The DSL (Digital Subscriber Line) technology allowed the fast growth of the Internet and popularisation of on-line services. The classic modem connection (dial-up Internet access) provides the 56 kbps speed. It also blocks the voice calls, so you cannot browse the Internet or call at the same time. At the beginning, the DSL technology has provided the Internet links with throughputs between 1 Mbps and 2 Mbps. Therefore, this solution was 20 times faster than the classic modem connection. The DSL uses the higher frequencies than the POTS (Plain Old Telephone Service), i.e. voice calls, so it is possible to use the Internet and to call at the same time.

This Internet access solution is very well thought out. It uses the normal telephone line, so the provider does not have to install any new cables. This ensured the success and popularity of the DSL technology. In order to use the Internet and the analogue phone at the same, it is required to install special filter which separates the digital data form the call.

The modern versions of the DSL technology provide aggregated speeds up to 250 Mbps, because it uses much wider bandwidth and advanced modulation and coding techniques. However, higher throughput requires also better quality cables and shorter distances.

The DSL is one of the most popular Internet access technique and it is estimated that this is the dominant technology for broadband access with over 360 million subscribers worldwide. This is the reason why the DSL is constantly being improved and a lot variants of the DSL technology was developed over the years. However, the most popular implementations are ADSL (Asymmetric Digital Subscriber Line) and VDSL (Very-high-bit-rate Digital Subscriber Line).