计算机网络双语论文-局域网的设计.doc

东北电力大学计算机网络双语论文 作 者： 学 号：院 系： 自动化工程学院 专 业： 自动化 题 目： 局域网的设计 指导教师： WANTechnologyAndVPNDesign Chapter1 Introduction.3Chapter 2 WAN.3Chapter 3 Routing7Chart 4 “infinite counting” question.14Chapter 5 Network Present Situation And Demand Survey.16Chapter 6 Realization of VPN Technology.18Chapter 7 Realizes The VPN Network Hardware Disposition.21Chapter 8 VPN Network Realization.23WAN Technology And VPN DesignAbstractIn recent years, the Internet with its rich internet applications can be spread in the community for its swift, internet technology, advanced, causing widespread concern in the enterprise. So the use of internet technology, the idea of the enterprise local area network (LAN), be applied to form an intranet Intranet become fashionable. So, to understand technology, wide area networks and wide area network to form a good network for our system is essential. Here, we compare the WAN and LAN, come to their differences and linkages. The same time, connect to the network of the most important type of equipment - routers in the network and address of the principle of the work of routing in-depth analysis.In the familiar with the wide-area network and wide area network technology, based on, we give an advantage of WAN, VPN technology, the words of a companys INTERNET Netcom had connected into a virtual local area network design. Through the hardware and software settings, use of IPsec security protocol of the VPN and encryption capabilities, to achieve between the two businesses across the Internet, internal network connections to achieve a secure internal data communications. The internal control system through the firewall policy on the VPN, the data can be an effective control and management of the enterprises internal network traffic has good scalability and manageability. Key words: WAN technology, routing algorithm, router, VPN design, IP addressChapter1 IntroductionThe role of local area network from the original host connectivity, file and print services, turning around the client / server model of the large data streaming applications, Intranet, WWW browsing, real-time audio / video transmission and other services has become increasingly large and growing data flow continues increase in network load. The same time, based on work group or department-level enterprise-class server solution has been replaced by the server to facilitate data flow to a fundamental change in the status of the network backbone and further improved. These have all contributed to local area network technology from the bridge technology, the backbone routing technology to LAN switching technology transition. The development of switching technology LAN switch provides an unprecedented opportunity for development, but also greatly contributed to the LAN switch technology and product upgrading.With the development and application of information technology, information security, content in the continuous extension of the confidentiality of information from the initial development of information integrity, availability, controllability and non-repudiation, which in turn developed into the attack (attack) , anti-(against), measured (test), control (control), tube (management), evaluation (assessment) and other aspects of the basic theory and implementation of technology. Modern information systems in the information security and its core issue is the password Theory and Its Applications, based on credible information system structure to make and evaluation. Overall, the current field of information security the focus of attention by people mainly the following aspects: 1) Password theory and technology; 2) security protocol theory and technology; 3) The security architecture theory and technology; 4) information against the theory and technology; 5) network security and security products.Chapter 2 WAN2.1 IntroductionA WAN is a data communications network that covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer. Figure 3-1 illustrates the relationship between the common WAN technologies and the OSI model.In general,a network technology is classified into one of three broad categories, depending on the size of networks that can be created LAN,MAN and WAN which can span sites in moltiple cities,countries or continents.2.2 The Difference Between LAN And WANTo appreciate the distinction,it is important to understand how the size of a network is measured.We have seen that although LAB thchnologies are designed to be used at a single site,techniques exist that can extend the distance spanned.In particular,a satellite bridge can connect two segments of a LAN over an arbitrary distance.However,a bridged LAN is not considered a Wide Area techonlogy because bandwidth limitations prevent a bridged LAN from serving arbitrarily many computers at arbitrarily many sites.The key issue that separates WAN technologies from LAN technologies is scalabilitya WAN must be able to grow as needed to connect many sites spread across large geographic distances,with many conputers at each site. For example,a WAN should be able to connect al the computers in a large corporation that has offices or factories at dozens of locations spread across thousands of square miles.Furthermore,a technology is not classified as a WAN unless it can deliber reasonable performance for large size networks.That is ,a WAN does not merely connect to many computers at many sitesit must provide sufficient capacity to permit the conputers to communicate simultaneouly.2.3 Forming A WANA group of switchboard interconnection constitutes WAN. A switchboard usually has many input/output interface, enables it to form