# Node Action Flow
Action flow determines which nodes will be executed. You determine the action flow with Lifeline connections and every Lifeline starts with a Lifeline generator node.
## Default Lifeline Generator Nodes
Default layer nodes: **Tick**, **On Begin,** or **On End**.
## Other Lifeline Generator Nodes
There are a lot of nodes that have **New message** lifeline output. These nodes are primarily designed to receive messages from the network and work in conjunction with receiving *Device nodes*.
{% hint style="info" %}
**Good to know:** A good indicator that a layer is active, is blinking connection lines.
{% endhint %}
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