@Override
  public int messageSpace(final int protocolVersion) {
    return switch (protocolVersion) {
      case EthProtocolVersion.V66, EthProtocolVersion.V67, EthProtocolVersion.V68 -> 17;
      case EthProtocolVersion.V69 -> 18;
      default -> 0;
    };
  }
Eth protocol messages as defined in <a
href="https://github.com/ethereum/devp2p/blob/master/caps/eth.md">Ethereum Wire Protocol
(ETH)</a>}
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/EthProtocol.java