ETSI TS 102 234 V1.2.1 (2004-10)

SLOVENSKI STANDARD
SIST-TS ETSI/TS 102 234 V1.2.1:2005
01-maj-2005
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Lawful Interception (LI); Service-specific details for internet access services
Ta slovenski standard je istoveten z: TS 102 234 Version 1.2.1
ICS:
33.020 Telekomunikacije na splošno Telecommunications in
general
SIST-TS ETSI/TS 102 234 V1.2.1:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TS ETSI/TS 102 234 V1.2.1:2005

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SIST-TS ETSI/TS 102 234 V1.2.1:2005

ETSI TS 102 234 V1.2.1 (2004-10)
Technical Specification


Lawful Interception (LI);
Service-specific details for internet access services

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SIST-TS ETSI/TS 102 234 V1.2.1:2005
 2 ETSI TS 102 234 V1.2.1 (2004-10)



Reference
RTS/LI-00013
Keywords
access, internet, IP, lawful interception, security,
service
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SIST-TS ETSI/TS 102 234 V1.2.1:2005
 3 ETSI TS 102 234 V1.2.1 (2004-10)
Contents
Intellectual Property Rights.5
Foreword.5
Introduction .5
1 Scope.6
2 References.6
3 Definitions and abbreviations.7
3.1 Definitions.7
3.2 Abbreviations.7
4 General.8
4.1 Internet Access Service (IAS) .8
4.2 Target identity and IP address .8
4.3 Lawful Interception requirements .9
4.3.1 Target identity.9
4.3.2 Result of interception.9
4.3.3 Intercept related information messages.10
4.3.4 Time constraints.10
4.3.5 Preventing over and under collection of intercept data.10
5 System model.11
5.1 Reference network topologies .11
5.1.1 Dial-up access.11
5.1.2 xDSL access.12
5.1.3 Cable modem access.13
5.1.4 IEEE 802.11B Access (with WiFi profile) .14
5.2 Reference scenarios.14
5.2.1 Logon.14
5.2.2 Multi logon.14
5.2.3 Multilink logon.14
5.2.4 IP transport.14
5.2.5 Logoff.15
5.2.6 Connection loss.15
6 Intercept Related Information (IRI) .15
6.1 IRI events.15
6.2 HI2 attributes.16
7 Content of Communication (CC) .16
7.1 CC events.16
7.2 HI3 attributes.16
8 ASN.1 for IRI and CC.17
Annex A (informative): Stage 1 - RADIUS characteristics.20
A.1 Network topology.20
A.1.1 RADIUS server.20
A.1.2 RADIUS proxy.21
A.2 RADIUS service.22
A.2.1 Authentication service.22
A.2.2 Accounting service.22
A.3 RADIUS protocol.23
A.3.1 Authentication protocol.23
A.3.2 Accounting protocol.24
ETSI

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 4 ETSI TS 102 234 V1.2.1 (2004-10)
A.4 RADIUS main attributes.24
A.5 RADIUS interception.25
A.5.1 Collecting RADIUS packets.25
A.5.2 Processing RADIUS packets.25
A.5.2.1 Mapping events to RADIUS packets.25
A.5.2.2 Functional model.26
A.5.2.3 RADIUS spoofing.29
A.5.3 Mapping RADIUS on the IRI structure.29
Annex B (informative): Stage 1 - DHCP characteristics.30
B.1 Network topology.30
B.2 DHCP service.30
B.3 BOOTP protocol.31
B.4 DHCP protocol.31
B.4.1 Address assignment.32
B.4.2 Message transmission and relay agents .33
B.4.3 Security and authentication .33
B.5 DHCP main attributes.33
B.6 DHCP interception.34
B.6.1 Introduction.34
B.6.2 DHCP packets.34
B.6.3 State machine.35
B.6.3.1 Mapping DHCP packets to events .35
B.6.3.2 Timers and administrative events .36
B.6.3.3 State information.36
B.6.3.4 State machine diagram.37
B.6.4 Mapping DHCP on the IRI structure.37
Annex C (informative): IP IRI Interception .39
C.1 Introduction.39
C.2 Requirements.39
C.3 Proposed implementation.39
Annex D (informative): TCP and UDP IRI interception .40
D.1 Introduction.40
D.2 Requirements.40
D.3 HI2 requirements.40
D.4 HI3 requirements.41
D.5 General requirements.41
Annex E (informative): Bibliography.42
Annex F (informative): Change Request history.43
History .44

ETSI

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SIST-TS ETSI/TS 102 234 V1.2.1:2005
 5 ETSI TS 102 234 V1.2.1 (2004-10)
Intellectual Property Rights
IPRs essential or potentially essential to the present document 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 (http://webapp.etsi.org/IPR/home.asp).
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.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Lawful Interception (LI).
Introduction
The intention of the present document has been to follow the advice given at ETSI meetings in all cases.
The present document focuses on intercepting IP data in relation to the use of Internet Access Services (IAS) and is to
be used in conjunction with the TS 102 232 [2]. In the latter document the handing over of the intercepted data is
described.
ETSI

