Content distribution technology has been widely usedIDCService ProviderApplications such as Adero, CacheWare, Exdous, Digital Isand, Mirror Image Internet, etc.According to Forrester Research InstitutePage VisitsAbout 600 million times/day, 48% of page visits are rented by themAkamaiCorporateCache serverTo complete.It can be seen that the content distribution technology not only brings the advantage of visiting speed to websites adopting this technology, but also providesValue added servicesIDC service providers bring considerableeconomic performance。The foundations of ChinaNetwork operatorIt has also begun to gradually establish and provide various forms of CDS.1 CDS technology is well known,ISPInternet bandwidth provided and website access bandwidthNetwork delayIt is the main factor affecting the speed of Internet access.While effectively solving the problem of Internet bandwidth, experts are also studying how to makeWeb serverGet as close as possible to customers everywhere, so as to reduce thenetwork nodeTo shorten the networktime delayThe purpose of.
There are two main solutions to shorten the "distance" between websites and customers.
Scheme I
cds
Off siteimageThe service is realized by updatingData CenterThe domain name record in the user's DNSWANload balance Device set as userapplication server Designated Authorization forDomain name resolutionThe server, so that when an Internet client visits the website, the WAN load balancing device will receive the domain name resolution request from the Internet client, and "indicate the way" for the client to visit the website nearby according to a certain load balancing algorithm.
Scheme II
Content distribution technology combines computer caching technology and distribution technology to distribute cache servers on major backbone nodes of the Internet. At the same time, it uses load balancing technology of other WAN to enable customers everywhere to visit the cache server closest to themselves when visiting the site, so as to get the fastest response.The "closest" is the networkdelay time minimum.
Technology involved
CDS system adopts different technologies according to different links, mainly involving the following four technologies.
⑴ WAN load balancing technology.
Enable Internet clients to access the cache server nearby, thereby reducingNetwork Delay 。WAN load balancing technology works according to the following principles·The WAN load balancing device queries thestatus information ；·Before accessing the service, the client first initiates a domain name resolution request to the WAN load balancing device·WAN load balancing equipment will be the closestIP addressReturn to the client as the domain name resolution result·The client requests access to the nearest node according to the obtained IP address;The nearest node responds to the client's request.
⑵ Local load balancing technology.
Used for load balancing andHigh availability。The load balance of the cache server group is realized on nodes around the country, which not only ensures the redundant design and high availability of the cache server, but also can be based on the polling method orresponse timeTo share Web requests from clients.
⑶ Cache technology.
By deploying on the IDC front endCache serverAnd reverseproxy pattern, which can speed up the response time of the server.The function of the cache server is to save the content accessed by users in the server so that other users can get it from the nearest cache server when they access the content again, thus reducing the response time of the server.The reverse proxy mode is a "pull" technology, that is, the content requested by the user is cached immediatelyServer nodeWhen does not exist in (that is, when the user accesses the content for the first time), the cache server will download it from the source Web server.In other words, the cache server is a passive way. Without user access, the cache server will not actively save relevant content in advance.
The content distribution and management technology can actively and timely update the content of the cache server, so that the content of the cache server is consistent and synchronized with the source Web server.This method is more effective for websites with frequently updated content or large webpage files.Content distribution and management technology is different from reverseProxy CacheA new technology of technology.Content distribution and management technology is a "push" technology.It mainly includes content distribution andContent managementTwo functions.
·Content distribution function: once the content of the source Web server is updated, the content distribution system will actively "push" it to the cache servers distributed around the country, so that the content of each cache server is consistent with the source Web server;Or actively distribute the content in the source Web server to cache servers in different places during a set period of time or when the network traffic is low, so that users who visit the new content or updated pages of the website do not have to wait too long for the cache server to temporarily download new page content.
·Contentmanagement function: Also called "log gateway".It is mainly used to collect data from distributed cache serversWebsite content。Access records of pages and Web objects, and centralized supervision.Statistics and analysis of the current status and performance of all cache servers for effective managementCDN。When the website content changes, the content distribution system can automatically delete the expired content in the cache server on a regular basis.
