If you surf the Internet a lot and don’t live in a region where DSL is not possible, you usually have a DSL connection. However, DSL customers also have a problem that seems like a luxury problem for Internet users without broadband access: the DSL line is too slow or is slowed down by a variety of factors. Often, however, the problems do not lie with the provider, but on the customer’s side. In this guide, we’ll show you what the reasons for running too slowly can be and how you might be able to eliminate them.
In a separate guide, we show you what to do if the provider doesn’t provide you with the promised speed.
Donwnstream and Upstream
DSL connections for private customers are usually ADSL connections – the A stands for asynchronous. This means that the specified “up to” MBit/s is related to the downstream, the upstream is significantly lower. For example, if you upload photos or videos to the net, you should not be surprised about a low speed, even with fast connections.
Bandwidth stands and falls with the copper line
The maximum possible speed is in any case the length of the copper line between the switchboard and the customer. In the switchboard is the DSL port, the counterpart to the DSL modem at the customer’s. In some cases, this DSL port may also be found in a so-called outdoor DSLAM, i.e. in a box between the intermediary and the customer. The customer has no influence on the length of the line. However, the rule of thumb applies: the longer the line, the lower the maximum bandwidth. However, the so-called line cross-section also has an influence on the bandwidth due to the associated attenuation. For technical reasons, therefore, it is not possible for the providers to really switch the speed that is advertised. This applies in particular to connections with “up to 16 Mbps”, but also to connections with 1 or 2 Mbps with downloadtime.org by download time calculator.
Data rate may vary for a variety of reasons
If a customer moves from one provider to the next, capacity may fluctuate slightly. This may be due to other lines within the intermediary, but also to the fact that a different technique is used in the switching station.
But big jumps are not to be expected here. This also applies to changed DSL speeds due to different ratings in the damping values. For example, Vodafone switches a 6 Mbps line with a line damping of 33 dB, while Deutsche Telekom only switches a 2 Mbps line. However, providers have different calculation methods for the values, so that the differences that initially seem drastic are relative again.
Only if a single provider should work with an outdoor DSLAM and another provider does not, then differences of several megabits per second are to be expected, as the cable length changes drastically. However, differences are also possible if a provider uses a rate-adaptive negotiation in its DSLAMs.
For example, while Telekom specifies a fixed data rate (e.g. 6 Mbps) to which the modem must connect, the rate-adaptive negotiation specifies the theoretical maximum possible value. The modem is trying to connect to these values. If this fails, an attempt is made to synchronize with the next best value. This can result in higher data throughputs in the end than at a fixed data rate – but the line is usually more stable at a fixed rate.
Incorrect profile or port may affect speed
In some cases, despite a short line and a booked ADSL2+ port with up to 16 Mbps in the downstream, only 8 Mbps may come out of the line. Here it is reasonable to assume that the DSL provider has switched its customer to an old ADSL port.
These offer a maximum performance of 8 Mbps. Contacting the provider usually helps here. As a result, the customer should be switched to the DSL port with the corresponding services. This can occur, for example, when an existing customer switches from a 6 Mbps port to a 16 Mbps port. This is where the profile is changed in the computer, but it can happen that the provider forgets to change the DSL port. The reverse is also conceivable.
