3.2.7.10 Fast Start Request
The server SHOULD provide a mechanism to inform the higher layer of a request by the client to receive packets at an accelerated rate. The higher layer SHOULD also be informed if the request used the X-Accelerate-Streaming header (section 2.2.6.13) or the X-Burst-Streaming header (section 2.2.6.17).
In response, the higher layer MUST deliver ASF packets at a rate that is less than or equal to the value that the client requested when the value of the State variable is PLAYING. The duration of the accelerated delivery SHOULD NOT exceed the duration requested by the client. The higher layer MUST report whether it is able to comply with the request and MUST report the accelerated rate and duration that was chosen.