A number of factors can have an influence on the connection speed that the subscribers reach in reality.
On the one hand that speed can be influenced by the attenuation of the signal on the xDSL networks. This attenuation is caused by the reduction in the strength of the signal between the subscriber and the xDSL equipment in the central, when the signal passes through the copper pair. The speed is thus dependent on the distance between the subscriber and the xDSL equipment.
On the other hand, the attainable speed may vary in the course of the time due to overloading. This is related to the effect of the shared use of the same bandwidth by different subscribers on the network of the ISP's. The achievable rate can also be affected by the management of traffic and the capacity of the network of ISP’s. Consequently, there are differences in performance between different platforms and between ISP’s operating on the same platform.
Also factors external to the networks of ISP’s can affect the connection speed achievable for the subscribers. We hereby think about the quality of the network within the home, the computer of the subscriber, the server to where the requests are being sent, the quality of the wireless network of the subscriber and the sharing of the connection between different terminals and / or applications. On these factors the ISP’s have no control.
(Source: translation of “Besluit van de Raad van het BIPT van 4 December 2012 betreffende de Communicatie van de Snelheid van de Vaste Breedbandverbinding, p. 4”)