The first 15 chapters
I began to introduce the network, which is a group of computers connected together to share resources and data. Network Technology focus is the underlying protocol and data transfer speed. Followed by expansion of geographical, we describe three networks, local area networks (LAN) covering a small geographic area is relatively small and the connected devices. A wide area network ( the WAN concept) interconnected network, the network together, cover a larger geographical area. Metropolitan Area Network ( MAN ) is designed for large cities. LAN topologies in three ways: a ring topology, bus topology and star topology. LAN Ethernet has become the standard topology. The OSI reference model is in principle open systems into a network processing of the 7 layers. Internet backbone is provided by a set of different companies high-speed network. Internet Service Provider ( ISP ) directly connected to the backbone network or connect to another ISP , providing Internet connectivity for home computing and business computing.
Commonly used techniques include home telephone modem connection, a digital subscriber line (DSL) and cable modem. Telephone modem transmit data in the form of an audio signal, the data transfer rate is relatively slow. DSL still using telephone lines, but the transmission in digital form on the device.
Internet transmission of the message is divided into packets, each packet is individually transmitted to the destination, all packets are reassembled into the original message. Before reaching its destination, the packet may be multiple transit in the network. There are three machines, the router is a network device guidance package passed in the network; repeater strengthen them before digital signal weakened too much; there are also layered network protocols, such as high-level agreements will be low-level protocol support. Support for Internet communication is the key to low-level protocol TCP / IP . IP protocols and software responsible for routing packets. TCP protocol and the software sends the message into packets, and the destination of the packet reassembly for the message, in addition to handling errors. There are high-level protocol SMTP, responsible for e-mail communication, the FTP is responsible for file transfer, the Telnet responsible for remote login session, HTTP responsible for Web traffic. Many types of documents and data formats have special MIME type. A firewall protects the network from unauthorized access, organizations applying specific access control policy to the network.
IP address consists of four numbers, separated by a dot, the host name is translated into IP addresses. IP portion of the address identifies the network, the other part identifies the particular host network. Domain Name System ( the DNS ) is responsible for translating host names into IP addresses.
Cloud computing is a storage space and other resources to provide services on the Internet, mainly frees you from the task of managing the data out, and no matter where you make the data can be accessed.
Chapter 16 World Wide Web
This chapter is equivalent to extending the previous chapter, from the web began to introduce a series of concepts such as the World Wide Web.
Web page contains not only information, but also includes references to other resources (such as images). By individuals or companies managed by a group of Web pages called Web site. Global various Web are links between pages, which is the source of the name World Wide Web.
You can specify the browser we want to use a Uniform Resource Locator (the URL of) Web documents. Some Web sites (such as google.com ) search engine, users simply enter a word or phrase, the site can search for relevant information based on these words or phrases. The search engine will provide a possible match list of candidate sites and user needs. Some search engines only to user-entered keywords as the basis, while others will try connotation explain keywords.
Weblog or blog (blog) is a tool regularly published articles on the web. A cookie is a small text files that Web sites store on your hard drive, so that when you return to the site, the site can get information about you and your last visit. They are often used to track user activity, user and use their sites are very helpful. cookie is not a program, it can not execute code on your computer.
HTML (HTML) is defined Web main method page. HTML document consists of information marked annotated, tagged and provides information on how to deal with a specific format. Web browser display HTML ignores extra spaces when all pages, blank lines and indentation. Browser relies entirely on the labeling guidelines, with a view Web pages may be slightly different in different browsers. HTML tags may be a predetermined structure of the entire document, you can perform basic formatting, such as headings, paragraphs, etc., and centered text. Mark can also specify the font style, such as bold and italic. Unordered lists and ordered lists have their own set of tags. Some HTML tag has attributes, the statement of additional information.
In addition, it is possible to dynamically create Web pages and interact with web pages. We are two supported-based Web interaction technology is Java applets and Java Server Pages. Java applets are embedded in the HTML page from the Web to perform browser Java programs. They have cross-platform features, because the Java applet will be compiled into Java byte code, it has a level characteristics. Java server pages the little script mixed with HTML code, the Web perform server, dynamic help to define the content of Web pages.
XML is an extensible markup language acronym. XML is a meta-language that can be used to define other languages.