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

SLOVENSKI STANDARD
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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

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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ETSI
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
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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
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.
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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
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).
ETSI
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 addresses, access device identifier).
b) Details of services used and their associated parameters.
c) Information relating to status.
d) Timestamps.
Content of Communication (CC) shall be provided for every IP datagram sent through the IAP's network that:
a) Has the target's IP address as the IP source address.
b) Has the target's IP address as the IP destination address.
The CC Content of communication shall contain:
a) A stream of octets for every captured datagram, containing a copy of the datagram from layer 3 upwards.
NOTE: Due to the possibility of IP source address spoofing, the fact that an intercepted packet has the target's IP
address as the IP source address does not guarantee that the packet was transmitted by the target; i.e. an
intercept in place at the interface connected to the target may not include packets originating from other
users spoofing the target's IP address and will not include packets from the actual target that contain a
spoofed IP address.
4.3.3 Intercept related information messages
Intercept Related Information shall be conveyed to the LEMF in messages, or IRI data records, respectively. Four types
of IRI records are defined:
1) IRI-BEGIN record at the first event of a communication attempt, opening the IRI transaction.
2) IRI-END record at the end of a communication attempt, closing the IRI transaction.
3) IRI-CONTINUE record at any time during a communication attempt within the IRI transaction.
4) IRI-REPORT record used in general for non-communication related events.
For a description of the use and purpose of the various IRI records refer to TS 102 232 [2].
4.3.4 Time constraints
The delays for generating the Intercept Related Information will only be caused by the access protocol handling and the
automated forwarding of this information to the delivery function.
The interception that takes places as a result of the identification of the target in the access service will experience no
unnecessary delay. The delay will only be caused by the access protocol handling and the automated forwarding of this
information to the interception function(s).
4.3.5 Preventing over and under collection of intercept data
Measures must be taken to:
1) enable timely detection of system-, network- or software failures that may cause the interception system to
over- or under collect data;
2) take appropriate action to prevent further over- or under collection; and
3) report on the anomaly to allow for corrective action by the LEA.
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11 ETSI TS 102 234 V1.2.1 (2004-10)
NOTE 1: The terms over and under collection refer to either wrongfully including data that is not part of the
intercept or not capturing data that should have been part of the intercept.
If an interception is started based on an IP-address binding event that contains session-timeout information and at the
time of the expected session-timeout no explicit session-termination event has been captured, the interception must be
stopped and the situation must be reported upon.
If an IP-address binding event is captured that contains an IP address already in use in an active intercept, but for a
different user, the intercept must be stopped and the situation must be reported upon.
NOTE 2: Due to various kinds of failures or delays in the LI infrastructure, the event indicating the logoff of a
target could be missed by the Interception function. The actual logoff would release the IP address for
reassignment to another user, which would lead to a serious kind of over collection.
5 System model
5.1 Reference network topologies
This clause describes a number of reference network topologies, typically used for Internet access over various types of
access networks.
5.1.1 Dial-up access
Internet access over a switched telephony network is typically referred to as dial-up access. Figure 2 shows the principal
equipment involved in this kind of Internet access.
IAP
PSTN
IP-enabled ("V.90")
Internet
NAS
network
ISDN
device
modem
AAA
IAP/ISP
Customer
NWO
Figure 2: Dial-up access
The CPE for dial-up access typically consists of a computer, laptop or PDA that is equipped with a modem connected to
the regular telephone network. Via this modem, the telephone number of the Network Access Server (NAS) of the IAP
is dialled. The NAS answers the call and the NAS and the end-user typically establish a Point-to-Point Protocol (PPP)
connection. Due to the distributed nature of dial-up access, a user may dial into any NAS in the network.
Once the PPP connection is established, the NAS will request the user to identify himself and to provide a password.
The NAS will then request the AAA server in the IAP infrastructure (for dial-up access typically a RADIUS server) to
perform the authentication based on the provided username and password. Additionally, the AAA server will check
whether the user is authorized to use the Internet Access Service (IAS). If so, the AAA server may provide the NAS
with an IP address that is to be used by the user. In other cases, the NAS allocates the IP address from a locally
configured pool of addresses and the AAA server does not know the IP address at the time of authentication.
