Chapter XV Network
15.1 Networking
1. The connection between the computer usually by wire or cable physically implemented. However, some connections using radio waves or infrared signaling data, this link is wireless.
2. The computer network equipment not only computer. For example, the printer can be directly connected to the network, while the network each user can use it.
3. Multimedia components (e.g. audio or video) is a major contributor to increase traffic.
The computer network (computer network): To communicate and share resources connected together a set of computing devices.
Wireless connection (wireless): no physical network connection wires.
Node (host) (node (host)): any network addressable device.
Data transfer rate (bandwidth) (data transfer rate (bandwidth) ): data transmission in the network from one location to another location in the rate.
4. In the networking process, we use specific protocols to explain how to format and process the data to be transferred.
5. Protocol (protocol): how to define the format and process the data in a set of rules on the web.
6. The client / server model (client / server model): The client sends a request to the server, the server responding to make distributed approach.
7
file server (file server):. Dedicated to computer network users to store and manage files.
8.Web server (Web server): dedicated computer in response to the page request.
15.1.1 type of network
1. LAN (Local-Area Network, LAN): a small computer network connection within small geographic area.
2. LAN management of various configurations called topology.
• a ring topology (ring topology): all the nodes connected to the LAN closed configuration.
• star topology (star topology): controls all LAN configuration messages transmitted by the central node.
Star network to a central node given a huge burden, if the central node does not work, then the entire communication network was paralyzed.
• bus topology, all nodes are connected to a communication line, the message may propagate bidirectional communication line. All nodes on the bus will check each message transmitted over the bus, but if the message is not to find the address of the node, it will ignore this message.
Bus topology (bus topology): all nodes share a communication line of a LAN configuration.
Ethernet (Ethernet): LAN-based industry standard bus topology.
3. The wide area network can communicate with each other so that the smaller networks. LAN usually have a particular node as a gateway, the communication processing between the LAN and other networks.
WAN (Wide-Area Network, WAN) : connects two or more local area networks.
Gateway (gateway): its processing node communications between the LAN and other networks.
4.Internet: all over the globe WAN.
5. MAN (Metropolitian-Area Network, MAN) : network infrastructure is developed in big cities.
Compared with the general wide area network, MAN is more suitable for use in a particular tissue or region.
6. The MAN typically connected via a wireless or optical connections.
15.1.2 Internet connection
1. There is no one person or company has the Internet, you can not even control it completely. As a local area network, which consists of a plurality of small networks. These small networks often belong to a person or company. Between these networks is how to connect a truly defines the Internet.
It is connected to a high data transfer rate (from 1.5M to 600 megabits per second, with a special fiber optic implementation) 2. backbone used.
Internet backbone network (Internet backbone): carrying a set of high-speed Internet network communication.
3.Internet service providers (Internet Service Provider, ISP): The company provides Internet access.
4. The home computer has a connection to the Internet much, the three most common is to use a telephone modem, digital subscriber line, cable modem.
Telephone modem (phone modem): to convert computer data into analog audio signals, and then converts the analog audio signal back to the computer data device.
DSL (Digital Subscriber Line, DSL): Internet connection for transmitting data signals with the conventional telephone line.
Cable modem (cable modem): CATV network using a home computer network communication device.
• Note: the regulator and the modem is an abbreviation demodulator.
5.DSL and cable modem connections are all broadband connections. DSL and cable modem download speed and upload speed may be different.
Wideband (broadband): providing a data transfer rate of 128Kbps is greater than the network technology.
Download (download): receive information on the Internet on a home computer.
Upload (upload): transmitting data to a destination machine on the Internet from a home computer.
15.1.3 Packet Exchange
1. In order to improve data transmission on the shared line validity of the message is divided into fixed size, there is a packet number.
2. Each message packets may take different routes to reach the final destination line. Thus, they arrive out of order may be different from the transmission order. After the packages in the required correct alignment easily recombined into the original message.
• Packet (packet): unit of data transmission on the web.
• packet switched (packet switching): The packets sent to a single destination then reassembled network communication technology.
3. If the machine due to problems downstream path is interrupted, or select the current path has a large amount of traffic, the router will probably send packets along another route.
• Router (router): Guidance for network transmission equipment to the final destination on the web.
4. The repeater then installed on the line, and to periodically strengthen the signal if the propagation distance across the communication line is very long (e.g., the sea).
Repeater (repeater): strengthening and propagate signals of network equipment over a longer communication line.
15.2 open systems and protocols
Protocol is defined as the code strictly follow the correct rules and procedures (such as in the foreign exchange) of. Computing terminology borrowed the word to describe the correct rules when communicating with other computers should be used.
