mrambossekandClaude Fable 5
4ffa6e4ae2
"3 % loss" sends an engineer looking in both directions at once. The server records every packet it received per sequence number, so the two cases are distinguishable: sent-but-never-seen is upstream loss, seen-but-no-reply is downstream. The findings say which, and say what is not implicated. Downstream loss is measured against what reached the server, not against what was sent — the other denominator counts every upstream loss twice and overstates the return path. Per-direction jitter comes out of the same records without needing synchronised clocks: (server_rx - client_tx) carries a constant unknown offset, and differencing successive samples cancels it, so RFC 3393 variation is honestly attributable to a direction even though absolute latency is not. Correlation is by wire sequence number, not loop index — the counter is shared with every packet type on the session. ProbeSession exposes it even for a lost probe, since that is precisely the packet whose direction is in question. Live against fmr: 0.08 ms upstream jitter vs 0.85 ms downstream, an asymmetry a round-trip test cannot see. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Echolot app
The production Android client (spec). Native Kotlin + Jetpack Compose. Multi-module; built bottom-up from a verifiable protocol spine.
Modules
| Module | Type | Status |
|---|---|---|
core-protocol |
pure Kotlin/JVM | done — client half of probe-protocol.md, verified live against the server |
core-measurement |
pure Kotlin/JVM | planned — measurement-schema.md types |
core-probe |
Android lib | planned — app-tier probes, ported from echolot-prober |
core-shizuku |
Android lib | planned — dual-path executor (UserService + newProcess fallback) |
app |
Android app | planned — Compose UI |
core-protocol is deliberately Android-free so it builds and unit-tests on any JDK (no Android
SDK) and can run integration tests against a live server.
core-protocol
Implements the control plane (SPKI-pinned enrollment/profile/sessions via HttpsURLConnection —
Android-API-1 compatible, hostname verification off because trust is the pin), the HKDF-SHA256
session-key schedule, and the binary ELT1 UDP data plane (HMAC gate, ECHO + observation block,
MTU probe) — byte-compatible with the Go server.
./gradlew :core-protocol:test # unit tests (crypto vectors, wire round-trip)
scripts/test-fmr.sh # live end-to-end test against the deployed server
test-fmr.sh mints an enrollment token over SSH, enrolls via the public control plane, computes
the SPKI pin from the served cert, and runs LiveServerTest — proving the client speaks the wire
protocol to the real server (enroll → profile → session → echo+observation → MTU → observations).
The live test self-skips when ECHOLOT_LIVE_* env vars are absent, so unit runs and CI stay green
offline.