The MNs can freely move in a control zone; they can also move from the control zone of one IN to the control zone of another IN. As the network topology changes dynamically, the INs are expected to keep up-to-date information. This is achieved with the co-operation of MNs. The MNs in a control zone register with the IN and periodically transmit local topology information to the IN.
MNs which are on the MAX_CZ_RADIUS-th hop from the IN, are called gateway nodes. In addition to having all the properties of an MN in a control zone, gateway nodes can also communicate with unregistered nodes in an ad hoc zone. They interface the control zone with an ad hoc zone. Note that the gateway nodes can also communicate with unregistered nodes in the ad hoc zone.