> For the complete documentation index, see [llms.txt](https://opendao-cc.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://opendao-cc.gitbook.io/docs/node-diffusion-model.md).

# Node Diffusion Model

OpenDAO's core objective is to develop a high-quality, large-scale node network. The guiding principle is that higher-tier nodes always receive a greater share in the Node Signal Model. To achieve this, OpenDAO has built the Node Diffusion Model, whose central function is to determine each node's tier.

A node, once promoted, is never demoted.

### Promotion Path

* **Nova**\
  Every node is a Nova on its first day in OpenDAO.
* **Voyager**\
  When a Nova's directly invited nodes include 2 Novas or higher-tier nodes, the Nova is promoted automatically to Voyager.
* **Navigator**\
  When a Voyager's directly invited nodes include 4 Voyagers or higher-tier nodes, the Voyager is promoted automatically to Navigator.
* **Commander**\
  When a Navigator's directly invited nodes include 6 Navigators or higher-tier nodes, the Navigator is promoted automatically to Commander.
* **Stellar Master**\
  When a Commander's directly invited nodes include 8 Commanders or higher-tier nodes, the Commander is promoted automatically to Stellar Master.

### Activity Checks

* **Self active:** at check time, the node itself must be active.
* **Subordinates active:** at check time, each subordinate node counted toward the promotion criterion must be active.

### Promotion Time

Each day after 00:00 UTC, and before the Node Signal Model distributes the day's dynamic rewards, OpenDAO automatically checks every node against the promotion criteria and applies any qualifying upgrades.

> If the criteria are met, a node may be promoted two or more tiers in the same day.

### Sub Network Bandwidth

Invited nodes are referred to as the leader's sub network and consume network bandwidth. The number of nodes a leader can invite directly (its slot count) is capped by the leader's tier.

| Node Tier      | Slot Limit |
| -------------- | ---------- |
| Nova           | 10         |
| Voyager        | 20         |
| Navigator      | 30         |
| Commander      | 40         |
| Stellar Master | 50         |

Once the slot limit is reached, a leader can still receive new applications but cannot approve any further ones. Once the leader's tier is upgraded, the slot limit expands and approval can resume.