What is the difference between ADSL2+ and ADSL? Belong

What is the difference between ADSL2+ and ADSL?

ADSL and ADSL2+ are different ways of delivering broadband to your home using a copper phone line. The key difference between these two services is speed.
 
Belong uses Telstra’s network, if you have an ADSL2+ service provides maximum download speeds of up to 20Mbps, and maximum upload speeds of up to 850 Kbps. If you are unable to get ADSL2+ you will be offered an ADSL service where available. An ADSL service provides maximum download speeds of up to 8Mbps, and maximum upload speeds of up to 384 Kbps.
 
Actual speeds will be lower, and will vary based on a number of factors including distance to the exchange, internet traffic in your neighbourhood, how you use your service, the quality of your telephone line, and the manner in which you are connecting to your Belong modem.

The below graph provides theoretical maximum download speeds based on distance from the exchange. Given the distance from the exchange is the same for all ADSL/2+ providers, the impact to speed should be similar. 

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