ETSI TS 103 221-1 V1.23.1 (2026-03)

Lawful Interception (LI); Internal Network Interfaces; Part 1: X1

RTS/LI-00310-1

General Information

• Status: Not Published
• Technical Committee: LI - Lawful Interception
• Current Stage: 12 - Citation in the OJ (auto-insert)
• Due Date: 15-Mar-2026
• Completion Date: 05-Mar-2026

Standards Content (Sample)

TECHNICAL SPECIFICATION
Lawful Interception (LI);
Internal Network Interfaces;
Part 1: X1

2 ETSI TS 103 221-1 V1.23.1 (2026-03)

Reference
RTS/LI-00310-1
Keywords
interface, lawful interception

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ETSI
3 ETSI TS 103 221-1 V1.23.1 (2026-03)
Contents
Intellectual Property Rights . 7
Foreword . 7
Modal verbs terminology . 7
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 9
3 Definition of terms, symbols and abbreviations . 10
3.1 Terms . 10
3.2 Symbols . 11
3.3 Abbreviations . 11
4 Overview . 12
4.1 Reference model . 12
4.1.1 Overview . 12
4.1.2 ADMF deployment model . 12
4.1.3 Triggering deployment model. 13
4.1.4 Mediation and delivery function deployment model . 13
4.2 Reference model for X1: requesting and responding . 14
4.3 Overview of security . 14
4.4 Relationship to other standards . 15
4.5 Release management . 15
5 Basic concepts . 15
5.1 The lifecycle of a Task . 15
5.1.1 Start and end of a Task . 15
5.1.2 Identification of a Task . 15
5.1.3 Destinations . 16
5.1.4 Generic Objects . 16
5.2 The lifecycle of an X1 request/response . 16
5.2.1 Identification of X1 request/response . 16
5.2.2 Responding to the request . 16
5.2.3 Behaviour if a response is not received . 17
5.3 Warnings and Faults . 17
6 Message Structure and Data Definitions . 17
6.1 X1 Message details . 17
6.2 Message definitions: starting, modifying and stopping tasks . 18
6.2.1 ActivateTask . 18
6.2.1.1 Summary . 18
6.2.1.2 TaskDetails. 19
6.2.2 ModifyTask. 22
6.2.3 DeactivateTask . 22
6.2.4 DeactivateAllTasks . 23
6.3 Message definitions: creating, modifying and removing Destinations . 23
6.3.1 CreateDestination . 23
6.3.1.1 Summary . 23
6.3.1.2 DestinationDetails . 24
6.3.2 ModifyDestination . 24
6.3.3 RemoveDestination . 25
6.3.4 RemoveAllDestinations . 25
6.4 Message details: getting information from NE . 26
6.4.1 Overview . 26
6.4.2 GetTaskDetails . 26
6.4.2.1 Summary . 26
6.4.2.2 TaskStatus . 26
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4 ETSI TS 103 221-1 V1.23.1 (2026-03)
6.4.3 GetDestinationDetails . 27
6.4.3.1 Summary . 27
6.4.3.2 DestinationStatus . 28
6.4.4 GetNEStatus . 28
6.4.4.1 Summary . 28
6.4.5 GetAllDetails . 28
6.4.5.1 Summary . 28
6.4.6 ListAllDetails . 29
6.4.6.1 Summary . 29
6.4.7 GetAllTaskDetails . 29
6.4.7.1 Summary . 29
6.4.8 GetAllDestinationDetails . 30
6.4.8.1 Summary . 30
6.4.9 GetAllGenericObjectDetails . 30
6.4.9.1 Summary . 30
6.5 Message details: reporting issues from the NE. 31
6.5.1 Overview . 31
6.5.2 ReportTaskIssue on given XID . 31
6.5.2.1 Summary . 31
6.5.2.2 Task report types . 32
6.5.3 ReportDestinationIssue on given DID . 32
6.5.3.1 Summary . 32
6.5.4 ReportNEIssue . 33
6.6 Message details: pings and keepalives . 33
6.6.1 Ping . 33
6.6.2 Keepalive . 34
6.7 Protocol error details . 35
