ADSLMax in another thread has recommended somebody join Plusnet as they 'don't throttle' unlike that person current provider, however this information is incorrect and in fact backwards...
Not really. He's correct in that PN do not deliberately reduce the amount of data you can receive below what your connection is capable of receiving. If your line can handle 75Mb/s of data and there is 75Mb of data to send you then it will take one second for you to receive it all. That is what most people would consider to be 'unthrottled'.
What PN does have is a QoS system. This adjusts incoming data to ensure that the 75Mb of data you receive in that second is the most important 75Mb of data that is available. If you cause 100Mb of data to be sent to you in one second then 25Mb of it has to be thrown away or at least delayed. PN's systems just try to ensure that the 25Mb that gets left out is the less important stuff that can be retransmitted without bothering you too much. The result is that time critical services (VoIP, gaming etc) are less likely to suffer issues when your connection is at maximum usage.
So: PN do do traffic shaping. However the goal is not to limit data flow down your connection. The goal is to provide you with a better experience should your connection become 'overloaded'.
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Andrue Cope
Brackley, UK