IPsec

The IP level is in the TCP/IP network most essential one, IP takes the network level agreement, its safety mechanism may provide the transparent cover type safekeeping of security to its upper formation each kind using the service. Therefore, the IP security is the entire TCP/IP security foundation, is the network security core. IPSec is the present only one kind can provide the safety control for any form Internet correspondence the agreement. The IPSec permission provides the security which one by one data stream or connects one by one, can therefore realize the very careful safety control. Regarding the user, then may regarding different need to define the different rank safekeeping of security (i.e. different protection intensity IPSec channel). IPSec was the network data transmission provides the data confidentiality, the data integrity, the data origin authentication, anti-to rebroadcast and so on safe service, caused the data when through the public network transmission, did not need the worry to monitor, to tamper with and fabricates. 　　IPSec is through uses each kind of encryption algorithm, the confirmation algorithm, the seal agreement and some special safekeeping of security mechanism realizes these goals, but these algorithms and the parameter are the preservation in carry on IPSec correspondence both sides SA (Security Association, security alliance), when in both sides SA establishment match, the both sides might carry on IPSec to correspond. 　　Has mainly used the IPSec technology in hypothesized private network (VPN).

Virtual Data Networks

The telecommunication domain is promoting many organizations to need to use between the long-distance place establishing the virtual data network the technology, these technologies mainly use in the campus environment, the urban region, the macrozonality, or the global region. The virtual data network all place all systems carried on the entire interconnection for the organization to provide compared to having rented the owner-use circuit and the establishment private network expense low many ways. Its goal is provides local area network's speed on WAN. 　　The packet switching service, for example the frame relay and the exchange type many megabit digital data services (SMDS, is providing the virtual data networking capability and to owner-use circuit's replacement demand. These services provide have the microsecond exchange capacity band width. The customer only need use for them serves carries on the payment. These services by long-distance telecommunication bureau, for example AT& T, MCI, and USSprint, as well as value-added network (VAC), for example CompuServe, Infonet and Tymenet and so on provide. Circuit switching service, for example exchange - 56, exchange - 384K (AT& T), exchanges T1 and exchanges T3, now with these telecommunication services equally also very popular use few expenses, now some very small place may also include in a very big business data network. 　　Moreover, individual demand is not now high, this is because these telecommunication services have processed the exchange element. Through the packet switching service, sole “the data pipeline” transmits the data from the customer place to the telecommunication bureau, then transmits again from this telecommunication bureau to other places. However, the network management personnel considered when entrusts with many network managements a public telecommunication bureau produces loses the control the question, although these telecommunication bureaus can also provide about these service suitable management information.

What is VPN

VPN's full name in English is the "Virtual Private Network", is translated through the "virtual private network." As the name suggests, virtual private network, we can understand it as a virtual enterprise out of line. It can be a special encrypted communication protocols in the Internet connection in different places at two or more enterprises to establish a network between the proprietary communication lines, is set up like a line, but it does not The real need to lay fiber optic cable like the physical line. It can be compared to apply for telephone line, but not for the cost of laying lines, there was no need to buy routers and other hardware equipment. VPN router technology used to be one of the important technologies currently in the switch, firewall software, such as equipment or WINDOWS2000 also features VPN support, saying, VPN is the core of the use of public networks in the establishment of virtual private network.
Virtual Private Network (VPN) is defined as through a public network (usually the Internet) to establish a temporary and safe connection is through a confusing network of public security, stability of the tunnel. Virtual Private Network is the expansion of the Intranet. Virtual Private Network can help remote users, branch companies, business partners and suppliers with the company's internal network to connect the establishment of credible security and guarantee the security of data transmission. Virtual private networks can be used for the growing global mobile users Internet access in order to achieve a secure connection; corporate Web site can be used to achieve secure communications between virtual private leased circuits, for cost-effective to connect to business partners and customers secure Extranet Virtual Private Network. We combine the following site related to Cisco and Microsoft VPN on the articles you for this information, more and a wealth of relevant aspects of our content will be added for days after.
For different user requirements, VPN There are three solutions: remote access virtual network (Access VPN), virtual enterprise network (Intranet VPN) and the expansion of enterprise virtual network (Extranet VPN), the three types of VPN with traditional long-distance Access network, enterprise and corporate Intranet network partners and corporate networks posed by the Extranet (external expansion) corresponds to.

