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MCQ

Chapter 1: Basics & Fundamentals of QoS (10 MCQs)

Q1. Quality of Service (QoS) in computer networks mainly refers to which of the following?
a) Providing maximum possible speed to all users equally
b) Providing predictable and reliable network performance to selected traffic
c) Encrypting all data sent over the network
d) Increasing the number of network users
Answer: b) Providing predictable and reliable network performance to selected traffic
Explanation: QoS controls delay, jitter, loss, and bandwidth for important traffic. 👉 (HIGHLY IMPORTANT)

Q2. Which of the following is NOT a typical QoS parameter?
a) Bandwidth
b) Delay (latency)
c) Jitter
d) Screen resolution
Answer: d) Screen resolution
Explanation: QoS deals with network performance parameters, not display quality.

Q3. In QoS, “latency” means:
a) Number of users on the network
b) Time taken for a packet to travel from source to destination
c) Amount of data lost during transmission
d) Variation in packet size
Answer: b) Time taken for a packet to travel from source to destination
Explanation: Latency is the one-way delay experienced by data. 👉 (HIGHLY IMPORTANT)

Q4. “Jitter” in QoS is best defined as:
a) Total number of packets lost in a day
b) Variation in packet arrival time at destination
c) Number of routers in a path
d) Speed of the processor
Answer: b) Variation in packet arrival time at destination
Explanation: Jitter is change in delay between packets, critical for voice/video.

Q5. Best-effort service in IP networks means:
a) Traffic is guaranteed bandwidth
b) Traffic is given highest priority
c) No guarantee of delivery or performance
d) Traffic is always encrypted
Answer: c) No guarantee of delivery or performance
Explanation: Best-effort gives no QoS assurance, packets are forwarded as possible.

Q6. Which type of applications are MOST sensitive to delay and jitter, and hence need strict QoS?
a) Email and SMS
b) File downloads
c) Voice over IP (VoIP) and video conferencing
d) Software updates
Answer: c) Voice over IP (VoIP) and video conferencing
Explanation: Real-time streams need low delay, low jitter, and low loss. 👉 (HIGHLY IMPORTANT)

Q7. Packet loss in QoS refers to:
a) Packets stored in cache
b) Packets dropped and not reaching the destination
c) Packets compressed to smaller size
d) Packets delayed but always delivered
Answer: b) Packets dropped and not reaching the destination
Explanation: Packet loss directly degrades quality of voice, video, and transactions.

Q8. Which of the following is the PRIMARY purpose of QoS in an enterprise network?
a) To increase advertising traffic
b) To ensure critical applications get required network resources
c) To disconnect non-paying users
d) To improve hardware life
Answer: b) To ensure critical applications get required network resources
Explanation: QoS prioritizes important business traffic over less important traffic.

Q9. In which OSI layer are QoS concepts MOST commonly associated?
a) Physical layer only
b) Network and Transport layers
c) Presentation layer
d) Session layer only
Answer: b) Network and Transport layers
Explanation: IP (Layer 3) and TCP/UDP (Layer 4) are primary for QoS handling.

Q10. In IP networking, QoS mainly helps to handle which common problem?
a) Shortage of IP addresses
b) Network congestion and performance degradation
c) DNS resolution errors
d) Virus and malware attacks
Answer: b) Network congestion and performance degradation
Explanation: QoS manages congestion by prioritizing and controlling traffic. 👉 (HIGHLY IMPORTANT)

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Chapter 2: QoS Models, Techniques & Mechanisms (15 MCQs)

Q11. Which QoS model is based on resource reservation using RSVP?
a) Best-effort model
b) Integrated Services (IntServ) model
c) DiffServ model
d) MPLS model
Answer: b) Integrated Services (IntServ) model
Explanation: IntServ uses RSVP to reserve bandwidth for specific flows.

Q12. Which QoS model uses DSCP values in the IP header to classify and treat traffic?
a) IntServ
b) DiffServ
c) Circuit switching
d) FDM
Answer: b) DiffServ
Explanation: DiffServ uses the Differentiated Services Code Point field for per-hop behavior. 👉 (HIGHLY IMPORTANT)

Q13. In DiffServ, DSCP values are stored in which part of the IPv4 header?
a) Source IP address field
b) Destination IP address field
c) Type of Service / DS field
d) Header checksum field
Answer: c) Type of Service / DS field
Explanation: The DS field (replacing old TOS) carries DSCP bits for QoS.

