is in microseconds to ensure that every Message Identification Number is unique. While a per-node sequential message counter would also create a unique identifier, our protocols require message generation time and source node identification for routing decisions, so this information is dual-purpose. Some scenarios studied would exceed the largest time in microseconds represented by a 32-bit timestamp, therefore we use 48-bits for the timestamp. The last hop field is the 16-bit Node Identification Number of the last node that forwarded the message. Nodes use the last hop to buffer incomplete messages for message reconstruction. The 32-bit total number of packets and the 32-bit packet index support reordering during message reassembly.

Message Handling
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In PacketEpidemic, nodes pushed all packets selected for transmission to the link layer immediately after completing the control packet exchange. ’s link layer contains a packet queue that has a limited size. This link-layer packet queue is and cannot be manipulated by higher layers in the network stack, they can only add packets [@NS3Manual]. When a node’s message buffer equals or exceeds the size of the packet queue, then the node will fill the packet queue and any new packets sent to the full queue are dropped. 