a so-called normal steady-state operation of the network has completed initialization, each node passes the token and data into the normal, and there is no node to join with the removal, no token is lost or network failures work 状态. Token-passing requirements from high addresses to low addresses, the last from low addresses to high addresses to pass. Token Bus Network in physics is the bus network, which is logically ring. Surrender the token conditions: one of the node is not waiting to send the data frame. Two nodes have already been sent to the end. 3, the maximum time to hold the token. A direct factor in promoting the development of local area network of personal computers widely used. If the network has N nodes, each node can be assigned to an average bandwidth of 10Mbps / N. Shared media LAN can also be divided into Ethernet, Token Bus, Token Ring and FDDI, as well as on this basis, developed Fast Ethernet, FDDI II and so on. Switched LAN can be divided into Switched Ethernet and ATM LAN, as well as developed on the basis of a virtual local area network. Fiber Distributed Data Interface is a kind of high-speed optical fiber as the transmission medium backbone. Gigabit Ethernet transmission speeds than Fast Ethernet (100Mbps) 10 times faster, to 1000Mbps, the traditional Ethernet to send each bit time from 100ns down to 1ns. According to the switch frame-forward mode, switches can be divided into three categories: a direct exchange. 2 store and forward exchange. 3 to improve the direct exchange. LAN switch features: a low switching propagation delay. Two high-transmission bandwidth. 3 allows 10Mbps/100Mbps. 4 LAN switches can support Virtual LAN Service. Virtual Network (VLAN) switching technology is built on the basis of. Virtual network is built on the LAN switch or ATM switch, and it is in the form of software to realize the division of logical groups and management, logical nodes of the Working Group composed of non-pcmcia ethernet card by the physical location restrictions. The definition of the virtual members of the network method has the following four kinds: one with the definition of the virtual local area network switch port number. (The most common approach) 2 with MAC address. 3 with the network layer address. (For example, using IP address to definitions). 4 IP multicast group. The establishment of such a virtual local area network is dynamic, it represents one group of IP addresses. 10 BASE-5 is the IEEE 802. 3 physical standards have been the most basic kind. It uses the transmission medium is the impedance of 50 dual baseband thick coaxial cable. NIC is short for Network Interface Card NIC, which constitute the basic components of the network. Card Category: Computer Supported by card types: standard Ethernet cards. PCMCIA card (for laptop computer). Supported by card transfer rate categories: ordinary 10Mbps. High-speed 100Mbps network card. 10/100Mbps Ethernet LAN networking. 1000Mbps network card. NIC supported by the transmission media types Category: twisted-pair Ethernet. Thick card. Thin card. Optical fiber network card. The ordinary two-port hub: one is used to connect access 
Point RJ-45 port, this port number can be 8,12,16 , 24 and so on. Another port can be used to connect the AUI port Thick, thin cable used to connect the BNC port can also be a fiber optic ports, such ports as up ports. According to transmission rate classification: 1. 10Mbps hub. 2. 100Mbps hub. 3. 10Mbps/100Mbps adaptive hub. Hub is or can be stacked by category: 1. Common hub. 2. Stackable hub. Or supported by the hub is a network management functions: 1. A simple ii-type pcmcia card slot hub. 2. Hub with a network management function. The definition of LAN switches. Private port, shared port. LAN switches can be divided into: a simple 10Mbps switch. 2 10Mbps/100Mbps adaptive LAN switches. The use of coaxial cable Ethernet is the most traditional form of networking mode. Thick coaxial and thin coaxial cable. Repeater is used to extend the length of coaxial cable as a bus. As a physical layer connection device, played acceptance, amplification, shaping transmitted data signals in the coaxial cable role. If you do not use repeaters, the largest thick cable length does not exceed 500 meters, if you are using repeaters, a maximum of Ethernet allowed four repeaters, the maximum length of 5 to connect to 500 meters thick cable, length no more than 2500 meters. If you do not use the repeater, the largest thin cable length of less than 185 meters if you are using repeaters, a maximum of Ethernet allowed four repeaters to connect five of the 185 meters maximum length of thick cable, length no more than 185 * 5 = 925 meters. Thick and thin cable cable cable hybrid structure maximum segment length of 500 meters. If the thick cable length L m, thin cable length T m, then the L, T of the relationship: L +3.28 * T "500 multi-hub cascade structure, usually the following two methods: 1. the use of twisted-pair, through the RJ-45 port hub to achieve cascade. 2. The use of coaxial cable or optical fiber, through the hub to connect the port to achieve upward cascading. Structured cabling systems with traditional cabling system, the biggest difference is: a structured cabling system structure and the current location of the connected device independent. Structured cabling system of pre-press building structure, building all the computers and peripheral equipment may be placed on the location of all good line of cloth, and then based on the actual situation of the connected devices, by adjusting the internal jumper device, will be All computer equipment and peripherals connected. Intelligent building systems a perfect addition to the structured cabling system, it also must contain the following systems: an office automation system. 2 communications automation systems. 3 building automation systems. 4 computer network. Building an integrated wiring system's main features are: 8 due to the building cabling system to support the integration of various systems and equipment, with all the existing voice and data systems to work together in order to protect users in hardware, software, training investment. 9 Building Cabling System helps to spread the cabling system, merging into a group of unified, standard cabling system. 10 Building an integrated structured cabling system design, enabling users to easily troubleshoot their own, enhanced system security, easy to manage. 