Q14. “Classification” in QoS refers to:
a) Splitting cables
b) Identifying and grouping packets into different traffic classes
c) Compressing packets for storage
d) Encrypting packets before sending
Answer: b) Identifying and grouping packets into different traffic classes
Explanation: Classification is the first step to apply different QoS policies.

Q15. “Marking” in QoS typically involves:
a) Modifying DSCP or priority bits in packet headers
b) Changing MAC addresses
c) Encrypting packet payload
d) Deleting headers
Answer: a) Modifying DSCP or priority bits in packet headers
Explanation: Marking labels packets by priority for downstream devices.

Q16. Traffic shaping in QoS is used to:
a) Increase packet size
b) Smooth outgoing traffic by buffering and sending at a controlled rate
c) Drop all excess traffic immediately
d) Change protocols
Answer: b) Smooth outgoing traffic by buffering and sending at a controlled rate
Explanation: Shaping delays packets to conform to a desired rate. 👉 (HIGHLY IMPORTANT)

Q17. Traffic policing in QoS is used to:
a) Always allow traffic bursts
b) Enforce traffic rate by dropping or remarking packets exceeding a limit
c) Encrypt traffic
d) Compress all traffic
Answer: b) Enforce traffic rate by dropping or remarking packets exceeding a limit
Explanation: Policing does not buffer; it penalizes traffic beyond the configured rate.

Q18. Which of the following is a common traffic shaping algorithm?
a) Leaky bucket
b) RSA
c) SHA-256
d) DHCP
Answer: a) Leaky bucket
Explanation: Leaky bucket and token bucket are classic shaping algorithms.

Q19. FIFO queueing stands for:
a) First In First Out
b) Fast Internet, Fast Output
c) Fixed Input, Fixed Output
d) Frame In Frame Out
Answer: a) First In First Out
Explanation: Packets are served strictly in the order they arrive.

Q20. Which queueing mechanism gives strict preference to certain high-priority queues?
a) FIFO
b) Priority Queueing (PQ)
c) Random Early Detection
d) Round Robin
Answer: b) Priority Queueing (PQ)
Explanation: PQ serves high-priority queue completely before lower queues.

Q21. Weighted Fair Queueing (WFQ) is designed to:
a) Ignore low-priority traffic
b) Share bandwidth fairly among flows, based on assigned weights
c) Only serve voice traffic
d) Work only at the application layer
Answer: b) Share bandwidth fairly among flows, based on assigned weights
Explanation: WFQ gives different bandwidth shares to classes according to weight.

Q22. Congestion-avoidance technique like RED (Random Early Detection) works by:
a) Dropping packets randomly before queues are full
b) Always dropping only largest packets
c) Encrypting packets during congestion
d) Disabling routing
Answer: a) Dropping packets randomly before queues are full
Explanation: RED prevents global synchronization and severe congestion.

Q23. Admission control in QoS is used to:
a) Allow all new flows without checking
b) Decide whether a new flow can be accepted based on available resources
c) Change IP addressing
d) Provide encryption keys
Answer: b) Decide whether a new flow can be accepted based on available resources
Explanation: It prevents over-commitment and protects existing QoS guarantees.

Q24. Which statement about IntServ vs DiffServ is TRUE?
a) IntServ scales better than DiffServ
b) DiffServ is more scalable and widely deployed than IntServ
c) Both are equally scalable
d) Both are obsolete and unused
Answer: b) DiffServ is more scalable and widely deployed than IntServ
Explanation: DiffServ is preferred in large networks due to lower state maintenance. 👉 (HIGHLY IMPORTANT)

Q25. Which layer-2 technology commonly uses 802.1p bits for QoS?
a) Wi-Fi Direct printing
b) Ethernet VLAN tagging (IEEE 802.1Q)
c) Bluetooth file transfer
d) USB communication
Answer: b) Ethernet VLAN tagging (IEEE 802.1Q)
Explanation: 802.1p priority bits within VLAN tags carry CoS information.

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Chapter 3: QoS with IP, MPLS, VoIP & Real-Time Traffic (15 MCQs)

Q26. In MPLS networks, QoS information is usually carried in which field?
a) MAC address
b) Time-to-Live (TTL)
c) EXP / Traffic Class bits in MPLS header
d) Frame Check Sequence
Answer: c) EXP / Traffic Class bits in MPLS header
Explanation: These bits are used for QoS marking and per-hop behavior in MPLS.