many kinds of different topology, connects many computers. For example，figure 1 - 1 had demonstrated changes planes WANs one kind of possibility situation which by four bawyos becomes with eight computer interconnections. Like the chart shows, WAN does not need interconnection and each connection between the symmetrical - switchboards capacity according to the anticipated current capacity to decide, and provides the redundancy by against breakdown. If on the example shows, the stand 1 switchboard connects two computers, and has an exterior connection (e.g. a T 1 line) and another switchboard is connected. But only connects a computer in the stand 2 switchboards, and has in two exterior connection and other stand switchboards is connected. The summary is as follows: the bawyo changes planes is WANs basic composition block. WAN changes planes the constitution by some interconnections bawyo and connects the computer from this. Other switchboards or the connection may when the need joins expands WAN.We can summarize:A packet switch is the basic building block of Wide Area Networks.A WAN is formed by interconnecting a set of packet switches,and then connecting computers.Additional switches or interconnections can be added as needed to increase the capacity of the WAN.Simulation telephone channelISDNPoint-to-point owner-use circuittypesCircuit switching, public, simulation.Circuit switching, public, digitPoint-to-point special-purposeBand width9.633.6kbit/sBRI 64128kbit/sPRI 2Mbit/sN64kbit/s1N30UsingAs data transmission physical linkAs high speed data transmission physical linkPhysical connection which provides as two verticesConnection vertex numberNo limitedNo limitedThe expense limit, can only be very fewPerformance superiorityMay realize any two vertex connection, the extendibility is good, the expense is lowHigh speed, digital transmission The call time is short,May realize the application environment which between any two vertices correspondsPerformance weak trendThe band width is low, the reliability is badThe correspondence expense does not suit the long time correspondence the application environmentThe line correspondence expense is highCost wayInstallation fee ，month rent ，working costInstallation fee ，month rent ，working costThe installation fee, collects the month rent according to the band width and the distanceSwitch at site 1Switch at site 2Switch at site 3Switch at site 4high-speed connections between switchesComputers connected to network Figure2-1 A small WAN formed by interconnecting packet switchse.2.4 Examples of WAN TechnologiesMany technologied have been created for experimental and production use in Wide Area Networks.This section presents a few example technologies that illustrate sone of the diversity.Each kind of WAN connection technology comparison like chart 1.Chart 1 Each kind of WAN connection technology comparisonReads the table to be possible to know, regarding the circuit switching network, the ISDN high band width, the redundant reliability most has the attraction. Regarding the owner-use circuit, the remote communication can only use the point-to-point owner-use circuit, but as the line attachment, x DSLb will certainly to become the user the first choice connection technology. Regarding the packet switching network, the frame relay is the most attractive connection technology, but develops and the SMDS popularization unceasingly along with the new application, SMDS and the ATM technology will definitely become the band width WANs main connection technology. Chapter 3 Routing3.1 Packet SwitchesHow can a WAN to hold many computers? The network own must be expandable. WAN is composed of many switchboards, each computer connects on the switchboard, but is not a computer rents from that kind of computer direct Lian Daoling the data link to compose point-to-point. The WAN initial scale is the computer number which and links into by the stand number decided that other switchboards may the on demand probably join, use for to connect other stands or the computer. in the WAN the basic electronic switchboard is called the bawyo to change planes (packet switch), because it a stand transmits entire Bao Cong to another stand. In the concept said that each bawyo changes planes is a small computer, has the processor and the memory, as well as uses for to receive the contract award the input/output unit. In the modern high speed WANs bawyo changes planes by the special hardware constitution, in the early WANs bawyo changes planes, then trades the duty by the execution bawyo the ordinary microcomputer constitution. Figure 3-1 had demonstrated includes two kind of input/output interface bawyo to change planes. in the chart the first kind of connection has the high speed, connects another bawyo through the digital circuit to change planes. The second kind of connection has the low speed, with connects a computer. Hardwares detail is decided in the WAN technology and needs the speed. The nearly all point-to-point communication way applies in WANs construction, including rents the data link, the optical fiber, the microwave, the satellite channel. Many WAN designs permits the customer choice Packet switch used to connect to other packet switchesUsed to connect to computersFigure 3-1 A packet switch with two types of I/O connectors:one type is used to connect to other packet switches,and the other is used to connect to computers.3.2 Store And ForwardUnlike a shared LAN that allows only one pair of computers to exchange a frame at a given time,a WAN permits many computers to send packets simultaneously. The macrozonality package of exchange systems