D413 WGU TELECOM EXAM 2025/2026 QUESTIONS AND ANSWERS 100% PASS., Question 1: Which layer of the OSI model is responsible for end-to-end communication, segmentation, and reassembly of data

D413 WGU TELECOM EXAM 2025/2026
QUESTIONS AND ANSWERS 100% PASS.,

Question 1: Which layer of the OSI model is responsible for end-to-end
communication, segmentation, and reassembly of data?
A) Network Layer
B) Data Link Layer
C) Transport Layer
D) Session Layer

Correct ,,,,,answer,,,: C) Transport Layer

Rationale: The Transport Layer (Layer 4) is responsible for end-to-end
communication, segmenting data into manageable pieces at the source,
reassembling them at the destination, and providing error recovery and
flow control. TCP and UDP operate at this layer .




Question 2: Which OSI layer addresses and routes packets across
networks?
A) Physical Layer
B) Data Link Layer
C) Network Layer
D) Transport Layer

Correct ,,,,,answer,,,: C) Network Layer

,Rationale: The Network Layer (Layer 3) is responsible for logical
addressing (IP addresses) and routing packets across different networks.
Routers operate at this layer .




Question 3: A switch operates at which layer(s) of the OSI model?
A) Layer 1 only
B) Layer 2 only
C) Layer 3 only
D) Layers 2 and 3

Correct ,,,,,answer,,,: B) Layer 2 only

Rationale: A standard network switch operates at the Data Link Layer
(Layer 2), using MAC addresses to forward frames to specific ports. Layer
3 switches can also route at the Network Layer, but basic switches are
Layer 2 devices .




Question 4: Which of the following is a characteristic of TCP?
A) Connectionless
B) Unreliable
C) Connection-oriented
D) No error recovery

Correct ,,,,,answer,,,: C) Connection-oriented

Rationale: Transmission Control Protocol (TCP) is connection-oriented,
establishing a session before data transfer, providing sequence numbers,

,acknowledgments (ACKs), and retransmission of lost packets. UDP is
connectionless and unreliable .




Question 5: What is the primary purpose of the Presentation Layer (Layer
6)?
A) Routing and addressing
B) Data formatting, encryption, and compression
C) Physical transmission of bits
D) Session management

Correct ,,,,,answer,,,: B) Data formatting, encryption, and compression

Rationale: The Presentation Layer translates data between the
application format and the network format. It handles data compression,
encryption/decryption, and character code conversion (e.g., ASCII to
EBCDIC) .




Question 6: Which of the following is a characteristic of UDP?
A) Connection-oriented
B) Provides guaranteed delivery
C) Low overhead, no error recovery
D) Slower than TCP

Correct ,,,,,answer,,,: C) Low overhead, no error recovery

Rationale: User Datagram Protocol (UDP) is connectionless, has low
overhead, and does not guarantee delivery, order, or error recovery. It is

, used for real-time applications like VoIP, streaming, and DNS where
speed is critical and occasional loss is acceptable .




Question 7: Which layer of the OSI model defines voltage levels, cable
specifications, and pinouts?
A) Physical Layer
B) Data Link Layer
C) Network Layer
D) Transport Layer

Correct ,,,,,answer,,,: A) Physical Layer

Rationale: The Physical Layer (Layer 1) defines the electrical, mechanical,
procedural, and functional specifications for the physical connection,
including voltage levels, cable types, connectors, and pinouts .




Question 8: What is a PDU (Protocol Data Unit) called at the Transport
Layer?
A) Frame
B) Packet
C) Segment
D) Bit

Correct ,,,,,answer,,,: C) Segment

Rationale: The PDU naming convention is: Bits at Physical Layer, Frames
at Data Link Layer, Packets at Network Layer, Segments at Transport
Layer, and Data at upper layers .