2x Questions

IF I set the CIR on a 900 Advantage SM to the following:

Uplink Sustained: 600
Downlink Sustained: 600
UPlink Burst: 800
Downlink Burst: 800

WIth 2x enabled does this mean that all the above numbers are Doubled so the user will actually get 1200/1600 respectively? If this is the case what is the main use of the 2x control in a bandwith limited sintuation?