Is out of date, ADSL Anecdotes

ADSL (Asymmetric Digital Subscriber Line) stands for asymmetric digital subscriber line, is called a non-symmetric, is due to the realization rate is up less than 1Mbps, down less than 7Mbps. It is a home or small business can make use of the existing telephone network with high-frequency digital compression for network service providers ISP for broadband access technology. This access method so it is a non-symmetrical manner, from ISP-ended client (downlink) requires large bandwidth to support, but from the client to the ISP side (upstream) bandwidth of only a small amount can be.

ADSL principle introduced

ADSL modem and ISDN and traditional as well as the transmission medium using the telephone network. When the two ends of a pair of telephone lines were in place an ADSL device, the use of modern frequency modulation and coding, this phone line will be able to create three information channels: a high-speed downlink channel (1.5 1.8Mbps), one is the speed duplex channel, one is the ordinary telephone channel, and these three channels can work simultaneously. That is, it can get the most out of existing telephone line data transmission capacity, so users can access a telephone line not only fast-track "Surf", you can call to send a fax, call or reduced without affecting the effect of Internet . Specific work flow is: ADSL Modem encoded by the signal transmitted through the telephone line telephone office and then by a signal recognition / separator, if it is transmitted voice signal on the telephone switch, if the digital signal to access Internet.

See Figure 1, ADSL service is composed mainly of the following:



Figure 1 ADSL diagram

* ATM Backbone (ATM backbone): is the ISP to provide broadband services to the core backbone network, is the intersection of all data. Not only provides high bandwidth, and because ATM has its own advantages, making use of the channel and data exchange more efficient.

* DSLAM (DSL ATM multiplexer): This is the central office equipment to provide ADSL services. Central Office on a similar program-controlled switches.

* Telephone lines to provide services: the current ADSL services provided through the normal analog telephone line that carries voice and data services. People were asked whether the ISDN line will be converted into ADSL line, in fact, provide ISDN is a digital transmission, and ADSL must rely on analog circuit implementation.

* Voice, data separation / integrator: This is an important part of the output in the central office DSLAM ADSL central office line and voice line when the device is integrated through a transmission line. To the client and then separated by a similar device to form a data line, a voice line.

* ADSL CPE equipment (ADSL customer premises equipment): This is a user-purchase or lease of equipment to the central office. Usually ADSL Modem or ADSL Router.

Some of the problems on the ADSL

* ADSL in the end be able to provide much speed? See from Figure 2, ADSL lines using a frequency higher than the Mandarin audio line (4400kHz), up to 1MHz. Therefore, to provide 8Mbps maximum bandwidth.



Figure 2 ADSL lines over the frequency of use of 4400Hz

* ADSL there are no weaknesses? It is susceptible to interference, high requirements for the line, with the cable length increases the quality of subsequent deterioration of data transmission.

* ADSL is not an outdated technology?

In fact, the application of each technique has its surface, just as Bluetooth technology is the same as 10 meters for communication, and wireless local area network suitable for a wider range communication. I believe that, ADSL as an ordinary telephone line can transfer the technology itself has very good flexibility, that is, each ADSL phone users are directly applicable. Also for home users and small and medium enterprises do not need a guarantee by buying bandwidth of 10M FTTB access the Internet, as 10M itself is virtual, if it is the commitment rate, then ISP, ISP to guarantee the export of the Internet bandwidth, this cost is not generally Users can affordable.






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IDC how to charge only reasonable

The Internet is an innovative, industry, and it can change each to the customer, to the end consumers more benefits. Data center industry as Internet infrastructure builders and operators, one of the pace of its more representative and forward-looking. Wind at the end of Qingping, pricing model indicates the transition bandwidth of our previous views on the need to rewrite.

Actual use of resources to pay

We face from everyone I start charging for telecommunications, which in fact has been a matter of common concern in recent years, the hot, like the way the phone charges, mobile and fixed phones, etc. to determine the minimum billing unit of time, such as that the use of fixed phones, why are they only say 1 minute, or even only a few seconds, 3 minutes have to pay the money? That which must exist irrational factors.

In fact, unreasonableness not only seen in the voice communications, data communications, there is the same, or even more serious. Bandwidth of the hire, the common unit charges generally 2M, 10M and 100M of three grades, which means that one would like to use the 15M bandwidth, customers will have to buy 100M. Although many consumers a few dollars, dozens of dollars unreasonable tariff and the cry for justice, but in data communications, the user has paid much more should not pay the cost, however, no doubt sound, this is really a bit strange. As the century, vice president of Internet Data Center Co., Ltd Chang Chun by analogy, the fixed bandwidth rental costs as phone users than the number of actual telephone call payments, but must choose to play 100 or 1000 phone; in order to prevent possible The telephone service was terminated embarrassing situation, he might have to buy their own business needs above telephone number, and to pay a lot of money. So why not use the basis of his actual phone number of charges?