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SIST-TS ETSI/TS 102 234 V1.2.1:2005
 6 ETSI TS 102 234 V1.2.1 (2004-10)
1 Scope
The present document contains a stage 1 description of the interception information in relation to the process of binding
a "target identity" to an IP address when providing Internet access and a stage 2 description of when Intercept Related
Information (IRI) and Content of Communication (CC) shall be sent, and what information it shall contain.
The study shall include but not be restricted to IRI based on application of Dynamic Host Configuration Protocol
(DHCP) and Remote Authentication Dial-in User Service (RADIUS) technology for binding a "target identity" to an IP
address and CC for the intercepted IP packets.
The definition of the Handover Interface 2 (HI2) and Handover Interface 3 (HI3) is outside the scope of the present
document. For the handover interface is referred to TS 102 232 [2].
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
[1] ETSI ES 201 671: "Telecommunications security; Lawful Interception (LI); Handover interface
for the lawful interception of telecommunications traffic".
[2] ETSI TS 102 232: "Lawful Interception (LI); Handover specification for IP delivery".
[3] IETF RFC 1122: "Requirements for Internet Hosts - Communication Layers".
[4] IETF RFC 1570: "PPP LCP Extensions".
[5] IETF RFC 1990: "The PPP Multilink Protocol (MP)".
[6] IETF RFC 2131: "Dynamic Host Configuration Protocol".
[7] IETF RFC 2486: "The Network Access Identifier".
[8] IETF RFC 2865: "Remote Authentication Dial In User Service (RADIUS)".
[9] IETF RFC 2866: "RADIUS Accounting".
[10] IETF RFC 3046: "DHCP Relay Agent Information Option".
[11] IETF RFC 3118: "Authentication for DHCP Messages".
[12] IETF RFC 3396: "Encoding Long Options in the Dynamic Host Configuration Protocol
(DHCPv4)".
[13] IEEE 802.11B-1999/Cor1-2001: " IEEE Standard for Information technology—
Telecommunications and information exchange between systems—Local and metropolitan area
networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) specifications—Amendment 2: Higher-speed Physical Layer (PHY)
extension in the 2.4 GHz band—Corrigendum1".
[14] ITU-T Recommendation X.680: "Information technology - Abstract Syntax Notation One
(ASN.1): Specification of basic notation".
ETSI

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 7 ETSI TS 102 234 V1.2.1 (2004-10)

3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in TS 102 232 [2] and the following apply:
access provider: Communications Service Provider (CSP), providing access to a network
NOTE: In the context of the present document, the network access is defined as IP based network access to the
Internet.
access service: set of access methods provided to a user to access a service and/or a supplementary service
NOTE: In the context of the present document, the service to be accessed is defined as the Internet.
accounting: act of collecting information on resource usage for the purpose of trend analysis, auditing, billing, or cost
allocation
authentication: property by which the correct identity of an entity or party is established with a required assurance
authorization: property by which the access rights to resources are established and enforced
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AAA Authentication, Authorization and Accounting
ANP Access Network Provider
AP Access Provider
ASN.1 Abstract Syntax Notation 1
ATM Asynchronous Transfer Mode
BOOTP BOOTstrap Protocol
CC Content of Communication
CHAP Challenge Handshake Authentication Protocol
CMTS Cable Modem Termination System
CPE Customer Premises Equipment
CSP Communications Service Provider (covers all AP/NWO/SvP)
DHCP Dynamic Host Configuration Protocol
DNS Domain Name System
DoS Denial of Service
DSL Digital Subscriber Line
DSLAM Digital Subscriber Line Access Multiplexer
GWR GateWay Router
HI1 Handover Interface 1 (for Administrative Information)
HI2 Handover Interface 2 (for Intercept Related Information)
HI3 Handover Interface 3 (for Content of Communication)
IAP Internet Access Provider
IAS Internet Access Service
IRI Intercept Related Information
ISDN Integrated Services Digital Network
ISP Internet Service Provider
LCP Link Control Protocol
LEA Law Enforcement Agency
LEMF Law Enforcement Monitoring Facility
LI Lawful Interception
MAC Media Access Control
NAS Network Access Server
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 8 ETSI TS 102 234 V1.2.1 (2004-10)
NWO NetWork Operator
PAP Password Authentication Protocol
PPP Point-to-Point Protocol
PPPoA Point-to-Point Protocol over ATM
PPPoE Point-to-Point Protocol over Ethernet
PSTN Public Switched Telephone Network
QoS Quality of Service
RADIUS Remote Authentication Dial-In User Service
SLIP Serial Line Interface Protocol
SvP Service Provider
TCP Transmission Control Protocol
TLV Type-Length-Value
UDP User Datagram Protocol
4 General
4.1 Internet Access Service (IAS)
An Internet Access Service (IAS) provides access to the Internet to end users via a modem connected to a telephone-,
cable- or wireless access network owned by a Network Operator (NWO). The IAS is typically provided by an Internet
Access Provider (IAP) or Internet Service Providers (ISP), where an ISP also provides supplementary services such as
E-Mail, Chat, News, etc. For the remainder of the document, the provider of the Internet Access Service (IAS) will be
referred to as IAP and although NWO and IAP may be the same party, in all figures in the present document, they are
depicted as separate entities.