Next, the NAS informs the user about the assigned IP address and other network configuration information, such as the
address of the DNS server and/or the address of the gateway to the Internet. The CPE can now set-up its IP protocol
stack and establish IP based communication with the Internet.
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12 ETSI TS 102 234 V1.2.1 (2004-10)
After the NAS has established a PPP session with the CPE, the NAS may provide the Accounting Server with
information indicating the start of the session and the parameters in use for the session (e.g. IP address, NAS address).
The Accounting Server may be a physically separate server from the Authentication/Authorization server. In the case in
which the NAS assigns IP addresses from a local pool, this is the first time the IP address assigned to the target is
known externally to the NAS.
At the end of the session, either when the user logs off or when the connection to the NAS is lost, the NAS will provide
the Accounting server with details regarding usage of the Internet connection, e.g. duration, bytes sent and received, etc.
This information can be used for accounting purposes.
From an LI perspective, the assignment of IP addresses, in relation to the usernames they are assigned to, as well as the
moment of deassignment, i.e. the exchange of accounting information, are of interest.
NOTE: Many IAPs also support tunnelling the PPP session from the NAS to a home gateway either at another
location within the IAP or residing on another network (e.g. another IAP or an enterprise). The standard
protocol used to support this is Layer 2 Tunnelling Protocol which tunnels the PPP frames from the NAS
to the home gateway. Proprietary tunnelling techniques might also be used based on the service provider.
Many of the technologies described in the present document may be used to support the tunnelling service
(e.g. RADIUS); however, since this service is not an Internet Access Service (IAS) as defined in the
present document, it is outside the scope of the present document.
5.1.2 xDSL access
Internet access over the local loop by means of using specialized equipment for achieving a high bandwidth over copper
wire is commonly referred to as xDSL Access. There is great variety of possible architectures and technologies that can
be applied for realizing an xDSL network. Therefore, figure 3 only shows the principal equipment involved in this kind
of Internet access.
PSTN
IAP
IP-enabled Router / xDSL Edge
GWR
Internet
local DSLAM
network
Bridge
modem router
device
loop
AAA
Customer IAP/ISP
NWO
Figure 3: xDSL access
The CPE can consist of a single IP enabled device which is connected to an xDSL modem or, in order to support
multiple IP enabled devices to share the xDSL connection, to a router or bridge that is connected to an xDSL modem.
The modem is connected to the copper wire of the telephone network, the local loop. In the telephone switch, this wire,
and wires from other xDSL lines, are connected to the DSL Access Multiplexer (DSLAM). By utilizing frequencies
above the telephone bandwidth, the xDSL modem and the DSLAM can encode more data to achieve a higher
bandwidth than would otherwise be possible in the restricted frequency range of a PSTN network.
For large scale xDSL infrastructures, two main approaches are used for protocol layering; PPP over ATM (PPPoA) and
PPP over Ethernet (PPPoE). In the PPPoA architecture, a CPE router encapsulates IP packets into PPP frames and then
segments them into ATM cells. The PPP link is commonly terminated at the Gateway router (GWR) of the IAP, which
concentrates PPP links from multiple Edge routers. The GWR routes the user's IP packets to their final destination. The
GWR typically uses a RADIUS server to authenticate and authorize the user. A DHCP server may be used to assign the
IP address. A PPPoA implementation involves configuring the CPE router with username and password.
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13 ETSI TS 102 234 V1.2.1 (2004-10)
In the PPPoE architecture, at the user premises an Ethernet-to-WAN bridge is used as opposed to a router and the PPP
session is established between the end user's computer and the GWR. PPPoE requires PPP client software to be
installed on the user's computer. The client software initiates a PPP session by encapsulating IP packets into PPP frames
into a MAC frames and then bridges the frames (over ATM/DSL) via the edge router to the GWR. From this point, PPP
sessions can be established, authenticated, etc. As well as in the PPPoA architecture, the GWR typically uses a
RADIUS server to authenticate and authorize the user and again DHCP may used to assign the IP address.
