Part VII communication layer
Chapter 15 Network
15.1 networking
The network is not defined physical connection, but by definition communication capabilities.
- A computer network (Network Computer) : To communicate and share resources and a set of computer devices connected together.
- E-mail, instant messaging and web are dependent on the underlying communication takes place in a computer network.
- Wireless connection (Wireless) : no physical network connection wires.
- Node (host) (Node (Host)) : Any addressable network devices.
Data transfer rate (bandwidth) (Data Transfer Rate (bandwidth)) : transfer of data from one location to another location in the network of the rate .
- Protocol (Protocol) : a set of rules that define how the data is formatted and processed in the network.
- Client / server model (Client / Server Model) : the requesting client to the server, the server responding to a distributed approach.
- File Server (File Server) : dedicated to the computer network users to store and manage files.
Web server (Web Server) : dedicated computer in response to the page request.
15.1.1 type of network
- LAN (Local-Area Network, LAN) : a small computer connected to the network within a small geographic area.
- Ring topology (Ring Topology) : all the nodes connected to LAN configured as a closed loop.
- Star topologies (Star Topology) : controls all LAN configuration messages transmitted by the central node.
Bus topology (Bus Topology) : all nodes share a communication line of a LAN configuration.
- WAN (Wide-Area Network, WAN) : connects two or more local area networks.
- Gateway (Gateway) : its processing node communications between the LAN and other networks.
- Internet : all over the globe WAN.
MAN (Metropolitan-Area Network, MAN) : developed for the metropolitan network infrastructure, which are usually connected or optical connections achieved by wireless. #### 15.1.2 Internet connection
Small network connection between how a truly defines the Internet.
- Internet backbone network (Internet Backbone) : carrying a group of high-speed Internet communications network, are used with high data rate connection.
Internet ISP (Internet Service Provider) : The company provides Internet access.
The home computer connected to the Internet or three common methods: a telephone modem, cable modem or a digital subscriber line.
1. The telephone modem (Modem Phone) : to convert computer data into an analog audio signal, and then converted back into analog data of the audio signal data of the computer device. An audio represent a binary 0, 1 for representing another. Phone companies do not need to do any special work, it is very simple to implement. Since the data is processed as a voice conversation, except at both ends so that, no special switching operation. But the data transfer rate is limited to the data transmission rate of the analog voice communications, typically up per 64KB.
2. Digital Subscriber Line (Digtal for Subscriber Line, the DSL) : the Internet connection with the transmission of digital signals of a conventional telephone line. To establish a DSL connection, your telephone company must be your ISP.
3. The cable modem (Cable Modem) : CATV network using a home computer network communication device. Data transmission cable is a cable transmission cable TV signal.
- DSL and cable modem connections are all broadband connections.
- Broadband (Broadband) : greater than the data rate provided to 128Kbps 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
- Packet (Packet) : unit of data transmitted over the network.
- Packet switched (Packet Switching) : send the packet to the destination separately and then assembled network communication.
- Router (Router) : Guidance for network transmission equipment to the final destination on the network.
- Repeaters (Repeater) : to strengthen the network devices and transmitting a signal over long communication lines.
15.2 open systems and protocols
For many reasons (usually for historical reasons), the status of certain protocols than other protocols.
15.2.1 Open Systems
- Proprietary systems (Proprietary System) : the use of a particular vendor system's proprietary technology.
- Interoperability (Interoperability) : from multiple vendors on multiple machines software and hardware capability to communicate with each other.
- Open system (the Open System) : in a network architecture general model based on a set of protocols and associated systems.
- Open Systems Interconnection Reference Model (the Open Systems Interconnection, (the OSI) Reference Model) : In order to facilitate the establishment of a logical division 7 layer communication standard of network interactions.
15.2.2 Network Protocol
- Protocol stack (Protocol Stack) : relying on each other protocol layering.
15.2.3 TCP/IP
- Transmission control protocol (Transmission Control Protocol) : The message is divided into packets, the destination of the packet reassembled into the message, and is responsible for handling network protocol error.
- Internet Protocol (the Internet Protocol) : network protocol, the routing process the packet passed to the final destination through a network interconnected.
- TCP / IP : A set of protocols and procedures to support low-level network communication.
- User Datagram Protocol (the User Datagram Protocol) : sacrifice some reliability to achieve a higher transmission rate network protocol is TCP replacement.
- the ping : to test a particular network computer as well as whether the program is accessible activities.
- Traceroute (the traceroute) : the package for displaying a route through the process of reaching the destination node.
15.2.4 high-level protocol
- Common high-level protocol:
1. Simple Mail Transfer Protocol ( the SMTP ) - to specify e-mail transmission protocol.
2. File Transfer Protocol ( the FTP ) - allows a user on one computer to the files to another machine or another machine from the returned file protocol.
3. the Telnet - protocol used to log a computer system from a remote computer.
4. Hypertext Transfer Protocol ( the HTTP ) - WWW document exchange protocol is defined, typically WWW document Hypertext Markup Language (HTML) written.
These protocols are built on top of TCP.
- Port (Port) : corresponding to certain high-level protocol numerical designations .
15.2.5 MIME Types
- MIME is the Multipurpose Internet Mail abbreviation expansion (multipurpose Internet mail extension) of.
- MIME type (MIME of the type) : define the format of e-mail attachments or files website standards.
