Unit 5: Messaging Queues and Publish/Subscribe Communications - Practice Quiz

1 What does MQTT stand for?

2 Which communication model is primarily used by MQTT?

3 What is the main role of an MQTT broker?

4 In MQTT, what is a topic?

5 Which protocol is generally designed to be lightweight for constrained IoT devices?

6 What does AMQP stand for?

7 Compared with MQTT, AMQP commonly provides which characteristic?

8 What is the purpose of session initiation in an IoT system?

9 Which information may be negotiated during IoT session initiation?

10 What is a major advantage of the publish/subscribe model?

11 What is a possible disadvantage of broker-based publish/subscribe communication?

12 Why can publish/subscribe systems scale well?

13 Why are lightweight sessions useful in IoT environments?

14 Which device is most likely to benefit from a lightweight session protocol?

15 What is the primary goal of a constrained session-initiation protocol?

16 Which feature is desirable in a protocol for constrained session initiation?

17 What normally happens first in session initiation?

18 What does a successful response to a session-initiation request indicate?

19 What is the purpose of session tear-down?

20 Which action is an example of session modification?

21 A battery-powered sensor sends readings over an unreliable wireless link. Every reading must reach the broker at least once, and occasional duplicates are acceptable. Which MQTT QoS level should be used?

22 A device publishes a retained message containing the latest room temperature. What happens when a new subscriber later subscribes to that topic?

23 A monitoring application subscribes to factory/+/temperature. Which published topic will match this MQTT subscription?

24 An MQTT client needs the broker to notify subscribers if the client disconnects unexpectedly. Which feature should the client configure?

25 A small environmental sensor has limited memory and transmits short telemetry messages. Which protocol is generally the more suitable starting choice?

26 A financial backend requires transactions, flexible queue routing, and enterprise messaging semantics. Which protocol is generally more appropriate?

27 Why might MQTT consume fewer network resources than AMQP for simple sensor reporting?

28 A temperature sensor publishes data without knowing which dashboards or alert services will consume it. Which publish/subscribe advantage does this demonstrate?

29 A broker fails, causing communication to stop for every publisher and subscriber connected only to that broker. Which disadvantage is illustrated?

30 A publisher sends data while a subscriber is temporarily offline. Which mechanism most directly helps the subscriber receive the missed data after reconnecting?

31 Before establishing an IoT communication session, two devices must determine whether they support compatible media formats and transport parameters. What is this process called?

32 Why can a conventional session initiation mechanism be inefficient for a constrained IoT node?

33 A sleeping IoT node wakes briefly to exchange data and then returns to sleep. Which session design best conserves its energy?

34 A constrained device reconnects frequently because its wireless connection is intermittent. Which technique most directly reduces repeated session setup overhead?

35 A constrained session initiation protocol runs over an unreliable datagram transport. Which mechanism is needed to improve signaling reliability?

36 Which design change would most effectively reduce the signaling size of a session initiation protocol for constrained devices?

37 An endpoint receives a session invitation and accepts the proposed parameters. What should happen next to confirm that both endpoints recognize the established session?

38 A sensor has finished streaming data and intentionally ends its session. Why is an explicit tear-down message preferable to simply becoming silent?

39 A device loses power before sending a session tear-down message. Which mechanism should the remote endpoint use to avoid retaining the session forever?

40 During an active video-monitoring session, available bandwidth decreases. What is the most appropriate session modification?

41 An MQTT 5.0 publisher sends a QoS 1 message with a Message Expiry Interval of 30 seconds. A matching subscriber has a persistent session but remains disconnected for 45 seconds. What should the broker do with the queued message?

42 A publisher sends an MQTT message at QoS 2, while a matching subscription was created with maximum QoS 1. At what QoS is the message delivered to that subscriber?

43 An MQTT client reconnects with the same Client Identifier after losing its connection midway through a QoS 2 exchange. Which configuration best allows the exchange to continue without treating the client as a new session?

44 A device publishes retained state ON to plant/pump/state, then later publishes a retained message with a zero-byte payload to the same topic. What is the resulting broker behavior?

45 An IoT backend requires broker-enforced routing based on multiple message headers, transactional grouping, and interoperable link-level flow control between heterogeneous vendors. Which protocol is the stronger direct fit?

46 A battery-powered sensor sends small telemetry records over a high-latency link and requires only topic-based routing with modest protocol overhead. Which design choice is generally most appropriate?

47 A gateway must apply explicit receiver credit so that a fast producer cannot send more transfers than a downstream consumer has authorized. Which protocol mechanism directly expresses this requirement?

48 A publisher emits an event while no subscribers are connected. The system must guarantee later delivery to an already registered consumer. Which additional property is essential beyond basic publish/subscribe decoupling?

49 Two subscribers independently consume every event from the same topic and each updates the same non-idempotent database record. Which publish/subscribe disadvantage is most directly exposed?

50 A safety controller requires a command response within 50 ms and must know immediately whether a specific actuator accepted the command. Why can pure publish/subscribe be a poor fit without extra conventions?

51 A constrained camera and a monitoring client must establish a session, but they support several incompatible media encodings. Which initiation function is necessary before resources are committed?

52 An IoT session setup request is retransmitted after its response is lost. The server has already allocated the requested session. Which design property best prevents the retransmission from creating a second session?

53 A sleepy IoT node communicates through a gateway and wakes only once per hour. Which session design minimizes energy use while preserving enough continuity to resume work?

54 A lightweight session protocol replaces periodic keepalives with a long inactivity timeout. What is the most important resource-management risk introduced by this change?

55 A constrained session-initiation protocol runs over an unreliable datagram transport. A client sends a non-idempotent session-creation request, but the response is lost. Which protocol feature is most critical for safe retries?

56 A constrained protocol compresses session descriptions by replacing common parameter names with numeric codes. Under which condition does this optimization remain interoperable?

57 During session establishment, an offer lists codecs in preference order C1, C2, C3; the answerer supports only C2 and C3 but selects C4. What is the correct outcome?

58 Endpoint A sends a session tear-down request, releases its local resources, and then receives a duplicate copy of the same request from the network. What behavior best supports robust tear-down?

59 A constrained endpoint loses connectivity permanently without sending an explicit session tear-down. Which mechanism most reliably prevents the peer from retaining resources forever?

60 Two endpoints simultaneously send incompatible session-modification offers for the same active session. Which strategy best avoids ending with divergent session state?