Q27. QoS is especially important for VoIP because:
a) VoIP can tolerate very high delay and loss
b) VoIP packets are very large
c) Humans are sensitive to delay, jitter, and loss in voice
d) VoIP does not use IP protocol
Answer: c) Humans are sensitive to delay, jitter, and loss in voice
Explanation: Voice quality quickly degrades with poor network conditions. 👉 (HIGHLY IMPORTANT)

Q28. Which of the following is TRUE about UDP in QoS for real-time applications?
a) It provides built-in retransmissions and ordering
b) It has lower overhead and is preferred for real-time traffic
c) It cannot be used with IP
d) It always encrypts data
Answer: b) It has lower overhead and is preferred for real-time traffic
Explanation: UDP is lightweight; delay is lower as it does not wait for ACKs.

Q29. A typical design goal in QoS for good VoIP quality is to keep one-way network delay:
a) Below a few seconds
b) Below approximately 150 ms
c) Above 500 ms
d) Exactly 1 second
Answer: b) Below approximately 150 ms
Explanation: ITU recommendations suggest about 150 ms one-way for good voice quality.

Q30. Which traffic type generally gets the LOWEST priority in a QoS policy?
a) Voice calls
b) Transaction messages
c) Real-time video
d) Bulk file download / software update
Answer: d) Bulk file download / software update
Explanation: Non-real-time, bandwidth-hungry traffic is often given lowest priority.

Q31. For video conferencing, which combination is MOST desirable?
a) Low bandwidth, high jitter, high loss
b) High bandwidth, low jitter, low loss
c) Low bandwidth, low jitter, high loss
d) High bandwidth, high jitter, high loss
Answer: b) High bandwidth, low jitter, low loss
Explanation: Continuous video stream needs stable bandwidth with minimal disturbances.

Q32. RSVP used with QoS stands for:
a) Resource Reservation Protocol
b) Router Speed Verification Protocol
c) Remote Service Validation Process
d) Realtime Service Vision Protocol
Answer: a) Resource Reservation Protocol
Explanation: RSVP reserves resources along the path for certain flows.

Q33. Which parameter is MOST critical for interactive stock trading applications?
a) Jitter only
b) Very low delay and packet loss
c) High compression ratio
d) Only high throughput
Answer: b) Very low delay and packet loss
Explanation: Even small delay can impact trade execution and financial outcome. 👉 (HIGHLY IMPORTANT)

Q34. Which of the following BEST describes “per-hop behavior” in DiffServ?
a) Behavior of end-user devices only
b) QoS treatment given by each router/switch to packets based on DSCP
c) Only encryption of data at each hop
d) Only error detection at each hop
Answer: b) QoS treatment given by each router/switch to packets based on DSCP
Explanation: Each hop uses DSCP to determine how to queue and forward traffic.

Q35. For interactive remote banking applications over WAN, QoS should:
a) Prioritize streaming media over transactions
b) Give higher priority to transactional and session traffic
c) Block all voice traffic
d) Give equal priority to all traffic
Answer: b) Give higher priority to transactional and session traffic
Explanation: Banking transactions and interactive sessions are business-critical.

Q36. Which of the following is a common symptom of inadequate QoS for VoIP?
a) High-resolution screens
b) Echo, choppy audio, and one-way speech
c) Faster downloads
d) Extra storage on the server
Answer: b) Echo, choppy audio, and one-way speech
Explanation: Voice call quality problems often indicate delay, jitter, or loss.

Q37. For video streaming QoS, buffering at the client side helps mainly to:
a) Encrypt data
b) Hide short variations in delay and jitter
c) Increase bandwidth
d) Reduce CPU speed
Answer: b) Hide short variations in delay and jitter
Explanation: Buffering smooths playback despite small network variations.

Q38. In IP networks, which header fields are MOST commonly used for traffic classification?
a) MAC address only
b) Source/destination IP, protocol type, source/destination port
c) Screen resolution and OS type
d) Printer configuration
Answer: b) Source/destination IP, protocol type, source/destination port
Explanation: These are commonly used to define traffic classes and policies.