15.2.1 Open Systems
1. In the early development of computer network vendors raised many businesses want to be able to adopt the technology. The problem is that these proprietary system has its own unique differences, can not communicate between different types of networks. With the development of Internet technology, the demand for interoperability more and more obvious, we need a different system to make computing vendors can sell way communication.
Proprietary system (proprietary system): System features proprietary technology vendors.
Interoperability (interoperability): capacity from multiple vendors of hardware and software communicate with each other on multiple machines.
Open systems (Open system): In general network architecture model is based on a set of protocols and associated systems.
Development System Reference Model linked to each other (Open System Interconnection (OSI) reference model): 7 layer to facilitate establishment of a logical division of the communication standard of network interactions.
| The number of layers | aspect |
|---|---|
| 7 | Application layer |
| 6 | Presentation layer |
| 5 | Session Layer |
| 4 | Transport Layer |
| 3 | Network layer |
| 2 | data link layer |
| 1 | Physical Layer |
15.2.2 Network Protocol
The basic concept of network protocol reference OSI reference model also stratified to OSI reference model of each layer can rely on their basic agreement, which is sometimes called a layered protocol stack.
• protocol stack (protocol stack): relying on each other protocol layering.
15.2.3 TCP/IP
1.TCP is an abbreviation for Transmission Control Protocol, IP is an abbreviation for Internet Protocol.
2. The transmission control protocol (Transmission Control Protocol, TCP): The message is divided into packets, the destination of the packet reassembled into the message, and is responsible for handling network protocol error
.
3. The Internet Protocol (Internet Protocol, IP): a network protocol, the routing process the packet passed to the final destination by the interconnected network.
4.TCP / IP suite of protocols and procedures supported by the underlying network communications.
The user datagram protocol (User Datagram Protocol, UDP): sacrifice some reliability to achieve a higher transmission rate network protocol is TCP replacement.
5.ping: one for testing and whether the program can reach a particular network computer is active.
6. traceroute (traceroute): for displaying the process comprising passing the destination node program.
15.2.4 high-level protocol
Some of the key executives agreed as follows:
• Simple Mail Transfer Protocol (SMTP) - Specifies the e-mail transmission protocol used.
• File Transfer Protocol (FTP) - allows a user on one computer to another machine files to the agreement or from another machine back to the file.
• Telnet-- used to log on a computer system from a remote computer protocol. If you have an account to allow Telnet connections on a specific computer, then you can run the program using tenet protocol, connection and log on to this machine, just like you are sitting in front of the machine the same.
• Hypertext Transfer Protocol (HTTP) - the definition of WWW document exchange, WWW documents often with HTML (HTML) written.
• Some higher-level protocol with a specific port number.
Port (port): a particular reference number corresponding to higher-level protocols.
15.2.5 MIME Types
Concepts related to network protocols and standardization is the MIME type of file. MIME expand abbreviations (Multippurpose Internet Mail Extension) is Multipurpose Internet Mail.
MIME type (MIME type): standard definition of e-mail or Web site file format.
15.2.6 Firewall
1. firewall (firewall): a gateway machine, its software by filtering network traffic to protect the network.
2. The primary role of a firewall to protect (to some extent hidden) resides in its "back" of a group of relatively lax management of the machine.
3. Firewall enforces an organization's access control policy. Access control policy (access control policy): a set of rules established by the organization, the provisions of the acceptance and rejection of what type of communication network.
4. The method of achieving this strategy of many, the most straightforward approach is to deny traffic specific ports.
5. The more communication state firewall can be determined, the more it is possible to protect the user. Of course, this security comes at a price. Some complex firewall network communications will bring significant delays.
15.3 Network Address
1. When you communicate through a computer network, are ultimately in communication with the computer somewhere in the world another.
2. In dealing with e-mail addresses and sites, we tend to use a host name, because they are easy to understand and remember. However, the network software but should translate the host name into the corresponding IP address, so the computer easier to use. IP addresses are usually four decimal numbers, separated by a dot.
The host name (hostname): name separated by a dot group consisting of the word, that uniquely identifies the Internet machines, each host name corresponds to a specific IP address.
IP address (IP Address): composed of four numeric address in dotted, represents the only machine on the Internet.
A major problem 3.IPv4 agreement is that it can limit the number of (approximately 4 billion) unique identification of the computer.
4.IPv6 successor protocol is the IPv4 protocol, different 32-bit (four groups using the 8-bit) and IPv4 protocol used previously, using the IPv6 address of 128 16-bit total of eight groups.
5.IPv6 addresses are normally written in hexadecimal digits to keep the length of the control.
Domain Name System
1. The host name consists of the computer name plus domain name.
Domain name (domain name): hostname described specific tissue or packet portions.
