令和2年度 ITパスポート試験問77

This question's explanation and your answers so far.

問77

頻出度★★★

IP 電話で使用されている技術に関する記述のうち, 適切なものはどれか。

出典　令和2年度 ITパスポート試験問77

解説

問 77

ア
正解 IP telephony uses VoIP technology, which converts voice into IP packets and exchanges them over an IP network. As long as it is an IP network, the transmission path does not matter, so it can be built not only on a public network such as the Internet but also on an internally closed corporate network such as a corporate LAN, as an internal (extension) telephone system. Therefore “ア” is appropriate.
Incorrectイ
Converting voice into IP packets is the technology of VoIP (encoding by a codec). IP-VPN is a WAN service that securely connects sites using a carrier's closed IP network; it is not a voice-packetization technology, so it is incorrect.
Incorrectウ
IP telephony can interconnect with the existing public telephone network (fixed-line and mobile phones) via a VoIP gateway, and can actually place calls to them. “Cannot make calls” is contrary to fact, so it is incorrect.
Incorrectエ
IP telephony operates over IP networks such as broadband. An ISDN line is not a prerequisite; rather, IP telephony is positioned to replace legacy circuit-switched networks such as ISDN, so it is incorrect.

ここがポイント

IP telephony uses VoIP technology to packetize voice into IP packets and makes calls over IP networks (including the Internet and closed networks such as a corporate LAN).
Distinguish that IP-VPN is a WAN service for connecting sites and ISDN is a circuit-switched network; neither is IP telephony's voice-packetization technology nor a required prerequisite.

用語

解答問77ア