WGU D413 TELECOMMUNICATIONS NEWLY
UPDATED COLLECTION OF EXAM QUESTIONS
AND VERIFIED ANSWERS DESIGNED TO
GUARANTEE YOUR SUCCESS ON THE LATEST
TEST VERSION
WGU D413 TELECOMMUNICATIONS & WIRELESS COMMUNICATIONS EXAM
SECTION 1: OSI & TCP/IP MODELS
1. Which layer of the OSI model is responsible for end-to-end error recovery and
flow control?
• A) Physical layer
• B) Data link layer
• C) Transport layer
• D) Application layer
Answer: C) Transport layer
Rationale: The Transport Layer (Layer 4) provides reliable data transfer, error
recovery, and flow control between end systems. Protocols like TCP operate at this
layer to ensure reliable data delivery .
2. The TCP/IP model combines which OSI layers into a single "Application layer"?
• A) Session, Presentation, Application
, • B) Physical, Data Link, Network
• C) Network, Transport, Session
• D) Data Link, Physical, Application
Answer: A) Session, Presentation, Application
Rationale: The TCP/IP model's Application layer corresponds to the top three
layers of the OSI model: Application (Layer 7), Presentation (Layer 6), and Session
(Layer 5) .
3. The Internet Protocol (IP) operates at which OSI layer?
• A) Physical
• B) Data Link
• C) Network
• D) Transport
Answer: C) Network
Rationale: IP is a Network layer (Layer 3) protocol responsible for logical
addressing and routing packets across interconnected networks .
4. Which protocol operates at the Transport layer of the TCP/IP model and
provides unreliable, connectionless communication?
• A) TCP
• B) UDP
• C) IP
• D) HTTP
Answer: B) UDP
Rationale: UDP (User Datagram Protocol) is connectionless and does not
guarantee delivery or provide error recovery. It is used for applications where
speed is prioritized over reliability .
5. Ethernet operates at which two OSI layers?
, • A) Physical and Data Link
• B) Network and Transport
• C) Session and Presentation
• D) Application and Physical
Answer: A) Physical and Data Link
Rationale: Ethernet covers the Physical Layer (signaling, cabling) and the Data Link
Layer (MAC addressing, framing). The Data Link Layer is responsible for moving
data across the physical link .
6. Which layer of the OSI model is responsible for routing and logical
addressing?
• A) Physical layer
• B) Data link layer
• C) Network layer
• D) Transport layer
Answer: C) Network layer
Rationale: The Network Layer (Layer 3) handles logical addressing (IP addresses)
and routing, determining the best path for data packets to travel from source to
destination across networks .
7. Which layer of the OSI model defines the electrical and mechanical
specifications for network media?
• A) Physical layer
• B) Data link layer
• C) Network layer
• D) Transport layer
Answer: A) Physical layer
Rationale: The Physical Layer (Layer 1) defines the electrical, mechanical, and
, functional specifications for the physical medium—including cable types,
connectors, and signaling .
8. The TCP/IP model's "Internet Layer" is equivalent to which OSI layer?
• A) Physical
• B) Data Link
• C) Network
• D) Transport
Answer: C) Network
Rationale: The Internet Layer in the TCP/IP model corresponds to the Network
Layer (Layer 3) in the OSI model. It handles logical addressing and packet routing
across networks .
9. Which core principle of the TCP/IP stack resolves the issue of a sending host
overflowing the receive buffer of a destination host?
• A) Congestion control via the TCP receive window
• B) Flow control via the TCP sliding window
• C) Segmentation via Maximum Segment Size (MSS) negotiation
• D) Sequence numbering to reassemble out-of-order packets
Answer: B) Flow control via the TCP sliding window
Rationale: Flow control is an end-to-end mechanism between sender and receiver
where the receiver advertises its available buffer space in the "Window Size" field
of every TCP segment. The sender must not send more unacknowledged data
than this window size, preventing buffer overflow .
