TCP provides reliable, ordered, and connection-oriented data delivery.
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19Which protocol in the TCP/IP suite is mainly responsible for logical addressing and packet routing?
TCP/IP protocol suite
Easy
A.Ethernet
B.IP
C.HTTP
D.TCP
Correct Answer: IP
Explanation:
IP supplies logical addresses and supports routing packets across networks.
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20Which type of address is primarily used at the data link layer?
Addressing mechanisms in layers
Easy
A.Port number
B.MAC address
C.IP address
D.Domain name
Correct Answer: MAC address
Explanation:
The data link layer uses MAC addresses to identify network interfaces on a local network.
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21During a live video conference, packets arrive with varying delays, causing uneven audio playback even though no data is corrupted. Which communication characteristic is primarily affected?
Data communication characteristics
Medium
A.Accuracy
B.Jitter
C.Delivery
D.Security
Correct Answer: Jitter
Explanation:
Jitter is the variation in packet arrival time. Excessive jitter disrupts real-time audio and video playback.
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22A payroll file reaches the intended server on time, but several employee records contain altered bits. Which data communication characteristic has failed?
Data communication characteristics
Medium
A.Accuracy
B.Jitter
C.Timeliness
D.Delivery
Correct Answer: Accuracy
Explanation:
Accuracy requires data to arrive without alteration. Changed bits indicate that the received data is not accurate.
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23Two devices are physically connected and operational, but they interpret the same sequence of bits using different frame formats. Which communication component is incompatible?
Components
Medium
A.Receiving device
B.Transmission medium
C.Message source
D.Protocol
Correct Answer: Protocol
Explanation:
A protocol defines the format and interpretation of exchanged data. Different frame formats indicate incompatible protocols.
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24A text system must represent English, Arabic, Chinese, and emoji characters while remaining compatible with ASCII for basic English text. Which encoding is most suitable?
Data representation
Medium
A.ASCII-7
B.UTF-8
C.EBCDIC
D.BCD
Correct Answer: UTF-8
Explanation:
UTF-8 represents Unicode characters, supports many writing systems, and preserves ASCII byte values for basic English text.
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25An uncompressed image has a resolution of pixels and uses 24 bits per pixel. How many bytes are required to store its pixel data?
Data representation
Medium
A.786,432 bytes
B.2,359,296 bytes
C.6,291,456 bytes
D.18,874,368 bytes
Correct Answer: 2,359,296 bytes
Explanation:
The storage required is bytes.
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26Two security officers use radios on which either officer can speak, but both cannot speak successfully at the same time. Which transmission mode is used?
Transmission modes
Medium
A.Multiplex
B.Full-duplex
C.Half-duplex
D.Simplex
Correct Answer: Half-duplex
Explanation:
Half-duplex communication supports transmission in both directions, but only one direction can be active at a time.
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27A telephone connection allows both participants to speak and hear each other simultaneously. Which transmission mode does this illustrate?
Transmission modes
Medium
A.Full-duplex
B.Simplex
C.Half-duplex
D.Serial simplex
Correct Answer: Full-duplex
Explanation:
Full-duplex communication permits simultaneous data transmission in both directions.
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28A fully connected mesh network contains 6 devices. How many point-to-point links are required?
Network design
Medium
A.30
B.12
C.18
D.15
Correct Answer: 15
Explanation:
A full mesh with devices requires links. For 6 devices, the result is .
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29In a star topology, all workstation cables are functional, but the central switch suddenly fails. What is the most likely result?
Network design
Medium
A.Traffic automatically follows a ring
B.All workstation communication stops
C.Each workstation communicates directly
D.Only one workstation loses access
Correct Answer: All workstation communication stops
Explanation:
The central device is the communication point in a star topology. Its failure prevents connected workstations from exchanging data.
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30A municipal authority connects offices throughout the same city using a high-speed network. Which classification best describes this network?
Network classifications
Medium
A.MAN
B.PAN
C.WAN
D.LAN
Correct Answer: MAN
Explanation:
A metropolitan area network, or MAN, generally connects sites across a city or large urban area.
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31A company connects regional networks located in Asia, Europe, and North America through leased telecommunications links. Which network type is being formed?
Network classifications
Medium
A.LAN
B.WAN
C.PAN
D.MAN
Correct Answer: WAN
Explanation:
A WAN connects networks over large geographical areas, including different countries or continents.
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32A sender places the destination field before the source field, while the receiver expects the opposite order. Which protocol element is inconsistent?