In the PPPoA architecture, the CPE router may keep the connection established, even if the user's computer has been
shutdown. Therefore, in this architecture IP address assignment will happen very rarely; only once until either the router
is shutdown or, if due to network or equipment failure, the connection is lost and re-established. In the PPPoE
architecture, the IP address is assigned every time the user's computer logs on.
In some cases the IAP will resort to assigning static IP addresses to xDSL users. When in this case the user establishes
an IP connection, the IP address will still be assigned by means of a RADIUS and or DHCP server, but it will always be
the same IP address. If this is the case, especially in combination with a PPPoA architecture, for LI purposes it is a lot
easier to obtain a user's IP address from the IAP administration, rather then to obtain it from the network by technical
means, e.g. capturing and interpreting RADIUS or DHCP traffic.
If it is decided to resort to technical means for intercepting the IP address, for a timely start of the interception, it may
be considered to bounce the user's connection in order to enforce assignment of a new IP address.
5.1.3 Cable modem access
Internet access over the cable network by means of using specialized equipment for achieving a high bandwidth over
coaxial wire is commonly referred to as cable modem access. As for xDSL, there is great variety of possible
architectures and technologies that can be applied for realizing a cable modem network. Therefore, figure 4 only shows
the principal equipment involved in this kind of Internet access.

IAP
Cable
IP-enabled
Cable Super
GWR
CMTS network Internet
network
hub
device modem
(Fiber/Coax)
AAA
DHCP
Customer NWO
IAP/ISP
Figure 4: Cable modem access
The CPE typically consists of an IP enabled device connected to a cable modem via an Ethernet port. The cable modem
connects to the Cable network using a coaxial cable. For downstream data, a cable modem is capable of receiving up to
36 Mbps of data. Upstream data is transmitted with data rates from 320 kbps up to 10 Mbps.
At the NWO end, the data channels are terminated at a Cable Modem Termination System (CMTS). This CMTS
aggregates multiple cable modem channels and routes the user's IP packets, either over Ethernet or over ATM, into an
IP network. Depending on the applied standards, network architecture and geographical factors, multiple CMTSs may
be aggregated by a distribution hub, multiple distribution hubs by a super hub and multiple super hubs by a Gateway
Router.
Typically, IP addresses are assigned by means of DHCP based on the MAC address of either the cable modem or the
users' computer, depending on applied standards and equipment, where either the computer or the cable modem will
broadcast a DHCP request. The DHCP servers are typically distributed at the Super hub level and provisioned from a
central location with the MAC addresses of authorized users. Typically IP addresses are assigned dynamically to most
users but may be fixed for particular users. The latter may be assigned by means of DHCP as well.
The IAP may authenticate and authorize users for the access service based on a username and password as well. Such
additional authentication can also be used for the provision process, for example when a user replaces his computer and
therefore changes his MAC address. The AAA protocol used for this may be RADIUS or proprietary.
ETSI
14 ETSI TS 102 234 V1.2.1 (2004-10)
From an LI perspective, the AAA process is less relevant than the DHCP based IP address assignment. An interception
solution in a cable modem environment will typically capture DHCP traffic in an attempt to identify a user based on his
MAC address. The potential geographical spread of DHCP servers may become an issue, since this implies that the
interception solution must therefore by distributed over a potentially large number of locations as well.
In some cases, the IAP may use PPPoE for access. This operation is similar to that described for xDSL.
5.1.4 IEEE 802.11B Access (with WiFi profile)
The IEEE 802.11B [13] Wireless LAN technology is not elaborated in the present document, since this technology is
just a wireless local LAN providing the last 100 metres to the infrastructure that provides the actual gateway to the
public Internet. The latter infrastructure will authenticate users by means similar to those described in clauses 5.1.1 to
5.1.3.
5.2 Reference scenarios
5.2.1 Logon
In order for a user to be able to use an Internet Access Services (IAS), the use
...