IPA IP 2020 Question 88

Topic: Networks

A question IPA Japan published in 令和2年度 10月 ITパスポート試験 公開問題 問88, translated into English. ITPEC is based on the same exams.

Among the descriptions concerning wireless LANs, which of the following lists all and only the appropriate ones?

AThe transmission speed is determined by the encryption technology that is used.BWhen interference with other wireless LANs occurs, the transmission speed decreases or communication becomes unstable.CWhen TCP/IP communication is performed over a wireless LAN, the ESSID is used instead of the IP address.

Explanation

Only B — wireless LANs that share or overlap a channel interfere, which lowers their speed and makes communication unstable.

  • •A: wrong. The transmission speed is set by the wireless standard (IEEE 802.11n, 802.11ac, 802.11ax), the frequency band, the channel width and the radio conditions. An encryption method such as WPA2 protects the data; it does not set the speed.
  • •B: right. Access points nearby on the same or overlapping channels share the radio waves, so frames collide or must wait, and throughput falls and connections drop.
  • •C: wrong. The ESSID is the name of the wireless network that a terminal chooses to join. Once connected, TCP/IP communication still addresses hosts by their IP addresses.

Answer (b)

Why not others:

  • •(a) — includes A, but encryption does not determine the transmission speed
  • •(c) and (d) — include C, but the ESSID only identifies the network; it does not replace IP addresses

Key rule: On a wireless LAN the standard and radio conditions set the speed, the ESSID names the network, encryption protects the data, and IP addresses still route the packets.

Networks · AI-written, may contain errors

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This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.