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TECHNICAL SPECIFICATION
Lawful Interception (LI);
Part 2: Internal Network Interface X2/X3 for
Lawful Interception
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2 ETSI TS 103 221-2 V1.1.1 (2019-03)
Reference
DTS/LI-00104-2
Keywords
interface, lawful interception
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3 ETSI TS 103 221-2 V1.1.1 (2019-03)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 8
3.1 Terms . 8
3.2 Symbols . 8
3.3 Abbreviations . 8
4 Introduction and reference model . 9
4.1 Reference model . 9
4.2 Assumptions . 9
4.2.1 Architecture . 9
4.2.2 Implementation/realization . 10
4.2.3 Deployment infrastructure . 10
4.2.4 Regulatory assumptions . 11
4.3 Other standards in the X1, X2, X3 series . 11
5 Message contents and parameters . 11
5.1 Overview . 11
5.2 PDU Header Fields . 12
5.2.1 Version . 12
5.2.2 PDU Type . 12
5.2.3 Header Length . 12
5.2.4 Payload Length . 12
5.2.5 Payload Format . 13
5.2.6 Payload Direction . 13
5.2.7 XID . 13
5.2.8 Correlation ID . 13
5.3 Conditional attribute fields . 13
5.3.1 General structure . 13
5.3.2 ETSI TS 102 232-1 Defined Attribute . 14
5.3.3 3GPP TS 33.128 Defined Attribute . 14
5.3.4 ETSI TS 133 108 Defined Attribute . 14
5.3.5 Proprietary Attribute . 14
5.3.6 Domain ID (DID) . 14
5.3.7 Network Function ID (NFID) . 15
5.3.8 Interception Point ID (IPID) . 15
5.3.9 Sequence Number . 15
5.3.10 Timestamp . 15
5.3.11 Source IPv4 address . 15
5.3.12 Destination IPv4 address . 15
5.3.13 Source IPv6 address . 15
5.3.14 Destination IPv6 address . 15
5.3.15 Source Port. 16
5.3.16 Destination Port . 16
5.3.17 IP Protocol . 16
5.3.18 Matched Target Identifier . 16
5.3.19 Other Target Identifier . 16
5.4 Payload . 16
5.4.1 Overview . 16
5.4.2 ETSI TS 102 232-1 Defined Payload . 17
5.4.3 3GPP TS 33.128 Defined Payload . 17
ETSI
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4 ETSI TS 103 221-2 V1.1.1 (2019-03)
5.4.4 ETSI TS 133 108 Defined Payload . 17
5.4.5 Proprietary Payload. 17
5.4.6 IPv4 Packet . 18
5.4.7 IPv6 Packet . 18
5.4.8 Ethernet Frame Packet . 18
5.4.9 RTP Packet . 18
5.4.10 SIP Message. 18
5.4.11 DHCP Message . 18
5.4.12 RADIUS Packet . 18
5.4.13 GTP-U Message . 18
5.4.14 MSRP Message . 18
6 Transport . 19
6.1 Summary . 19
6.2 TLS Transport Profile . 19
6.2.1 General . 19
6.2.2 Profile . 19
6.2.3 Authentication . 19
6.2.4 Keepalive mechanism for reliability . 19
Annex A (normative): Requirements . 20
A.1 X2 Protocol & Architecture requirements . 20
A.1.1 Basic Functionality . 20
A.1.2 Flexible . 20
A.1.3 Extensible . 20
A.1.4 Lightweight . 20
A.1.5 Delay . 20
A.1.6 Permanent and Dynamic Connections . 20
A.1.7 Reliability . 20
A.1.8 Error detection . 20
A.1.9 Redundancy . 20
A.1.10 Correlation . 21
A.1.11 Mediation into HI2/HI3 . 21
A.2 X2 Security requirements . 21
A.2.1 Authentication and Authorization . 21
A.2.2 Accounting and Audit . 21
A.2.3 Integrity Protection . 21
A.2.4 Confidentiality Protection . 21
A.2.5 Replay Protection . 21
A.2.6 Standalone interface . 21
A.2.7 Minimum Security Level . 21
A.2.8 Underlying Infrastructure Trust . 21
A.2.9 Firewall and NAT Transversal . 22
A.2.10 Certificate and Key Management . 22
A.3 X3 Protocol & Architecture requirements . 22
A.3.1 Basic Functionality . 22
A.3.2 Flexible . 22
A.3.3 Extensible . 22
A.3.4 Lightweight . 22
A.3.5 Delay . 22
A.3.6 Permanent and Dynamic Connections . 22
A.3.7 Reliability . 22
A.3.8 Error detection . 22
A.3.9 Redundancy . 23
A.3.10 Correlation . 23
A.3.11 Mediation into HI2/HI3 . 23
A.4 X3 Security requirements . 23
A.4.1 Authentication & Authorization . 23
A.4.2 Accounting/Audit . 23
A.4.3 Integrity Protection . 23
ETSI
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5 ETSI TS 103 221-2 V1.1.1 (2019-03)
A.4.4 Confidentiality Protection . 23
A.4.5 Replay Protection . 23
A.4.6 Standalone interface . 23
A.4.7 Minimum Security Level . 24
A.4.8 Underlying Infrastructure Trust . 24
A.4.9 Firewall and NAT Transversal . 24
A.4.10 Certificate and Key Management . 24
Annex B (informative): Illustrative deployment scenarios . 25
B.1 Introduction . 25
B.2 Simple deployment scenario . 25
B.3 Individual X3 POIs with shared X2 POI . 25
B.4 Separated interfaces . 26
Annex C (informative): Change History . 27
History . 28
ETSI
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6 ETSI TS 103 221-2 V1.1.1 (2019-03)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
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ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Lawful Interception (LI).
