ZIP: 251
Title: Deployment of the ${NU4} Network Upgrade
Owners: Daira Hopwood <daira@electriccoin.co>
Status: Draft
Category: Consensus
Created: 2020-02-28
License: MITThe key words "MUST", "MUST NOT", "SHOULD", and "MAY" in this document are to be interpreted as described in RFC 2119.1
The term "network upgrade" in this document is to be interpreted as described in ZIP 200.2
The terms below are to be interpreted as follows:
- ${NU4}
Code-name for the fifth Zcash network upgrade, also known as Network Upgrade 4.
- Testnet
The Zcash test network, as defined in3.
- Mainnet
The Zcash production network, as defined in4.
This proposal defines the deployment of the ${NU4} network upgrade.
The primary sources of information about ${NU4} consensus protocol changes are:
- The Zcash Protocol Specification5
- ZIP 200: Network Upgrade Mechanism6
- ZIP 207: Funding Streams7
- ZIP 214: Consensus rules for a Zcash Development Fund8
- ZIP 1014: Establishing a Dev Fund for ECC, ZF, and Major Grants9
- TODO: other ZIPs
The network handshake and peer management mechanisms defined in ZIP 20110 also apply to this upgrade.
The following network upgrade constants11 are defined for the ${NU4} upgrade:
- CONSENSUS_BRANCH_ID
0xTODO- ACTIVATION_HEIGHT (${NU4})
Testnet: TODO
Mainnet: 1046400
Nodes compatible with ${NU4} activation on testnet MUST advertise protocol version TODO or later. Nodes compatible with ${NU4} activation on mainnet MUST advertise protocol version TODO or later. The minimum peer protocol version that ${NU4}-compatible nodes will connect to is 170002.
Pre-${NU4} testnet nodes are defined as nodes on testnet advertising a protocol version less than TODO. Pre-${NU4} mainnet nodes are defined as nodes on mainnet advertising a protocol version less than TODO.
For each network (testnet and mainnet), approximately 1.5 days (defined in terms of block height) before the corresponding ${NU4} activation height, nodes compatible with ${NU4} activation on that network will change the behaviour of their peer connection logic in order to prefer pre-${NU4} peers on that network for eviction from the set of peer connections:
/**
* The period before a network upgrade activates, where connections to upgrading peers are preferred (in blocks).
* This was three days for upgrades up to and including Blossom, and is 1.5 days from Heartwood onward.
*/
static const int NETWORK_UPGRADE_PEER_PREFERENCE_BLOCK_PERIOD = 1728;The implementation is similar to that for Overwinter which was described in 12.
Once ${NU4} activates on testnet or mainnet, ${NU4} nodes SHOULD take steps to:
- reject new connections from pre-${NU4} nodes on that network;
- disconnect any existing connections to pre-${NU4} nodes on that network.
Prior to the network upgrade activating on each network, ${NU4} and pre-${NU4} nodes are compatible and can connect to each other. However, ${NU4} nodes will have a preference for connecting to other ${NU4} nodes, so pre-${NU4} nodes will gradually be disconnected in the run up to activation.
Once the network upgrades, even though pre-${NU4} nodes can still accept the numerically larger protocol version used by ${NU4} as being valid, ${NU4} nodes will always disconnect peers using lower protocol versions.
TODO: delete if inapplicable. Unlike Overwinter and Sapling, and like Blossom and Heartwood, ${NU4} does not define a new transaction version. ${NU4} transactions are therefore in the same v4 format as Sapling transactions; use the same version group ID, i.e. 0x892F2085 as defined in13 section 7.1; and use the same transaction digest algorithm as defined in14. This does not imply that transactions are valid across the ${NU4} activation, since signatures MUST use the appropriate consensus branch ID.15
Support for ${NU4} on testnet will be implemented in zcashd version 3.1.0, which will advertise protocol version TODO. Support for ${NU4} on mainnet will be implemented in zcashd version 4.0.0, which will advertise protocol version TODO.