iperf3 Network Speed Test

Built-in iperf3 in Tempest — measure throughput, latency, and jitter to any server without installing iperf3 on either side.

Tempest ships an embedded iperf3 so you can measure server bandwidth, latency, and jitter without apt install iperf3 on either end. Open the iperf3 panel inside any tab, point it at the host, and Tempest runs the TCP / UDP test natively — no client to install, no server-side dependency, just a chart in your terminal.

This is the fastest way to answer "is this slow because of the network or the app?" when you're already SSH'd into a box.

Run a speed test

1. Open any SSH connection (or use Tempest's local shell).

2. Open the iperf3 panel from the tab toolbar.

3. Choose direction:

   • Download (server → client) — most common

   • Upload (client → server)

   • Bidirectional

4. Optional: choose TCP (default, throughput) or UDP (latency / jitter / packet loss).

5. Set duration (default 10 s) and parallel streams.

6. Click Run.

The chart updates per-second; results panel shows aggregate throughput, retransmits (TCP), or jitter / loss (UDP).

Native implementation

Tempest links iperf3 directly into the binary (Rust FFI to the upstream C library), so:

• No install on the remote — Tempest spins up an in-process iperf3 server when needed.

• No install on your machine — it's part of Tempest.

• Works on macOS, Windows, and Linux with identical behavior.

When you'd use this

• Diagnosing slow git clone / apt update — is it the network or the registry?

• Validating a new VPS provider's advertised bandwidth before committing

• Comparing two cloud regions before deciding where to deploy

• Verifying a VPN / Tailscale / WireGuard tunnel is operating at line speed

• Pre-flight check before a large rsync job

Limitations

• iperf3 measures end-to-end network throughput, not application performance. A curl against an HTTP API still depends on the server's ability to respond fast.

• UDP tests can be rate-limited by intermediate routers; treat results as a lower bound.

See also

• Tempest Monitoring — live network I/O gauge for the same SSH session

• SSH Port Forwarding — tunnel iperf3 over an SSH connection if direct UDP is blocked