The present document is part 2 of a multi-part deliverable. Full details of the entire series can be found in part 1 [1].
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
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7 ETSI TS 103 221-2 V1.1.1 (2019-03)
1 Scope
The present document defines an electronic interface for the transmission of intercepted information as part of Lawful
Interception. This interface is used from points of interception to LI mediation functions.
Typical reference models for LI define an interface between law enforcement agencies (LEAs) and communication
service providers (CSPs), called the handover interface. They also define an internal network interface within the CSP
domain between administration/mediation functions for lawful interception and network internal functions, which
facilitates the interception of communication. This internal network interface typically consists of three sub-interfaces;
administration (called X1), transmission of intercept related information (X2) and transmission of content of
communication (X3). The present document specifies a protocol for delivering X2 and X3.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI TS 103 221-1: "Lawful Interception (LI); Part 1: Internal Network Interface X1 for Lawful
Interception".
[2] ETSI TS 102 232-1: "Lawful Interception (LI); Handover Interface and Service-Specific Details
(SSD) for IP delivery; Part 1: Handover specification for IP delivery".
TM
-2017: "IEEE Standard for Information Technology - Portable Operating
[3] IEEE Std 1003.1
System Interface (POSIX )".
[4] IETF RFC 791: "Internet Protocol".
[5] IETF RFC 8200: "Internet Protocol, Version 6 (IPv6) Specification".
TM
[6] IEEE 802.3 : "IEEE Standard for Ethernet".
[7] IETF RFC 3550: "RTP: A Transport Protocol for Real-Time Applications".
[8] IETF RFC 3261: "SIP: Session Initiation Protocol".
[9] IETF RFC 2131: "Dynamic Host Configuration Protocol".
[10] IETF RFC 2865: "Remote Authentication Dial In User Service (RADIUS)".
[11] ETSI TS 129 281: "Universal Mobile Telecommunications System (UMTS); LTE; General Packet
Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U) (3GPP TS 29.281)".
[12] IETF RFC 5246: "The Transport Layer Security (TLS) Protocol Version 1.2".
[13] IETF RFC 7525: "Recommendations for Secure Use of Transport Layer Security (TLS) and
Datagram Transport Layer Security (DTLS)".
[14] IETF RFC 6125: "Representation and Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of
Transport Layer Security (TLS)".
ETSI
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8 ETSI TS 103 221-2 V1.1.1 (2019-03)
[15] ETSI TS 133 108: "Universal Mobile Telecommunications System (UMTS); LTE; Digital cellular
telecommunications system (Phase 2+) (GSM); 3G security; Handover interface for Lawful
Interception (LI) (3GPP TS 33.108)".
[16] IETF RFC 1123: "Requirements for Internet Hosts - Application and Support".
[17] IETF RFC 4975: "The Message Session Relay Protocol (MSRP)".
[18] ETSI TS 102 232-5: "Lawful Interception (LI); Handover Interface and Service-Specific Details
(SSD) for IP delivery; Part 5: Service-specific details for IP Multimedia Services".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] OWASP TLS Cheat Sheet.
NOTE: Available at https://www.owasp.org/index.php/Transport_Layer_Protection_Che
...