A single connection may carry many different communications simultaneously. To do this the sender breaks each communication into PACKETS each of which contains control information so that the receiver can identify it. The sender transmits packets for all current communications to the receiver which sorts them and forwards them as necessary. This system provides multiplexing (passing multiple messages at the same time) and routing (using the control information to forward a packet through intermediate nodes to the target node). The way in which packets are routed through the network is determined by the type of network which can be classified into two types: Datagram Networks and Virtual Circuit Networks. Some versions of both types are also called Packet Switch Exchange (PSE) Networks. X.25 (see below) is one example of a PSE.