FA-7286 / Transport flow control / Open access

Delayed ack is forced by second full segment or timer · case 01

Delayed ack is forced by second full segment or timer.

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

ROOT CAUSE

The faulty implementation uses `segments > 2 or expired` for the delayed-ack-is-forced-by-second-full-segment-or-timer decision.

VERIFIED REPAIR

Apply the explicit delayed-ack-is-forced-by-second-full-segment-or-timer contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `segments >= 2 and expired` and still violates a separate fixture.

Case contract

Bounded offline decision model: delayed ack is forced by second full segment or timer. 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 delayed-ack-is-forced-by-second-full-segment-or-timer 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(segments, expired):
    return segments > 2 or expired
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, False), True)", "check('fixture 2', solve(0, True), True)", "check('fixture 3', solve(1, False), False)", "check('fixture 4', solve(2, True), True)"]
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 fixture	Actual	Expected	Outcome
fixture 2	`True`	`True`	Passed
fixture 3	`False`	`False`	Passed
fixture 4	`True`	`True`	Passed
fixture 1	`False`	`True`	Failed

SHA-256 / 4b8a2cd12749464c9020ca403f39484dedc404dbb79318165f1f78246676d3ac

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(segments, expired):
    return segments >= 2 and expired
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, False), True)", "check('fixture 2', solve(0, True), True)", "check('fixture 3', solve(1, False), False)", "check('fixture 4', solve(2, True), True)"]
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 fixture	Actual	Expected	Outcome
fixture 2	`False`	`True`	Failed
fixture 3	`False`	`False`	Passed
fixture 4	`True`	`True`	Passed
fixture 1	`False`	`True`	Failed

SHA-256 / f5dffbf786de3d21aa888a7fc1063d03a962513f9ac9e69502be09f76f2032a6

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(segments, expired):
    return segments >= 2 or expired
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(2, False), True)", "check('fixture 2', solve(0, True), True)", "check('fixture 3', solve(1, False), False)", "check('fixture 4', solve(2, True), True)"]
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 fixture	Actual	Expected	Outcome
fixture 2	`True`	`True`	Passed
fixture 3	`False`	`False`	Passed
fixture 4	`True`	`True`	Passed
fixture 1	`True`	`True`	Passed

SHA-256 / b1e7537efedea7000238e9e3217a7a628983c2fe24921791d0ff8bde22946ffc

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 2026-09-29T14:38:10.242402+00:00.

Case digest / 0096114d821012597caa1b8ec230addeda56cd06ea1d29f6b8f79d140d8967e7