Document maximum number of IBFT 2.0 validators (#895)

* Document maximum number of IBFT 2.0 validators

Signed-off-by: Roland Tyler <roland.tyler@consensys.net>

* Space

Signed-off-by: Roland Tyler <roland.tyler@consensys.net>

* Incorporate feedback

Signed-off-by: Roland Tyler <roland.tyler@consensys.net>

* Non-validator clarification

Signed-off-by: Roland Tyler <roland.tyler@consensys.net>

* Review feedback

Signed-off-by: Roland Tyler <roland.tyler@consensys.net>

docs/HowTo/Configure/Consensus-Protocols/IBFT.md

@@ -25,12 +25,21 @@ Existing validators propose and vote to
 [add or remove validators](Add-Validators.md#ibft-20). Adding or removing a validator
 requires a majority vote (greater than 50%) of validators.
 
-## Minimum number of validators
+## Validators
+
+### Minimum number of validators
 
 IBFT 2.0 requires four validators to be Byzantine fault tolerant. Byzantine fault tolerance is the
 ability for a blockchain network to function correctly and reach consensus despite nodes failing or
 propagating incorrect information to peers.
 
+### Maximum number of validators
+
+As the number of validators increase, the message complexity increases, which can decrease performance.
+In [network tests](https://wiki.hyperledger.org/display/BESU/Maximum+Validator+count+for+an+IBFT2+Network), IBFT 2.0 handles up to 30 validators with no loss of performance.
+
+Non-validator nodes don't affect performance and don't count towards the maximum limit.
+
 ## Genesis file
 
 To use IBFT 2.0, Besu requires an IBFT 2.0 [genesis file](../Genesis-File.md). The genesis file defines properties