問82
頻出度★★★
光ファイバを使った家庭向けの通信サービスを示す用語はどれか。
平成24年度 春期 ITパスポート試験 問82
テクノロジ系ネットワーク › ネットワーク応用
This question's explanation and your answers so far.
解説
問 82
- ア
正解 The correct answer is “ア”, FTTH. FTTH stands for Fiber To The Home. It is an access-line service in which the telecommunications carrier runs optical fiber cable directly from its central office into the building of each home, where a terminating device (ONU) is installed to provide Internet access and similar services. FTTH is the only term whose very definition satisfies at the same time both conditions the question asks for: that optical fiber is used, and that it is a communication service for homes. Note that arrangements in which the fiber stops at the shared area of a building or a multi-dwelling block, or near a utility pole, and metal (copper) cabling is used from there onward, are called FTTB or FTTC instead; the identifying point of FTTH is that the H stands for Home, meaning the fiber reaches all the way to the home.
Incorrectイ
ISDN (Integrated Services Digital Network) is a service that uses the existing metal (copper) telephone lines to transmit both voice and data digitally over a single line. It was offered to homes as well, but its transmission medium is copper wire, not optical fiber, and its speed on the basic interface is only about 64k bits per second × 2 channels. It does not satisfy the condition of using optical fiber, so it is wrong.
Incorrectウ
TCP/IP is the name of the family of communication protocols (agreed rules for communication) used as the standard on the Internet; centered on TCP and IP, it defines communication procedures in a layered structure. It is not a term that denotes a type of line or a form of service, and the same TCP/IP runs over optical fiber, over wireless, and over copper wire alike. It connects to neither a transmission medium nor a home-oriented service, so it is wrong.
Incorrectエ
Wi-Fi is an interoperability certification brand based on the IEEE 802.11 family of wireless LAN standards, a technology that connects a device to an access point wirelessly using radio waves. It is widely used inside homes as well, but what it uses for transmission is radio waves, not optical fiber, and it is an indoor, local-area network technology rather than the name of an access-line service provided by a carrier, so it is wrong.
ここがポイント
- FTTH = Fiber To The Home. It refers to a home-oriented broadband access service that runs optical fiber from the central office into each home. The names differ by how far the fiber is laid: FTTH (to the home) / FTTB (to the building) / FTTC (to the curb, that is, a utility pole or roadside equipment).
- Tell similar acronyms apart along three axes: transmission medium, coverage, and layer. ISDN = a digital communication service over metal (copper) lines; Wi-Fi = a wireless LAN standard (local area, radio waves); TCP/IP = a protocol suite (independent of the medium). None of them is the name of an access-line service.
用語