CS 6250 Computer Networks Exam 1
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which statement most accurately describes the primary function of a
computer network's protocol?
A. It guarantees that every packet reaches its destination through the
shortest possible physical path.
B. It defines rules governing communication between networked entities,
including message formats, ordering, and actions taken when messages are
exchanged.
C. It eliminates the need for addressing because routers identify hosts by
physical location.
D. It ensures that all network applications use the same transport-layer
mechanism.
Answer: B. It defines rules governing communication between networked
entities, including message formats, ordering, and actions taken when
messages are exchanged.
Rationale: A network protocol specifies the syntax, semantics, and rules
governing communication. Protocols may define message formats,
sequencing, error handling, addressing, and the expected behavior of
communicating entities.
, 2. In the Internet's layered architecture, which layer is primarily
responsible for providing process-to-process communication between
applications running on different hosts?
A. Application layer
B. Network layer
C. Transport layer
D. Link layer
Answer: C. Transport layer
Rationale: The transport layer provides logical communication between
application processes on different hosts. Protocols such as TCP and UDP
operate at this layer and use port numbers to distinguish application
processes.
3. Which statement best explains why layered network architectures are
useful?
A. Every layer must understand the implementation details of all lower
layers.
B. Layering eliminates all network overhead associated with encapsulation.
C. Layering allows protocols at one layer to provide services while hiding
implementation details from higher layers.
D. Layering requires every application to use exactly the same protocol
stack.
Answer: C. Layering allows protocols at one layer to provide services while
hiding implementation details from higher layers.
Rationale: Layering promotes modularity and abstraction. A higher layer
can use the service of a lower layer without needing to know how that
service is implemented, making networks easier to design, modify, and
maintain.
, 4. A web browser sends an HTTP request to a web server. Which
sequence correctly represents the encapsulation process as the
request moves downward through a typical Internet protocol stack?
A. HTTP → TCP → IP → Link-layer frame
B. HTTP → IP → TCP → Link-layer frame
C. TCP → HTTP → IP → Link-layer frame
D. HTTP → Link-layer frame → TCP → IP
Answer: A. HTTP → TCP → IP → Link-layer frame
Rationale: The application generates an HTTP message, which is carried by
TCP at the transport layer, encapsulated within an IP packet at the
network layer, and finally encapsulated in a link-layer frame for
transmission over the local network.
5. Which networking device primarily operates at the network layer and
makes forwarding decisions using destination IP addresses?
A. Hub
B. Ethernet switch
C. Router
D. Repeater
Answer: C. Router
Rationale: Routers operate primarily at the network layer and use
destination IP addresses and forwarding tables to determine the next hop
for packets. Ethernet switches primarily make forwarding decisions using
MAC addresses.
6. Which statement correctly distinguishes a circuit-switched network
from a packet-switched network?
A. Circuit switching divides every message into independently routed
packets.
B. Packet switching requires a dedicated physical circuit for each
, communicating pair.
C. Circuit switching typically reserves resources for a communication
session, whereas packet switching dynamically shares network resources
among packets.
D. Packet switching can only be used for unreliable applications.
Answer: C. Circuit switching typically reserves resources for a
communication session, whereas packet switching dynamically shares
network resources among packets.
Rationale: Circuit switching establishes a dedicated resource allocation
before communication, while packet-switched networks statistically
multiplex traffic over shared links. Packet switching is particularly efficient
for bursty computer-network traffic.
7. Which characteristic of packet switching makes it especially
appropriate for typical Internet traffic?
A. Internet applications continuously transmit at a constant rate.
B. Packet switching allows network resources to be statistically multiplexed
among users with bursty traffic patterns.
C. Packet switching guarantees zero queueing delay.
D. Packet switching requires every application to reserve bandwidth before
sending data.
Answer: B. Packet switching allows network resources to be statistically
multiplexed among users with bursty traffic patterns.
Rationale: Computer applications often generate data in bursts rather than
at a constant rate. Packet switching allows many users to share links
efficiently instead of reserving dedicated capacity that may remain
unused.
8. Suppose a packet travels through three store-and-forward links with
transmission rates of 10 Mbps, 5 Mbps, and 20 Mbps. Ignoring
propagation, processing, and queueing delays, what determines the
end-to-end transmission time for a single packet of fixed size?
