A Fork which is not backwards compatible results in a Hard Fork, meaning that clients that do not update their protocol, which involves a combination of upgrading the client software and adding new chain configuration, are unable to sync blocks from the rest of the network, and new blocks they propose will be rejected by other nodes in the network.
On Ethereum mainnet, such planned Hard Forks are designated to take effect at set block numbers at a future date. In Permissioned blockchains, Hard Forks need to be scheduled depending on the chain's current block height.
In this webinar Kaleido's Sr. Protocol Engineer, Vinod Damle will be giving an in depth look at how we automated the process of updating the Protocol with a Hard Fork on all nodes in the chain. Hard Forks can be applied if your environment is at or later than release 1.0.28. With this Hard Fork, `constantinopleBlock` is applied to certain older environments which do not have the Constantinople genesis chain configuration.