Transferring messages in networks made up of subnetworks with different namespaces

1. Field of the Invention Techniques employed in packet networks for transferring a packet across subnetworks with different namespaces. When a packet enters a given subnetwork and has a destination in a subnetwork with a different namespace, the given subnetwork encapsulates the packet by adding a header which specifies a decapsulator in the namespace. When the packet arrives at the decapsulator, the decapsulator strips the header and provides the packet to a subnetwork with a different namespace. A particular use of the technique is in a network used for broad-band interactive service. The network has two sub-networks. The first subnetwork is a TV channel which functions as a high-bandwidth forward channel and the second subnetwork is a packet network accessible via a public modem pool which functions as a lower-bandwidth return channel. The encapsulator establishes a connection with the public modem pool and receives an address in the second subnetwork which is temporarily associated with the connection. When the encapsulator receives a packet which is produced in response to a packet received from the TV channel and has a destination address in the sub-network of the TV channel, the encapsulator places a header on it which contains the temporary address and the address of the decapsulator. When the packet arrives at the decapsulator, the decapsulator removes the header and provides the packet to the second sub-network.