Advanced
Load Test: Simulate Sustained Heavy Traffic
Real homes and offices generate concurrent load: someone is streaming 4K, another is on a video call, a backup is uploading, and IoT devices are chattering. The Load Test simulates this realistic mix to verify your connection holds up under multi user, multi app conditions instead of just a single download stream.
What It Measures
This tool measures connection load capacity by running multiple concurrent download and upload streams while sampling latency, jitter, and per-stream throughput. It reveals how your connection allocates bandwidth under contention and whether quality of service holds up.
How It Works
- Starts multiple concurrent TCP streams (default 4 download, 4 upload)
- Samples per stream throughput and overall latency continuously
- Detects fairness, bufferbloat, and stream collapse
- Reports total throughput, fairness index, and latency under load
Why It Matters
A 1 Gbps connection that crumbles when 3 streams compete is not actually a 1 Gbps connection in practice. Realistic load testing reveals whether your hardware, ISP, and configuration deliver the bandwidth you paid for under the conditions your household actually creates.
Understanding Your Results
Total throughput under load should reach close to your plan speed. Per stream throughput should be roughly equal (good fairness). Latency under load should stay within 30ms of idle latency (no significant bufferbloat). Stream collapse, where one stream takes everything and others get nothing, indicates poor congestion control and is a problem.
Frequently Asked Questions
How is this different from a regular speed test?
A regular speed test measures peak throughput with one or two streams. The load test runs many concurrent streams to simulate realistic household traffic. It exposes problems with router CPU, ISP shaping, and queue management that single stream tests miss because they never push the connection into contention.
What is fairness in network load testing?
Fairness measures how evenly bandwidth is divided among concurrent streams. Good fairness means each stream gets a roughly equal share. Poor fairness means some streams take most of the bandwidth and others starve. TCP congestion control normally produces good fairness, but problems in queueing or shaping can break it.
Why does latency matter under load?
Latency under load determines how your network feels when other people in your household are using it. A connection where one person can stream 4K without affecting another's video call has well managed latency under load. A connection where streaming makes calls choppy has bufferbloat or poor queueing.
What if my connection collapses under load?
If total throughput under load is much less than your plan speed, the bottleneck is likely your router CPU, an ISP rate cap, or NAT table exhaustion. The Router Performance and Bandwidth Saturation tests can isolate which. Stream collapse where one stream wins everything points to broken queue management on your router or ISP side.
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