# 20192419 semester 2019-2020-1 "Introduction to cyberspace security professionals," the seventh week study summary (reading experience)

Reading experience:
   the "Introduction to Computer Science" study of Part VII of the communication layer, I is a group to share resources and data from computers connected together Chapter XV learned network. Network Technology focus is the underlying protocol and data transfer speed. With our growing dependence on the Internet, the emergence of client / server model of this important software technology.
   They are usually classified according to the scope of the network. A local area network (LAN) covering a small geographic area is relatively small and the connected devices. Concept of a wide area network (WAN) interconnecting network, the network together, cover a larger geographical area. Metropolitan Area Network (MAN) is designed for large cities. LAN topologies include ring topology, bus topology and star topology. LAN Ethernet has become the standard topology.
   On open systems is common network and protocol architecture model, interoperable. The OSI reference model is in principle the open system into a seven-layer network processing.
   Intermet backbone is provided by a set of different companies high-speed network. Intenet service provider (ISP) directly connected to the backbone network or connect to another ISP. Internet access is available for home computing and business computing. Commonly used techniques include home telephone modem connection, a digital subscriber line (DSL) and cable modem. Telephone modem drink is transmitted in the form of the first repeater number data, when the data transmission speed prime slower. Still using DSL phone lines, but the transmission of data in digital form. Cable modem is to transmit data in digital form, but uses a cable television line.
   Intenet transmission of the message is divided into packets, each packet is individually transmitted to a destination where all packets are reassembled into the original message. Before reaching its destination, the packet may be multiple transit networks in the wind. Router is the guiding packet delivery network device in the network. Repeaters strengthen the digital signal before they weaken too much.
   There 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 protocols and software package made responsible for the news division as well as the destination for the message the restructuring package, in addition to handling errors. There are high-level protocol SMTP, responsible for e-mail communication, FTP file transfer is responsible, telnet responsible for remote login session, HTTP responsible for Web traffic. Some higher-level protocol has port numbers to assist control and processing network 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. Some firewalls will block traffic on specific ports, and some sophisticated firewall can analyze the content of network traffic.
   Inlenet network address must be accurate to a particular machine. Asked the host name consists of a single easy to read and understand, separated by a dot. IP address consists of four numbers, separated by a dot, the host name is translated into an IP address. Part of the IP address identifies the network, another portion of the network identification wide specific hosts. P is how to divide the address referenced by the network address of the categories (A, B or C) determined.
Domain Name System (DNS) negative put the host name into an IP address. DNS has evolved into a distributed system to assign tasks to millions of name servers from a single file, including all the original information. Top-level domains (such as .com and .edu) have become overcrowded, so by the new top-level domains (such as .info and .biz). Cloud computing is providing storage space and other resources of one kind of another service 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. There are various costs of cloud services to choose from.
   I learned from Chapter XVI, although the terms Internet and Web are often confused, but they are not identical. World Wide Web infrastructure software, information and access to information scattered throughout the world on a computer constituted. Web relies on the underlying network (especially the Internet) to exchange information between users.
   Web page contains not only information, but also includes references to other resources (such as images). By individuals or companies managed by a set of web pages is called a Web site. There are links between the world's various Web page, which is the origin of the name World Wide Web.
   The so-called access a Web site, in fact, is a request to store Web page on a remote Web server, in order to take it to the browser on the local computer. You can specify the document we want to browse the Web using Uniform Resource Locator (URL).
   Some Web sites (such as google.com) search engine, users can input 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 users based on input keywords, and some keywords will try to explain connotation.
   Instant messaging (IM) applications for the Web provides another interactive mode, which allows users to chat online. Through continuous development, IM program now supports images and even video.
   Weblog or blog (blog) is a tool regularly published articles on the web. More and more serious blog has become an important information resource specific topics. Some blog created a "citizen reporters", their work is a good complement to the mainstream media.
   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 passband with user activity for addition, users and the use of their sites are very helpful. cookie is not a program, it can not execute code on your computer.
   HTML (HTML) Web page is the main method of definition. HTML document consists of information marked annotated, tagged and provides information on how to deal with a specific format. Web browser display will ignore all extra spaces HTML page, 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 tags have attributes, declares additional information. For example, the image source tag attribute declaration file stored images. Anchor tag defines the link, declares the position of the target Web page with a property.
   In addition, it is possible to dynamically create Web pages and interact with web pages. We are two supported Web-based interactive technology is the Java applets and Java Server Pages. Java applets are embedded in the HTML page is executed by the Web browser's Java program. They have cross-platform features, because the Java applet will be compiled into Java byte code, it has a level characteristics.
   Java Server Pages script mixed with the little man in the HTML code, executed by the Web server to dynamically help define the content of Web pages. Small scripting language with full power. JSP is particularly suitable for coordinating interaction between the Web page and the underlying database.
   XML is an extensible markup language acronym. XML is a meta-language that can be used to define other languages. HTML tags are focused on the data format, XML mark the declaration of the nature of the data. The user does not stick to use a specific set of markers, but may define any beneficial mark description data.
XML markup format and define relationships between them in a Document Type Definition (OTD) document. XSL (Extensible Stylesheet Language) defines a method to convert XML documents into other formats suitable for the user.
   Social networking is an important part of many people interact on the network. Facbook services like LinkedIn and facilitate communication between people with similar interests, such online support largely eliminates the problem of distance. The social network has a long history, it provides a mechanism for sociological research more interactive, including the spread of the disease as well as ideas.