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
- Define supported service profiles and data classifications per interface.
- Bind producer identity to approved administration state.
- Validate object, scope reference, time, and anti-replay attributes.
- Separate X2 and X3 queues, keys, capacity, and access.
- Normalize only what the downstream profile requires.
- 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.