Basic Knowledge of Proxy

English name: Proxy Server,
Function: Deputy users access to network information. The image that it is a transit point for the network information.
Under normal circumstances, we use the Web browser to connect directly to other Internet sites to obtain information network, is directly connected to the purpose of the site server, and then by the purpose of the site server to send back information. Proxy server is in the range of browsers and Web servers between another server, it has been following the browser rather than directly to the Web server to get back to the page, but issued a request for a proxy server, the signal will be sent to the proxy server, By the proxy server to get the browser and the information they need to send to your browser.
Www.51an.com in the URL box you want to visit the Web site address, click agent will open a new browser window to link a proxy server, you can wait a few seconds, if the link can not appear at this time, and other server error, please above Try to choose the other server, proxy server because of the large consumption of resources, and there are time-sensitive, so sometimes can not open, we must try several times a proxy server. Automatic Updates can be used day-to-date server.
Most of the proxy server has a buffer function, just like a big Cache, it has a lot of storage space, it will continue to get new data stockpile to its local memory, the browser if the requested data in it Machines already exist on memory and up-to-date, it will not re-check the data from the Web server, and the memory directly on the data to the user's browser, which can significantly increase the speed and efficiency of the browser.
More importantly: the proxy server is the Internet gateway provided by the link level is an important safety feature, which is mainly in the open systems interconnect (OSI) layer model of dialogue in order to play the role of the firewall.
For these reasons, most of the proxy server is used to connect INTERNET (Internet) and INTRANET (LAN). At the national level, the so-called China Public Multimedia Information Network and Education Network is an independent state-level large-scale local area network, and is isolated from the Internet. For a variety of needs, some groups or individuals in the network between the two set up a proxy server, if we know the address of the proxy server, you can use it to reach Web site abroad.

Why has to open the proxy server?

1st, connects Internet and Intranet acts as firewall (firewall): Because all intranet user through agent server visit outside time, the mapping is only a IP address, therefore the outside cannot visit the intranet directly; Simultaneously may establish the IP address filtration, the limit intranet to the exterior access authority; Moreover, two interconnection intranet, may also carry on the interconnection through the third party agent server to exchange the information. 　　

2nd, saves the IP expenses: If front says, all users only take IP outward, therefore does not need to rent the excessively many IP addresses, reduces the network the maintenance cost. Thus, in the confined bureau has not been possible to connect outside the net with the outside net connected numerous machine through in net's agent server, reduces the expense greatly. Certainly also has its disadvantageous one side, if many network hackers hide their real IP address through this method, but escapes the surveillance. 　　

3rd, enhancement access speed: The itself band width is small, through band width big proxy and goal main engine connection. Moreover the usual agent server establishes a big hard disk buffer (possibly to reach as high as several GB or bigger), when has the outside information through, simultaneously also preserves it in the buffer, when other users visit the same information again, then takes out the information directly by the buffer, passes to the user, thus achieves the enhancement access speed the goal. Uses the agent server to have these advantage? 　　In our country, the surfer divides into 163 and 1692 kinds. 169 users divide into three kinds (throughout the land classification caliber possibly different), a kind of user has outside the net the power, may enjoy internet's all services directly; Another kind is the registration user, the use registration account number surfer, the third order is called the GUEST user, uses account number surfer which male uses, adopts the calling to record spends the system. Does not have outside the net the power user's moderate cost, but can only with the Chinese multimedia information networks in (the IP address by 10 openings) website connection. So-called \ " Has a good swim network world \ " But is the sentence empty talk! You have experienced whether also such pain: Because the bill limits, every day can only pace back and forth on 169, raises is looking at 163 pile of internet information, the resources and the free western-style food, the saliva cocurrent ......Ya! 　　Now has been good, had the agent server, we may go abroad willfully, obtained 163 services with 169 inexpensive prices! Just like front talks about, if we knew that these agent server's address, may use it to arrive at outside the net the net, from 169 arrives 163. What Arab League Z searches and provides is the completely free agent server address, does not have any limit completely, cannot pay any extra cost! On INTERNET free email, main page space, ICQ, FTP, each kind of information resource ......Opens entirely is coming! You still only need pay 169 inexpensive surfer expenses! Moreover, because the goal server can only find out agent server's IP which you use, therefore also has some self-evident advantage, for example was not easy in the chatroom to kick out easily by the human! The use proxy's surfer speed is what kind of? 　　The agent server in fact is in a network high speed buffer, after it accepts the terminal application, to the network server proposed first requests document which and accepts transmits, then transmits the terminal again. When information first process this kind of stopover station, the speed possible more or less to have given a discount. 　　But the agent server is in itself equal to a high speed buffer, if you must glance over the homepage some time ago some people had glanced over, moreover on the agent server preserves time newest record, the agent server does not need to arrive at on the main engine to apply for the data again, but is directly the homepage transmission for you, like the speed in the quite straight union the goal server quick many! Specially the agent server itself has the high speed export, but the server scale the very high words, the influence nearly may neglect to the speed do not record! After the test, the good proxy from sends out applies to receive the document the time less than 10 milliseconds, generally also only then 0.5-1 second, moreover the speed may achieve 5-6K. From the actual operation, cannot distinguish the use proxy nearly and directly with 163 differences, certain areas will also present 169+ agent server to quickly in 163 phenomena! 　　Certainly, if the agent server incorrect words, possible on and so on a several minutes page not to have been able to demonstrate completely, you can not but switch off the browser multimedia and other functions, facing an arid network world! What the home station goal is as far as possible is you provides quickly the better agent server, has a look, to guarantee that frequently you have the harvest greatly!

