In some cases , the far end system may have more functionality than a simple demultiplexer and so , at the same time as the demultiplexing still exists logically , it may never actually happen physically , such as in network address translation where a number of IP private network users are multiplexed over a single public IP address . In some cases , the far end system may have more functionality than a simple demultiplexer and so , while the demultiplexing still exists logically , it may never actually happen physically .