6.8 Message definitions: managing general objects . 37
6.8.1 CreateObject . 37
6.8.1.1 Summary . 37
6.8.1.2 Generic Object Structure . 37
6.8.1.3 GenericObjectID . 37
6.8.2 ModifyObject . 38
6.8.2.1 Summary . 38
6.8.3 DeleteObject . 38
6.8.3.1 Summary . 38
6.8.4 GetObject . 38
6.8.4.1 Summary . 38
6.8.5 ListObjectsOfType. 39
6.8.5.1 Summary . 39
6.8.6 Delete AllObj ects . 39
6.8.6.1 Summary . 39
7 Transport and Encoding . 40
7.1 Introduction . 40
7.2 Profile A . 40
7.2.1 Encoding . 40
7.2.2 Transport layer . 40
7.2.2.1 HTTPS and HTTP . 40
7.2.2.2 How HTTP is used . 40
7.2.2.3 Profile . 41
8 Security. 41
8.1 Overview . 41
8.2 Transport Security . 41
8.2.1 Summary . 41
8.2.2 Profile . 42
8.2.3 Key generation, deployment and storage . 42
8.2.4 Authentication . 42
8.3 Additional security measures (beyond transport layer) . 42
Annex A (normative): Requirements . 43
ETSI
5 ETSI TS 103 221-1 V1.23.1 (2026-03)
A.1 Basic requirements . 43
A.1.1 Existing standards. 43
A.2 Protocol & Architecture requirements. 43
A.3 Security requirements . 44
A.4 Other requirements . 45
A.4.1 Performance statistics (for further study) . 45
A.4.2 Capability detection . 46
A.4.3 Remote triggering . 46
A.4.4 Requirements to be handled by the transport layer . 46
Annex B (normative): Use of extensions . 47
B.1 Overview . 47
B.2 Extension definitions . 47
Annex C (normative): Using Task Object at Mediation and Delivery Functions . 48
C.1 Overview . 48
C.2 TaskDetails . 48
C.2.1 General . 48
C.2.2 MediationDetails structure . 48
Annex D (normative): Hashed Identifiers . 51
D.1 Overview . 51
D.2 Hashed Identifier Usage . 51
D.2.1 Overview . 51
D.2.2 Hash Context . 52
D.2.3 HashedIdentifier . 52
D.2.3.1 Structure . 52
D.2.3.2 Hashing procedure . 52
D.3 Worked examples . 53
D.3.1 Worked example 1. 53
D.3.1.1 Initial information . 53
D.3.1.2 Construction of the Hash Context . 53
D.3.1.3 Binary representation of the target identity . 53
D.3.1.4 Concatenation with the salt . 54
D.3.1.5 Calculation of the hash digest . 54
D.3.1.6 Construction of the HashedIdentifier . 54
Annex E (normative): Destination Sets . 55
E.1 Overview . 55
E.2 Destination Set Usage . 55
E.2.1 Overview . 55
E.2.2 DestinationSetDetails Object. 56
Annex F (normative): Traffic Policies and IRI Policies . 57
F.1 Overview . 57
F.2 Traffic Policy Usage . 57
F.2.1 Overview . 57
F.2.2 Traffic Policy Object . 57
F.2.3 Traffic Rule Object . 57
F.3 IRI Policy Usage . 57
F.3.1 Overview . 57
F.3.2 IRI Policy Object . 58
F.3.3 IRI Rule Object . 58
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6 ETSI TS 103 221-1 V1.23.1 (2026-03)
Annex G (normative): Certificate binding URN . 59
G.1 Overview . 59
G.2 URN format . 59
G.3 Validity . 59
Annex H (normative): Configuration Information . 60
H.1 Overview . 60
H.2 X1ConfigurationDetails . 61
Annex I (informative): Tasking and operational flows . 62
I.1 Overview . 62
I.2 Example flows . 62
I.2.1 Single LIID . 62
I.2.2 Multiple LIIDs sharing an XID . 64
I.2.3 Multiple LIIDs with separate XIDs . 67
I.2.4 Triggering and triggered POIs . 69
I.2.5 Triggering with multiple LIIDs and separate XIDs . 71
Annex J (informative): Change history . 75
History . 78

