MCIP Draft - Protocol Version Statement Type

text/MCIP-koe-protocolVersionStatementType.md

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+```
+  MCIP: ?
+  Layer: Peer Services
+  Title: Protocol Version Statement Type
+  Authors: koe <[email protected]>
+  Status: Draft (DO NOT USE)
+  Type: Standards Track
+  Created: ?
+  Requires: [SCP statement types]
+```
+
+## Abstract
+
+MCIP-[scp hard forks] requires a new MCIP-[statement types] statement type. This MCIP specifies a 'Protocol Version' statement type.
+
+
+
+## Motivation
+
+MCIP-[statement types] statement types can only be proposed with a Peer Services Standards Track MCIP. MCIP-[scp hard forks] is a Process MCIP, so it is not appropriate to propose a new statement type there. Moreover, a 'Protocol Version' statement type may be more broadly usable than MCIP-[scp hard forks], so it should not depend on that proposal to be implemented.
+
+
+
+## MCIP-[statement types] statement type `0x01`
+
+- Let type `0x01` be 'Protocol Version'.
+  - serialize as a 4-byte unsigned integer
+  - record in little-endian form in the least significant 4 bytes of the SCP statement value
+- A `0x01` statement should be considered invalid by a node if that node does not believe the recorded version number is scheduled (see MCIP-[scp hard forks] for example).
+  - In particular, a `0x01` statement is only valid if greater than the previous block's version.
+- For MCIP-[Versatile SCP] 'optional ballot creation', version statements are not required to make a ballot.
+- When combining confirmed nominated statements into a ballot, take the lowest `0x01` statement and discard all others.
+- An MCIP-[Versatile SCP] 'simplify' function that takes a set of nomination statements and returns a minimized set of statements should not discard any `0x01` statements.
+
+
+
+## Rationale
+
+None at this time.
+
+
+
+## Backward compatibility
+
+N/A
+
+
+
+## Reference implementation
+
+Not completed
+
+
+
+## References
+
+- None