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which statement most accurately describes the primary function of a
computer network's protocol?
A. It guarantees that every packet reaches its destination through the
shortest possible physical path.
B. It defines rules governing communication between networked entities,
including message formats, ordering, and actions taken when messages are
exchanged.
C. It eliminates the need for addressing because routers identify hosts by
physical location.
D. It ensures that all network applications use the same transport-layer
mechanism.
Answer: B. It defines rules governing communication between networked
entities, including message formats, ordering, and actions taken when
messages are exchanged.
Rationale: A network protocol specifies the syntax, semantics, and rules
governing communication. Protocols may define message formats,
sequencing, error handling, addressing, and the expected behavior of
communicating entities.
, 2. In the Internet's layered architecture, which layer is primarily
responsible for providing process-to-process communication between
applications running on different hosts?
A. Application layer
B. Network layer
C. Transport layer
D. Link layer
Answer: C. Transport layer
Rationale: The transport layer provides logical communication between
application processes on different hosts. Protocols such as TCP and UDP
operate at this layer and use port numbers to distinguish application
processes.
3. Which statement best explains why layered network architectures are
useful?
A. Every layer must understand the implementation details of all lower
layers.
B. Layering eliminates all network overhead associated with encapsulation.
C. Layering allows protocols at one layer to provide services while hiding
implementation details from higher layers.
D. Layering requires every application to use exactly the same protocol
stack.
Answer: C. Layering allows protocols at one layer to provide services while
hiding implementation details from higher layers.
Rationale: Layering promotes modularity and abstraction. A higher layer
can use the service of a lower layer without needing to know how that
service is implemented, making networks easier to design, modify, and
maintain.
, 4. A web browser sends an HTTP request to a web server. Which
sequence correctly represents the encapsulation process as the
request moves downward through a typical Internet protocol stack?
A. HTTP → TCP → IP → Link-layer frame
B. HTTP → IP → TCP → Link-layer frame
C. TCP → HTTP → IP → Link-layer frame
D. HTTP → Link-layer frame → TCP → IP
Answer: A. HTTP → TCP → IP → Link-layer frame
Rationale: The application generates an HTTP message, which is carried by
TCP at the transport layer, encapsulated within an IP packet at the
network layer, and finally encapsulated in a link-layer frame for
transmission over the local network.
5. Which networking device primarily operates at the network layer and
makes forwarding decisions using destination IP addresses?
A. Hub
B. Ethernet switch
C. Router
D. Repeater
Answer: C. Router
Rationale: Routers operate primarily at the network layer and use
destination IP addresses and forwarding tables to determine the next hop
for packets. Ethernet switches primarily make forwarding decisions using
MAC addresses.
6. Which statement correctly distinguishes a circuit-switched network
from a packet-switched network?
A. Circuit switching divides every message into independently routed
packets.
B. Packet switching requires a dedicated physical circuit for each
, communicating pair.
C. Circuit switching typically reserves resources for a communication
session, whereas packet switching dynamically shares network resources
among packets.
D. Packet switching can only be used for unreliable applications.
Answer: C. Circuit switching typically reserves resources for a
communication session, whereas packet switching dynamically shares
network resources among packets.
Rationale: Circuit switching establishes a dedicated resource allocation
before communication, while packet-switched networks statistically
multiplex traffic over shared links. Packet switching is particularly efficient
for bursty computer-network traffic.
7. Which characteristic of packet switching makes it especially
appropriate for typical Internet traffic?
A. Internet applications continuously transmit at a constant rate.
B. Packet switching allows network resources to be statistically multiplexed
among users with bursty traffic patterns.
C. Packet switching guarantees zero queueing delay.
D. Packet switching requires every application to reserve bandwidth before
sending data.
Answer: B. Packet switching allows network resources to be statistically
multiplexed among users with bursty traffic patterns.
Rationale: Computer applications often generate data in bursts rather than
at a constant rate. Packet switching allows many users to share links
efficiently instead of reserving dedicated capacity that may remain
unused.
8. Suppose a packet travels through three store-and-forward links with
transmission rates of 10 Mbps, 5 Mbps, and 20 Mbps. Ignoring
propagation, processing, and queueing delays, what determines the
end-to-end transmission time for a single packet of fixed size?
