DSL ("Digital Subscriber Line") is a collective term for various broadband technologies that run over copper lines. Within these technologies, ADSL and VDSL are the two most important variants. ADSL, which stands for "Asymmetric Digital Subscriber Line", has long been the standard for Internet connections. It is characterised by the fact that the download speed is significantly higher than the upload speed, which makes sense for most users as they retrieve more data from the internet than they upload.

VDSL, or "Very High Speed Digital Subscriber Line", is the direct successor to ADSL and offers significantly higher speeds. This was made possible by technological developments such as vectoring and supervectoring (Annex Q), which reduce interference on the copper lines and thus enable higher bandwidths. While ADSL generally achieves a maximum download speed of up to 16 Mbit/s, VDSL - depending on the expansion stage - can achieve up to 250 Mbit/s.

In comparison, fibre optic (FTTH - "Fibre to the Home") is the most modern solution. Here, fibre optic cables are laid directly to the customer's flat or house, which has decisive advantages over DSL technologies. Optical fibre enables significantly higher and more stable speeds, is insensitive to electromagnetic interference and offers the best long-term conditions for increasing demands on internet usage.

In the following table you will find a comparison of internet speeds.

Technology Download Upload
ADSL Annex B 16 1
ADSL Annex J 16 2.8
VDSL 50 10
VDSL Vectoring 100 40
VDSL Supervectoring (Annex Q) 250 40
FTTH 1000 500

Internet technologies in detail

ADSL

ADSL stands for “Asymmetric Digital Subscriber Line” with “asymmetric” signifying the fact that transmission speed will differ depending on direction. In the direction of reception, to you ("downstream"), transmission rates of up to 16,000 kbit/s (approx. 16 Mbit/s) are possible. In the direction of transmission ("upstream"), i.e. from you to the Internet, up to 1152 kbit/s (approx. 1 Mbit/s) are achieved.
ADSL utilises the classic copper lines of the existing telephone network for data transmission. In the past, this had great advantages as no new lines had to be laid and technological improvements could be made simply within the switch box. Compared with telephone modems (up to 56 kbit/s) and ISDN connections (with two bundled channels of 64 kbit/s each), the data rate could thus be increased enormously with comparatively little effort.
An important further development of ADSL is ADSL2+ (Extended bandwidth Asymmetric Digital Subscriber Line 2), which theoretically allows up to 24 Mbit/s downstream.

With the first ADSL connections with the addition of Annex B, it was still possible to operate traditional analog telephony in parallel with digital data transmission. To do this, the signal simply had to be split between the modem and the telephone using a splitter. With the introduction of Annex J as standard, this was no longer possible. Although connections with Annex J are faster, the areas of the signal previously reserved for analog telephony were now also utilised for data transmission. Due to this, calls are nowadays are mostly made over the internet seeing the rise of Voice over IP (VoIP).

VDSL

VDSL stands for “Very High Speed Digital Subscriber Line,” which increases data transmission speed yet again by harnessing technologies such as vectoring and supervectoring.  
The background to this development was that copper cables experience relatively high signal lose which negative impacts on signal quality. As a result, the maximum Internet speed drops rapidly over long distances.  
To get around this problem, VDSL uses modern fiber optic cables to cover long distances. This allows data to reach a distributor near the customer at high speed. Only the last few meters to the household are still covered by the old copper cables.
With basic VDSL, user can expect speeds up to 50 Mbit/s in the direction of reception, ie downstream. However, by using vectoring and supervectoring, this can be increased to up to 100 Mbit/s and 250 Mbit/s respectively.

FTTH

FTTH stands for "fibre to the home", i.e. a fibre optic connection that reaches directly into the customer's home. In contrast to DSL technologies, where data transmission is partly via copper cables, FTTH only uses fibre optic cables. This eliminates the attenuation losses that occur with copper cables, meaning that high speeds can be achieved even over long distances.

The background to the development of FTTH was the ever-increasing demand for higher bandwidths and more stable internet connections. While DSL connections are limited by physical boundaries, optical fibre offers almost unlimited capacity for future requirements.

 

With FTTH from Easybell, speeds of up to 1,000 Mbit/s download and 500 Mbit/s upload are possible.

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Created on: 04. March 2025