From Two to Two Thousand: Data, Topologies, and Trust

Module 7 Examination

Assessment contract

90 minutes. Part A (code): build a miniature in-page SFU simulation — three loopback peers, one simulcast sender, learner-written forwarding and layer-selection logic with hysteresis, stats-driven adaptation — asserted end-to-end; a data-channel transfer with tighter backpressure bounds plus injected channel-close-and-reopen resumption; an E2EE transform with a key-rotation schedule. Part B (scenarios): a 200-person call architecture design (structured answer: topology, simulcast/SVC choice, cascade plan, numeric bandwidth fields graded exactly); 'SFU CPU pegged' → MCU-mode transcoding left on. Part C (concepts): SCTP reliability menu, SFrame header rationale, WHIP verbs, O(n²) math, E2EE tradeoffs.

The examination rewards working code and discriminating evidence. Each assertion gives local feedback; the scorecard combines the code problems with the concept review. Reference answers remain available after a serious attempt.

Part A — Protocol and production benchExecutable

Plan a backpressured transfer. Compute chunk and threshold boundaries before sending a large message stream.

Lab 1

Plan a backpressured transfer

Graded in the browser against 2 assertions; the editor and harness require JavaScript.

Compute topology cost. Prove mesh, SFU, and MCU bandwidth differences numerically.

Lab 2

Compute topology cost

Graded in the browser against 3 assertions; the editor and harness require JavaScript.

Select layers without flapping. Move down immediately, move up after stability, and preserve the current layer during short improvements.

Lab 3

Select layers without flapping

Graded in the browser against 3 assertions; the editor and harness require JavaScript.

Transform the encoded frame. Preserve the clear routing prefix while protecting the encoded body.

Lab 4

Transform the encoded frame

Graded in the browser against 2 assertions; the editor and harness require JavaScript.

Construct the WHIP lifecycle. Produce the SDP resource creation and teardown operations in protocol order.

Lab 5

Construct the WHIP lifecycle

Graded in the browser against 1 assertion; the editor and harness require JavaScript.

Part B — Concepts and judgmentExplain the mechanism

Check your understanding

Auto-graded check

5 auto-graded questions with an explanation for every wrong answer. Requires JavaScript. (m7-exam-quiz)

Examination score

The scorecard totals this page’s graded work as you go. It requires JavaScript.

WebRTC: From First Principles · Module 7 Examination