Digital Subscriber Line (DSL)
Digital Subscriber Line (DSL) technology transmits digital data through the wires of the regular telephone network. DSL, also called xDSL, form a category of digital transmission technologies with the use of local telephone networks. Asymmetric Digital Subscriber Line (ADSL) is the widely known and used form of DSL, which transmits data over copper telephone lines in a quick and efficient way. Formerly Digital Subscriber Line was referred to as Digital Subscriber Loop, which acquired its current name due to its operation over telephone lines.
DSL uses high frequency, enabling it to be utilized in the same telephone line simultaneously, as low frequency is used by regular telephones. The typical working of a Digital Subscriber Line is by dividing the frequencies, which are utilized in a single phone line, into two main "bands." The ISP data is transmitted over the high-frequency band, which is 25 kHz and above. In lower-frequency bands of about 4 kHz and below, the voice data is transmitted. By installing a DSL filter on each phone, the higher frequencies are filtered out from the phone line so as to enable the phone to receive or send lower frequencies such as voice. The DSL modem can be simultaneously used on the line alongside the normal telephone equipment, with no interference between them.
Digital Subscriber Line (DSL) technology brings high-bandwidth data through ordinary telephone lines. The variants of DSL such as Asymmetric Digital Subscriber Line (ADSL), High bit-rate Digital Subscriber Line (HDSL), Rate-adaptive DSL (RADSL) are collectively referred to as xDSL. The telephone company (telco) offers DSL service enabling to receive data including video, audio, and graphics, at rates of up to 6.1 mbits/sec with continuous flow in data transmission. Both data and voice signals are carried over the DSL line, with the line for data transmission always connected. A signal splitter is required by most of the DSL technologies so as to split the frequencies efficiently. However, splitterless DSL (AKA DSL Lite, G.Lite, or Universal ADSL) have also come into vogue, and the splitting can be managed remotely from a central business location.
In establishing a DSL connection, a DSL Modem (Also called DSL Transceiver or ATU-R) is linked to the phone line. The other end of the line is connected to a Digital Subscriber Line Access Multiplexer (DSLAM), which facilitates the telephone line to connect to the Internet faster. The DSLAM comprises many number of individual DSL connections into a single box, and is located depending on the telephone company. The DSL modem converts the data from digital signals that computers use, into the right frequency of voltage signals to be applied to the telephone line.
The download speed of DSL services depend upon the type of DSL technology used, the service level implemented, and the line conditions. In consumer DSL services, the download speed ranges between 256 kbits/sec and 24,000 kbits/sec. While in ADSL service the upload speed is lower than the upload speed, the upload and download speed are equal in the rarely used Symmetric Digital Subscriber Line (SDSL) service. Individual DSL connections provide between 1.544 Mbps and 512 Kbps speed for downloading and about 128 Kbps for uploading data. DSL is advantageous due to the following factors:
- The Internet connection can be "always on" while also using the phone line simultaneously for voice calls
- Higher speed than regular modem
- New wiring is unnecessary; the existing phone line can be used
- The telephone company offering DSL service normally provides the modem too
The use of cable modems, satellites, and other telecommunication links are used increasingly as DSL service. Although DSL offers many benefits, there are still certain constraints that impede its application at a large scale and as a sole provider in large enterprises. The DSL connection is more efficient if the location of the company is closer to the provider′s central facility. Distance from the central location gradually weakens the signal. Receiving data from the Wide Area Network (WAN)/Internet is faster than sending data. The DSL service cannot be availed everywhere. Companies that require continuous Internet connectivity resort to using multiple data lines, wherein different services can be used.
FatPipe Networks (www.fatpipe.com), a technology solutions provider, is the provider of highly redundant, reliable and high-speed Internet access for mission-critical applications. A robust WAN determines the business continuity in companies and hence FatPipe Networks, the pioneer of router clustering technology is sought for its technology products. FatPipe makes use of DSL technology and brings in efficiency using its multiple options for load balancing datalines. It clusters the routers of multiple datalines regardless of the quality or the speed of the DSL lines. It ensures that the data flow is smooth and uninterrupted in the event of failures. FatPipe technology takes disparate WAN connections and dynamically load balances across the lines and fails over traffic to available lines should one of the connections fail. FatPipe′s technology devices also provide features such as dynamic load balancing, Quality of Service (QoS), data compression, enhanced VPN security, and VPN encryption.
