FA-7281 / Transport flow control / Open access

Nagle buffering applies only with outstanding data and small write · case 01

Nagle buffering applies only with outstanding data and small write.

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

ROOT CAUSE

The faulty implementation uses `size < mss` for the nagle-buffering-applies-only-with-outstanding-data-and-small-write decision.

VERIFIED REPAIR

Apply the explicit nagle-buffering-applies-only-with-outstanding-data-and-small-write contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `outstanding > 0` and still violates a separate fixture.

Case contract

Bounded offline decision model: nagle buffering applies only with outstanding data and small write. 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 nagle-buffering-applies-only-with-outstanding-data-and-small-write 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(outstanding, size, mss):
    return size < mss
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(0, 2, 10), False)", "check('fixture 2', solve(2, 10, 10), False)", "check('fixture 3', solve(2, 2, 10), True)", "check('fixture 4', solve(0, 10, 10), False)"]
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`	`False`	Passed
fixture 3	`True`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`True`	`False`	Failed

SHA-256 / 6a113150c895adefc74188c4fa6537861a6cca8b42d6d274a301ac6a5d5fb88a

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(outstanding, size, mss):
    return outstanding > 0
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(0, 2, 10), False)", "check('fixture 2', solve(2, 10, 10), False)", "check('fixture 3', solve(2, 2, 10), True)", "check('fixture 4', solve(0, 10, 10), False)"]
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`	`False`	Failed
fixture 3	`True`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / a0661fdddedfce929e8667fe7d4b4a972f7e4dc3e5af456a63692049f9df7b56

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(outstanding, size, mss):
    return outstanding > 0 and size < mss
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(0, 2, 10), False)", "check('fixture 2', solve(2, 10, 10), False)", "check('fixture 3', solve(2, 2, 10), True)", "check('fixture 4', solve(0, 10, 10), False)"]
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`	`False`	Passed
fixture 3	`True`	`True`	Passed
fixture 4	`False`	`False`	Passed
fixture 1	`False`	`False`	Passed

SHA-256 / 471cbdee52c20b81bae71d943d3c0728bedfa78f425730d48658e882e4e2d8ec

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 2026-09-29T14:38:10.153141+00:00.

Case digest / b059e2d57185daaa4aeaf17c19be01f26c67fb999b68034457a61170d10f91b5