Attempt the level 101 exercise before reading these answers. Questions 2 and 4 use the optional packet and congestion-control lessons.

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1. Loss and a frozen video call

TCP delivers its byte stream in order, so missing data can delay delivery of later bytes. QUIC can avoid this delivery dependency between independent streams. It does not remove loss, decoder dependencies, or shared congestion limits. Therefore, a freeze is consistent with head-of-line blocking, but its duration alone does not prove the cause. Check your answer: identify both the benefit and one reason QUIC cannot guarantee a freeze-free call.

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2. The larger Initial header

Using the exercise’s empty token and two-byte Length field:
The earlier example was 28 bytes, so the difference is 26 bytes. Each connection ID adds 12 bytes. Together, the IDs account for 24 bytes of the increase. The packet number adds the remaining two bytes. This is the header calculation, not the full encrypted packet size. Check your answer: retain the assumptions about Token Length and Length encoding when comparing the two totals.

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3. Robot position telemetry

Datagrams can fit a latest-state policy when the next reading replaces the previous reading. Include sequence or timestamp information so the receiver can identify stale data. This answer concerns telemetry, not an emergency-stop mechanism or a command requiring acknowledgment. Check your answer: explain what the application does when no fresh reading arrives.

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4. Slow start and loss

The RFC 9002 example controller grows its congestion window as acknowledgments arrive during slow start. A qualifying congestion event causes the controller to reduce its window and enter congestion avoidance. Actual bytes sent also depend on whether the application has data and whether flow control permits sending. Not every QUIC implementation uses this controller. Check your answer: distinguish the congestion window from the application’s actual sending rate.

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5. Application-limited sending

A fixed-rate media source can send less data than the network could carry. The resulting delivery rate may reflect the source rate, not the path’s full capacity. A large download is more likely to keep data available and exercise the sending allowance. That distinction is a tendency, not a guarantee for every download. Check your answer: state what the sender can and cannot infer from the observed rate.

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6. A track from the documentation

Answers depend on the track and the current SDK documentation. For example, position telemetry can justify datagrams when newer values replace old ones. A command transaction can justify reliable delivery together with an application acknowledgment and an expiry policy. Media can also use reliable streams when dependency and deadline requirements justify them. Check your answer: name the track, cite the documentation page, and explain the delivery policy from its requirements. Next: 102 · The stack.