15.2.6 Firewall
- Firewall (Firewall) : a gateway machine, its software filtering network traffic to protect the network. Its main role is to protect (to some extent hidden) reside in it "behind" a set of management had been more lax machines.
- 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 network traffic.
15.3 Network Address
- The host name (hostname) : name separated by a dot group consisting of the word, that uniquely identifies a machine on the Internet; Each host name corresponds to a specific IP address.
- IP address (IP address) : address value consisting of four numbers separated by only shows the machine on the Internet.
- Host name consists of the computer name plus domain name.
- Domain (Domain name) : hostname described specific tissue or part of a packet.
- Top-level domain (Top-Level Domain) : The last part of the domain name, type or belongs declared national organizations.
- ICANN : Ratification of international organizations top-level domain.
- Cybersquatting (Domain the Squatting) : purchase a domain name, the sole purpose of selling at high prices really want to use it person or organization.
- Domain Name System (Domain name System) : host name resolution management distributed systems.
- Domain name server (Domain name Server) : translating computer host names into IP addresses.
15.4 Cloud
- Cloud computing (Cloud Computing) : provides storage services and other resources on the Internet.
- There are several different types of cloud services:
1. Public Cloud: Allows users to access any subscription;
2. Private cloud: purpose-built for a specific group or organization, and limit access to groups within the organization;
3. Community cloud: cloud shared between multiple organizations with similar requirements;
4. hybrid cloud: some combination of the above types of cloud services.
Chapter 16 World Wide Web
16.1 Web Profile
Internet and the web is not equivalent.
- WWW (World Wide Web) : information infrastructure, and networking software for accessing information.
- Web page (Web Page) : contains or refers to various types of document data, these data including text, images, graphics and programs.
- Link (Link) : a connection between two Web pages.
- Web site (Website) : A group of related Web pages are usually designed and controlled by the same person or company.
- Internet makes communication possible, but the Web makes communication easier, richer and more interesting.
- 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) : Description of the standard mode of the Web address.
16.1.1 search engine
Web search engine to help you locate the site of other Web sites.
Search engine by searching a database with information of millions of Web sites to generate a list of candidate sites.
- Search based on the concept: Try to determine the context of the search performed.
Based on the concept of search is much more responsible than keyword search, search technology based on concept is not perfect.
Keyword search is very challenging, because the natural language itself is ambiguous.
16.1.2 Instant Messaging
- Instant messaging (the Instant Messaging, IM) : is the most popular web applications. As the name suggests, it is that you can give to friends or partners send messages in real time.
- Unsafe: IM message sent by various protocols, and is not encrypted, may be an intermediate point on the way network communication interception , unencrypted e-mail is also unsafe.
16.1.3 blog
- Blog (Weblog) : the site is regularly published articles in a way.
16.1.4 cookie
- Definitions : on your computer's hard drive is a small text file that a Web server storage. For users, it enhances web practicality.
- Sites may be stored in a cookie on the user's machine, the interaction between the machine and the site prior to capture.
- There are many uses of the cookie, some Web sites use cookie to determine how many unique visitors, interactive Web site with some cookie stores the user's preferences, so that customized site.
- cookie is not a program that will not do anything on your computer. It also does not collect personal information about you or your computer.
16.2 HTML
- HTML (HyperText Markup Language) : language used to create Web pages.
- Markup language (Markup Language) : use tags to annotate language information document.
Tag (Tag) : a markup language for describing how to display syntax elements of information.
- HTML tag described general properties of a piece of information (e.g., a paragraph, an image, or a list of items) and how to display it (such as font, size and color).
Each HTML file consists of two parts, namely the head of the document and the document body. Head of the document contains the information about the document itself, while the body of the document is stored in the information to be displayed.
16.2.1 basic HTML format
16.2.2 image link
- Property (attribute) : tag portion for providing additional information about the elements.
16.2.3 HTML5
HTML5 released in 2011.
16.3 interactive web pages
16.3.1 Java applets
- Java applet (Java applet) : is embedded in the HTML document procedures designed to be able to perform in a browser Web transmission. It is embedded in an HTML document with the APPLET tag. We can not fully meet the needs of Web users interact.
16.3.2 Java Server Pages
- JSP small script (JSP scriptlet) : embedded in an HTML document for a Web page to provide dynamic content snippet.
- JSP script small enclosed in special tag <% and%> between.
16.4 XML
- HTML is fixed, that is to say, there is a predefined set of tags, each with its own semantics.
- Extensible Markup Language (eXtensible Markup Language) : allows the user to describe the language of the document content.
Metalanguage (metalanguage) : language used to define other languages.
- Document type definition ( the Document Type Definition ): Statute of the XML document structure.
- Extensible Stylesheet Language (eXtensible Stylesheet Language) : XML document to define the language conversion between the other output formats.
XML is a mark specification language, XML files are data.
16.5 social networks
- Social networking (social Network) : to allow people with common interests to communicate interactive online services.
- Small world phenomenon : Refers to connect any acquaintance relationship between two people of the society generally short chain of assumptions. "Six Degrees of Separation"
problem
cookie cache is what we usually say it? Why "for various reasons, cookie has not been widely accepted?"
Resolution process
Internet search: https://blog.csdn.net/ssspk_/article/details/92611751
