formula to choose ip allocation sizes

keps/sig-network/3070-reserved-service-ip-range/README.md

@@ -207,28 +207,31 @@ func (rss randomScanStrategy) AllocateBit(allocated *big.Int, max, count int) (i
 ### Proposed Services ClusterIPs allocation model
 
 The proposal is to implement a new strategy on the Service IP allocation bitmap that logically subdivide the range
-in two bands based on a predefined percentage of the whole range (15%):
+in two bands based on the following formula `min(max($min, cidrSize/$step), $max)`, described as ~never less than $min or more than $max, with a graduated step function between them~, with $min = 16, $max = 256 and $step = 16.
 
 - lower band, used preferably for static ip assignment.
 - upper band, used preferably for dynamic IP assignment.
 
-Dynamically IP assignment will use the upper band, once this has been exhausted it will use the
+Dynamically IP assignment will use the upper band by default, once this has been exhausted it will use the
 lower range. This will allow users to define static allocations on the lower band of the predefined
 range with a low risk of collision, keeping the implementation backwards compatible.
 
+Example:
+
+- Service IP CIDR: 192.168.0.0/16
+- Range Size: 2^16 = 65536
+- Band Offset: min(max(16,65536/16),256) = min(4096,256) = 256
+- Static band start: 192.168.0.1
+- Static band ends: 192.168.1.1
+
            ┌─────────────┬─────────────────────────────────────────────┐
            │             │                                             │
-           │             │                                             │
-           │             │                                             │
            │   static    │                    dynamic                  │
            │             │                                             │
-           │             │                                             │
-           │             │                                             │
            └─────────────┴─────────────────────────────────────────────┘
 
            ◄────────────► ◄────────────────────────────────────────────►
-
-                15%                              85%
+    192.168.0.1     192.168.1.1                                 192.168.255.254
 
 ```go
 // randomScanReservedStrategy choose a random address from the provided big.Int and then scans