What does a DSL mean? What does Mbps mean?

Digital Subscriber line or DSL is a technology that provides digital connectivity via copper or local telephone networks. Its history dates back to the 1988, when an engineer at Bell Labs designed a method that allows digital signals to be loaded into unused bands on a telephone line, which provides data communication on a regular telephone line without compromising the voice service. But Bell's management is not enthusiastic about this, because if users install two lines will bring more profit. The situation was not improved until the late 1990 when cable companies started selling broadband Internet access. When it became aware that most users would absolutely abandon the installation of two phone lines to access the Internet, Bell was moving out of the DSL technology that they had discussed for 10 years to compete for cable network companies ' broadband market share.

By 2005, DSL technology was a major competitor for cable modems providing broadband access to home users in Europe and North America.

Working principle

Telephone system design, mainly used to transmit voice calls, for economic reasons, the telephone system designed to transmit frequency range in the range of 300Hz to 3.4kHz signal (although the human voice can be 15kHz, but this range is very easy to identify each other).

However, the copper cable to the end-user of the local telephone network can actually provide higher bandwidth, at least from the lowest frequency to 200-800khz, depending on the quality of the circuit and the complexity of the device (it is generally considered that the fewer connectors between the end-user splitter, the better the bandwidth, the transmission passing through the environment, The smaller the electronic interference, the greater the bandwidth of the line.

The DSL service successfully overcomes the difficulty of transmitting large amounts of data on the audio band by using the additional bands of the telephone line (see Shannon's theorem).

DSL services typically retain 0.3-4khz this range of bands to voice services, which is known as the common old-fashioned telephone service ({lang|en| POTS}) to transmit data using frequencies outside of this range.

The DSL connection is established between the user device DSL modem and the telephone switch, and then the switch establishes the connection through some other protocol to the (typical) ISP that the user really wants to connect to. This is different from the normal public telephone network and the user end-to-end telephone connection. If the user is more than 5.5 km away from the switch, the quality of the service will fall sharply due to interference.

Equipment

User Terminal equipment is a DSL modem. It converts binary data to digital electrical pulses, allowing the signal to be transmitted within the frequency band of the digital audio stream.

In addition, if users use old-fashioned phones on the same line earlier, a passive electronic filter (many called "Filters", "splitters" or "Taps") may also be added (which might help improve the DSL terminal signal to suppress the echo signal). This ensures that DSL modems and telephones only accept the signals they are designed to use. If the "wires-only" service is used, the user can insert the filter into an existing telephone slot, or the DSL operator may install it.

Using the Digital subscriber line access Multiplexer (DSLAM) at the switching station, the data on the DSL circuit is aggregated and forwarded to other networks. It can also isolate the voice part.

Protocols and configurations

Many DSL technologies are implemented in low-level bitstream ATM tiers to ensure that different technologies can be implemented on the same link.

DSL devices can create a network bridge or a routed network, in bridge mode, a group of users ' computers can be conveniently connected to a subnet. Early devices use the DHCP service to assign some configuration details such as the IP address of the network card, authentication based on the MAC address, or assigning a host name. Later devices typically use PPPoE (PPP on Ethernet) or PPPOA (point-to-DOT protocol on an ATM network), authenticate with a user name and password, and then use the PPP principle to assign network configuration (IP address, subnet mask, gateway, DNS, etc.)

DSL technology

The Reach range (from the telephone Exchange center to the user's line length) is inversely proportional to the data rate, and technology like VDSL can only provide short-distance links (typically fttc-light to the roadside).

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Mbps This is supposed to be the broadband speed that your computer can support (Internet speed units)
100Mbps = (100÷8) MB/s is 100Mbps Internet bandwidth, the maximum download speed is 12.5mb/s