higher order bit stream similar to that done in communications networks. Multiple program transport streams can in turn be multi- plexed into higher order streams. In some cases statistical multiplex- ing techniques may be used to allocate unused aggregate bits to each of the program sources, depending on activity. The main point to make here is that the connection between the multiplex and demultiplex can be any standard communications channel capable of interfacing the end units and providing the band width, class, and quality of service required by the television signals being transported. Note that in this depiction, audio, video, and data are arbitrarily shown with one-way paths. These could easily be two- way, requiring full-duplex network facilities. Note also the 10/100BT access requires full-duplex layer 2 as well. Standard Program Content Interface Standard Network Interface Video Video Audio Audio 10/100BT 10/100BT Equipment & Network Equipment & Network Management Management FIGURE 4-5 Program Content Multiplex and Demultiplex Concept 4 NETWORK TECHNOLOGY AND METHODOLOGY ROUTING Routing and switching mean different things to different people. For example, both terms apply to switching and transmission facil- ities. Routing in the circuit switched or voice services world means that a call is routed according to service configuration parameters in a PBX or end office switch. For example, least-cost routing is established when the originating switch is programmed to use the least expensive route between the origination point and termination point for a telephone call. Alternate routes may be a point-to-point private line, a virtual private network (VPN), or the public network, where the private line is the lowest and fixed cost, the VPN is the next least expensive, and the public network is the most expensive. Wholesale routing of traffic occurs when the traffic is moved from one transmission facility to another. For example, traffic normally routed from New York to Atlanta may go direct, but an alternat