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+# Measurement methodology
+
+## Definitions
+
+### Handshake latency
+
+Time from sending `ClientHello` until the TLS session is ready to exchange
+application data (handshake completed).
+
+Operationally:
+
+- measured at application level (recommended) using timestamps around the TLS
+  connection establishment, OR
+- measured via packet capture (tcpdump) by correlating handshake messages.
+
+### TTLB (Time-to-Last-Byte)
+
+Time from starting the request until the last byte of the response body is
+received by the client.
+
+Operationally:
+
+- measured in the client application by timestamping:
+  - T0: immediately before connect / first write attempt
+  - T_end: after reading the full response payload
+
+## Measurement principles
+
+- Prefer monotonic clocks (e.g., `std::time::Instant`)
+- Run many iterations; report distribution (p50/p95/p99) not only mean
+- Separate:
+  - cold handshakes (no resumption)
+  - optional: resumed handshakes (if you choose to include later)
+
+## What to record per run
+
+- key exchange mode: `x25519` | `x25519mlkem768`
+- payload size (bytes)
+- concurrency level
+- number of iterations
+- warmup iterations
+- CPU pinning info (if used)
+- system info (kernel, CPU, governor)
+- network profile (baseline / netem parameters)
+
+## Output format
+
+Write newline-delimited JSON (NDJSON) for easy aggregation:
+
+Example record:
+
+```json
+{
+    "mode": "x25519",
+    "payload_bytes": 1024,
+    "concurrency": 1,
+    "iter": 42,
+    "handshake_ms": 8.3,
+    "ttlb_ms": 12.1
+}
+```