問77
頻出度★★☆
プロトコルに関する記述のうち, 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77
テクノロジ系ネットワーク › 通信プロトコル
This question's explanation and your answers so far.
解説
問 77
Incorrectア
HTML (HyperText Markup Language) is a markup language that uses tags to describe the structure and content of a web page, such as headings, paragraphs, tables, and links; it is not a protocol (an agreed set of communication procedures) at all. HTML is the format of the data being exchanged, not the procedure that carries it, and that is where the statement is wrong. The protocol for sending and receiving web data is HTTP (HyperText Transfer Protocol), and HTTPS is used when the content of the communication is encrypted.
Incorrectイ
HTTP (HyperText Transfer Protocol) is the protocol for sending and receiving web data such as HTML documents and images between a web browser and a web server; it is not for network monitoring. The protocol used to collect and monitor information such as the operating status and traffic volume of network devices is SNMP (Simple Network Management Protocol). The statement swaps the two purposes, so it is wrong.
Incorrectウ
POP (Post Office Protocol; the version widely used today is POP3) is the protocol for retrieving (receiving) email addressed to you that is stored in your mailbox on the receiving mail server, bringing it to your own device; it is not for remote operation. The protocols for remotely operating a computer at a distant location from a device at hand are Telnet, and SSH, which encrypts the communication so that remote operation can be done securely.
- エ
正解 The correct answer is エ. A protocol (communication convention) is a set of rules that define in advance the procedures and formats used when devices or pieces of software communicate with each other, and a separate protocol is standardized for each purpose. Among them, SMTP (Simple Mail Transfer Protocol) is the protocol responsible for “sending” email. Specifically, it is used both when a user's mail software (mail client) sends a message out to the outgoing mail server they subscribe to, and when the sending mail server relays and forwards the message to the receiving mail server of the destination domain. By default it uses TCP port 25 (port 587, dedicated to mail submission, is used when a user sends mail). On the other hand, once a message has arrived at the receiving mail server and been stored in the user's mailbox, POP3 or IMAP4, not SMTP, is used at the stage where the user retrieves it onto their own device. In other words, the roles are divided as “SMTP for sending, POP3 / IMAP4 for receiving,” and statement エ correctly describes this role of SMTP. Therefore, the appropriate statement is エ.
ここがポイント
- The division of roles among email-related protocols: sending (sending a message from the client out to the server, and forwarding between servers) uses SMTP, while receiving (retrieving mail from the mailbox on the server to your device) uses POP3 or IMAP4. IMAP4 differs from POP3 in that it lets you manage mail while leaving it on the server.
- Identifying representative protocols by purpose: HTTP / HTTPS for sending and receiving web data, SNMP for network monitoring and management, Telnet / SSH for remote operation, FTP for file transfer, DNS for mapping domain names to IP addresses, and DHCP for automatic IP address assignment. It also tests the point that HTML is not a protocol but a markup language, that is, the distinction between a “language / data format” and a “communication procedure”.
用語