Protocols
Medium
A.Timing
B.Synchronization
C.Semantics
D.Syntax
Correct Answer: Syntax
Explanation:
Syntax specifies the structure, format, and ordering of fields in a message.
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33As application data moves downward through a layered network architecture, each relevant layer adds control information. What is this process called?
Layered architecture
Medium
A.Encapsulation
B.Multiplexing
C.Fragmentation
D.Decapsulation
Correct Answer: Encapsulation
Explanation:
Encapsulation occurs when layers add headers, and sometimes trailers, to data before transmission.
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34A network replaces Ethernet with Wi-Fi, but its web applications continue operating without modification. Which benefit of layering does this demonstrate?
Layered architecture
Medium
A.Clock synchronization
B.Layer independence
C.Address compression
D.Path redundancy
Correct Answer: Layer independence
Explanation:
Layer independence allows one layer's implementation to change without requiring changes to unrelated higher layers.
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35A router examines a destination logical address and selects the next path toward a remote network. At which OSI layer does this operation primarily occur?
OSI model
Medium
A.Data link layer
B.Network layer
C.Transport layer
D.Physical layer
Correct Answer: Network layer
Explanation:
The network layer provides logical addressing and routing between different networks.
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36A large message is divided into smaller units, numbered, and reassembled reliably at the destination. Which OSI layer is primarily responsible?
OSI model
Medium
A.Presentation layer
B.Network layer
C.Transport layer
D.Session layer
Correct Answer: Transport layer
Explanation:
The transport layer performs end-to-end segmentation, sequencing, reliability, and reassembly.
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37In the TCP/IP model, protocols such as HTTP and DNS belong to a layer that combines the functions of which OSI layers?
TCP/IP protocol suite
Medium
A.Session, presentation, and application
B.Data link and network
C.Physical and data link
D.Network and transport
Correct Answer: Session, presentation, and application
Explanation:
The TCP/IP application layer incorporates the functions of the OSI session, presentation, and application layers.
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38Which statement correctly distinguishes the primary roles of IP and TCP?
Correct Answer: IP routes packets; TCP provides reliable delivery
Explanation:
IP provides logical addressing and best-effort routing, while TCP adds reliable, ordered, connection-oriented delivery.
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39A server runs both a web service and an email service using the same IP address. Which addressing mechanism allows incoming data to reach the correct service?
Addressing mechanisms in layers
Medium
A.Domain labels
B.Port numbers
C.Logical addresses
D.Physical addresses
Correct Answer: Port numbers
Explanation:
Transport-layer port numbers identify particular applications or services running on the same host.
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40When an IP packet passes through a router to the next network, which addressing change normally occurs?
Addressing mechanisms in layers
Medium
A.Both IP addresses are replaced
B.Domain names are replaced
C.Frame MAC addresses are replaced
D.Both port numbers are replaced
Correct Answer: Frame MAC addresses are replaced
Explanation:
A router creates a new frame for the next link, so link-layer MAC addresses change while end-to-end IP addresses normally remain unchanged.
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41A voice stream delivers every packet correctly, but variable network delays cause some packets to arrive too late for playback. Which data-communication characteristic is primarily violated?
Data communication characteristics
Hard
A.Accuracy, because delayed packets contain unusable data
B.Timeliness, because valid data arrives after its deadline
C.Jitter, because every packet experiences the same delay
D.Delivery, because packets miss the playback application
Correct Answer: Timeliness, because valid data arrives after its deadline
Explanation:
Timeliness requires data to arrive within its application deadline. Jitter describes delay variation, but the resulting failure to meet playback deadlines is a timeliness violation.
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42Host A and Host B use identical physical links but interpret the same received bit sequence as different frame types. Which communication component is most directly inconsistent?
Components
Hard
A.The protocol governing message interpretation
B.The receiver detecting the physical signal
C.The medium carrying the encoded signal
D.The sender generating the original message
Correct Answer: The protocol governing message interpretation
Explanation:
A protocol defines message format and interpretation. Correct signal delivery cannot ensure communication when the endpoints apply incompatible framing rules.
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43A UTF-8 string is transmitted as the byte sequence 41 C3 A9. A receiver reverses the bytes because its processor uses little-endian storage. What is the fundamental error?
