問55
頻出度★★★
公衆回線を, あたかも専用回線であるかのごとく利用できるようにするために使われる技術を何というか。
平成26年度 春期 ITパスポート試験 問55
This question's explanation and your answers so far.
解説
問 55
Incorrectア
ADSL is a subscriber access line technology that carries digital communication over metallic telephone lines (analog phone lines), with asymmetric upstream and downstream speeds. It is a transmission method for using a line faster, not a mechanism for creating a closed path equivalent to a dedicated line over a public line.
Incorrectイ
LAN (Local Area Network) refers to the on-premises network itself that connects a limited, small area such as an office or a home. It is a classification name based on the scale of a network, not a technology that makes a public line look like a dedicated line.
- ウ
正解 The correct answer is ウ, VPN (Virtual Private Network). A VPN is a technology that creates a communication path over a public line shared by an unspecified number of users, such as the Internet or a carrier network, by combining authentication, encryption, and tunneling (a mechanism that wraps communication data in another protocol to carry it), so that from the users point of view it looks like a closed line reserved just for them. Laying a physical leased line is expensive, but a VPN can reuse the existing public line while holding down the risk of eavesdropping and tampering, safely connecting sites to each other or connecting remote-work devices to the company LAN. This is exactly the description given in the question, “making a public line usable as if it were a dedicated line”.
Incorrectエ
WAN (Wide Area Network) is a classification name for a wide-area network that links the LANs of distant sites through carrier lines. A VPN can be one of the means used when building a WAN, but WAN itself is not a term for the mechanism that makes a line look like a dedicated line.
ここがポイント
- VPN = a technology that builds a virtual dedicated line over a public line (the Internet, etc.) by means of authentication, encryption, and tunneling. It achieves secure site-to-site and remote-work connections at a lower cost than laying a real leased line.
- LAN / WAN are classification names based on the “range” a network covers, while ADSL is a “transmission method” for the subscriber access line. Learn to distinguish whether a term is a network classification, an access line technology, or a security (virtual dedicated line) technology.
用語