In the previous example, Alice sends the message "secret" to Bob, but the network she uses for that is not made explicit.
We now introduce the network as a grey bar located to the right of the agents. Compared to the previous example, we now have an extra step, which represents the message going through the network.
To visualise what is going in the network, we indicate on the arrow from the sender to the network the message number (e.g.,  for the first message sent on the network), and the full message can be found in the Network Stack (and displayed when hovering the number above the arrow). Each message in the stack is associated with a unique identifier, and a status, which starts with the "/" symbol. We consider two statuses at this stage:
We introduce the attacker in the next part.