Tools

Physical Clocks and Clock Synchronization

Procedure

This simulation demonstrates clock synchronization in distributed systems. Users can explore how various network conditions and parameters affect synchronization accuracy.

Note: Use landscape mode on mobile devices for optimal viewing.

Getting Started

  1. Load the Simulation: Open the Simulation tab in your browser

  2. Select a Scenario: Choose from predefined network configurations:

    • Local Area Network (LAN) - clean, noisy, or asymmetric
    • Metropolitan Area Network (MAN) - noisy or asymmetric
    • Wide Area Network (WAN) - noisy or asymmetric
    • Globally Distributed Network - noisy or asymmetric
    • Custom - configure your own parameters

  3. Run Basic Simulation:

    • Click Start Simulation to begin
    • Observe the client and server clocks
    • Introduce client clock skew and watch the divergence
    • Click Synchronize Now to trigger synchronization
    • Observe how Cristian's algorithm corrects the client's clock

Simulation Controls

Action Buttons

  • Start/Stop Simulation: Begin or halt the simulation
  • Synchronize Now: Force immediate synchronization (may send multiple packets)
  • Send Packet: Manually add a packet to improve synchronization accuracy
  • Clear Plot: Reset the round-trip time vs. synchronization error graph

Key Parameters

Network Configuration

  • Round trip time (ms): Total packet travel time between client and server
  • Round trip time variation (ms): Network jitter simulation
  • Round trip time asymmetry variation (ms): Difference between forward/return path delays
  • Simulation speed (ms/s): Rate at which simulation time progresses

Client Settings

  • Initial time offset (ms): Starting clock difference from server
  • Drift rate (ppm): Clock drift in parts per million
  • Synchronization interval (ms): Time between sync attempts
  • Synchronization period (ms): Duration of each sync session
  • Synchronization packet interval (ms): Time between packets during sync

Server Settings

  • Time error (ms): Server's clock error relative to actual time
  • Response delay (ms): Server processing delay before responding

Experimental Steps

Modify parameters individually and observe their effects on the synchronization graph:

1. Network Delay Effects

  • Adjust Round trip time: Observe how longer delays increase synchronization uncertainty
  • Modify Round trip time variation: See how jitter affects accuracy and predictability

2. Network Asymmetry Impact

  • Increase Round trip time asymmetry variation: Note greater offset calculation discrepancies
  • Compare symmetric vs. asymmetric scenarios

3. Client Clock Behavior

  • Set different Initial time offset values: Watch correction over multiple sync attempts
  • Increase Drift rate: Observe the need for more frequent synchronization

4. Synchronization Strategy

  • Adjust Synchronization interval and period: Balance accuracy vs. network load
  • Modify Synchronization packet interval: See how multiple measurements improve accuracy

5. Server Performance

  • Change Server response delay: Observe increased synchronization uncertainty
  • Combine with network delays to simulate real-world conditions

6. Combined Scenarios

  • Test multiple parameters simultaneously to understand complex interactions
  • Compare results across different predefined scenarios

Understanding the Results

The plot displays round-trip time versus synchronization error, helping visualize:

  • How network conditions affect accuracy
  • The effectiveness of multiple packet exchanges
  • Trade-offs between synchronization frequency and precision
  • Impact of asymmetric network paths on clock offset calculations