Uses of Proxy Servers

In the day-to-day network, there are many uses, here we are familiar with some of the role of the summary and analysis, classification:
First, sharing network
The most common is to use a proxy server may be shared online, many people unconsciously in, for example, through sygate, wingate, isa, ccproxy, NT systems bring their own network sharing, and so on, can provide enterprise-class file ease Survival, reproduction and address filtering, and other services, to make full use of the limited export of local area network bandwidth to speed up the network within the user's access speed, can be solved only with a line of a IP, IP resources, with a lot of local area network for Internet access function, as well as A firewall, network and outside the quarantine network, and they provide a network to monitor and record the information transmission function to enhance the local area network security, and easy to manage users on the Internet.
Second, the visit to Deputy
Visit the Web site to speed up the pace in the emergence of network congestion or failure, through a proxy server website purpose of the visit. For example, A visit to site C, but A to C network problems can bypass the assumption that B is a proxy server, A through B, and then from B to C. You will recall that a few months ago, the network time is not normal, basic access to foreign sites can not, such as GOOGLE, YAHOO, and even the CCF are unable to visit, was very anxious. The results through a proxy server, can be found in the visit, good speed, in such circumstances, the proxy server will be able to play a big role. There is also a type of proxy server to back up a considerable number of cache files that if we visit by the current data in the proxy server's cache file can be read directly without having to re-connect to a remote Web server. In this way, to accelerate the pace of the visit.
Third, to prevent attacks
To hide their true address information, but also to hide their own IP, to prevent attacks by hackers. By analyzing the designated IP address, users can query to the current location. For example, we see that in a number of forums, the forum clearly marked the location of the current users to post, which is in accordance with the Forum members log on at the time of the IP address resolution. Weekdays, we have the most commonly used version of IP significantly QQ, "sending messages" window, you can view each other and resolve the IP location. When we use the proxy server corresponding agreement, will be able to reach their current location of the hidden purpose of the address.
Fourth, limit break
Proxy server can also break through the network restrictions. For example, Internet users on the LAN port, the purpose of the site, the agreement, games, instant messaging software, and other restrictions, can break through these constraints, I can see this message, how to break through local area network for Internet users will not repeat some of the restrictions. For example: GOOGLE We all like to use, in fact, to GOOGLE a function somewhat similar to the proxy server functionality, is a snapshot of the page, the site is frequent changes in address or Web site clearance, site of the server broke down, or has been updated But we still have to check before very useful information on the web page snapshot of the use Paishang, Google with its complex and fully automated search methods ruled out any man-made factors on the search results, to ensure that the page rank of an objective and fair , Google can easily, honest and objective to help you find valuable information online. GOOGLE has a massive database, if can not find server, Google's page snapshot storage may also help in an emergency. Although the page snapshot of the information may not be up-to-date, but a snapshot of the page to find information than in the actual pages much faster, at this time can be encrypted proxy access Google, and then visit its website snapshots to help in an emergency.
Fifth, to hide the identity of
Proxy server is hacking basic knowledge, the hacker's activities, many through a proxy server, such as scanning, spying on the local area network within the machine to carry out infiltration, hacker attacks in general are a lot of transit-class springboard to attack the target machine. To hide the identity and ensure their safety.
Sixth, speed
Increase the download speed to break through the download limit. For instance, some Web site to download the resources to do a thread-IP restrictions, which can be used when the conveyor belt audio-visual, multi-threaded set for each agent to set up a thread. IP restrictions for a breakthrough in the situation very well, as long as a different proxy server, you can download at the same time a number of resources to apply from the WEB and FTP download. But if there is a forum of resources, each user an account and a restricted account a IP, proxy server could not break through on. As an example, here we are, telecommunications users on the movie Web site can not be Unicom, China Unicom users of telecommunications can not be on the film site, as long as the situation of the telecommunications Unicom to find an agent, IP address Unicom is on the line. Unicom, a telecommunications agent to find. Will be able to download movies to their film. Education Network through a proxy server can leave the country without authority or permission to visit a section of the IP-related computer resources.