Unit 6: Application Layer and Wireless Networks - Practice Quiz

1 What is the main purpose of the Domain Name System (DNS)?

2 Which DNS record maps a domain name to an IPv4 address?

3 Which protocol is commonly used to send email from a client to a mail server?

4 Which email protocol normally keeps messages on the server and synchronizes them across devices?

5 What is the primary purpose of FTP?

6 Which two connections are traditionally used by FTP?

7 What medium is commonly used to transmit data in a wireless network?

8 Which device commonly connects wireless clients to a wired local network?

9 The IEEE 802.11 standards are mainly associated with which technology?

10 What does SSID identify in an IEEE 802.11 network?

11 Which frequency band is used by IEEE 802.11a?

12 What is the maximum theoretical data rate of IEEE 802.11b?

13 What is the maximum theoretical data rate of IEEE 802.11g?

14 Which technology is a major feature of IEEE 802.11n?

15 What is a small Bluetooth network with one central device and connected devices called?

16 What is formed when multiple Bluetooth piconets are interconnected?

17 Bluetooth is mainly designed for which type of communication?

18 Which Bluetooth layer handles radio transmission and reception?

19 Which Bluetooth layer adapts upper-layer protocols to the lower baseband layer?

20 Which Bluetooth protocol emulates a serial cable connection?

21 A DNS resolver has cached an address record with a TTL of 900 seconds. A client requests the same record 600 seconds later. What should the resolver normally do?

22 An administrator wants email for example.com to be delivered to mail.example.com. Which DNS record should be configured for example.com?

23 A network administrator needs to determine the hostname associated with the IP address 192.0.2.25. Which DNS operation is required?

24 A user wants messages and folder changes to remain synchronized across a laptop and a phone. Which protocol is most appropriate for retrieving the messages?

25 An email containing a JPEG attachment must travel through systems originally designed for text messages. Which mechanism enables the attachment to be represented correctly?

26 An FTP client is behind a firewall that blocks unsolicited incoming connections. Which FTP mode is generally more suitable?

27 During an FTP session, a large file is being transferred while the client sends a command to list another directory. Which FTP feature supports this behavior?

28 Stations A and C can both reach station B but cannot hear each other. Their simultaneous transmissions repeatedly collide at B. Which technique most directly reduces this hidden-terminal problem?

29 A company wants wireless clients to communicate with each other and access its wired LAN through a central device. Which network arrangement should it deploy?

30 A wireless station detects that an IEEE 802.11 channel is busy. Under CSMA/CA, what should it normally do before attempting transmission?

31 A unicast IEEE 802.11 data frame is received correctly, but the sender does not receive the expected acknowledgment. What will the sender normally infer?

32 An office has heavy interference from older 2.4 GHz devices and uses only clients compatible with both bands. Why might 802.11a be selected?

33 An 802.11b client moves farther from its access point and experiences a weaker signal. Which rate adaptation is consistent with the standard's supported data rates?

34 An 802.11g access point permits an 802.11b client to join the network. What is a likely consequence for the wireless cell?

35 An 802.11n access point uses multiple antennas to transmit independent data streams at the same time. Which feature is being applied?

36 An administrator configures an 802.11n access point to combine two adjacent 20 MHz channels. What is the main intended benefit?

37 Eight Bluetooth devices must participate actively in a single piconet. How should their roles normally be arranged under classic Bluetooth?

38 A Bluetooth device participates in one piconet and also connects to devices in another piconet. What larger arrangement is formed?

39 Several upper-layer Bluetooth protocols need to share one lower-layer connection, and large packets may require segmentation. Which layer provides these functions?

40 A legacy application expects an RS-232-style serial connection, but it must communicate over Bluetooth. Which Bluetooth protocol is designed for this purpose?

41 A recursive resolver receives an authoritative NXDOMAIN response for api.example.com with a negative-cache TTL of seconds. After seconds, the zone administrator creates an A record for that name, but the resolver is not notified. What response may the resolver legitimately return at seconds?

42 A parent zone delegates child.example to ns1.child.example and ns.outside.net. Which handling of address records in the referral is correct?

43 A zone contains both pay.example. CNAME host.vendor.net. and pay.example. MX 10 mail.example.. Ignoring DNSSEC-generated records, what is the fundamental configuration error?

44 An SMTP message body contains the logical lines alpha, ., and ..beta. Which sequence must be transmitted after DATA, including the SMTP end marker?

45 A forwarder retransmits a message without changing its signed headers or body. SPF fails because the forwarder's IP is not authorized for the original envelope-sender domain. Under what condition can DMARC still pass?

46 An IMAP client caches messages by UID. On reconnecting, it finds that the mailbox's UIDVALIDITY value has changed, although several old UID numbers are still present. What is the correct action?

47 A client behind a NAT successfully establishes an FTP control connection but sends a PORT command containing its private address. The directory listing then fails. Which change most directly addresses the problem?

48 A compressed archive is uploaded through FTP using TYPE A. Its byte count changes and its checksum no longer matches the source. Which explanation and remedy are correct?

49 Stations A and C cannot hear each other, but both can communicate with access point B. They simultaneously send RTS frames to B. What limitation of RTS/CTS is illustrated?

50 A transmits to B. Station C hears A and therefore defers, even though C could transmit to D without interfering with reception at B. Which phenomenon is present?

51 In an IEEE 802.11 RTS/CTS exchange, a station cannot hear the sender's RTS but does hear the receiver's CTS. Why should it still defer?

52 An 802.11 DCF station selects a backoff of slots. It counts down idle slots, then another transmission makes the medium busy. Assuming its own frame has not yet been transmitted, what happens after the medium becomes idle again?

53 Why does an 802.11 sender normally not retransmit a broadcast data frame at the MAC layer when one receiver misses it?

54 An 802.11a-only access point transmits beacons normally, but an 802.11b-only client does not discover it. What is the primary reason?

55 Which mapping of legacy 802.11b data rates to physical-layer coding is correct?

56 An 802.11g network's throughput falls after a legacy 802.11b station associates, even though that station sends little application data. What is the best explanation?

57 On an error-prone 802.11n link, which aggregation method permits successful subframes to remain accepted while only corrupted MPDUs are retransmitted using Block ACK information?

58 A Bluetooth device bridges two classic piconets whose masters use different hopping sequences. How does the bridge normally participate?

59 In a classic Bluetooth piconet, which information primarily determines the channel-hopping sequence and phase followed by connected slave devices?

60 A classic Bluetooth application must discover a remote serial-port service and then exchange a serial-style byte stream. Which protocol sequence is appropriate?