ETSI
7 ETSI TS 103 221-1 V1.23.1 (2026-03)
Intellectual Property Rights
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Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Lawful Interception (LI).
The present document is part 1 of a multi-part deliverable covering the Internal Network Interfaces for Lawful
Interception (LI), as identified below:
Part 1: "X1";
Part 2: "X2/X3".
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
8 ETSI TS 103 221-1 V1.23.1 (2026-03)
1 Scope
The present document defines an electronic interface for the exchange of information relating to the establishment and
management of Lawful Interception. Typically, this interface would be used between a central LI administration
function and the network internal interception points.
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 and mediation functions for lawful interception and network internal functions, which
facilitates the interception of communication. This internal network interface typically consists of several
sub-interfaces: initial configuration of the network internal elements of lawful interception (X0), administration (X1),
transmission of intercept related information (X2) and transmission of content of communication (X3). The present
document specifies the administration interface X1.
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 in the
ETSI docbox.
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 133 107: "Universal Mobile Telecommunications System (UMTS); LTE; Digital cellular
telecommunications system (Phase 2+) (GSM); 3G security; Lawful interception architecture and
functions (3GPP TS 33.107)".
[2] IETF RFC 4122: "A Universally Unique IDentifier (UUID) URN Namespace", (July 2005). ®
[3] W3C Recommendation 28 October 2004: "XML Schema Part 2: Datatypes Second Edition".
[4] ETSI TS 103 280: "Lawful Interception (LI); Dictionary for common parameters".
[5] Recommendation ITU-T E.212: "The international identification plan for public networks and
subscriptions".
[6] ETSI TS 123 003: "Digital cellular telecommunications system (Phase 2+) (GSM); Universal
Mobile Telecommunications System (UMTS); LTE; 5G; Numbering, addressing and identification
(3GPP TS 23.003)".
[7] IETF RFC 3261: "SIP: Session Initiation Protocol", (June 2002).
[8] IETF RFC 3966: "The tel URI for Telephone Numbers", (December 2004).
[9] IETF RFC 3508: "H.323 Uniform Resource Locator (URL) Scheme Registration", (April 2003).
[10] IETF RFC 7542: "The Network Access Identifier", (May 2015).
[11] IETF RFC 2865: "Remote Authentication Dial In User Service (RADIUS)", (June 2000).
[12] IETF RFC 2818: "HTTP over TLS", (May 2000).
ETSI
9 ETSI TS 103 221-1 V1.23.1 (2026-03)
[13] IETF RFC 7230: "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
(June 2014).
NOTE: Obsoleted by IETF RFC 9110, IETF RFC 9112.
[14] IETF RFC 5246: "The Transport Layer Security (TLS) Protocol Version 1.2", (August 2008).
NOTE: Obsoleted by IETF RFC 8446.
[15] Void.
[16] IETF RFC 7525: "Recommendations for Secure Use of Transport Layer Security (TLS) and
Datagram Transport Layer Security (DTLS)", (May 2015).
NOTE: Obsoleted by IETF RFC 9325.
[17] 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)", (March 2011).
[18] IETF RFC 4519: "Lightweight Directory Access Protocol (LDAP): Schema for User
Applications", (June 2006).
[19] ETSI TS 103 221-2: "Lawful Interception (LI); Internal Network Interfaces; Part 2: X2/X3".
[20] IETF RFC 8446: "The Transport Layer Security (TLS) Protocol Version 1.3", (August 2018).
[21] IETF RFC 7540: "Hypertext Transfer Protocol Version 2 (HTTP/2)", (May 2015).
NOTE: Obsoleted by IETF RFC 9113.
[22] ETSI TS 133 127: "Digital cellular telecommunications system (Phase 2+) (GSM); Universal
Mobile Telecommunications System (UMTS); LTE; 5G; Lawful Interception (LI) architecture and
functions (3GPP TS 33.127)".
[23] IETF RFC 6530: "Overview and Framework for Internationalized Email", (February 2012). ®
[24] W3C Recommendation 21 March 2017: "XPath and XQuery Functions and Operators 3.1".
[25] IETF RFC 6920: "Naming Things with Hashes", (April 2013).
[26] FIPS PUB 202: "SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions".
[27] IETF RFC 7042: "IANA Considerations and IETF Protocol and Documentation Usage for