2. The last part of the domain name is called top-level domain (TLD).
Top-level domain (Top-Level Domain, TLD) : The last part of the domain name, declares the type of organization or Country.
3.ICANN representatives assigned Names and Numbers, the Internet company, is managing top-level domain (TDL) international authority.
A TLD is typically used a specific type of tissue, such as .com for commercial organizations, .edu for universities and colleges.
5. Some TLD is subject to strict control (such as .edu), while others are less stringent (such as .com)
• ICANN: top-level domain approved by international organizations.
• Cybersquatting (domain squatting): purchase a domain name, the sole purpose of selling at high prices really want to use it person or organization.
6. Domain Name System (DNS) is mainly used to translate host names into numeric IP addresses.
• DNS (domain name system): hostname resolution management distributed systems.
• Domain Name Server (domain name server): translating computer host names into IP addresses.
7.DNS is a distributed database, no organization is responsible for updating host name / IP mappings.
15.4 Cloud
1. Adoption of cloud computing, you can obtain the storage space, the device automatically synchronize and access other resources on the Internet.
Cloud computing (Cloud Computing) : provides storage services and other resources on the Internet.
2. There are several different types of cloud services:
• Public cloud: Allows users to access any subscription.
• Private cloud: purpose-built for a specific group or organization, and limit access to groups within the organization.
• Community cloud: Cloud shared between multiple organizations with similar needs.
• Hybrid cloud: some combination of the above type of cloud service.
Summary
• The network is a group to share resources and data computers connected together. Network Technology focus is the underlying protocol and data transfer speed.
• generally classify them according to the scope of the network. It has become a standard Ethernet LAN topology.
• foundation of open systems is a common protocol and network architecture model, with interoperability.
• 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.
• Internet transmission of the message split into packets, each packet is individually transmitted to the destination, again all packets are reassembled into the original information.
• 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.
• There are high-level protocol SMTP, responsible for e-mail communication, FTP file transfer is responsible, telent is responsible for remote login session, HTTP responsible for Web traffic.
• 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.
• Internet network address must be accurate to a particular machine.
• Domain Name System (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 XVI World Wide Web
16.1 Web Profile
1. Compared with the Internet, the World Wide Web is a relatively new concept.
2. WWW (World Wide Web, Web): information and network infrastructure software used to access the information.
3.Web page (Web page): contain or reference documents of various types of data.
4. The link (link): a connection between the two Web pages.
5.Web site (Website): A group of related Web pages, usually the same person or company to design and control.
6.Internet make communication possible, but the Web makes communication easier, richer and more interesting.
7.Web browser is a Web page request processing and after it reaches its displays software tools.
8.Web address is a Uniform Resource Locator (URL) of the core part, URL uniquely identifies a Web page stored in the entire world.
Web browser (Web browser): software tool to retrieve and display Web pages.
Web server (Web server): in response to the Web page computer requests.
Uniform Resource Locator (Uniform Resource Locator, URL): Description of the standard mode of the Web address.
9. In addition to text, the Web pages are typically further comprise a number of independent elements, such as images.
16.1.1 search engine
1.Web search engine to help you locate the site of other Web sites.
2. Search engines by searching a database with information of millions of Web sites to generate a list of candidate sites.
3. Most search engines compare a set of keywords and keyword index the site as user input.
4. Some search engine performs a search based on the concept that attempts context of the search performed is determined.
5. Perform a search word based on the concept basic premise is that the ferret, and contrast similar.
16.1.2 Instant Messaging (Instant Messaging, IM)
As the name suggests, the use of these programs, you can give a friend or partner to work to send messages in real time. If the sender and the receiver runs the instant messaging application at the same time, the message arrives like a pop up immediately, so that two people can be online "conversation." Now the leading IM applications are America Online (AOL) Instant Messenger (AIM)
16.1.3 blog
Weblog referred to as the blog (blog), it is in a way the site regularly publishes articles.
16.1.4 cookie
• cookie is another Web-based technologies for the user, it enhances the Web practicality. A cookie is a small text file stored on the Web server, including computer hard drive. Sites may be stored in a cookie on the user's machine, the interaction between the machine and the site prior to capture before.
Pieces of information stored • cookie is the name - the name of the site and the value of stored information. For example:
UserID KDFH547FH398DFJ www.goto.com
16.2 HTML
1.Web page is created with HTML (HTML).
HTML (HyperText Markup Language, HTML): language used to create Web pages.
Markup language (markup language): use tags to annotate language information document.
Mark (tag): a markup language for describing how to display syntax elements of information.
The following shows the bottom of a Web page's HTML document, which defines the format of all the information you see in this Web.
