Tools

Chord System

1. Setup and Familiarization

Objective: Understand the lab interface and basic Chord ring structure.

  1. Open the virtual lab in a web browser.
  2. Observe the circular Chord ring (mod 64 identifier space) and control panel.
  3. Review the input fields and buttons:
    • Node ID (0-63): For adding/removing nodes.
    • Key (0-63): For inserting, looking up, or removing keys.
    • Node Details Panel: Displays finger tables, keys, and neighbors when a node is clicked.

2. Basic Node Operations

Objective: Learn how nodes join/leave the ring and how the topology updates.

  1. Add Nodes:
    • Click Add Node to place nodes (e.g., IDs 8, 20, 35, 50).
    • Observe their positions on the ring.
    • Question: Why do nodes occupy specific positions?
  2. Remove Nodes:
    • Remove a node (e.g., 20) and watch its keys transfer to its successor.
    • Question: How does the ring handle node departures?

3. Key Management

Objective: Explore how keys are stored using consistent hashing.

  1. Insert Keys:
    • Insert keys (e.g., 15, 25, 40) and note which nodes store them.
    • Question: Which node becomes responsible for key 25? Why?
  2. Remove Keys:
    • Remove a key and verify its deletion from the successor node.

4. Finger Table Analysis

Objective: Understand how finger tables enable efficient lookups.

  1. Click a node to view its finger table, successor, and predecessor.
  2. Observe Finger Entries:
    • Entries are successors of node.id+2k−1mod  64\text{node.id} + 2^{k-1} \mod 64.
    • Question: How do finger entries reduce lookup hops?

5. Key Lookup Simulation

Objective: Trace the path of a key lookup using finger tables.

  1. Perform a Lookup:
    • Enter a key (e.g., 45) and click Lookup Key.
    • Study the feedback showing the path (e.g., Node 8 → Node 35 → Node 50).
  2. Analyze Hops:
    • Compare the number of hops to O(log⁡N)O(\log N) efficiency.

6. Dynamic Ring Changes

Objective: Observe how the ring adapts to node joins/leaves.

  1. Add a New Node:
    • Insert a node (e.g., 30) and watch keys transfer from its successor.
    • Verify its finger table updates.
  2. Remove a Critical Node:
    • Delete a heavily loaded node and observe key redistribution.

7. Interactive Challenges

Objective: Test understanding of Chord mechanics.

  1. Click Start Challenge to answer auto-generated questions:
    • Example 1: "Which node stores key 18?"
    • Example 2: "What is finger[3] for node 20?"
  2. Use feedback to correct mistakes and refine understanding.

8. Advanced Exploration

Objective: Investigate fault tolerance and load balancing.

  1. Simulate Node Failures:
    • Remove multiple nodes and check if lookups still succeed.
  2. Analyze Load Distribution:
    • Insert 20 keys and observe distribution across nodes.
    • Question: How can you balance the load?