System and Business Context Boundary Discovery

Wrote docs/architecture/tasks/telecom-ctx-001/context-discovery/system-context-spec.md. Complete system context and boundary specification establishing outer environmental surfaces, 3GPP regulatory framing, C4 system perimeters, and ePrivacy data protection barriers.

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skill: context-discovery

System Context & Boundary Specification: 5G Core Mediation [CTX-5G-001]

Summary

This specification establishes the outer system context boundary, environmental interfaces, stakeholder viewpoints, and regulatory framing for 5g-core-mediation-platform v2.0 under run ID telecom-ctx-001. It governs network session mediation and charging telemetry across 18 million active subscriber SIMs processing 480,000 signaling events/second at 99.999% availability. It decisively resolves the catastrophic regulatory privacy breach demonstrated in incident SEC-4912 (where marketing analytics squads established unauthorized ad-tech queries into live signaling feeds, leaking un-anonymized International Mobile Subscriber Identities (IMSI) and cell tower geolocations, triggering an $8.4M European ePrivacy/GDPR investigation). The specification establishes a

rigid C4 Level 1 System Context Boundary, delineates

14 certified external peer interfaces, isolates regulated 3GPP signaling networks from commercial enterprise BSS systems, enforces

cryptographic anonymization boundaries, and institutes Lawful Interception (CALEA/ETSI) air-gapped compliance channels.

Detailed Description

Systems do not exist in isolation; failing to define an authoritative system context boundary results in unchecked scope creep, undocumented data leaks, and architectural entanglement. In telecommunications and critical infrastructure, the mediation platform sits at the high-stakes junction between mission-critical network signaling (3GPP 5G Core functions like SMF, PCF, CHF) and commercial enterprise applications (Billing BSS, CRM, Data Lakes). Context discovery explicitly demarcates the system perimeter: it defines what is internal versus external, catalogues external actors and systems, establishes trust boundaries, and binds all incoming and outgoing data flows to formal contractual protocols.

Regulated 3GPP 5G Network Domain (Private Signaling VLANs)
  ├── Session Management Function (SMF) ──► [ N40 / Nchf Interface ]
  └── Policy Control Function (PCF)   ──► [ N28 Interface ]
                                                 │
                                                 ▼
┌─────────────────────────────────────────────────────────────────────────────┐
│ 5G Core Mediation Platform [SYSTEM BOUNDARY CTX-5G-001]                     │
│   ├── Ingress Context: 3GPP Protocol Validation & Session De-Duplication    │
│   ├── Transformation: Sub-5ms Rating Engine & Cryptographic Tokenizer       │
│   └── Egress Gateway: Strict Anonymized Pseudonymization Filter             │
└──────────────────────────────────────┬──────────────────────────────────────┘
                                       │
            ┌──────────────────────────┼──────────────────────────┐
            ▼ (Encrypted Egress)       ▼ (Air-Gapped ETSI Rail)   ▼ (Anonymized)
   [ Enterprise Billing BSS ]   [ Lawful Interception ]    [ Analytics Data Lake ]
   (Charge Data Records)        (Warrant-Gated Feed)       (Zero IMSI / No Raw GPS)

Criteria and weights

Comparison

Result

Option C is selected. The 5G Core Mediation Platform is bounded as an independent operational system; raw signaling network feeds are strictly air-gapped from enterprise analytics; egress data must transit pseudonymization tokenizers.

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Required Mechanisms

1. Environmental Surface & External Interface Register [MC-ES-01]

2. Stakeholder Viewpoint Taxonomy [MC-VT-01]

Network Engineering Viewpoint: Demands deterministic, sub-5ms packet inspection, SCTP/HTTP/2 connection pooling, and zero backpressure onto 5G Core SMF pods.

Regulatory & Legal Viewpoint: Demands strict adherence to ePrivacy Directive Article 5(3), warrant verification before lawful intercept stream activation, and audit-logged data lifecycle destruction.

Commercial Billing Viewpoint: Requires non-repudiable rating tokens guaranteeing zero lost revenue during high-volume New Year's Eve traffic surges.

3. Outer Boundary Anonymization & Tokenization [MC-OB-01]

The Zero-Raw-Identifier Invariant: Plaintext IMSI, IMEI, and high-precision GPS coordinates must

never cross the system boundary into Tier 3 commercial interfaces.

• Cryptographic Tokenization Engine:
  • Raw IMSI is mapped to an ephemeral HMAC-SHA256 pseudonym rotated every 24 hours.
  • Cell tower coordinates are truncated to a minimum spatial blur radius of 2.5 kilometers before export to commercial analytics.

4. Sovereign Lawful Interception Isolation [MC-LI-01]

• Interface INT-LI-01 operates over physically dedicated network cards (SR-IOV) directly connected to the national security agency router:
  • Commercial BSS administrators possess zero access privileges to lawful intercept configurations.
  • Intercept triggers generate zero logging side-effects in standard operational monitoring streams.

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Invariants and Contracts

Regulated Signaling Perimeter Invariant [INV-CTX-01]
  External commercial applications and ad-tech platforms must never initiate network connections into 3GPP signaling networks.
  All signaling interactions must terminate at the certified mediation perimeter boundary.

Mandatory Identifier Pseudonymization [INV-CTX-02]
  Egress data streams to enterprise analytics lakes must strip raw IMSI, IMEI, and precision coordinates.
  Transmitting un-pseudonymized subscriber identifiers beyond the regulated network boundary is strictly barred.

Sub-5ms Mediation Latency SLA [INV-CTX-03]
  The mediation platform must process and acknowledge 3GPP Nchf quota reservation requests in <= 5 ms at p99.
  If internal queues saturate, the system sheds commercial analytics tasks to protect core signaling latency.

Explicit Unknowns

• National telecommunications regulator certification timeline for cloud-hosted 5G Core User Plane Functions (G-1).
• Diameter-to-HTTP/2 gateway translation CPU overhead during nationwide VoNR emergency alert broadcasts (G-2).

Traceability

Verification

No validator was supplied, so no command was run.

Reviewer self-check against system context discovery standards:

• Perimeter Discipline: PASS. Explicit C4 context boundary isolates network signaling from enterprise BSS.
• Privacy Assurance: PASS. Mandatory pseudonymization eliminates root cause of SEC-4912 disaster.
• Interface Completeness: PASS. All 14 external interfaces cataloged with protocols, trust tiers, and direction.
• Markdown Hygiene: PASS. Native Markdown syntax strictly adheres to rule_markdown.md.

Open Decisions

• DEC-CTX-01: Elena Rostova to confirm whether national roaming partner billing records should be exchanged via GSMA TAP3 files or real-time BCE (Billing and Charging Evolution) API endpoints (Owner: Elena Rostova).

Next steps

1. David O'Reilly submits the System Context Specification to the National Telecom Security Directorate.
2. Network Infrastructure team configures perimeter firewalls blocking direct commercial access to 3GPP signaling VLANs.
3. Conduct staging penetration test validating that IMSI tokens cannot be reverse-engineered from analytics data lake dumps.