as will be described below the roaming status of the mn is transparent to the cn so the cn sends a packet to the mn with cnaddr as the source address and haddr as the destination address the process of sending packets from the cn to the mn is shown in fig4 a and 4 b at step 1 c the cn sends the packet over the ipn which routes it to the hn on the basis of the destination address the packet is intercepted by the ha which is aware of the roaming status of the mn and forwards the packet at step id through the tunnel to the mha at the scoa in other words the packet is encapsulated as follows the mha decapsulates the packet by stripping off the outer ip header and sends the inner packet at step 1 e to the mn as this step is performed within the fn it is immaterial that the destination address of the packet is not the current address of the mn for example the fn may route the packet to the mn using an address resolution protocol arp which discovers a medium access control mac address for communication with the mn within the fn the mac layer operates between the ip layer and the physical layer and determines how packets are transported over the physical layer as the present description is concerned primarily with the mobile ip layer and mac protocols are well known the mac layer will not be discussed further however the ip layer of the mn will only deliver to the upper layers the packets addressed to haddr as the roaming status of the mn is transparent to the upper layers although not to the mobile ip layer below it steps 1.