Q39. Which statement about QoS and encryption (like IPSec) is MOST appropriate?
a) QoS cannot work at all with encryption
b) QoS must classify and mark traffic before encryption
c) QoS works only after encryption is done
d) Encryption automatically sets QoS priority
Answer: b) QoS must classify and mark traffic before encryption
Explanation: After encryption, header information may be hidden, so marking must be done earlier.

Q40. Which of the following is a TRUE statement regarding QoS queues?
a) Only one queue can exist on an interface
b) Multiple queues can be configured to handle different traffic classes
c) Queues are never used in QoS
d) Queues are used only for multicast traffic
Answer: b) Multiple queues can be configured to handle different traffic classes
Explanation: Separate queues allow different scheduling and priority treatment.

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Chapter 4: QoS in Banking, Payments & Latest Trends (10 MCQs)

Q41. In banking networks, QoS is MOST critical for which of the following?
a) Staff recreational browsing
b) Core Banking System (CBS) transaction traffic
c) Internal email circulation
d) HR policy downloads
Answer: b) Core Banking System (CBS) transaction traffic
Explanation: CBS transactions directly affect customers and financial records. 👉 (HIGHLY IMPORTANT)

Q42. Which banking service is MOST sensitive to network latency and uptime?
a) Library services
b) RTGS/NEFT settlement and UPI payments
c) Internal circular distribution
d) Static intranet pages
Answer: b) RTGS/NEFT settlement and UPI payments
Explanation: Payment systems require near real-time, reliable communication.

Q43. QoS for ATM networks is important because:
a) ATMs use only offline data
b) ATMs need reliable, timely connectivity with host/CBS servers
c) ATMs do not send any transaction data
d) ATMs only display ads
Answer: b) ATMs need reliable, timely connectivity with host/CBS servers
Explanation: Any failure or delay may cause transaction failure or cash not dispensed.

Q44. In bank call centres using IP-based telephony, QoS ensures:
a) Customers always get busy tone
b) Clear voice, minimum delay, and fewer call drops
c) Only video quality is improved
d) Only text chat is enhanced
Answer: b) Clear voice, minimum delay, and fewer call drops
Explanation: Contact centres depend on VoIP voice clarity for customer service.

Q45. POS (Point of Sale) terminals in shops and merchant locations require QoS because:
a) They store movies
b) Card authorisation must be quick and reliable
c) They work completely offline
d) QoS only affects printers
Answer: b) Card authorisation must be quick and reliable
Explanation: Delays at POS directly affect customer experience and business.

Q46. Which of the following traffic should generally be placed in the HIGHEST QoS class in a bank’s WAN?
a) Software updates and backups
b) Video streaming for training
c) Real-time payment transactions and authentication traffic
d) Social media browsing
Answer: c) Real-time payment transactions and authentication traffic
Explanation: These are mission-critical and must be sent with top priority. 👉 (HIGHLY IMPORTANT)

Q47. Software distribution and backup traffic in a bank should be configured as:
a) Highest-priority traffic
b) Low-priority, scheduled during off-peak hours
c) Always blocked
d) Equal priority with VoIP
Answer: b) Low-priority, scheduled during off-peak hours
Explanation: Such bulk traffic should not disturb real-time/banking transactions.

Q48. In modern bank WANs, SD-WAN with QoS is preferred over traditional MPLS only because:
a) It removes the need for any QoS
b) It can use multiple cheaper internet links with application-aware QoS
c) It works only on dial-up modems
d) It reduces encryption needs
Answer: b) It can use multiple cheaper internet links with application-aware QoS
Explanation: SD-WAN intelligently routes traffic over multiple paths based on QoS needs.

Q49. For mobile banking applications, QoS between the bank’s data centre and external networks helps to:
a) Improve user response time and reliability for login and transactions
b) Reduce application security
c) Disable notifications
d) Only increase app size
Answer: a) Improve user response time and reliability for login and transactions
Explanation: Better QoS means smoother mobile banking experience.

Q50. Service Level Agreements (SLAs) related to bank networks typically specify QoS targets like:
a) Number of employees in IT department
b) Maximum latency, packet loss, uptime percentage, and throughput
c) Number of branches in the bank
d) Colour of data centre racks
Answer: b) Maximum latency, packet loss, uptime percentage, and throughput
Explanation: SLAs define measurable QoS metrics that service providers must maintain. 👉 (HIGHLY IMPORTANT)