11 high-performance unshielded twisted pair and fiber cabling systems of buildings can support up to 100Mbps, or even higher data transfer rates. Industrial cabling system is designed specifically for industrial environments cabling standards and equipment. Network operating system, can take advantage of low-level local area network to provide data transmission capabilities to provide network users to share high-level resource management services, as well as other network service functions of the LAN system software, so that networked computers can be convenient and efficient sharing of network resources for network Users provide the required services of a collection of software and protocols. Two-fold function: to provide users with a variety of simple and effective means of access to local resources. 2 rational organizational system work flow, can effectively have management systems. Is divided into two categories: task-oriented type and Universal. General-purpose and can be divided into: deformation system and the base-level system. Experienced from the structure of reciprocal and non-structural evolution process. Non-peer network operating system structure, design ideas, will be Internet nodes are divided into the following categories: two web servers. Three networked workstations. Virtual disk body can be divided into the following three categories: special plate body, shared disk and shared disk physical body. File-based services, network operating system, is divided into two sections: two file servers. 3 workstation software. A typical local area network can be viewed as composed of the following three components: network servers, workstations and communications equipment. Network operating system's basic functions are: two file services. 3 print service. 4 database service. 5 communications services. 6 information services. 7 Distributed Services. 8 network management services. 9 Internet / Internet Services. The basic tasks of network operating system: shielding the local resources and network resources, differences, to provide users with a variety of basic Web services capabilities to share system resources to complete network management, and provide network services to the operating system E-MAIL. WINDOWS NT SERVER operating system on a "domain" as a unit to achieve centralized management of network resources. The primary domain controller and backup domain controller. WINDOWS NT SEVER use of thread management and preemptive multitasking, making the application more efficient operation. Built-in 4 standard network protocols: 1.TCP/IP agreement. 2.Microsoft's MWLink agreement. 3.NetBIOS extended user interface NetBEUI. 4. Data link control protocol. The use of the task domain and the domain trust relations between pairs of large network management. NetWare operating system is based on the file server-centric, which consists of three parts: the kernel file servers, workstations and low-level communication protocol shell. The connection between servers and workstations through communications software, network cards, the transmission medium to achieve. Communications software, including network card drivers and communication protocol software. Re-definition of procedures for the workstation running NetWare Shell is responsible for the user command interpretation. In the NetWare environment, access to a file path is: file server name / volume name: directory name \ directory name \ file name the user is divided into: a network administrator. By setting user permissions to implement network security protection measures. 2 group administrator. Three network operators. 4 ordinary Internet users. NetWare operating system, fault-tolerant technology is mainly available as follows: three fault-tolerant mechanisms. First-class system fault-tolerant SFT I use a dual directory and file allocation table, disk hot-Road Repair and read-after-write verification measures. Second-level systems, including fault-tolerant disk mirroring with SFT II hard drives duplex function. Third-level system provides a fault-tolerant SFT III file server mirroring. NetWare's Transaction Tracking System is used to prevent the process of writing database records due to system failures caused data loss. IntranetWare operating system's main features: 1 IntranetWare operating system can create powerful enterprise internal network. 2 IntranetWare operating system can protect the user the current throw. 3 IntranetWare operating system, easy management of networks and ensure network security. 4 IntranetWare operating system to the base into a business all the network resources. 5 ntranetWare operating system can significantly reduce network management costs. LINUX system: low price, the original code is open, install and simple to configure. The use of the same kinds of bridges on the LAN can be dispersed in different geographic locations to interconnect multiple LANs. Shaped LAN can also be used to interconnect bridges, ATM local area network LAN interconnection with the traditional shared media LAN emulation problem must be solved. Router or gateway is to achieve LAN and WAN interconnection of major equipment. Data Link Layer device is a bridge interconnect. Play bridge in the network interconnect data reception, address the role of transition and data forwarding, which is among the multiple network system data exchange. Network layer interconnection device is the router. If the network layer protocol is different from a multi-protocol routers. Layers above the transport layer protocol for interconnection between different networks belonging to high-level interconnect. To achieve high-level interconnect device is the gateway. Many high-level interconnect gateway application layer gateway, usually referred to as application gateway. Interconnection is the basis, interoperability is the means, interoperability is the goal. The so-called network interconnection, is distributed in different geographic locations of network equipment connected to form a larger interconnected network system, interconnected system of shared network resources. Network interconnection function has the following two categories: a basic function. Two extensions. Bridge is the data link layer to achieve different network interconnect devices. Need to interconnect networks in the data link layer and above the same agreement. Bridge is often used in the LAN will be a large local area network that is both independent and can be divided into sub-networks are interoperable interconnect structure, which can improve the performance of each sub-network and security. Based on these two standards of the bridge are: a transparent bridge. (The Bridge) 2 Yuen Road bridge election. (Source node) router is a network layer interconnect multiple network devices. Required for each LAN network-layer protocols over the same high-level, data link layer and physical layer protocols can be different. If the high-level protocol is different, multi-protocol router. Gateway