Impairment Injection

How to inject controlled network impairments to test system behavior.

Why Inject Impairments?

Real networks aren't perfect. Packets experience delay, jitter, and loss. By injecting controlled impairments, you can:

• Verify tolerance — Does your system handle network degradation gracefully?
• Find breaking points — At what delay/loss does the system fail?
• Test recovery — How quickly does the system recover when conditions improve?
• Reproduce issues — Recreate field conditions in the lab

Available Impairments

Impairment	Effect	Typical Use
Delay	Adds fixed latency	Simulate geographic distance
Jitter	Adds random delay variation	Simulate congested networks
Loss	Drops packets randomly	Simulate wireless/lossy links
Bandwidth	Limits throughput	Simulate constrained links

Configuring Impairments

Delay

Adds a constant delay to all packets passing through the bridge.

Parameter	Range	Description
Delay	0–10,000 ms	Fixed latency added to each packet

Example use cases:

• 50 ms: Simulate cross-continent link
• 150 ms: Simulate satellite link
• 300 ms: Simulate geostationary satellite

Jitter

Adds random delay variation on top of base delay.

Parameter	Range	Description
Jitter	0–1,000 ms	Random variation (uniform distribution)

The actual delay for each packet is: base_delay + random(0, jitter)

Example use cases:

• 5 ms jitter: Typical enterprise WAN
• 20 ms jitter: Congested network
• 50+ ms jitter: Severely degraded path

Packet Loss

Drops packets randomly at the specified rate.

Parameter	Range	Description
Loss	0–100%	Probability of dropping each packet

Example use cases:

• 0.1%: Typical internet background loss
• 1%: Noticeable degradation
• 5%: Significant degradation
• 10%+: Severe conditions

Bandwidth Limiting

Limits the throughput through the bridge.

Parameter	Range	Description
Bandwidth	0–10,000 Mbps	Maximum throughput

Excess packets are queued (up to a limit) then dropped.

Example use cases:

• 100 Mbps: Simulate Fast Ethernet constraint
• 10 Mbps: Simulate ADSL/VDSL
• 1 Mbps: Simulate constrained IoT link

Applying Impairments

1. Open the web interface
2. Navigate to the Impairments panel
3. Set desired values for each impairment type
4. Click Apply

Impairments take effect immediately and are applied bidirectionally.

Impairment Patterns

Constant Degradation

Apply fixed impairment values to test steady-state behavior:

Delay: 100 ms
Jitter: 10 ms
Loss: 0.5%

Run your application and verify it operates correctly under these conditions.

Stress Testing

Gradually increase impairments to find breaking points:

1. Start with normal operation (no impairments)
2. Increase delay in steps (0, 50, 100, 200, 500 ms)
3. Record behavior at each level
4. Identify the threshold where the system degrades

Burst Testing

Alternate between normal and impaired conditions:

1. Run normally for 60 seconds
2. Apply severe impairments for 10 seconds
3. Return to normal
4. Observe recovery behavior

Real-World Profiles

Simulate specific network conditions:

Profile	Delay	Jitter	Loss	Notes
LAN	0	0	0	Baseline
WAN (US)	50 ms	5 ms	0.1%	Cross-country
WAN (Global)	150 ms	10 ms	0.5%	Intercontinental
Satellite	300 ms	20 ms	1%	Geostationary
Mobile (good)	50 ms	20 ms	0.5%	4G/LTE
Mobile (poor)	200 ms	100 ms	5%	Cell edge
WiFi (congested)	10 ms	30 ms	2%	Busy environment

Verification

After applying impairments, verify they're taking effect:

1. Check the Impairments panel shows correct values
2. Monitor the timing measurement chart—you should see increased delay/jitter
3. Run a ping through the bridge to confirm delay
4. Check application behavior matches expectations

Best Practices

1. Start small — Begin with mild impairments and increase gradually

2. Test one variable — Change one impairment at a time to isolate effects

3. Document thresholds — Record the impairment levels where behavior changes

4. Test recovery — Verify systems recover when impairments are removed

5. Use realistic values — Base impairments on actual network measurements

6. Consider bidirectional effects — Impairments affect both directions

Limitations

• Impairments require inline deployment (not passive mode)
• Maximum delay is bounded by buffer size
• Very high loss rates may affect management traffic
• Bandwidth limiting adds latency at high utilization

Further Reading

For detailed information about impairment injection, see the JitterTrap documentation.