How are Updatable network parameters rolled out to the decentrlaized network, and how are they depreciated?

Question

CIP-0009 contains upgradeable parameters, if certain keyholders sign them, they appear to be changeable without updates to node software or configuration files: https://github.com/cardano-foundation/CIPs/blob/master/CIP-0009/README.md#updatable-protocol-parameters

We just saw a change to block-size and Plutus script size in epoch 306, how was this change effected if it is not reflected in software or config files, is it an on-chain transaction? How can we discover those in an explorer?

How are Upgrade-able parameters removed? For example the decentralization flag still shows in mainnet-shelley-genesis.json, has it been removed now, and if so, how?

Answer 1

The "certain keyholders" that you are talking about are called genesis keys, and are (for now) the only real way to affect changes/governance on the actual protocol. Before we get to the Voltaire/Governance era, these keys are controlled by IOG, Emurgo, and the Cardano Foundation. Over time and as we transition into the Voltaire Era, those three entities will slowly relinquish the keys' power over to the community.

Answer 2

Upgrade-able network parameters are modified by changing the parameters by writing a transaction into the block-chain itself, nodes then read the parameters from the block history.

Example transaction that changed the block size for epoch 306: https://cardanoscan.io/transaction/bf095309ba20174d1a5c30ea03580cbf8bfe7dd75da1203d9ed51bfd151bb327?tab=protocolupdates