Epidemic implementation, the 16-bit Summary Vector Length counts the number of Message Identification Numbers in the `SummaryVectorHeader`. A 16-bit unsigned integer is large enough cover a `SummaryVectorHeader`. Since the `MessageType` Header encapsulates the `SummaryVectorHeader`, a node identifies the other node using the Node Identification Number instead of the address because nodes can have more than one address.

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PacketEpidemic did not support control packet fragmentation. In order to support fragmentation, the Fragmentation Block identifies whether there are more `SummaryVectorHeader` packets. When the Fragmentation Block is one, more `SummaryVectorHeader` packets remain. When the Fragmentation Block is zero, that packet is the last `SummaryVectorHeader`. Once a node receives one with the Fragmentation Block set to zero, the node continues the message exchange sequence. The control packet fragmentation can tolerate packet loss if the lost packet had the fragmentation block set to one, but the fragmentation protocol does not support retransmission of control packets. If the lost control packet had the fragmentation block set to zero, then the control packet sequence would stop until a beacon restarts the exchange sequence.

Evaluation
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Our primary interest in implementing DTN protocols in ns-3 is to gain fidelity and account for the 