Implement bounded address-family fallback in the client fixture
An unreachable IPv6 address delays a working IPv4 connection until a long timeout.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- IPv6 · Connection management
Estimated field mix
- Networking70%
- Performance engineering30%
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
A fictional desktop sync client works on one office network but intermittently fails on another. Application retries hide whether DNS, IPv6, or transport limits are responsible.
Setup prerequisites
- Author synthetic packet traces and local IPv4/IPv6 endpoint doubles; use no third-party scanning or captured personal traffic.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Race or sequence families under a declared bounded policy.
- Cancel losing attempts and release sockets.
- Preserve meaningful final errors when both fail.
Implementation constraints
- Use deterministic timers and loopback doubles.
Verification to include
- Reach IPv4 when the IPv6 fixture stalls.
- Fail both families without leaked attempts.
Deliverables
- Address-family fallback policy.
Rollout and recovery
Compare with the previous policy under identical traces before adoption.
Value of the work
For the engineer: Practice layered network diagnosis and reproducible troubleshooting.
For the team: Produce precise support diagnostics that distinguish application defects from connectivity conditions.
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.