| 摘要 |
An apparatus that supports a communication link (such as DSL) in the local loop has hardware to distribute a copy of one or more data flows to any of a number of devices (e.g. "set-top boxes") that are each connected to the apparatus by the link. In some embodiments, the apparatus receives only one copy of a number of video feeds for distribution from a video head end that is coupled thereto e.g. via an ATM network. In such embodiments, the apparatus selectively transfers a copy of one of the video feeds being received, to each set-top box. Distribution of data flows in the apparatus can be implemented by a point to multipoint virtual circuit, although a change in a video feed being supplied to a subscriber requires tearing down the subscriber's old virtual circuit leaf and setting up a new virtual circuit leaf to the subscriber. The time delay and overhead associated with such virtual circuit changes are eliminated in certain embodiments by changing only an internal mapping. Specifically an association between a subscriber's virtual circuit and a first virtual circuit carrying the currently-supplied video feed is erased, and a new association is formed between the subscriber's virtual circuit and a second virtual circuit that is carrying the video feed to be supplied. During such a change, the subscriber's virtual circuit is kept intact (and in addition, the first and second virtual circuits are kept intact as well), because a simple change in VC-VC associations implements channel change. |
