Module 12 · Transport layer · Drill

Transport layer drill

Scenario prompts that check whether transport layer is usable under pressure. Answer out loud, then compare.

4 prompts25 minNew

0 of 4 graded

Prompt 1
A mobile app in Sydney calls an API hosted only in us-east-1 (about 200 ms round trip). Each screen makes a fresh HTTPS request returning about 80 KB of JSON, and users report screens take nearly a second to load even on fast connections. Account for the time with TCP, TLS and congestion control, then propose changes that cut it by more than half.
Say your answer out loud first. Thirty seconds is enough.
Prompt 2
A service's metrics show tens of thousands of sockets in CLOSE_WAIT on its hosts, and separately its outbound calls to an internal API intermittently fail with 'cannot assign requested address'. Explain both states, what causes each here, and the fixes.
Say your answer out loud first. Thirty seconds is enough.
Prompt 3
Nightly replication between two regions 120 ms apart moves 2 TB over a dedicated 10 Gbit/s link but achieves only about 400 Mbit/s with no packet loss. Find the bottleneck from first principles and say what to change; then explain what would happen if the link also had 0.1 percent random loss.
Say your answer out loud first. Thirty seconds is enough.
Prompt 4
Design the transport for three features of one product: a real-time collaborative cursor and voice channel, a file upload of up to 5 GB, and a public DNS-like lookup service. For each choose TCP, UDP or QUIC, and name the guarantees you rely on and what you must build yourself.
Say your answer out loud first. Thirty seconds is enough.