Data representation
Hard
A.The sequence must include a byte-order mark before decoding
B.UTF-8 requires every character to occupy two bytes
D.Endianness applies to ordered protocol fields, not byte streams
Correct Answer: Endianness applies to ordered protocol fields, not byte streams
Explanation:
UTF-8 defines an ordered sequence of bytes. Processor endianness affects the in-memory representation of multibyte numeric values, not the order of bytes in a UTF-8 stream.
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44Two stations share one radio frequency. Either station may transmit, but simultaneous transmission is prohibited and control alternates the direction. Which mode is being used?
Transmission modes
Hard
A.Half-duplex with bidirectional turn-taking
B.Multiplexed simplex with symmetric traffic
C.Simplex with a return control channel
D.Full-duplex with time-separated encoding
Correct Answer: Half-duplex with bidirectional turn-taking
Explanation:
Half-duplex supports communication in both directions, but not at the same instant. Alternating access to one shared frequency matches this definition.
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45A network must remain connected after the failure of any single physical link. Which graph property is the minimum relevant design requirement?
Network design
Hard
A.The graph must have no bridge edges
B.Every node must have an even degree
C.Every pair must have one shortest path
D.The graph must contain one spanning tree
Correct Answer: The graph must have no bridge edges
Explanation:
A bridge is a link whose removal disconnects the graph. Therefore, tolerating any single-link failure requires a connected topology with no bridges.
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46A university owns fiber links connecting several buildings across one campus and operates the infrastructure itself. Which classification is most defensible?
Network classifications
Hard
A.A LAN, because ownership determines geographic scope
B.A campus network, composed of interconnected LANs
C.A WAN, because multiple buildings require carrier links
D.A PAN, because all users share one organization
Correct Answer: A campus network, composed of interconnected LANs
Explanation:
A campus area network interconnects LANs across a limited institutional site. Multiple buildings alone do not make the network a WAN.
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47A receiver understands every field in a request and receives it at the permitted time, but treats a field value as a sequence number while the sender intends it as a byte count. Which protocol element differs?
Protocols
Hard
A.Syntax, because the field position is disputed
B.Encoding, because the physical bits are disputed
C.Semantics, because the field meaning is disputed
D.Timing, because the field controls synchronization
Correct Answer: Semantics, because the field meaning is disputed
Explanation:
Syntax specifies structure, while semantics specifies the meaning of each field. Both endpoints recognize the field but assign it different meanings.
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48Layer receives data from layer , adds its own header, and passes the result downward. At the peer destination, which entity interprets that header?
Layered architecture
Hard
A.The next-hop entity at layer
B.The source entity at layer
C.The destination entity at layer
D.The destination entity at layer
Correct Answer: The destination entity at layer
Explanation:
Headers carry control information for peer entities at the same logical layer. Lower layers transport the header but do not generally interpret its layer-specific meaning.
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49A router receives an Ethernet frame carrying an IPv4 packet and forwards the packet onto a different Ethernet link. Which operation best describes the router's processing?
OSI model
Hard
A.It removes the IP header and forwards the transport segment directly
B.It preserves both headers and changes only the Ethernet checksum
C.It preserves the frame and replaces only the IP addresses
D.It removes the frame header and creates a new link-layer frame
Correct Answer: It removes the frame header and creates a new link-layer frame
Explanation:
A router decapsulates the incoming layer-2 frame, processes the layer-3 packet, and encapsulates that packet in a new frame suitable for the outgoing link.
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50A long application exchange uses synchronization checkpoints so that communication can resume from the latest checkpoint after interruption. Which OSI layer was explicitly designed for this function?
OSI model
Hard
A.Transport layer
B.Presentation layer
C.Session layer
D.Network layer
Correct Answer: Session layer
Explanation:
The OSI session layer manages dialogs and synchronization points. Transport provides end-to-end delivery but does not define application-session checkpoints as its primary role.
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51Which mapping most accurately represents the relationship between the five-layer Internet model and the seven-layer OSI model?
TCP/IP protocol suite
Hard
A.Internet combines OSI transport and network into one layer
B.Transport combines OSI session, transport, and network layers
C.Link combines OSI network, data-link, and physical layers
D.Application combines OSI application, presentation, and session
Correct Answer: Application combines OSI application, presentation, and session
Explanation:
The Internet application layer normally incorporates functions assigned to the OSI application, presentation, and session layers. Transport and network remain distinct.
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52Host A sends an IP packet to Host B on a remote network through router R. On the first Ethernet link, which destination addresses are normally used?
