{"abstract":"Path mtu payload budget subtracts all protocol overheads.","category":"Transport flow control","checks":4,"contract":"Bounded offline decision model: path mtu payload budget subtracts all protocol overheads. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.","contract_signature":"mtu, ip, transport","evaluation_group":"xh-path-mtu-payload-budget-subtracts-all-protocol-overheads","failed_approach":"The attempted repair uses `max(0,mtu-max(ip,transport))` and still violates a separate fixture.","family":"xh-path-mtu-payload-budget-subtracts-all-protocol-overheads","id":"FA-7316","implementations":{"attempt":{"sha256":"fc339315f18104cb06da64c702562b367fb7960a2c89bed3a83e8708fe70130a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport ipaddress\nimport re\nfrom urllib.parse import urlsplit, urljoin\nN = 1\nobservations = []\ndef solve(mtu, ip, transport):\n    return max(0,mtu-max(ip,transport))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(1500, 20, 20), 1460)\", \"check('fixture 2', solve(30, 20, 20), 0)\", \"check('fixture 3', solve(100, 0, 0), 100)\", \"check('fixture 4', solve(1280, 40, 8), 1232)\"]\nfor _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:\n    exec(_line)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"dd05307b040411c223190ad9ed2aa99220e53e1b8049d51d0c2095d20a2c2751","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport ipaddress\nimport re\nfrom urllib.parse import urlsplit, urljoin\nN = 1\nobservations = []\ndef solve(mtu, ip, transport):\n    return mtu-ip\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\n_fixtures = [\"check('fixture 1', solve(1500, 20, 20), 1460)\", \"check('fixture 2', solve(30, 20, 20), 0)\", \"check('fixture 3', solve(100, 0, 0), 100)\", \"check('fixture 4', solve(1280, 40, 8), 1232)\"]\nfor _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:\n    exec(_line)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"Bounded deterministic policy model over validated inputs; not a complete protocol stack or an interoperability claim. The five variants rotate the same explicit fixture set. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xh-path-mtu-payload-budget-subtracts-all-protocol-overheads","generated_at":"2026-09-29T14:38:10.607379+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic transport flow control model isolates the path-mtu-payload-budget-subtracts-all-protocol-overheads policy at a network component boundary.","root_cause":"The faulty implementation uses `mtu-ip` for the path-mtu-payload-budget-subtracts-all-protocol-overheads decision.","sha256":"0bbda1ac41feb557d9af839956adc839e27f4f1d276700b40c6d3d59b06896f3","title":"Path mtu payload budget subtracts all protocol overheads · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":55.081,"exit_code":1,"observations":[{"actual":10,"check":"fixture 2","expected":0,"passed":false},{"actual":100,"check":"fixture 3","expected":100,"passed":true},{"actual":1240,"check":"fixture 4","expected":1232,"passed":false},{"actual":1480,"check":"fixture 1","expected":1460,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": 10, \"expected\": 0, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": 100, \"expected\": 100, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 1240, \"expected\": 1232, \"passed\": false}, {\"check\": \"fixture 1\", \"actual\": 1480, \"expected\": 1460, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":45.979,"exit_code":1,"observations":[{"actual":10,"check":"fixture 2","expected":0,"passed":false},{"actual":100,"check":"fixture 3","expected":100,"passed":true},{"actual":1240,"check":"fixture 4","expected":1232,"passed":false},{"actual":1480,"check":"fixture 1","expected":1460,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 2\", \"actual\": 10, \"expected\": 0, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": 100, \"expected\": 100, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 1240, \"expected\": 1232, \"passed\": false}, {\"check\": \"fixture 1\", \"actual\": 1480, \"expected\": 1460, \"passed\": false}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}