MNs are wireless-equipped devices which can communicate with each other in a peer-to-peer fashion. In general, communication is multi-hop with (intermediate) MNs relaying packets from the source to the destination.
An IN is a node similar to the MN but it performs the additional task of maintaining the network topology of a portion of the network around itself, which is called its ``control zone''. Hence, the IN provides route information to all the nodes in its control zone.
The INs and the Internet gateway are connected to a backbone network. This backbone network is used to provide Internet access to the nodes and for IN-IN communication.