IEEE 802 Parameters", (October 2013).
[28] ETSI TS 103 120: "Lawful Interception (LI); Interface for warrant information".
[29] IETF RFC 5280: "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation
List (CRL) Profile", (May 2008).
[30] ETSI TS 104 000: "Lawful Interception (LI); Internal Network Interface X0".
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 may be useful in implementing an ETSI deliverable or add to the reader's
understanding, but are not required for conformance to the present document.
[i.1] OWASP: "Transport Layer Security Cheat Sheet".
ETSI
10 ETSI TS 103 221-1 V1.23.1 (2026-03)
[i.2] ETSI TR 103 308: "CYBER; Security baseline regarding LI and RD for NFV and related
platforms".
[i.3] ETSI GS NFV-SEC 009: "Network Functions Virtualisation (NFV); NFV Security; Report on use
cases and technical approaches for multi-layer host administration".
[i.4] ETSI GS NFV-SEC 012: "Network Functions Virtualisation (NFV) Release 3; Security; System
architecture specification for execution of sensitive NFV components".
[i.5] OWASP: "XML Security Cheat Sheet".
[i.6] GSMA RCC.07: "Rich Communication Suite - Advanced Communications Services and Client
Specification".
[i.7] 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".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
destination: point to which xIRI and/or xCC is delivered by the NE
Destination IDentifier (DID): identifier to uniquely identify a Destination internally to the X1 interface
Destination Set: collection of DIDs and their associated preference of use
Destination Set IDentifier (DSID): identifier to uniquely identify a Destination Set internally to the X1 interface
Network Element (NE): element performing the LI operations such as interception, or mediation and delivery
NOTE: The NE may be embedded in an NF or standalone.
Network Function (NF): function that contains an associated or embedded NE
protocol error: error at the X1 protocol level (rather than any fault with ADMF or NE)
NOTE: In the present document, the term "error" in general refers to a protocol error, whereas issues with
systems not behaving correctly are called "faults".
task: continuous instance of interception at a single NE carried out against a set of target identifiers, identified by an
X1 Identifier, starting from an activate command and ending with a deactivate command or terminating fault
terminating fault: fault signalled from NE to ADMF which terminates the specific Task
X1: LI interfaces internal to the CSP for management tasking
X1 Context: portion of Controlled Function ("NE") state associated with the X1 operations controlled by a specific
Controlling Function ("ADMF")
NOTE: When multiple ADMFs operate on an NE, the NE maintains a separate independent X1 Context for each
of the ADMFs. System-wide, a X1 Context is uniquely identified by a combination of ADMF ID and NE
ID.
X1 IDentifier (XID): identifier to uniquely identify a Task internally to the X1 interface as well as across related X2
and X3 interfaces
NOTE: The XID is also either associated to only one LIID or can be allowed to be associated to multiple LIIDs.
X1 Transaction ID: identifier used to identify a specific request/response pair
X2: LI interfaces internal to the CSP for xIRI delivery
ETSI
11 ETSI TS 103 221-1 V1.23.1 (2026-03)
X3: LI interfaces internal to the CSP for xCC delivery
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ADMF ADMinistration Function
AVP Attribute-Value Pair
AXRI Additional XID Related Information
CC Content of Communication
CIDR Classless Inter Domain Routing
CIN Communication Identity Number
CSP Communication Service Provider
DID Destination IDentifier
DSID Destination Set IDentifier
EUI Extended Unique Identifier
FQDN Full Qualified Domain Name
GTP-C GPRS Tunnel Protocol (Control plane)
GTP-U GPRS Tunnel Protocol (User plane)
HI Handover Interface
HI1 Handover Interface 1 (for administrative information)
HI2 Handover Interface 2 (for IRI)
HI3 Handover Interface 3 (for CC)
HTTP HyperText Transfer Protocol
HTTPS HTTP over TLS
IMEI International Mobile Equipment Identity
IMEISV International Mobile Equipment Identity Software Version
IMPI IP Multimedia Private Identity
IMPU IP Multimedia PUblic identity
IMSI I
...