📝 Resource reservation in QoS (12 MCQs)

📖 From Data Communication and Networks • 30. Quality of Service • 12 questions available

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What is Resource reservation in QoS?

Resource reservation is the process of explicitly allocating network resources such as bandwidth and buffer space along a path before data transmission begins, ensuring that sufficient capacity exists to meet the quality of service requirements of a specific flow.

Easy

Medium

Hard

📝 All Resource reservation in QoS MCQs

Q1. What is the primary purpose of resource reservation in network communication?

A.To guarantee a predefined quality of service ✅

B.To minimize latency at all costs

C.To increase total bandwidth

D.To enhance security

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: Resource reservation is used to ensure that a flow receives the bandwidth, latency, and jitter characteristics required for its application, effectively providing a predefined quality of service. Without reservation, competing traffic could degrade performance, making QoS guarantees impossible.

Q2. A network node has a total reservation capacity of $255$ units. If a single flow requests $90$ units, can the request be granted without exceeding capacity?

A.No, because any reservation reduces capacity

B.Yes, because

90 < 255

✅

C.Only if other flows release resources

D.It depends on the flow’s priority

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Since the requested $90$ units are less than the available $255$ units, the node can allocate the resources while staying within its capacity limit. The decision does not require additional conditions, making the request acceptable under simple capacity checking.

Q3. After allocating a reservation of $185$ units from a pool of $255$ units, how many units remain unreserved?

A.60

B.80

C.70 ✅

D.90

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: Subtracting the allocated amount from the total pool gives the remaining capacity: $255 - 185 = 70$ units. This remainder represents the resources still available for other flows or future reservations, assuming no other allocations have been made.

Q4. Three concurrent flows request $45$ , $90$ , and $110$ units respectively. With a total capacity of $255$ units, is there enough leftover to accept an additional flow requiring $16$ units?

A.Yes, 10 units remain

B.No, capacity is exhausted ✅

C.Only if the new flow has higher priority

D.Insufficient information

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The three existing requests sum to $45 + 90 + 110 = 245$ units, leaving only $10$ units free. Because the new flow needs $16$ units, which exceeds the remaining capacity, the system cannot admit it, regardless of priority.

Q5. Which statement best distinguishes static reservation from dynamic reservation in the context of the given values?

A.Static reserves fixed amounts like the repeated

255

entries, while dynamic adjusts based on current demand

B.Dynamic always uses the maximum value

255

C.Static allows values such as

45

and

90

to change

D.Static reservations keep values constant, whereas dynamic reservations can vary with traffic ✅

💡 Difficulty: medium | ✅ Correct: D

📖 Explanation: Static reservation pre‑allocates a fixed amount of resources, often represented by constant values such as $255$ . In contrast, dynamic reservation monitors ongoing traffic and modifies allocations in real time, allowing the system to adapt to fluctuating demand patterns.

Q6. If many flows request the maximum value $255$ units, what is the most likely impact on system performance?

A.Severe resource exhaustion leading to admission denial

B.Improved throughput due to uniform allocation

C.Severe resource exhaustion leading to admission denial ✅

D.Enhanced fairness among flows

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: When numerous flows each demand the full $255$ units, the total requested bandwidth quickly exceeds the system’s capacity, causing severe resource exhaustion. Consequently, new requests will be rejected, and overall performance degrades because the system cannot satisfy all demands simultaneously.

Q7. Differentiating per‑flow from per‑class reservation, which scenario best matches the pattern 45, 90, 110 versus a single class reserving $255$ units?

A.Per‑flow uses varied smaller values, per‑class uses the uniform maximum

B.Per‑class uses a single large reservation (255) while per‑flow uses multiple smaller reservations such as 45, 90, 110 ✅

C.Both allocate

255

units to each entity

D.Neither approach applies to these numbers

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Per‑flow reservation assigns individual flows distinct resource amounts (e.g., 45, 90, 110), reflecting their specific needs. Per‑class reservation treats an entire class as a single entity, often allocating a uniform large block like $255$ units, which simplifies management but may waste resources.

Q8. To allocate resources proportionally to demand, the shares for requests $45$ , $90$ , and $110$ from a total of $255$ should be approximately what percentages?

A.20%, 30%, 50%

B.15%, 25%, 60%

C.10%, 40%, 50%

D.18%, 35%, 43% ✅

💡 Difficulty: medium | ✅ Correct: D

📖 Explanation: Compute each request’s share: $45/255≈0.176$ (≈18 %), $90/255≈0.353$ (≈35 %), and $110/255≈0.431$ (≈43 %). These percentages sum to 100 % and reflect a proportional distribution that honors each flow’s relative demand.

Q9. If the admission control threshold is set at $240$ units, which of the following reservation combinations would be rejected?

A.Requests of 120 and 110 (total 230)

B.Requests of 45, 90, and 110 (total 245) ✅

C.Requests of 16, 11, and 10 (total 37)

D.A single request of 185

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The combination of 45 + 90 + 110 equals 245 units, which exceeds the admission threshold of 240 units. Therefore, this set would be denied admission, whereas the other options stay below the threshold.

Q10. How does decreasing the reservation granularity from $24$ units to $10$ units affect overhead in a system that records the values 16, 11, 10?

A.Reduces overhead because smaller units allow finer packing ✅

B.Increases overhead due to more entries needed

C.Has no effect on overhead

D.Improves security

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: When the granularity is finer (e.g., 10‑unit steps), the system can represent resource usage more precisely, often requiring fewer large entries and allowing tighter packing of allocations. This reduces bookkeeping overhead compared with coarser granularity that may waste space.

Q11. Given existing reservations totaling $245$ units, will an additional reservation of $24$ units be accepted?

A.No, because total would exceed

255

B.Yes, because the system can exceed capacity temporarily

C.Only if lower‑priority flows are preempted ✅

D.Cannot determine without priority information

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: The current total of $245$ units leaves only $10$ units free. To admit a new $24$ -unit reservation, the system would need to preempt lower‑priority flows to free enough capacity. Without such preemption, the request cannot be satisfied.

Q12. Comparing two reservation tables, one with values [45, 90, 110] and another with [255, 255, 255], which table shows higher overall utilization of a $255$ -unit capacity?

A.The first table, because its sum is 245

B.The second table, because each entry equals the capacity ✅

C.Both have equal utilization

D.Utilization cannot be compared

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: If each entry corresponds to a separate resource pool of $255$ units, the second table fully utilizes every pool (100 % each). The first table, while summing to 245, leaves unused capacity in each pool, resulting in lower overall utilization.

🔗 Related Topics (MCQs)

📝 Data flow characteristics in QoS MCQs 📝 QoS definitions in computer networks MCQs 📝 Application sensitivity to QoS parameters MCQs 📝 Flow classes in quality of service MCQs 📝 Flow control techniques for QoS MCQs

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