問70
頻出度★★★
社外からインターネット経由で PC を職場のネットワークに接続するときなどに利用する VPN (Virtual Private Network) に関する記述のうち, 最も適切なものはどれか。
平成23年度 秋期 ITパスポート試験 問70
This question's explanation and your answers so far.
解説
問 70
Incorrectア
Preparing multiple connection lines to the internet is line redundancy (duplication or multihoming), an availability measure that lets communication continue even if one line is cut by a failure. Its purpose is to avoid outages, not to protect the content of the communication. A VPN works even over a single line, so it has nothing to do with the number of lines.
Incorrectイ
Guaranteeing the maximum delay time by controlling the transmission timing is the idea behind priority control and bandwidth control in QoS (Quality of Service), a mechanism that protects the quality of communication requiring real-time performance, such as voice and video. Since a VPN passes over the internet, it cannot guarantee the delay itself. Ensuring security and guaranteeing communication quality are different technical areas.
Incorrectウ
Compressing communication data is only a way to reduce the amount of data sent and improve transfer efficiency; it is a different thing from bandwidth guarantee, which secures a certain bandwidth when the line is congested. A guaranteed minimum bandwidth is provided by guaranteed-bandwidth services or by QoS functions, and it does not correspond to the essential purpose of a VPN, which is ensuring security through authentication and encryption.
- エ
正解 The correct answer is エ. A VPN (Virtual Private Network) is a technology that virtually creates a closed communication path (a tunnel) over a public network used by an unspecified number of people, such as the internet, as if a dedicated line existed. Because a public network as it is can be subject to eavesdropping, tampering, and spoofing along the route, a VPN ensures safety by combining (1) authentication, which confirms that the connecting user or device is legitimate, and (2) encryption, which keeps the communication data flowing through from being read by third parties. The situation in the question, connecting a PC to a workplace network from outside the company via the internet, is exactly a typical example: it achieves secure access to the internal network while using the internet, without paying the high cost of installing a dedicated line. Implementation methods include ones that use IPsec, and SSL-VPN, which uses the SSL/TLS of a web browser.
ここがポイント
- Definition of a VPN: a technology that sets up tunneling over a public network (the internet) and realizes a virtual dedicated line through authentication and encryption. It costs less than a dedicated line and provides a secure communication path that prevents eavesdropping, tampering, and spoofing. Representative methods include IPsec-VPN and SSL-VPN.
- Distinguishing it from confusingly similar neighboring technologies: preparing multiple lines improves availability (redundancy), guaranteeing delay or bandwidth is done by QoS and guaranteed-bandwidth services, and data compression improves transfer efficiency. Remember them by role: what a VPN handles is not quality assurance but ensuring security.
用語