fundamental mode is saves the repeater (store and forward) to exchange. In order to complete the memory repeater function, the bawyo changes planes must carry on the cushion in the memory to the package. The store operation is when the package arrives carries out: The bawyo changes planes the input/outputs the hardware to place a package transcription in the memory and informs the processor (e.g. use interrupt). Then carries on the repeater (f o r w a r d) to operate. The processor inspection package, decided that which connection should deliver, and starts the output hardware equipment to transmit the package. the use memory repeater patterns system can cause the package the quickest speed which may allow by the hardware to transmit in the network. More importantly, if has many packages to deliver the identical output unit, the bawyo changes planes can wrap has saved in the memory vacates until this output unit. For example, considered wraps in Figure 2 -1 to show in the network to transmit, the supposition stand 1 two computers nearly simultaneously send out a package to a stand 3 computer, these two computers a package of transmission for switchboard. When each package arrives, in switchboards input/outputs the hardware to place the package in the memory and informs the processor, the processor to inspect each packages destination address and knew that the package sends out the stand 3. When a package arrives, if stand 3 exports just right idle, the processor starts to transmit immediately; If just busy, the processor places the package with this export related formation. Once transmits a package, this export the extraction next package and starts from the formation to transmit. The summary is as follows: the macrozonality package of exchange system use saves - the repeater technology, will arrive at switchboards package to disperse into a formation, and at appropriate time continues to retransmit forward toward the destination. This technology causes the bawyo to change planes can simultaneously arrive short-time arises suddenly the package to carry on the cushion.3.3 Physical Addressing In A WANLooking from the company computers angle, WANs operation is similar to the local area network. Each kind of WAN technology precise definition computer when has received and dispatched the data uses the frame form, and arrived at on WANs each computer for the company to assign a physical address. When transmission frame to other computer, the sender must give the goal computers address. the many WAN use level address plan (hierarchical addressing scheme), causes the repeater efficiency to be higher. The level address divides into an address several parts. The simple the level address plan divides into an address two parts: The first part expresses the bawyo to change planes, the second part expresses Lian Daogai on switchboards computer. For example, Figure 3 - 2had demonstrated assigns changes planes on the company computers two section of type level address for a pair of bawyo. the chart use a pair of decimal base system integer to express that an address, including arrives at the bawyo to change planes 2 on port 6 computers addresses for 2,6. Is expresses the address in the practical application with a binary number: The binary number some expression address first part, other, then expresses the second part. Because each address indicated with a binary number, the user and the application procedure may regard as the address integer - they not to need to know this address is the lamination.Switch 1Switch 2addressaddress2,11,2addresss address1,5 2,6Figure 3-2 Example of hierarchical address in a WAN3.4 Next-hop ForwardingThe packet switch must choose a way to transfer the contract award. If a package of destination is a direct connected computer, the bawyo changes planes sends out the package this computer. If a package of destination is the computer which another bawyo changes planes, the package should through lead to this switchboards high speed connection repeater. Must make this kind of choice, the bawyo changes planes must use package of the destination address.how does the bawyo change planes does not need to preserve arrives at all possible destinations the complete information. On the contrary, assigns the switchboard only contains to enable this package to arrive at the destination should finally to transmit as soon as under which stands (next hop) the information. The next station repeater (n e x t - h o pf o r w a r d i n g) this concept is similar to the airplane flight table. Supposes one to fly to Miamis passengers from San Francisco to discover that the route has three sections: The first section arrives at Russ from San Francisco, the second section from Dallas to Atlanta, the third section from Atlanta to Miami. The entire travels destination is the same: Miami, as soon as however stands in each airports under is dissimilar. When this passenger when San Francisco, the next station is Dallas; When passenger when Dallas, the next station is Atlanta; when Atlanta, the next station is Miami. Figure 2 - 3 have demonstrated in the package of exchange network next station repeater technology:as the figure above shows, the next-hop information may make a table. In the table each item has listed a destination address as well as the corresponding next station. When to anteversion contract award, the switchboard inspection package of destination address, searches the item which matches with it, then next station which sections out this package sending-out item. How in the chart did the example extol shows the bawyo to change planes 2 is transfers the contract awar