Upstream and downstream speeds of ADSL bandwidth

Source: Internet
Author: User

How fast should the ADSL bandwidth rate go up, the downstream bandwidth rate and the uplink and downlink speed be? Many users have reported that the download rate of ADSL does not reach the nominal 5 12 K. After the network is connected through ADSL, a download speed indicator is displayed during download, the download speed shown above is generally about 50 KByte/s! This is a misunderstanding caused by unclear conversion relationships. First, we understand that Asymetric Digital Subscriber Loop (ADSL) technology is an asymmetric Digital user Loop technology that uses an existing pair of telephone copper wires to provide users with asymmetric upstream and downstream transmission rates (bandwidth) upstream (from the user to the network) can reach 640 Kbps; downstream (from the network to the user) can reach 6-8 Mbps. It is a broadband access technology targeting the asymmetry of online and downstream data streams in the Internet and on-demand video services. Uplink: transfers information from the user's computer to the network. (Note: The uplink speed of Xiamen ADSL is 384 KB.) downlink: Refers to browsing WWW webpages and downloading files. The maximum speed is 8 Mbps. 1. What does 512KADSL mean? 512 K = 512 Kbps = 512 Kbits/s = 64 Kbytes/s 2. What does 64 Kbytes/s mean? The true meaning of this 64 K is "maximum download bandwidth exclusive to individual users". So what does this mean? I wonder if anyone has noticed the Application Form for installing China Telecom ADSL, the above bandwidth projects are written at least kb and "no higher than 8 MB". That is to say, we can have a maximum of 64 KB of proprietary bandwidth under normal circumstances. Note that the value is "no higher than". That is to say, in many cases, our private bandwidth may be less than 64 KB. Why? In fact, China Telecom's ADSL is running on the ATM, and the bandwidth from the ATM to the chinanet edge router is 155 M. Each edge router can connect 3000 users. If these users access the Internet at the same time, in fact, each user only has 50 kbit/s of bandwidth, that is, 7 Kbytes/s. In addition, with the attenuation of the router, the speed of the common modem may end up. Of course, the above is just a hypothetical situation. After all, it is almost impossible for 3000 people to connect to an edge router at the same time. China Telecom will not allow the router to be connected at full load, making the speed drop so huge. However, 64 K is undoubtedly the highest private bandwidth. 3. Why does my 512KADSL download speed reach kb or more? We figured out that 64 K is the maximum private bandwidth, but not equal to the maximum bandwidth. In fact, when dialing ADSL, we have allocated a download bandwidth of approximately 8 Mbps, that is, 1 Mbytes/s, however, China Telecom limits our VPC bandwidth to a maximum of 64 K, so when there are few vro connected users, we can obtain a portion of the shared bandwidth that exceeds the proprietary bandwidth (obviously, telecom does not need to idle the bandwidth ), of course, the K rate of ADSL can never reach the download speed of 1 Mbit/s by occupying the shared bandwidth, because after all, there are still many people surfing the internet at the same time, moreover, China Telecom certainly has some load balancing mechanisms. 4. Influence of ADSL upload speed on download TCP/IP rules. Each packet requires a back-to-back of acknowledge information. That is to say, a reply to the received data is required for the transmitted data, in order to determine the subsequent transmission speed and whether to re-transmit the lost data. Part of the upstream bandwidth is used to transmit the acknowledge data. When the upstream load is too high, the transmission speed of acknowledge data will be affected, and the download speed will be affected. This has a particularly significant impact on Asymmetric Digital loops, that is, connections with upstream bandwidth much less than the download bandwidth. Some experiments have proved that when the upload is full, the download speed is about 40% of the ideal speed, which can explain why many friends get a higher download speed when using BT to download. In this case, we cannot limit the speed of all people, because it is unrealistic and unscientific for ADSL users. The appropriate speed limit is correct. 5. The speed of ADSL gradually decreases as the connection time increases. As mentioned above, the maximum download bandwidth of 8 Mbps will be set up when ADSL is re-called. This bandwidth will never change! However, in fact, because of the noise detection mechanism of ADSL, if the line is not good, the connection established at the beginning is obviously impossible to reach the theoretical value. It may end with 5 Mbps, and the bandwidth will not change. So why is the speed of ADSL getting slower and slower? This is because the ADSL connection may be interrupted at any time even if the user does not turn off the modem power. For example, when the communication status deteriorates due to increased noise and frequent errors occur. After the link is interrupted, the system will immediately re-Debug and re-confirm the link. However, if the noise that causes the link interruption still exists at this time (this is usually relatively large), The relink speed will be lower than the original speed. Since the link speed determined in the debugging is fixed, even after the noise disappears, the link speed will not increase. The longer the ADSL modem is used, the higher the possibility of such a situation, and the slower the connection speed. At this point, if the user restarts the modem, the link will be re-established, and the speed may be improved accordingly. This knowledge can be used as a countermeasure to solve the problem after the link speed is reduced. Of course, the above situations are only discussed based on the ADSL connection itself. The actual situation also includes the Internet situation, website response, and so on. After learning about the above knowledge, you may be enlightened. The original KB is not kb, only 64 KB ~~~ You cannot download KB per second. The most important thing to pay attention to when realizing the high speed of ADSL is that the user host must be configured to ensure the speed of ADSL access on the hardware. As the saying goes, "without Diamond, do not take porcelain ware live". If the processing performance of personal computers is high, you can quickly run Web browsers and email software to speed up the Internet. If a 1 Mbps ADSL instance is installed, but a personal computer can only be installed with Windows 95 or 98, it will certainly feel slow. In particular, if the memory is only 64 MB or 128 MB, broadband is just as useless as a hero. If you update your PC and the operating system can use Windows XP, the access speed of natural broadband will increase. In addition, Windows XP requires more memory than the original Windows system. We recommend that you have at least MB of memory. If you do not have the ability to update your PC, you can increase the memory, as long as you increase the memory, you can feel the speed is improved. In addition, the ADSL modem used for broadband access must support high speed to ensure the access speed. There are also some ways to maintain ADSL on the hardware, such as shortening the telephone line between the telephone outlet and the ADSL modem as much as possible, which can minimize the line loss, in this way, the distance between the telephone outlet and the ADSL modem can be shortened, and the network cable connecting the modem to the PC can be extended. In addition, do not place office devices (including personal computers) that emit electromagnetic waves near the ADSL modem, or household appliances and mobile phones such as televisions and refrigerators, which may interfere with the modem. People familiar with computers should know that the performance of personal computers depends not only on their own hardware base, but also on the software optimization of computers in the future can become the driving force for the Network to fly. On the one hand, the system's own performance can be improved through a number of "extensive" system optimization software, such as the CPU vacancy rate, memory usage, and hard disk fragment cleaning, can be improved through the power of software. On the other hand, some special software can also be used to optimize the broadband access connection network and randomly adjust some network connection settings to achieve the best connection effect.

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