Scheme comparison
RemoteMirror siteScheme, each website company can independently chooseUser groupSet up mirror sites in large regions.However, this scheme needs to build the same system as the original server in the remote data center, and pay the correspondingHostingcost.Therefore, the initial investment is large, the maintenance cost is high, and with the increasing number of remote mirror sites, the cost will rise straightly.The adoption of CDS scheme is beneficial to ISPICP, IDC, andend userEtc.For end users, CDS shortens the waiting time for their access and reduces the cost of Internet access;For ISPs, because most of the users' Web requests are responded by the local cache server, bandwidth resources are saved for ISPs;For IDC, content distribution service is avalue-added service Provide it to website companies to gain new profit growth points for IDC;More importantly, CDS is improving the websiteCustomer satisfactionAt the same time, it also reduces the load on the source Web server of the website to a certain extent, and reduces the cost of building and maintaining remote mirror sites in different places.comandEnterprise websiteWe are happy to rent this service.Content distribution technology is an important supplement to network acceleration technology, but it is not the only form.The content distribution service and remote mirror service have certaincomplementarity, different services can be used for different users.For example, for large websites with considerable strength and scaleTarget customer baseSelect domestic or international focuskey cityEstablish your own remote mirror site to ensure the high availability of the entire website system on the WAN;CDS mainly faces the needs of small and medium-sized websites, or large websites in non central cities, so as to improve the access speed of various places with less investment and maintenance costs.
Establish principles
The establishment of CDN must meet the appropriate conditions.First, there should be a rich Internetnetwork resource, including network coverage, domestic inter network bandwidthInternational export bandwidthEtc;Secondly, there should be a certain number and scale of IDC in all places.For those with various scales nationwideIDC operatorFor example, we can use WAN load balancing, LAN load balancing, cache servers, content distribution and management equipment in the data centers of cities covered by CDN to form a CDN covering major cities across the country.In principle, CDN should be easy to configure, manage and maintain, with strongScalability、usabilityAnd performance.In addition, the whole system should have a strongFlow statisticsAnd condition monitoringManagement ability。
In order to expand the domestic CDN to foreign countries, we can consider cooperating with overseas operators to establish an overseas CDNContent Distribution Network。At the same time, it can also cooperate with the national standard CDN that has established a global CDN to extend its network to major cities in China.In this way, domestic users can visit well-known foreign websites at a high speed, and foreign users can also visit excellent Chinese websites at a high speed.The specific cooperation mode needs to be based on the networkInvestment amountAnd market demand.At the same time, when setting up the content distribution system, special attention should be paid to ensure that this content distribution system can have a certain degree ofcompatibilityThe system should support the international mainstream content distribution service organization alliance as far as possible.
testing software
Announce
edit
GSM/GPRS/Edge road test software, mainly includingdata acquisitionAnd background analysis function, which can support multipleMobile phone testwirelessdata service Test functions, such as MMS, Kjava
Credit default swap is a kind of tradable policy with floating priceLoan riskGuarantee.
ISDA(International Swaps and Derivatives Association) established standardized credit default in 1998Swap contractAfter that, CDS transactions have developed rapidly.The emergence of credit default swaps has solved the liquidity problem of credit risk, making credit risk similar tomarket risk It also conducts transactions, thus transferring the risk of the guarantor, and reducing the difficulty and cost of corporate bond issuance.
The content of loan default insurance is:
Theoretical process
definition:
A: Applicant
B: Lenders (banks or other financial institutions)
C: Insurance provider
A applies to B for a loan, and B lends to A for interest. The money lent out always has risks (such as A's bankruptcy and inability to repay the interest and principal). At this time, C will come out and C will make an insurance commitment to B for this risk, provided that B pays a certain amount of insurance premium to C every year.If A goes bankrupt, C will compensate B for the losses suffered.
Actual process
definition:
e: Target bonds of CDS or corresponding packaged loans
f: CDS purchasers (financial institutions can only haveCBRCApproved commercial banks)
g: CDS counterparty, CDS seller (financial institutions can only be commercial banks with CBRC approval qualification in mainland China)
stayCDODuring the transaction, the underlying bond of the CDS is e,The CDS specifies the amount of the subject-matter bond insured and the amount of the insured part that the CDS buyer f should pay to the CDS seller g (i.e., the CDO buyer) every year. If the subject-matter bond e corresponding to the CDS does not default, the fee from f to g will become the profit of g; if e defaults, the amount of the default part will be paid by g to f.f. G As CDS counterparties, neither of them needs to hold e.Therefore, CDS is also a kind of bet contract. The bet content is whether the underlying bond e corresponding to CDS will default.
