When using VOIP, it is recommended to be on a 1MB ADSL line rather than, for example, a 2MB or 10MB line.
The reason for this being that the smaller line is more synchronised with regards to uploading speed & downloading speed.e.g. When using a 1MB line, your statistics might look something like this:
Uploading-speed: 700Kb/s
Download speed: 300Kb/s
When using a 1MB line, your statistics might look something like this:
Uploading-speed: 900Kb/s
Download speed: 1500 Kb/s
Thus due to stability incompatibility in the larger line is not ideal for calls, Call quality will become degraded.