Customer

Access
IAP

Premises
  Internet
Network
Network

Equipment

(CPE)


Customer NWO IAP/ISP

Figure 1: Internet access
The customer typically connects to the IAP via a Telco or cable company owned access network, such as the
PSTN/ISDN telephony network for dial-up and xDSL access, the cable-TV network for cable modem access or
alternatively a IEEE 802.11B [13] wireless network for WiFi access.
The service provided by the IAP is no more and no less than to provide a user with a valid IP address for transporting
and receiving data over an IP based network and to provide transit access to the Internet for this data.
4.2 Target identity and IP address
Before the IAP can provide a user with a valid IP address, there is a need for Authentication, Authorization and during
or at the end of the communication session there is a need for Accounting.
In order to perform these functions, the IAP may deploy equipment in its network that implements an Authentication,
Authorization and Accounting (AAA) protocol such as RADIUS. The other protocol mentioned in the scope
declaration, DHCP, is not really an AAA protocol, since it does very limited authentication and no authorization or
accounting. DHCP can assign IP addresses and provide network configuration information to the user and is therefore
often used in combination with RADIUS or other (proprietary) equipment.
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 9 ETSI TS 102 234 V1.2.1 (2004-10)
When a user is authenticated and authorized, the IAP will assign an IP address to the user. The assignment of the IP
address can be performed by using RADIUS, DHCP or a combination of the two. In the latter case, often the RADIUS
server will act as a client to the DHCP server, where the DHCP server assigns the IP address and the RADIUS server
forwards the information towards the user. The user will use the assigned IP address to communicate over the Internet
and therefore, for the duration of the session, traffic from and to this user can be identified by means of this IP address.
In some cases (e.g. dial-up access), the Network Access Server (NAS) may assign the IP address to the user; either from
a local IP address pool or by using DHCP and does not use RADIUS authentication for IP address assignment.
From an LI perspective, the moments of assignment and deassignment of the IP address and the protocol used for it are
of interest. It is at the moment of assignment, and only at that particular moment, that the target identity can be tied to a
dynamically assigned IP address, which can then further be used to intercept IP traffic from the particular user. At the
moment of deassignment, interception of IP data based on that particular IP address must stop immediately, since the IP
address may be handed out to another user shortly after.
4.3 Lawful Interception requirements
This clause lists the requirements for Lawful Interception. These requirements are derived from higher-level
requirements listed in ES 201 671 [1] and TS 102 232 [2] and are specific to Internet Access Services (IAS). These
requirements focus on both the administrative part of Internet access for delivery over HI2 as well as capturing traffic
for delivery over HI3.
4.3.1 Target identity
Where the special properties of a given service, and the justified requirements of the LEAs, necessitate the use of
various identifying characteristics for determination of the traffic to be intercepted, the provider (CSP) shall ensure that
the traffic can be intercepted on the basis of these characteristics.
In each case the characteristics shall be identifiable without unreasonable effort and shall be such that they allow clear
determination of the traffic to be intercepted.
The target identity will be dependant on the access mechanism used and the parameters available with the AP. The
target identity could be based on:
a) Username or Network Access Identifier (as defined in RFC 2486 [7]).
b) IP address (IPv4 or IPv6).
c) Ethernet address.
d) Dial-in number calling line identity.
e) Cable modem identifier.
f) Other unique identifier agreed between AP and LEA.
The target identity must uniquely identify the target in the provider's network. Investigations prior to the interception
might involve other identifiers such as a DNS name (Fully Qualified Domain Name). Further study may yield more
types of target identity.
4.3.2 Result of interception
The network operator, access provider or service provider shall provide Intercept Related Information (IRI), in relation
to each target service:
a) When an attempt is made to access the access network.
b) When an access to the access network is permitted.
c) When an access to the access network is not permitted.
d) On change of status (e.g. in the access network).
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 10 ETSI TS 102 234 V1.2.1 (2004-10)
e) On change of location (this can be related or unrelated to the communication or at all times when the apparatus
is switched on).
The IRI shall contain:
a) Identities used by or associated with the target identity (e.g. dial-in calling line number and called line number,
access server identity, Ethernet
...