Credit default swapIt's a newFinancial derivatives, similarinsurance contract 。The creditor sells the debt risk through such a contract,contract priceIt's the premium.If the purchase of credit default swap contracts is priced too low by investors, whensubprime When the default rate rises, this "premium" will rise and then increase in value.
CDS（Credit default swap）It is a kind of transaction between two counterpartiesDerivative products, similar to forBond defaultInsurance for.CDSpurchaserUsually, payment is made to the seller to purchase certain bonds. If the seller defaults, the compensation can be obtained from the seller. The contract may last for one to five years.The price is expressed in BP, and the higher the price is, the more likely the two parties think the bond will default.1000 BP is equivalent to 1Standard contractAn annual premium of $1 million is required for bonds of $10 million each year.
CDS is also often used by hedge fundsinvestment bankIt is used to bet whether a company will go bankrupt in the future, while the traders do not really hold the bonds of a company.American CDSmarket size Huge, covering a bond and loan market of up to $62 trillion.
In the CDS contract, the CDS buyer regularly pays a certain fee to the CDS seller, which is generally expressed as a fixed base point based on the face value.If notCredit subjectEvent of Default, the CDS seller has no cash outflow;Once the credit subject defaults, the CDS seller is obliged to compensate in cashface value And after the event of defaultBond valueOr purchase bonds held by CDS buyers at face value.The CDS seller canLead underwriterOr a third party such as a commercial bankInter-bank marketOr other markets to transfer their ownGuarantee risk。
staybonds issued by an enterpriseIntroduced in the releaseCredit default swapIt can achieve a win-win situation for enterprises, CDS buyers and sellers.For enterprises, issuing corporate bonds with CDS can not only reduce the threshold for bond issuance, but also get rid ofBank guaranteeAnd is conducive to improving thecredit rating , lowerfinancing cost 。From the perspective of CDS buyers, by paying a certain amount of fees, enterprises can effectively avoid credit risks and obtain stable income.From the perspective of CDS sellers, the company realizes its own income by charging corresponding fees, and can hedge the guarantee risk by selling CDS.
At the same time, the introduction of default guarantee swaps in corporate bond issuance will help promote China'sfinancial marketDevelopment and improvement of.First, CDS transferredbonds issued by an enterpriseThe guarantee risk of the banksystem risk Decline, thus ensuringBank assetsSafety;Secondly, CDS promotesChina bondsDiversification of varieties enrichesbond marketInvestment products of, forMarket supplyDiversified investment tools can meet the needs of investors with different risk preferences;Thirdly, CDS will play a positive role in China's innovation of financial products, the development of real credit products, and the market's attention to credit risk pricing.Its transaction will realize the transfer of credit risk of fixed income products between buyers and sellers.In the transaction, the buyer of CDSUnderlying assetsA certain proportion of the nominal value shall be paid to the Seller regularly until it is due or the specified event of default occurs.The Seller shall pay the face value of the underlying assets to the Buyer when the event of default occurs or on the due date.
Related Introduction
Announce
edit
cds
CDS (Credit Default Swap) business has been officially approved, and relevant transaction guidelines will be released in the near future.
Of course, this news did not get enough attention from ordinary investors.CDS is still strange to Chinese investors. This derivative tool once triggered the US in 2008financial crisis。[1]
Initial modelderivativeWhen the tools came out in the United States, evenhedge fund The manager doesn't know what it is for.Wall Street designs a product, and always deliberately says it is very complicated, so as to show that it is very good.
Wall Street's interpretation: CDS refers to the agreement reached between the two parties that the buyer of credit protection will pay credit protection fees to the seller of credit protection in accordance with the agreed standards and methods within a certain future period, and the seller of credit protection will provide the buyer of credit protection with one or more agreed reference entitiescredit risksProtected financial contracts belong to the contract categorycredit risk mitigation 。
In 2021, with "surging"Arithmetical forceCDS first cloud pan rendering with the theme of "Rendering the Vision"New product launchstaySuzhouSuccessfully held.With edge clouds and exclusive clouds as the main form and GPU computing power as the main core, the Star Map Cloud Computing Power Platform will deploy more than 40 computing power nodes in nearly 30 provinces across the country, which can cover major provinces and more than 80% of the population in 15 seconds, so as toDeep learning、AIThe calculation business mainly includes calculation and over calculation.[2]
