FAILURE MAP
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FA-7271 / Transport flow control / Open access

Congestion loss threshold has two segment floor · case 01

Congestion loss threshold has two segment floor.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The faulty implementation uses `flight//2` for the congestion-loss-threshold-has-two-segment-floor decision.

VERIFIED REPAIR

Apply the explicit congestion-loss-threshold-has-two-segment-floor contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `min(flight//2,2*segment)` and still violates a separate fixture.

Case contract

Bounded offline decision model: congestion loss threshold has two segment floor. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.

Why this case matters

This deterministic transport flow control model isolates the congestion-loss-threshold-has-two-segment-floor policy at a network component boundary.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(flight, segment):
    return flight//2
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, 2), 4)", "check('fixture 2', solve(20, 2), 10)", "check('fixture 3', solve(0, 1), 2)", "check('fixture 4', solve(8, 2), 4)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
fixture 21010Passed
fixture 302Failed
fixture 444Passed
fixture 114Failed

SHA-256 / 85ba6efdcf33a09a6c018c32f79e0535c6ce350b8a1e7c77d8b4cd27915cc3e5

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(flight, segment):
    return min(flight//2,2*segment)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, 2), 4)", "check('fixture 2', solve(20, 2), 10)", "check('fixture 3', solve(0, 1), 2)", "check('fixture 4', solve(8, 2), 4)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
fixture 2410Failed
fixture 302Failed
fixture 444Passed
fixture 114Failed

SHA-256 / f5c5b064ef79b12f6bf1bd59b20c9ac583ca0f9ae185401addbe0d44898bb17d

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(flight, segment):
    return max(flight//2,2*segment)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, 2), 4)", "check('fixture 2', solve(20, 2), 10)", "check('fixture 3', solve(0, 1), 2)", "check('fixture 4', solve(8, 2), 4)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
    exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
fixture 21010Passed
fixture 322Passed
fixture 444Passed
fixture 144Passed

SHA-256 / 6269aafaf1a641d382934da7bbd928785d10c50007cb9c3e4e31a43e46429755

Verification & scope

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.

Observations recorded using Python 3.12.14 at 2026-09-29T14:38:09.970506+00:00.

Case digest / eed864ba80904b561fecf9a0d5c7a0b717b9bf3c35cefcc6cdf8e29be2c0f3d1