137 lines
4.9 KiB
ReStructuredText
137 lines
4.9 KiB
ReStructuredText
::
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ZIP: 250
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Title: Deployment of the Heartwood Network Upgrade
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Owners: Daira Hopwood <daira@electriccoin.co>
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Status: Final
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Category: Consensus / Network
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Created: 2020-02-28
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License: MIT
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Terminology
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===========
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The key words "MUST", "MUST NOT", "SHOULD", and "MAY" in this document are to be
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interpreted as described in RFC 2119. [#RFC2119]_
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The term "network upgrade" in this document is to be interpreted as described in
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ZIP 200. [#zip-0200]_
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The terms below are to be interpreted as follows:
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Heartwood
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Code-name for the fourth Zcash network upgrade, also known as Network Upgrade 3.
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Testnet
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The Zcash test network, as defined in [#protocol]_.
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Mainnet
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The Zcash production network, as defined in [#protocol]_.
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Abstract
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========
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This proposal defines the deployment of the Heartwood network upgrade.
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Specification
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=============
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Heartwood deployment
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--------------------
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The primary sources of information about Heartwood consensus protocol changes are:
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- The Zcash Protocol Specification [#protocol]_
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- ZIP 200: Network Upgrade Mechanism [#zip-0200]_
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- ZIP 213: Shielded Coinbase [#zip-0213]_
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- ZIP 221: FlyClient - Consensus-Layer Changes [#zip-0221]_.
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The network handshake and peer management mechanisms defined in ZIP 201 [#zip-0201]_
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also apply to this upgrade.
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The following network upgrade constants [#zip-0200]_ are defined for the Heartwood
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upgrade:
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CONSENSUS_BRANCH_ID
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``0xF5B9230B``
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ACTIVATION_HEIGHT (Heartwood)
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Testnet: 903800
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Mainnet: 903000
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Nodes compatible with Heartwood activation on testnet MUST advertise protocol version
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170010 or later. Nodes compatible with Heartwood activation on mainnet MUST advertise
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protocol version 170011 or later. The minimum peer protocol version that
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Heartwood-compatible nodes will connect to is 170002.
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Pre-Heartwood testnet nodes are defined as nodes on testnet advertising a protocol
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version less than 170010. Pre-Heartwood mainnet nodes are defined as nodes on mainnet
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advertising a protocol version less than 170011.
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For each network (testnet and mainnet), approximately 1.5 days (defined in terms of
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block height) before the corresponding Heartwood activation height, nodes compatible
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with Heartwood activation on that network will change the behaviour of their peer
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connection logic in order to prefer pre-Heartwood peers on that network for eviction
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from the set of peer connections::
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/**
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* The period before a network upgrade activates, where connections to upgrading peers are preferred (in blocks).
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* This was three days for upgrades up to and including Blossom, and is 1.5 days from Heartwood onward.
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*/
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static const int NETWORK_UPGRADE_PEER_PREFERENCE_BLOCK_PERIOD = 1728;
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The implementation is similar to that for Overwinter which was described in
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[#zip-0201]_.
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Once Heartwood activates on testnet or mainnet, Heartwood nodes SHOULD take steps to:
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- reject new connections from pre-Heartwood nodes on that network;
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- disconnect any existing connections to pre-Heartwood nodes on that network.
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Backward compatibility
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======================
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Prior to the network upgrade activating on each network, Heartwood and pre-Heartwood
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nodes are compatible and can connect to each other. However, Heartwood nodes will
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have a preference for connecting to other Heartwood nodes, so pre-Heartwood nodes will
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gradually be disconnected in the run up to activation.
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Once the network upgrades, even though pre-Heartwood nodes can still accept the
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numerically larger protocol version used by Heartwood as being valid, Heartwood nodes
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will always disconnect peers using lower protocol versions.
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Unlike Overwinter and Sapling, and like Blossom, Heartwood does not define a new
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transaction version. Heartwood transactions are therefore in the same v4 format as
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Sapling transactions, use the same version group ID, i.e. 0x892F2085 as
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defined in [#protocol]_ section 7.1, and the same transaction digest algorithm as
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defined in [#zip-0243]_. This does not imply that transactions are valid across the
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Heartwood activation, since signatures MUST use the appropriate consensus branch ID.
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[#zip-0243]_
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Support in zcashd
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=================
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Support for Heartwood on testnet will be implemented in ``zcashd`` version 2.1.2,
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which will advertise protocol version 170010. Support for Heartwood on mainnet will
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be implemented in ``zcashd`` version 3.0.0, which will advertise protocol version
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170011.
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References
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==========
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.. [#RFC2119] `RFC 2119: Key words for use in RFCs to Indicate Requirement Levels <https://www.rfc-editor.org/rfc/rfc2119.html>`_
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.. [#protocol] `Zcash Protocol Specification, Version 2021.2.16 or later <protocol/protocol.pdf>`_
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.. [#zip-0200] `ZIP 200: Network Upgrade Mechanism <zip-0200.rst>`_
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.. [#zip-0201] `ZIP 201: Network Peer Management for Overwinter <zip-0201.rst>`_
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.. [#zip-0213] `ZIP 213: Shielded Coinbase <zip-0213.rst>`_
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.. [#zip-0221] `ZIP 221: FlyClient - Consensus-Layer Changes <zip-0221.rst>`_
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.. [#zip-0243] `ZIP 243: Transaction Signature Validation for Sapling <zip-0243.rst>`_
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