< HTML>
<TITLE.Student Dynamices
< BODY >
< CENTER>< IMG SRC="stuDynamics.gif">< /CENTER>
< HR >
< CENTER >< I >A student-based community organization.< I >< / CENTER>
< HR >
< P >Plan to participate in our upcoming events:< / p >
< UL >
< LI >Visit Children's Hospital (March 23)< / LI>
< LI >Help clean renovated school grounds (April 4 )< /LI >
< LI > Continue the < a href="outreach.html" >K-12 outreach program.< /a >< IMG SRC="updated.gif" >< /LI >
< /UL >
< P> < B >< I >You should be involved!< /B > < / I >Help our active and energetic team make a difference in the lives of people.Our< a herf="execBoard.html">executive board < /a > is always willing to anwser any questions you may have.< / P>
< P >How can we help you? What suggestions do you have ragarding new activeties?< a href="suggestions.html">Let us know!< / a >< /P >
< P >We are always in need of donations : equipment, monet, or (better yet) you < /P >
< CENTER >< H3 >Join us for our Spring Pincnic in May !< /H3 >< CENTER >
< / BODY >
< /HTML>
16.2.1 basic HTML format
• paragraph tag (<P> ...... </ P >) of which should be described as a separate paragraph text processing.
• centrally tag (<CENTER> ...... </ CENTER>)
• <the HR> horizontal line will be inserted in a page, the Web page is typically divided into a few portions.
• UL element represents an unordered list, LI element represents a list item.
16.2.2 image link
1. Many tags have attributes, it illustrates additional details or information on how to display the information on the package.
Property (attribute): tag used to provide additional information related to the element.
2. The form of the following attributes:
attribute name = value
16.2.3 HTML5
Streamline the marking system and support for dynamic HTML content of the latest standards.
Including:
• <Section> - defined portion of the page.
• <header> - defines the page's header.
• <footer> - defined footer on the page.
• <nav> - defined navigation elements on the page.
• <article> - defines the page or the main content of the article
• <aside> - defined secondary content may appear in the sidebar.
• <figure> - defined comment article image.
Another exciting aspect of it is that the page content 3.HTML5 its dynamic changes can still be changed when the user does not interact with the page.
16.3 interactive web pages
16.3.1 Java applets
Java applet (Java applet): a program designed to embed an HTML document, be able to perform in a browser Web transmission.
Java applets use APPLET tag embedded in the HTML document, such as:
<= the APPLE code "MyApplet.class" width = 250 height = 160.>
</ APPLET>
16.3.2 Java Server Pages
1.Java server page (Java Server Page, JSP) JSP is embedded in a Web page tiny script.
2.JSP small script (JSP scriptlet): embedded in an HTML document for a Web page to provide dynamic content snippet.
16.4 XML
1. Extensible Markup Language (eXtensible Markup Language, XML): allows the user to describe the language of the document content.
2.XML is a meta-language. By meta-language enables us to accurately use conventional language beyond the conventional language, talking about language or define other languages, like English description of the rules of English grammar.
Metalanguage (metalanguage): language used to define other languages.
3. The document type definition (Document Type Definition, DTD): Statute of the XML document structure.
4. Extensible Stylesheet Language (eXtensible Stylesheet Language, XSL): language defines an XML document to convert between the other output formats.
16.5 social networks
1. social networking (social network): allow people with common interests to communicate interactive online services.
2. The current popular social networks including Facebook, Twitter, LinkedIn. Facebool currently has over 800 million users.
3. Online social network users are usually divided into two categories: internal users, participants in a closed or private community (such as companies, associations or organizations) of; external users, there is no limit on participants.
Summary
• Although the terms Internet and Web are often confused, but they are not identical.
• Web page contains not only information, but also includes references to other resources (such as images).
• The so-called access a Web site is actually a Web page request is stored on a remote Web server, in order to take it to the browser on the local computer.
• Some Web site is a search engine, users simply enter a word or phrase, the site can search for relevant information based on these words or phrases.
• Instant messaging (IM) applications for the Web provides another interactive mode, which allows users to chat online.
• blog is a tool published an article on the network on a regular basis.
• cookie enables Web sites to store small text file on your hard drive, so that when you return to the site, the site can get information about you and your last visit.
• HTML (HTML) Web page is the main method of definition.
• HTML tag can either specify the structure of the entire document, you can also perform basic formatting, such as headings, paragraphs, and so on is centered tip text.
• Some HTML tags have attributes, declares additional information.
• Java server pages the little script mixed with HTML code, there is a Web server to perform, to help define dynamic Web pages to content.
• XML is the Extensible Markup Language abbreviated.
The relationship between formats and their definitions • XML tag in the Document Type Definition (DTD) document.
• Social networking is an important part of many people interact on the network.