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TCP/IP Applications and TechnologiesTCP/IP actually is a suite of protocols used on the Internet for routing and transporting information. The following sections discuss the major application protocols that rely on TCP/IP. ISPAn ISP (Internet service provider) provides the connection between an individual PC or network and the Internet. ISPs use routers connected to high-speed, high-bandwidth connections to route Internet traffic from their clients to their destinations. HTTP/ HTTPSHypertext Transfer Protocol ( HTTP ) is the protocol used by Web browsers, such as Internet Explorer and Netscape Navigator, to access Web sites and content. Normal (unsecured sites) use the prefix http:// when accessed in a Web browser. Sites that are secured with various encryption schemes are identified with the prefix https:// .
SSLSecure Socket Layers ( SSL ) is the encryption technology used by secured (https://) Web sites. To access a secured Web site, the Web browser must support the same encryption level used by the secured Web site (normally 128-bit encryption) and the same version(s) of SSL used by the Web site (normally SSL version 2.0 or 3.0). HTMLHypertext Markup Language (HTML) is the language used by Web pages. An HTML page is a specially formatted text page that uses tags (commands contained in angle brackets) to change text appearance, insert links to other pages, display pictures, incorporate scripting languages, and provide other features. Web browsers, such as Microsoft Internet Explorer and Netscape Navigator, are used to view and interpret the contents of Web pages, which have typical file extensions such as .HTM, .HTML, .ASP (Active Server pages generated by a database), and others.
You can see the HTML code used to create the Web page in a browser by using the View Source or View Page Source menu option provided by your browser. Figure 21.6 compares what you see in a typical Web page (top window) with the HTML tags used to set text features and the underlined hyperlink (bottom window). The figure uses different text size and shading to distinguish tags from text, and so do most commercial Web-editing programs used to make Web pages. Figure 21.6. A section of an HTML document as seen by a typical browser (top window) uses the HTML tags shown in the bottom window for paragraph breaks ( <P> tags), font settings ( <FONT> tags), and hyperlinks ( <A HREF> tags).
Tags such as <P> are used by themselves , and other tags are used in pairs. For example, <A HREF...> is used to indicate the start of a hyperlink (which will display another page or site in your browser window), and </A> indicates the end of a hyperlink. FTPFile Transfer Protocol ( FTP ) is a protocol used by both Web browsers and specialized FTP programs to access dedicated file transfer servers for file downloads and uploads. When you access an FTP site, the site uses the prefix ftp://. tip
Windows contains ftp.exe , a command-line FTP program; type FTP , press Enter, and then type ? at the FTP prompt to see the commands you can use. FTP sites with downloads available to any user support anonymous FTP; if any credentials are required, it's typically the user's email address as a password (the username is preset to anonymous). Some FTP sites require the user to log in with a specified username and password. TelnetTelnet enables a user to log in to a particular computer on the Internet and use it as if he were a regular user sitting in front of it, rather than simply downloading pages and files as he would with an http:// or ftp:// connection.
Windows contains a command-line Telnet program. To open a connection to a remote computer, enter a command such as telnet a.computer.com To use other commands, open a command prompt, type telnet , and press the Enter key. To see other commands, type ?/help . DNSThe domain name system ( DNS ) is the name for the network of servers on the Internet that translate domain names such as www.selectsystems.com into the matching IP addresses. If you manually configure an IP address, you typically provide the IP addresses of one or more DNS servers as part of the configuration process. If you want a unique domain name for either a Web site or email, the ISP that you will use to provide your email or Web hosting service often provides a registration wizard you can use to access the domain name registration services provided by various companies such as VeriSign. caution
A domain name has three major sections, from the end of the name to the start:
For example, Microsoft.com is located in the .com domain, typically used for commercial companies. Microsoft is the domain name. The Microsoft.com domain has the following servers:
Many companies have only WWW servers, or only WWW and FTP servers. All email systems provide transfer of text messages, and most have provisions for file attachments, enabling you to send documents, graphics, video clips, and other types of computer data files to receivers for work or play. Email clients are included as part of Web browsers, and are also available as limited-feature, freely downloadable, or more-powerful commercially purchased standalone email clients. Some email clients, such as Microsoft Outlook, are part of application suites (like Microsoft Office) and also feature productivity and time-management features. tip
To configure any email client, you need
To access Web-based email, you need
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