Merge pull request #928 from zcash/draft-nu7-deployment

[ZIP-254] Deployment of the NU7 Network Upgrade

zips/zip-0254.md

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+
+    ZIP: 254
+    Title: Deployment of the NU7 Network Upgrade
+    Owners: Arya <[email protected]>
+    Status: Draft
+    Category: Consensus / Network
+    Created: 2024-10-31
+    License: MIT
+    Discussions-To: <https://github.com/zcash/zips/issues/839>
+
+# 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 NU7 network upgrade.
+
+# Specification
+
+## NU7 deployment
+
+The primary sources of information about NU7 consensus protocol changes are:
+
+* The Zcash Protocol Specification [^protocol].
+* ZIP 200: Network Upgrade Mechanism [^zip-0200].
+
+The network handshake and peer management mechanisms defined in ZIP 201 [^zip-0201] also apply to this upgrade.
+
+The following network upgrade constants [^zip-0200] are defined for the NU7 upgrade:
+
+CONSENSUS_BRANCH_ID
+: `0x77190AD8`
+
+ACTIVATION_HEIGHT (NU7)
+: Testnet: TBD
+: Mainnet: TBD
+
+MIN_NETWORK_PROTOCOL_VERSION (NU7)
+: Testnet: `170130`
+: Mainnet: `170140`
+
+For each network (Testnet and Mainnet), nodes compatible with NU7 activation on that network MUST advertise a network protocol version that is greater than or equal to the MIN_NETWORK_PROTOCOL_VERSION (NU7) for that activation.
+
+# Backward compatibility
+
+Prior to the network upgrade activating on each network, NU7 and pre-NU7 nodes are compatible and can connect to each other. However, NU7 nodes will have a preference for connecting to other NU7 nodes, so pre-NU7 nodes will gradually be disconnected in the run up to activation.
+
+Once the network upgrades, even though pre-NU7 nodes can still accept the numerically larger protocol version used by NU7 as being valid, NU7 nodes will always disconnect peers using lower protocol versions.
+
+# 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)
+
+[^protocol]: [Zcash Protocol Specification, Version 2024.5.1 or later](protocol/protocol.pdf)
+
+[^protocol-networks]: [Zcash Protocol Specification, Version 2024.5.1 [NU6]. Section 3.12: Mainnet and Testnet](protocol/protocol.pdf#networks)
+
+[^zip-0200]: [ZIP 200: Network Upgrade Mechanism](zip-0200.rst)
+
+[^zip-0201]: [ZIP 201: Network Peer Management for Overwinter](zip-0201.rst)