📝 Chord protocol in peer to peer networks (9 MCQs)

📖 From Data Communication and Networks • 29. Peer to Peer Paradigm • 9 questions available

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What is Chord protocol in peer to peer networks?

The Chord protocol is a structured P2P system that organizes nodes into a logical ring to efficiently locate data by using consistent hashing, ensuring that any node can find any piece of information in logarithmic time relative to network size.

Easy

Medium

Hard

📝 All Chord protocol in peer to peer networks MCQs

Q1. A new node with identifier 18 joins a Chord ring where node 14’s successor is node 20. Which statement correctly describes the immediate effect on node 14’s routing information?

A.Node 14’s successor changes to node 18 ✅

B.Node 14’s predecessor changes to node 18

C.Node 14’s finger table entry for start 16 now points to node 18

D.No change occurs until stabilization

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: When node 18 inserts itself between 14 and 20, the ring ordering forces node 14 to update its successor pointer to the newly adjacent node 18. The predecessor of 14 remains unchanged, and finger table entries are only adjusted during the stabilization phase, not instantly.

Q2. In a Chord network with identifier space modulo $2^{5}$ , a lookup for key 27 starts at node 5. Which sequence of nodes is most likely visited before reaching the key’s successor?

A.5 → 9 → 17 → 27

B.5 → 6 → 12 → 24 → 27

C.5 → 10 → 20 → 26 → 27

D.5 → 8 → 16 → 24 → 27 ✅

💡 Difficulty: medium | ✅ Correct: D

📖 Explanation: The identifier space is $0$ – $31$ . Node 5’s finger table contains entries that jump to the closest preceding nodes. The most efficient path follows the power‑of‑two steps: from 5 to 8, then 16, then 24, and finally reaches the node responsible for key 27. This matches option D.

Q3. If nodes 2, 7, and 15 are present in a Chord ring of size $2^{4}=16$ , and node 7 fails unexpectedly, what is the most immediate inconsistency that can arise in node 2’s finger table?

A.Entry for start 4 points to node 7 (failed) ✅

B.Entry for start 8 points to node 15 (still correct)

C.Successor pointer becomes null

D.Predecessor pointer incorrectly set to node 7

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: Node 2’s finger table entry for start 4 should point to the first node that succeeds identifier 4, which was node 7. After node 7 crashes, that entry still contains the stale identifier of the failed node, causing an immediate inconsistency until stabilization repairs it.

Q4. Which of the following best contrasts the finger table with the successor list in Chord?

A.Finger table provides logarithmic routing shortcuts; successor list provides redundancy for immediate next nodes ✅

B.Finger table stores all nodes in the ring; successor list stores only power-of-two entries

C.Finger table is used only during node join; successor list is used only during lookup

D.Both structures serve identical purposes but differ in storage format

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: The finger table contains $m$ entries that give logarithmic‑size shortcuts, enabling fast lookups, while the successor list holds a small set of immediate successors to tolerate failures. This distinction directly matches option A.

Q5. In a Chord system with identifier length $m$ bits, how does increasing $m$ from 8 to 12 affect the average lookup path length, assuming the number of nodes remains constant?

A.Average hops increase proportionally to

m

B.Average hops remain unchanged because they depend on node count, not identifier space ✅

C.Average hops decrease because larger

m

yields more granular finger entries

D.Average hops increase slightly due to larger finger table maintenance overhead

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Lookup cost in Chord depends primarily on the number of active nodes $N$ , not on the size of the identifier space. Expanding $m$ merely enlarges the potential key space, leaving the average number of hops—approximately $\log_2 N$ —unchanged, which is captured by option B.

Q6. Consider two maintenance strategies: (1) Chord’s periodic stabilization where each node contacts its successor; (2) a naive approach where nodes broadcast their full finger tables after every join. Which statement correctly captures a key difference?

A.Strategy 1 scales with

O(\log N)

messages per node, while Strategy 2 incurs

O(N)

messages per join ✅

B.Strategy 1 requires global knowledge, Strategy 2 requires only local knowledge

C.Strategy 1 updates only predecessor pointers, Strategy 2 updates only successor pointers

D.Both strategies have identical message complexity but differ in latency

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: Chord’s stabilization is designed to be lightweight: each node periodically sends a small number of messages (constant‑time) to its successor, leading to overall $O(\log N)$ traffic. Broadcasting full finger tables after every join would generate a message count that grows linearly with the number of nodes, i.e., $O(N)$ , making option A the accurate comparison.

Q7. Given a Chord ring with 1024 nodes ( $N = 2^{10}$ ), what is the expected number of hops for a lookup if finger tables are perfectly populated?

A.Approximately 5 hops

B.Exactly 10 hops

C.Approximately

\log_2 N = 10

hops

D.Approximately

\log_2 N / 2 = 5

hops ✅

💡 Difficulty: medium | ✅ Correct: D

📖 Explanation: When finger tables are complete, the expected lookup length is about $\frac{\log_2 N}{2}$ . For $N = 1024$ , $\log_2 N = 10$ , so the average number of hops is roughly 5, matching option D.

Q8. If three consecutive nodes in a Chord ring fail simultaneously, how does the network ensure continued correct routing for lookups?

A.Successor lists allow each remaining node to bypass the failed segment by using the next alive successor ✅

B.Finger tables automatically rewire to skip the failed nodes without any protocol

C.The ring collapses and must be rebuilt from scratch

D.Lookups fail until a manual rejoin operation is performed

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: Chord nodes maintain a successor list of several immediate successors. When a block of consecutive nodes disappears, each surviving node can still reach a live node via its successor list, effectively bypassing the gap and preserving routing correctness, which is described in option A.

Q9. In Chord, what is the primary purpose of a finger table?

A.To store the identifiers of all nodes in the network

B.To provide a logarithmic shortcut routing mechanism ✅

C.To maintain a list of immediate predecessor nodes

D.To record the physical IP addresses of neighboring nodes

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: A finger table contains $m$ entries that point to nodes at exponentially increasing distances around the identifier circle. This structure gives each node a logarithmic‑size set of shortcuts, enabling lookups to be performed in $O(\log N)$ hops, which is the purpose stated in option B.

🔗 Related Topics (MCQs)

📝 Peer to peer architecture introduction MCQs 📝 P2P networks in computer networks MCQs 📝 Distributed Hash Table DHT in P2P MCQs 📝 Chord identifier space and hashing MCQs 📝 Chord finger table explained MCQs

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