Communication Method, User Device, Content Server and Controller

A user device, comprising:

• a transmitter configured to send a first access request for a segment of depended content to a content server, wherein the depended content comprises at least one segment;
• a receiver configured to receive an access receipt from the content server, wherein the access receipt contains information describing present access to the segment of the depended content requested by the first access request sent by the transmitter;
• and
• a memory coupled to the transmitter and receiver and configured to store the access receipt received by the receiver.

A content server, comprising:

• a receiver configured to receive a first access request for a segment of depended content from a user device;
• a processor coupled to the receiver and configured to generate an access receipt according to the first access request received by the receiver, wherein the access receipt contains information describing present access to the segment of the depended content by the user device;
• and
• a transmitter coupled to the processor and configured to send the access receipt generated by the processor to the user device.