Addressing mechanisms in layers
Hard
A.R's MAC address and B's IP address
B.R's MAC address and R's IP address
C.B's MAC address and B's IP address
D.B's MAC address and R's IP address
Correct Answer: R's MAC address and B's IP address
Explanation:
The frame is addressed to the next hop, so its destination MAC address is R's interface address. The packet retains B's destination IP address for end-to-end routing.
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53A TCP server supports many simultaneous client connections on local port 443. Which information distinguishes one established connection from another?
Addressing mechanisms in layers
Hard
A.The source and destination IP-port pairs
B.The destination IP address and frame type only
C.The source and destination MAC addresses only
D.The server's port and protocol number only
Correct Answer: The source and destination IP-port pairs
Explanation:
A TCP connection is identified by the source IP, source port, destination IP, and destination port. Clients can therefore share the same server address and port.
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54An IPv4 NAT device changes a packet's source IP address but leaves the TCP segment otherwise unchanged. Which values generally require updating?
TCP/IP protocol suite
Hard
A.The IPv4 checksum and TCP checksum
B.Only the Ethernet frame-check sequence
C.Only the TCP sequence and acknowledgment numbers
D.The IPv4 identification and TCP window fields
Correct Answer: The IPv4 checksum and TCP checksum
Explanation:
The IPv4 header checksum covers the changed source address. The TCP checksum also covers IP addresses through its pseudo-header, so both checksums must be updated.
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55A physical link transmits at . Line coding carries data bits per transmitted bits, and framing consumes of the coded payload. What is the maximum application-data rate before higher-layer overhead?
Network design
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Coding yields . After framing overhead, the rate is .
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56A transport layer offers reliable byte-stream service even though the network layer may lose or reorder packets. Which layered-design principle does this illustrate?
Layered architecture
Hard
A.Each layer must expose every lower-layer limitation
B.A layer may enhance the service provided below it
C.Reliability must originate exclusively in the lowest layer
D.Peer layers communicate through direct physical links
Correct Answer: A layer may enhance the service provided below it
Explanation:
A higher layer can use sequencing, acknowledgments, retransmission, and buffering to provide stronger service than the lower layer directly offers.
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57Two implementations use identical packet formats and timers, but one sends data before completing the required handshake. Which protocol specification is being violated?
Protocols
Hard
A.The encoding of individual header fields
B.The ordering rules of the protocol state machine
C.The signal representation of the physical medium
D.The addressing scope of the lower-layer frame
Correct Answer: The ordering rules of the protocol state machine
Explanation:
Protocols define valid sequences of actions and state transitions, not merely message formats and timer values. Sending data in the wrong state violates those ordering rules.
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58Packets in a stream experience delays of , , , and ms, while no packet is corrupted or lost. Which mechanism most directly compensates for the observed impairment at the receiver?
Data communication characteristics
Hard
A.A de-jitter buffer that delays playback
B.A checksum that corrects late packets
C.A routing loop that equalizes path length
D.A larger address field that orders packets
Correct Answer: A de-jitter buffer that delays playback
Explanation:
The delay varies substantially between packets, indicating jitter. A de-jitter buffer temporarily stores packets and schedules smoother playback at the cost of additional latency.
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59A sensor produces analog temperature values, but the network interface accepts only digital bit streams. Which component function must occur before transmission over the digital interface?
Components
Hard
A.Quantization and encoding of the source data
B.Routing and forwarding of the analog waveform
C.Port addressing of each sampled amplitude
D.Session synchronization of the physical signal
Correct Answer: Quantization and encoding of the source data
Explanation:
The analog measurements must be sampled, quantized, and encoded into a digital representation before they can be carried as bits by the interface.
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60A newly booted IPv4 host has no configured address and broadcasts a DHCP discovery message. Which addressing combination is normally used before a DHCP server responds?
Addressing mechanisms in layers
Hard
A.Source IP 0.0.0.0, destination IP 255.255.255.255, broadcast destination MAC
B.Source IP 127.0.0.1, destination IP 255.255.255.255, unicast destination MAC
C.Source IP link-local, destination IP 0.0.0.0, unicast destination MAC
D.Source IP 0.0.0.0, destination IP of the DHCP server, broadcast destination MAC
Correct Answer: Source IP 0.0.0.0, destination IP 255.255.255.255, broadcast destination MAC
Explanation:
Before obtaining an address or learning a server's location, the client uses 0.0.0.0 as its source, the limited IPv4 broadcast as its destination, and a link-layer broadcast frame.
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