for MAC
addressing and switching?
A) Physical
B) Data Link
C) Network
D) Transport
Answer: B) Data Link
Rationale: The Data Link layer (Layer 2) packages data into
frames, provides error detection, and uses MAC addresses for
delivery within a local network. Switches and bridges operate at
this layer.
5. At which layer would you find the HTTP and FTP protocols?
A) Transport
B) Session
C) Presentation
D) Application
Answer: D) Application
Rationale: HTTP and FTP are application-level protocols that
provide network services directly to end-user applications. They
reside at Layer 7 of the OSI model.
6. Which PDU (Protocol Data Unit) is associated with the
Transport layer?
, A) Bits
B) Frames
C) Packets
D) Segments
Answer: D) Segments
Rationale: The Transport layer segments data into segments (for
TCP) or datagrams (for UDP). Frames are Layer 2, Packets are
Layer 3, and Bits are Layer 1.
7. A network administrator wants to ensure that data sent
from a web server is encrypted before transmission. Which
OSI layer handles this encryption?
A) Application
B) Presentation
C) Session
D) Physical
Answer: B) Presentation
Rationale: Encryption and decryption are functions of the
Presentation layer (Layer 6), which ensures data is in a readable
format for the Application layer. While TLS/SSL are often
discussed at the Application layer, the function of encryption
resides in the Presentation layer per the OSI model.
Exam Prep Document 2026/2027 |
Network Fundamentals,
Infrastructure
EXAM
Questions 1–15: OSI Model (Layers, Functions, and PDUs)
1. At which layer of the OSI model does a router primarily
operate?
A) Layer 1 – Physical
B) Layer 2 – Data Link
C) Layer 3 – Network
D) Layer 4 – Transport
Answer: C) Layer 3 – Network
Rationale: Routers use logical IP addresses to forward packets
between different networks. This is a Network layer (Layer 3)
function. Hubs operate at Layer 1, switches/bridges at Layer 2, and
TCP/UDP operate at Layer 4.
,2. Which OSI layer is responsible for data formatting,
encryption, and compression?
A) Application
B) Session
C) Presentation
D) Transport
Answer: C) Presentation
Rationale: The Presentation layer (Layer 6) translates data
between the application and the network, handling formatting
(e.g., JPEG, MPEG), encryption (SSL/TLS), and compression. The
Application layer interfaces with user programs; the Session layer
manages dialogues.
3. The TCP protocol operates at which layer of the OSI model?
A) Layer 2
B) Layer 3
C) Layer 4
D) Layer 5
Answer: C) Layer 4
Rationale: TCP (Transmission Control Protocol) is a Transport
layer protocol responsible for reliable, connection-oriented data
delivery, segmentation, and retransmission of lost packets.
,4. Which layer of the OSI model is responsible for MAC
addressing and switching?
A) Physical
B) Data Link
C) Network
D) Transport
Answer: B) Data Link
Rationale: The Data Link layer (Layer 2) packages data into
frames, provides error detection, and uses MAC addresses for
delivery within a local network. Switches and bridges operate at
this layer.
5. At which layer would you find the HTTP and FTP protocols?
A) Transport
B) Session
C) Presentation
D) Application
Answer: D) Application
Rationale: HTTP and FTP are application-level protocols that
provide network services directly to end-user applications. They
reside at Layer 7 of the OSI model.
6. Which PDU (Protocol Data Unit) is associated with the
Transport layer?
, A) Bits
B) Frames
C) Packets
D) Segments
Answer: D) Segments
Rationale: The Transport layer segments data into segments (for
TCP) or datagrams (for UDP). Frames are Layer 2, Packets are
Layer 3, and Bits are Layer 1.
7. A network administrator wants to ensure that data sent
from a web server is encrypted before transmission. Which
OSI layer handles this encryption?
A) Application
B) Presentation
C) Session
D) Physical
Answer: B) Presentation
Rationale: Encryption and decryption are functions of the
Presentation layer (Layer 6), which ensures data is in a readable
format for the Application layer. While TLS/SSL are often
discussed at the Application layer, the function of encryption
resides in the Presentation layer per the OSI model.
