WGU D413 – Telecommunications & Wireless Communications Objective Assessment Practice OA V1 and V2 | Questions and Answers | 2026 Update | 100% Correct.

WGU D413 – Telecommunications & Wireless Communications Objective
Assessment Practice OA V1 and V2 | Questions and Answers |
2026 Update | 100% Correct.




Section 1: Networking Fundamentals & OSI Model
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

Rationale: The Transport layer (Layer 4) provides reliable data transfer, error recovery,
and flow control between hosts. TCP operates at this layer, ensuring data arrives
correctly through acknowledgments and retransmissions.




2. Ethernet operates at which two OSI layers?

 A) Physical and Data link ✔
 B) Network and Transport
 C) Session and Presentation
 D) Application and Physical

Rationale: Ethernet covers the Physical layer (signaling, cabling) and Data Link layer
(MAC addressing, framing). It handles how data is physically transmitted and how
devices address each other on the local network.

, 3. 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

Rationale: TCP/IP's Application layer corresponds to OSI Layers 5, 6, and 7 (Session,
Presentation, and Application). This simplified model collapses the top three OSI layers
into one.




4. The Internet Protocol (IP) operates at which OSI layer?

 A) Physical
 B) Data link
 C) Network ✔
 D) Transport

Rationale: IP is a network layer protocol (Layer 3) responsible for logical addressing and
routing packets across networks.




5. Which protocol operates at the transport layer and provides unreliable,
connectionless communication?

 A) TCP
 B) UDP ✔
 C) IP
 D) HTTP

Rationale: UDP (User Datagram Protocol) is connectionless and does not guarantee
delivery, ordering, or error recovery. It is used for applications where speed matters
more than reliability, such as streaming media.

, 6. Which layer of the OSI model is responsible for establishing, managing, and
terminating sessions?

 A) Transport
 B) Network
 C) Data Link
 D) Session ✔

Rationale: The Session layer (Layer 5) establishes, manages, and terminates connections
between applications. It handles dialog control and synchronization points.




7. Which device separates collision domains but not broadcast domains?

 A) Router
 B) Hub
 C) Switch ✔
 D) Repeater

Rationale: Switches create separate collision domains per port (each port is its own
collision domain) but all ports remain in the same broadcast domain unless VLANs are
configured. Routers separate both collision and broadcast domains.




8. What is the purpose of a subnet mask?

 A) Encrypt data
 B) Define which portion of an IP address is the network and which is the host ✔
 C) Assign MAC addresses
 D) Monitor network traffic

Rationale: Subnet masks divide an IP address into network and host portions, allowing
proper routing and subnetting. For example, 255.255.255.0 indicates the first three
octets identify the network.

, 9. How many octets are in an IPv4 address?

 A) 2
 B) 3
 C) 4 ✔
 D) 8

Rationale: An IPv4 address consists of 4 octets, each 8 bits, totaling 32 bits. Each octet
can range from 0 to 255.




10. What is the range of numbers in an IPv4 octet?

 A) 0 to 100
 B) 0 to 127
 C) 0 to 255 ✔
 D) 0 to 511

Rationale: An IPv4 octet represents 8 bits (2^8 = 256 possible values), so the range is 0
to 255.




11. How many hosts can a Class C network support?

 A) 65,534
 B) 254 ✔
 C) 16,777,214
 D) 1,024

Rationale: Class C networks have a 24-bit network portion and an 8-bit host portion,
allowing for up to 254 usable hosts (2^8 - 2 = 254).




12. Which IP class is reserved for multicast addressing?

 A) Class A