Width does not equal fast

At present, the telecommunications industry with CKS surging tide of change. Advances in technology to promote the traditional circuit-switched to packet-switched transfer of pace. This change is comprehensive, it also brings the telecommunications business model and fee adjustments. We are now facing some of the irrational factors that are actually content with the old rates of new business caused by incompatible way.

The current telecom operators, especially Internet data center operators usually 2M, 10M and 100M bandwidth unit receives a fixed fee per month. These figures actually refer to the server from the client to the operator connected with the backbone network bandwidth between routers, rather than any visitor can enjoy bandwidth. Some customers may have felt was not proportional to the bandwidth and access speed, this is because the Internet is a shared network, numerous nodes, the network users to access a company's Web site actually been a lot of packet nodes , any node of the delay will allow users to find the site to respond fast enough, and this delay is beyond the control of a single operator's. From this perspective, the width does not mean fast, simple bandwidth charges to the user or data center in terms of the perspective of both the existence of certain one-sidedness.

Long overdue attempt

In fact in the world, at all levels of telecom operators are trying to use the new pricing model to give customers more transparency, more flexibility and more fair price, while leading a more rational purchase and use of bandwidth. But in China, due to the lag of awareness, technical power shortages and restrictions 缃戠粶 hardware environment, pricing model of transition Cai just Kaishi, Qizhongdongzuo of a century faster Internet network Shuju 涓績. They have begun to recommend their clients use the new pricing model, that is not simply buy bandwidth based on customer receives a fixed monthly fee, but by the Shiji of data traffic charges. This requires a considerable foundation.

First, from the technical point of view, charging a fixed monthly fee simple and direct, while data traffic charges by means of the continuous flow of customers to monitor and measure, technical requirements greatly increased. But the point is still worth the trouble, because that their customers can have a clear understanding traffic, but also can know Liuliang time and space distribution of the business development and market strategy adjustment of great significance. Century is connected with MRTG (Multiple Router Traffic Grapher) software for data traffic statistics. It is a 5-minute sampling interval, and then generate a detailed chart, intuitive and clear. Some of the world famous Internet data center operators, such as AboveNet and Exodus, adopted the software for monitoring and billing. Century, while Internet use MRTG statistics also adopted the principle of the customer 5% of the peak traffic out of the baseline beyond the billing, so customers need not worry about traffic accidents caused by large transient rise in the price.

In addition to technical means to ensure network resources are also affected by the charging method in which one of the determinants. A data center operator may own the hardware environment is very advanced, fiber optic cabling used in all interior rooms, routers and switches is also the top, but it also depends on the final speed of access and backbone networks, export-bandwidth Internet connection. It's a bit like Beijing's Third Ring Road, the road itself is very good condition, light on the fast track is the four-looked, but because of the narrow exit, poor traffic flow, affecting road capacity. This network data center may prefer a fixed rate pricing model, because it can not guarantee that the final speed of access. The Century Internet bandwidth resources fairly obvious advantages, it is first approved by Ministry of Information Industry access to the national Internet Exchange (NAP) of professional IDC company, broadband access NAP with nine state-owned public peering backbone ( Public Peering). It also with China Telecom, China Unicom and China Netcom signed a commercial peering (Private Peering) agreement and the agreement with ChinaNet Internet bandwidth 922M, is by far and ChinaNet peer networking connectivity and bandwidth of the IDC's largest companies buy .

Responsibility for the data center

Chang Chun-century Internet that the Internet does not exist a real exclusive bandwidth, everything is shared, and customers are most concerned about is speed rather than "exclusive" or "shared" bandwidth. Exclusive distribution of the bandwidth speed is only one way to ensure it can not effectively control costs. Another way to non-full-bandwidth. With the highway, for example, enjoys a bandwidth as the four loop are assigned to a customer to use, although the speed is faster, but the customer has to pay the huge independent expenditures occupy four loop. In the new model, all customers can use the Fourth Ring Road, the customer traffic over the network once the peak capacity of 60% of the road will be widened. Thus, not only the customer can be assured the server response time and reduce costs.

"The new pricing model enable service providers to assume more responsibility," Chang Chun said, "It also advocates user scientific, planned use of network bandwidth, according to the actual amount paid, less pay less, use more, pay. For customers, the payment will be according to actual use of savings, and to more efficient use of bandwidth. "







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