Merge pull request #878 from zcash/draft-zip-253-nu6

[ZIP 253] Initial draft

zips/zip-0253.md

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+
+    ZIP: 253
+    Title: Deployment of the NU6 Network Upgrade
+    Owners: Arya <[email protected]>
+    Status: Draft
+    Category: Consensus / Network
+    Created: 2024-07-17
+    License: MIT
+    Discussions-To: <https://github.com/zcash/zips/issues/806>
+
+# Terminology
+
+The key word "MUST" in this document are to be interpreted as described in
+BCP 14 [^BCP14] when, and only when, they appear in all capitals.
+
+The term "network upgrade" in this document is to be interpreted as described in ZIP 200 [^zip-0200].
+
+The terms "Testnet" and "Mainnet" are to be interpreted as described in
+section 3.12 of the Zcash Protocol Specification  [^protocol-networks].
+
+# Abstract
+
+This proposal defines the deployment of the NU6 network upgrade.
+
+# Specification
+
+## NU6 deployment
+
+<!-- TODO: Update these references once ZIP numbers are assigned to the draft ZIPs -->
+
+The primary sources of information about NU6 consensus protocol changes are:
+
+* The Zcash Protocol Specification [^protocol].
+* Network Upgrade Mechanism [^zip-0200].
+* Lockbox Funding Streams [^zip-2001].
+* Block Reward Allocation for Non-Direct Development Funding [^draft-nuttycom-funding-allocation].
+* Blocks should balance exactly [^zip-0236].
+
+
+The network handshake and peer management mechanisms defined in ZIP 201 [^zip-0201] also apply to this upgrade.
+
+The following ZIPs have been updated in varying degrees to take into account NU6:
+
+* ZIP 207: Funding Streams [^zip-0207].
+* ZIP 214: Consensus rules for a Zcash Development Fund [^zip-0214].
+
+The following network upgrade constants [^zip-0200] are defined for the NU6 upgrade:
+
+CONSENSUS_BRANCH_ID
+: `0xC8E71055`
+
+ACTIVATION_HEIGHT (NU6)
+: Testnet: TBD
+: Mainnet: TBD
+
+MIN_NETWORK_PROTOCOL_VERSION (NU6)
+: Testnet: `170110`
+: Mainnet: `170120`
+
+For each network (Testnet and Mainnet), nodes compatible with NU6 activation on that network MUST advertise a network protocol version that is greater than or equal to the MIN_NETWORK_PROTOCOL_VERSION (NU6) for that activation.
+
+# Backward compatibility
+
+Prior to the network upgrade activating on each network, NU6 and pre-NU6 nodes are compatible and can connect to each other. However, NU6 nodes will have a preference for connecting to other NU6 nodes, so pre-NU6 nodes will gradually be disconnected in the run up to activation.
+
+Once the network upgrades, even though pre-NU6 nodes can still accept the numerically larger protocol version used by NU6 as being valid, NU6 nodes will always disconnect peers using lower protocol versions.
+
+NU6 does not define a new transaction version or impose a new minimum transaction version. NU6 transactions are therefore in the same v4 or v5 formats as NU5 transactions. This does not imply that transactions are valid across the NU6 activation, since signatures MUST use the appropriate consensus branch ID.
+
+# References
+
+[^BCP14]: [Information on BCP 14 — "RFC 2119: Key words for use in RFCs to Indicate Requirement Levels" and "RFC 8174: Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"](https://www.rfc-editor.org/info/bcp14)
+
+[^zip-0200]: [ZIP 200: Network Upgrade Mechanism](zip-0200.rst)
+
+[^protocol-networks]: [Zcash Protocol Specification, Version v2023.4.0 or later. Section 3.12: Mainnet and Testnet](protocol/protocol.pdf#networks)
+
+[^protocol]: [Zcash Protocol Specification, Version v2023.4.0 or later](protocol/protocol.pdf)
+
+[^zip-2001]: [ZIP 2001 Lockbox Funding Streams](draft-nuttycom-lockbox-streams.rst)
+
+[^zip-0236]: [ZIP 236: Blocks should balance exactly](draft-hopwood-coinbase-balance.rst)
+
+[^draft-nuttycom-funding-allocation]: [ZIP ???: Block Reward Allocation for Non-Direct Development Funding](draft-nuttycom-funding-allocation.rst)
+
+[^zip-0201]: [ZIP 201: Network Peer Management for Overwinter](zip-0201.rst)
+
+[^zip-0207]: [ZIP 207: Funding Streams](zip-0207.rst)
+
+[^zip-0214]: [ZIP 214: Consensus rules for a Zcash Development Fund](zip-0214.rst)