Learn
Five tracks, 9 lessons.
Every claim in every lesson comes with the capture that shows it. Take them in any order — the tracks do not depend on each other, only the lessons inside one do.
Why is the network slow?
Packets and links
Latency, bandwidth and queueing are three different problems with three different fixes, and every one of them is called the same thing by whoever reports it.
What does a connection cost?
TCP: connections
The handshake, the teardown, and the sixty seconds one side spends in TIME_WAIT afterwards. Everything a request pays before it has sent a byte.
What happens when a packet does not arrive?
TCP: reliability
Retransmission timers, exponential backoff, fast retransmit, and the congestion window that decides how much may be in flight at once.
How does a client make an outage worse?
Timeouts, retries and pools
Connect against read against total, backoff without jitter, a pool that cannot reuse, and the retry of a POST that charges the customer twice.
What did this client actually do?
Reading a capture
The thesis track. A client somebody generated, a capture of what it did, and the defect that is invisible in the code and obvious on the wire.