62 lines
4.6 KiB
Markdown
62 lines
4.6 KiB
Markdown
# network-sync-strategy Specification
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## Purpose
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Define how client and server route high-frequency gameplay synchronization traffic, reject stale updates, reconcile authoritative state, and process clock-sync samples independently of session lifecycle.
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## Requirements
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### Requirement: Hosts assign delivery policies to synchronization message types
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The shared networking core SHALL allow hosts to map business message types to delivery policies. `MoveInput` and `PlayerState` MUST be assignable to a high-frequency sync policy that is independent from the reliable ordered control policy used by login and lifecycle traffic, while `ShootInput` and `CombatEvent` MUST remain independently routable business messages that can stay on the reliable ordered lane.
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#### Scenario: High-frequency movement and state messages use a dedicated policy
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- **WHEN** the client or server sends `MoveInput` or `PlayerState`
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- **THEN** the runtime resolves a high-frequency sync delivery policy for that message type
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- **THEN** the message is sent through the sync lane configured for that policy instead of defaulting to reliable ordered delivery
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#### Scenario: Shooting and combat events keep reliable ordered delivery
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- **WHEN** the client or server sends `ShootInput` or `CombatEvent`
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- **THEN** the runtime resolves the reliable ordered delivery policy for that message type
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- **THEN** those messages continue to use the reliable transport path
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#### Scenario: Control traffic keeps reliable delivery
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- **WHEN** the runtime sends login, logout, heartbeat, or other session-management messages
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- **THEN** the runtime resolves the reliable ordered control policy
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- **THEN** those messages continue to use the reliable transport path
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### Requirement: Sequenced sync receivers discard stale gameplay updates
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The high-frequency sync strategy SHALL tag gameplay synchronization messages with monotonic sequencing information and MUST discard stale `MoveInput` or `PlayerState` updates that arrive older than the last accepted update for the same peer or entity stream. `ShootInput` and `CombatEvent` MUST NOT be discarded by the latest-wins stale filter.
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#### Scenario: Older movement input is ignored
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- **WHEN** the server receives a `MoveInput` update with a tick or sequence older than the latest accepted input for that player
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- **THEN** the server drops that stale movement update
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- **THEN** the newer accepted movement input remains authoritative for simulation
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#### Scenario: Older player state does not rewind a client
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- **WHEN** the client receives a `PlayerState` update with a tick or sequence older than the latest applied authoritative state for that player
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- **THEN** the client ignores the stale state update
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- **THEN** visible movement continues from the newer authoritative state without rewinding to older data
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#### Scenario: Reliable gameplay events bypass stale-drop filtering
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- **WHEN** the runtime receives a `ShootInput` or `CombatEvent` message
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- **THEN** the latest-wins stale filter does not reject that message solely because of sync-sequence rules
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- **THEN** reliable ordered handling remains responsible for preserving event delivery semantics
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### Requirement: Authoritative correction prunes acknowledged prediction history
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The client sync strategy SHALL reconcile local prediction against authoritative player-state updates by pruning acknowledged movement inputs at or before the authoritative tick and only reapplying newer pending `MoveInput` messages.
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#### Scenario: Reconciliation removes already acknowledged movement inputs
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- **WHEN** the client accepts an authoritative `PlayerState` update for tick `N`
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- **THEN** locally buffered predicted `MoveInput` messages with tick less than or equal to `N` are removed from the replay buffer
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- **THEN** only `MoveInput` messages newer than `N` remain eligible for re-simulation
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### Requirement: Clock synchronization is a separate sync-policy concern
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The shared networking core SHALL process server-tick or clock-synchronization samples through a dedicated sync-policy component rather than storing clock-sync ownership inside `SessionManager`.
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#### Scenario: Heartbeat response contributes a clock sample without mutating lifecycle
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- **WHEN** a heartbeat or gameplay sync message carries a server-tick sample
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- **THEN** the runtime forwards that sample to the clock-sync strategy
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- **THEN** session lifecycle state remains unchanged except for liveness or RTT bookkeeping
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#### Scenario: Hosts can consume smoothed clock data for prediction
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- **WHEN** prediction or reconciliation code needs the current server-time estimate
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- **THEN** it reads that estimate from the clock-sync strategy or state object
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- **THEN** it does not query `SessionManager` for authoritative clock ownership |