can complete the conversion between the different network protocols. Main methods to achieve protocol conversion are: 1. Network information package format directly into the output network information package format. N (N-1) .2. To enter the network information packets into a uniform format for the standard format of network packets between .2 N. a gateway can be constituted by two half-gateways. Internet a major role: a wealth of information Resources (www); convenient communication services (E-MAIL); quick e-commerce (China's first commercial platform for 8488). Internet backbone: ANSNET. from the web designer point of view, the Internet is a computer network. from the user point of view, the Internet is a network of information resources. the Internet in the communication lines are summed up in two categories: wireline and wireless lines. Internet was used mainly by the communication lines, routers, servers and client machines, information resources, the four parts. all connected to the Internet collectively referred to as the host computer on. Server is the Internet service providers and information resources. client services and information resources of the Internet users .TCP / IP protocol is that the ties that bind them .TCP / IP protocol is a set of , it means the Internet host address, host naming mechanism for information transmission rules, and a variety of service functions of a detailed agreement. IP (traffic rules) are mainly responsible for the transmission of data between computers report addressing, and manage these data reported fragmentation process. runs a network layer IP protocol for high-level users to provide the following three kinds of services: 1. not two. reliable data delivery service 3. Works .4. connectionless-oriented transport service 5. Works .6. do their utmost to deliver services 7. services. IP address consists of two parts, 1. network number and 2. host number. as long as the two hosts have the same network number, regardless of their physical location, all belong to the same logical network. A Class IP addresses for large networks. B class IP address for medium-sized networks. C category for small-scale networks, can connect up to 256 devices. D Class IP for multi-destination address to send. E Class will be kept for future use. re-division of IP address of the network number and host number part of the subnet mask to use to differentiate. IP datagram header format can be divided into two major areas and data areas, which need to transfer data area including high-level data, header area is high-level data in order to properly transmit the additional control information. the Internet, it is necessary routing equipment commonly used table-driven routing algorithm. routing table, there are two basic forms: 1. static routing table 2. dynamic routing table . dynamic routing table is a network router automatically send routing information with each other dynamically created. TCP for the application layer to provide reliable data transmission services. TCP is an end to end transport protocol, because it can provide a host of one from a application to the remote host to connect directly to another application. (virtual connection) is a TCP and UDP ports in order to identify a host of multiple targets and design. Internet domain name from the TCP / IP protocol is defined concentration of the Domain Name System . the Internet naming structure of this organization represents a kind of logical way and do not represent the actual physical connection. With a group collaboration is an independent domain name server to complete, there are a large number of Internet domain name server, each domain name the server holds the domain host name and IP address of the comparison table, this group of name servers is the analytic heart of the system. Domain Name two ways: 1. recursive resolution .2. repeatedly parsing. basic services provided by the Internet are: 1. E-mail E-MAIL.2. telnet Telnet 3. File Transfer FTP.4.WWW service 5. services. e-mail service using the client / server mode. users to send and receive e-mail needs the help installed on the client's e-mail application to complete. e-mail application should have the following two of the most basic functions: 1. Create and send e-mail .2. to receive, read, manage e-mail. e-mail applications to send messages to the mail server to use Simple Mail Transfer Protocol SMTP. from the mail server to read when you can use the POP3 protocol or IMAP protocol. When using e-mail application to access IMAP server, the user can decide yes or e-mail copies to the client, as well as yes or IMAP server, to retain a copy of messages, the user can directly read and manage e-mail server. E-mail consists of two parts: the message header and message body (the actual transmission of the content). a remote terminal protocol, both Telnet protocol, Telnet protocol is TCP / IP protocol part of its precise definition of the local client and remote server interaction. the Internet to provide remote access to services can be achieved: 1. a local user and a remote computer, run programs interact with each other .2. user logs on to a remote computer, on the remote computer can perform any application, and can shield the different 3. the difference between the computer models .4. Users can use a personal computer to complete a number of only the mainframe to complete tasks. Network Virtual Terminal: Provides a standard keyboard definition, the various computer systems used to mask the differences in keyboard input. Internet users to use FTP client applications typically have three types, both the traditional command-line FTP, browser, and FTP downloading large files. this in the text the connection with other text that contains features, forming the largest hypertext characteristics: disorder. selection process of hot words, in fact is to choose certain types of information linked clues process. Hyper Text Transfer Protocol HTTP is a WWW client and WWW server between the application layer transport protocol. HTTP session includes the following four-step process Minato: 1. Connect .2. request .3. Answer .4. Close. URL consists of three parts: protocol type, host name and path and file name . WWW server page is stored in a structured document, using Hypertext Markup Language HTML writing made. HTML main features of the document can contain links to other items, both the other pages of the URL. Another feature is the sound , images, video and other multimedia information together. For the body, the Home WWW server is usually the default page, not only when the user need only enter the URL given WWW server host name, rather than
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