Slow start

How it works

A 50 KB file may finish during slow start and never see the path's capacity. A 5 GB file pays the ramp once and then runs at rate. People benchmark with a small file and understate the path.

A 100 KB health check copies at an effective 2 Mbps. A 2 GB file on the same path averages 80 Mbps. The path did not change. The first transfer never left slow start.

How it differs

Slow start is not a throttle you configured. It is TCP. QUIC has its own startup.

Disabling slow start is not a normal file-tool switch.

Benchmark with a file the size you actually send.

On the ticket

• The practical close is a log line: time, actor, byte count, result.
• Without that line the transfer is a story.
• With it, the next person can see whether this door did what the ticket claimed.
• If the path is shared, say so in the partner profile so a later change does not silently pick a different limit, key, or region.
• On a real ticket, write down the door, the byte count, and the clock.
• For slow start, that means naming the host or bucket, the expected size, and the time the other side must have a complete file.
• A progress bar is not that record.
• A 200 response that arrives before the complete call is not that record.
• If a retry is allowed, say how many and whether it resumes.
• If a person must approve the send, name the person.
• Partners who receive slow start files should match on hash or size before they import.
• A same-length corrupt file passes a size check and fails a hash.
• Keep the published hash off the only channel an attacker can edit, or treat it as a corruption check rather than a substitution check.
• When the path changes, new key, new region, new cap, update the profile the same day so the next run does not use a stale limit.