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# System prepended metadata

title: Node strategy when depth changes

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title:  Node strategy when depth changes
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## Node strategy

- ultimately: maximise profit
- indirectly: comply with the rules of the reserve

### Network growth

- Increase of demand lead to depth change: `d -> d' (d'=d+1)`
	- When by following the rules of the reserve, all chunks of a PO is evicted (moved to cache) and a chunk of a higher PO  is deleted first
- Pull syncing as a neighbour now only with peers within node's storage depth
	- Peers in PO `d`of old depth switch live pull syncing only their PO `d` 
	- Some peers in PO `d` can now be disconnected as Kademlia topology dictates
	
### Network contraction

- Decrease of demand lead to depth change: `d -> d' (d'=d-1)`
	- When following the rules of the reserve, keep making sure there is consensus on the reserve
- Triggered 
	- When there is a chance that PO `d'` can be syncronised
 	- by too low utilisation (<50%) of node reserve of chunks in `PO >= d` 
- Pretend storage is already `d-1`:
	- Repopulate from cache all chunks of PO `d'`
	- Connect to peers in PO bin `d'` to achieve full connectivity
	- Pull sync peers of PO `d'` their PO bin-s PO-s`>= d` historically
	- if all 3 successful then we reset `d` to `d'` 

## Rules of the reserve

![](https://hackmd.io/_uploads/rJrxNUnH2.png)
![](https://hackmd.io/_uploads/HydgEI2r3.png)