10. Ethernet 10Base2 uses which type of cabling and data rate?
• A) Category 5 UTP, 10 Mbps
• B) RG-58 coaxial cable, 10 Mbps
• C) Fiber optic cable, 10 Mbps
UPDATED COLLECTION OF EXAM QUESTIONS
AND VERIFIED ANSWERS DESIGNED TO
GUARANTEE YOUR SUCCESS ON THE LATEST
TEST VERSION
WGU D413 TELECOMMUNICATIONS & WIRELESS COMMUNICATIONS EXAM
SECTION 1: OSI & TCP/IP MODELS
1. Which layer of the OSI model is responsible for end-to-end error recovery and
flow control?
• A) Physical layer
• B) Data link layer
• C) Transport layer
• D) Application layer
Answer: C) Transport layer
Rationale: The Transport Layer (Layer 4) provides reliable data transfer, error
recovery, and flow control between end systems. Protocols like TCP operate at this
layer to ensure reliable data delivery .
2. The TCP/IP model combines which OSI layers into a single "Application layer"?
• A) Session, Presentation, Application
, • B) Physical, Data Link, Network
• C) Network, Transport, Session
• D) Data Link, Physical, Application
Answer: A) Session, Presentation, Application
Rationale: The TCP/IP model's Application layer corresponds to the top three
layers of the OSI model: Application (Layer 7), Presentation (Layer 6), and Session
(Layer 5) .
3. The Internet Protocol (IP) operates at which OSI layer?
• A) Physical
• B) Data Link
• C) Network
• D) Transport
Answer: C) Network
Rationale: IP is a Network layer (Layer 3) protocol responsible for logical
addressing and routing packets across interconnected networks .
4. Which protocol operates at the Transport layer of the TCP/IP model and
provides unreliable, connectionless communication?
• A) TCP
• B) UDP
• C) IP
• D) HTTP
Answer: B) UDP
Rationale: UDP (User Datagram Protocol) is connectionless and does not
guarantee delivery or provide error recovery. It is used for applications where
speed is prioritized over reliability .
5. Ethernet operates at which two OSI layers?
, • A) Physical and Data Link
• B) Network and Transport
• C) Session and Presentation
• D) Application and Physical
Answer: A) Physical and Data Link
Rationale: Ethernet covers the Physical Layer (signaling, cabling) and the Data Link
Layer (MAC addressing, framing). The Data Link Layer is responsible for moving
data across the physical link .
6. Which layer of the OSI model is responsible for routing and logical
addressing?
• A) Physical layer
• B) Data link layer
• C) Network layer
• D) Transport layer
Answer: C) Network layer
Rationale: The Network Layer (Layer 3) handles logical addressing (IP addresses)
and routing, determining the best path for data packets to travel from source to
destination across networks .
7. Which layer of the OSI model defines the electrical and mechanical
specifications for network media?
• A) Physical layer
• B) Data link layer
• C) Network layer
• D) Transport layer
Answer: A) Physical layer
Rationale: The Physical Layer (Layer 1) defines the electrical, mechanical, and
, functional specifications for the physical medium—including cable types,
connectors, and signaling .
8. The TCP/IP model's "Internet Layer" is equivalent to which OSI layer?
• A) Physical
• B) Data Link
• C) Network
• D) Transport
Answer: C) Network
Rationale: The Internet Layer in the TCP/IP model corresponds to the Network
Layer (Layer 3) in the OSI model. It handles logical addressing and packet routing
across networks .
9. Which core principle of the TCP/IP stack resolves the issue of a sending host
overflowing the receive buffer of a destination host?
• A) Congestion control via the TCP receive window
• B) Flow control via the TCP sliding window
• C) Segmentation via Maximum Segment Size (MSS) negotiation
• D) Sequence numbering to reassemble out-of-order packets
Answer: B) Flow control via the TCP sliding window
Rationale: Flow control is an end-to-end mechanism between sender and receiver
where the receiver advertises its available buffer space in the "Window Size" field
of every TCP segment. The sender must not send more unacknowledged data
than this window size, preventing buffer overflow .
10. Ethernet 10Base2 uses which type of cabling and data rate?
• A) Category 5 UTP, 10 Mbps
• B) RG-58 coaxial cable, 10 Mbps
• C) Fiber optic cable, 10 Mbps
