---
title: "ETSI TS 103 221-2: X2 and X3 delivery"
chapter: "09"
---

# ETSI TS 103 221-2: X2 and X3 delivery

X2 and X3 define provider-internal delivery paths for IRI and CC toward mediation/delivery functions. They create a clean boundary between service-specific observation and standardized handover processing.

> **Safety boundary:** this chapter teaches lawful, governed system design from
> public standards. It does not provide operational targeting, activation,
> decryption, surveillance-evasion, or covert collection instructions.

## The mental model

| Concept | Plain meaning | Control that must travel with it |
|---|---|---|
| **X2** | Internal transfer of intercept-related information | Preserve event identity, timestamps, and scope |
| **X3** | Internal transfer of content of communication | Isolate throughput and confidentiality |
| **POI identity** | Identifies the producing function and trust context | Do not confuse network identity with target identity |
| **Mediation input** | Receives service-specific objects for normalization | Reject incompatible or unauthorized inputs |
| **Sequence/gap handling** | Detects missing, late, or duplicate delivery | Define recovery rather than hiding counters |
| **Flow control** | Protects functions during congestion | Dropping policy must be explicit and reportable |

## Apply it as a controlled workflow

1. Define supported service profiles and data classifications per interface.
2. Bind producer identity to approved administration state.
3. Validate object, scope reference, time, and anti-replay attributes.
4. Separate X2 and X3 queues, keys, capacity, and access.
5. Normalize only what the downstream profile requires.
6. Reconcile production, mediation acceptance, and handover delivery.

## Evidence to demand

- Load tests use synthetic data and cover receiver slowdown and failover.
- Gap and duplicate alarms expose counts and identifiers, never payload.
- A producer cannot send for a case it was not provisioned to serve.
- Mediation preserves source evidence and transformation version.

## Failure to reason about

During congestion, CC traffic fills a shared queue and delays IRI status records. Separate resource pools and declared priorities prevent one data class from hiding another’s completeness evidence.

## Feynman check

X2 carries allowed event notes from service machinery; X3 carries allowed content. Mediation checks, labels, and safely prepares both for the outside handover.