Every time a node receives a control packet or data packet from another node; it updates its record of connected nodes. A node considers a connection broken when the node does not receive anything from the neighbor for two beacon intervals.

A node can have more than one radio interface and address, so address is not a sufficient identifier to prevent two nodes from restarting a connection when they detect the second radio interface. The `BEACON` control packet is a `MessageType` header with the field set to `BEACON`. The `MessageType` header field indicates the type of control packet. Since a node does not know whether another node has more than one address, the beacon must include the Node Identification Number. Therefore, the `MessageType` header includes the 16-bit Node Identification Number. Figure \[fig:DTNMtype\] illustrates the `MessageType` Header. provides a unique number to every node in a simulation. A node uses the Node Identification Number to determine whether a node is considered connected. If a node is not connected, then the node adds the Node Identification Number with a timestamp to its list of connected nodes. Then, the node continues the control packet exchange. If the Node Identification Number is in the 