FA-7261 / Transport flow control / Open access

Rto includes variation and clock granularity · case 01

Rto includes variation and clock granularity.

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

ROOT CAUSE

The faulty implementation uses `srtt+variation` for the rto-includes-variation-and-clock-granularity decision.

VERIFIED REPAIR

Apply the explicit rto-includes-variation-and-clock-granularity contract, including the tested boundary and negative cases.

Unsuccessful approach: The attempted repair uses `srtt+4*variation` and still violates a separate fixture.

Case contract

Bounded offline decision model: rto includes variation and clock granularity. 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 rto-includes-variation-and-clock-granularity 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(srtt, variation, granularity):
    return srtt+variation
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(10, 2, 1), 18)", "check('fixture 2', solve(10, 0, 3), 13)", "check('fixture 3', solve(0, 0, 1), 1)", "check('fixture 4', solve(10, 1, 8), 18)"]
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	`10`	`13`	Failed
fixture 3	`0`	`1`	Failed
fixture 4	`11`	`18`	Failed
fixture 1	`12`	`18`	Failed

SHA-256 / 750a4b3da7edec94ce4cbd4dfccaa77a0b6ee66d7b05db6cab65820bc9a48ed4

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(srtt, variation, granularity):
    return srtt+4*variation
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(10, 2, 1), 18)", "check('fixture 2', solve(10, 0, 3), 13)", "check('fixture 3', solve(0, 0, 1), 1)", "check('fixture 4', solve(10, 1, 8), 18)"]
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	`10`	`13`	Failed
fixture 3	`0`	`1`	Failed
fixture 4	`14`	`18`	Failed
fixture 1	`18`	`18`	Passed

SHA-256 / 37774406061e299993abc404b4ed7693bba90905a5e27d63ed6b34871f42d4e4

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(srtt, variation, granularity):
    return srtt+max(granularity,4*variation)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(10, 2, 1), 18)", "check('fixture 2', solve(10, 0, 3), 13)", "check('fixture 3', solve(0, 0, 1), 1)", "check('fixture 4', solve(10, 1, 8), 18)"]
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	`13`	`13`	Passed
fixture 3	`1`	`1`	Passed
fixture 4	`18`	`18`	Passed
fixture 1	`18`	`18`	Passed

SHA-256 / 03274d414401ec32906cb9c43b35f64b8444d7e38467aa092c6e58ef4bc61755

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 2026-09-29T14:38:09.927888+00:00.

Case digest / d28c0cf9dd5bb8d6ba8992fddfcb63e9b1fa8e04a27ebadbb0463c76a5b5d142