Handle emulated device sequence wrap without accepting stale frames
Sequence 0 after 65535 is rejected as old, while delayed frames sometimes overwrite current readings. Define a bounded modular-order window.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Sequence arithmetic · Ordering
Estimated field mix
- Embedded and edge50%
- Networking30%
- Distributed systems20%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
Fictional environmental-display devices send synthetic noncritical readings to a local gateway. Implement a byte-stream emulator; no physical device, radio, credentials or safety-critical control is involved.
Setup prerequisites
- Specify a small frame format with length sequence payload and checksum.
- Generate local byte streams with fragmentation corruption and reconnects.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- CFRAME-101 · Decode emulated device frame integers with explicit byte order
- CFRAME-102 · Reject emulated device frames above the receiver limit
- CFRAME-103 · Verify emulated device frame checksums before dispatch
- CFRAME-104 · Assemble fragmented emulated frames across arbitrary read boundaries
- CFRAME-105 · Resynchronize emulated device framing after a corrupt header
- CFRAME-106 · Discard incomplete emulated frames after an idle deadline
Acceptance criteria
- Legitimate wrap is accepted
- Duplicates do not dispatch twice
- Outside-window frames are rejected or require reset
Implementation constraints
- State the maximum reorder window and session boundary.
Verification to include
- Feed wrap boundary sequence
- Replay delayed pre-wrap frame
Deliverables
- Sequence policy and boundary cases
Rollout and recovery
Require a new session when sequence ordering is ambiguous.
Value of the work
For the engineer: Practice incremental parsing, fixed resource limits and protocol recovery.
For the team: Inspect whether a device adapter survives malformed input without corrupting accepted readings.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.