問71
頻出度★★★
ネットワークの交換方式に関する記述のうち, 適切なものはどれか。
平成28年度 春期 ITパスポート試験 問71
テクノロジ系ネットワーク › ネットワーク方式
This question's explanation and your answers so far.
解説
問 71
- ア
正解 The correct answer is ア. In the circuit switching method, before communication begins, a single communication path (line) is established between the sender and the receiver, and during communication both parties keep exclusively occupying that path. Because the path is secured in a fixed way, its bandwidth is never taken away by other communications along the way, so it is easy to guarantee the connection speed (transmission bandwidth) and the line quality (stable delay and error rate). The telephone network is a typical example, where quality stays constant during a call. Since this statement that “because the path is occupied, quality is easy to guarantee” correctly describes the essential feature of the circuit switching method, ア is appropriate.
Incorrectイ
Incorrect. The signals handled by the circuit switching method are not limited to analog. Mechanisms such as ISDN that transmit digital signals over circuit switching also exist, and digital communication is possible even over metallic lines (copper wires). The assumption that “a metallic line means analog only” is wrong. The switching method (how the path is secured) and whether the signal is analog or digital are separate matters.
Incorrectウ
Incorrect. The packet switching method splits data into small packets, and multiple terminals share the same transmission path in a time-division manner (statistical multiplexing). Because packets of other communications can be sent the moment the path is free, the utilization efficiency of the communication line is in fact “high.” This statement claims “not sharing the transmission path leads to poor efficiency,” which is doubly wrong: both the point about sharing and the assessment of efficiency are reversed.
Incorrectエ
Incorrect. Both the packet switching method and the circuit switching method can be used over either wired or wireless transmission media. The switching method (how the path is secured and how data is sent) and whether the medium is wired or wireless are independent concepts, so the one-to-one correspondence of “packet switching means wireless only / circuit switching means wired only” does not hold.
ここがポイント
- Circuit switching = a dedicated connection that establishes a path before communication and occupies it during communication, making bandwidth and quality easy to guarantee (typical example: the telephone network). Packet switching = splits data into packets and shares the transmission path among multiple terminals (statistical multiplexing), giving high line utilization efficiency (typical example: the Internet).
- The switching method (circuit switching / packet switching) is a classification of “how the path is secured,” and it is a concept independent of the analog/digital distinction and the wired/wireless distinction. Any statement that links the two one-to-one is wrong.
用語