Name: IPIS, IP Interception System

Text: Application Note

IP Interception System - IPIS

The IP Interception System offers flexible and scalable
solutions to mark and intercept at multiple and varied
points in the Internet and to deliver this data to one or
more authorised Law Enforcement Agencies.
Where integrated in Internet components, IPIS
supports the embedded LI functions. With no
embedded LI, IPIS offers a range of Data Collectors to
capture and filter the data.

The IP Interception System (IPIS) performs
Lawful Interception (LI) based on captured data
from the Internet, mediation of various
network devices and delivery of the intercepted
data to Law Enforcement Agencies (LEA).
It can operate with the Siemens Monitoring
Center or other Law Enforcement Monitoring
Facilities (LEMF) chosen by the LEA. It supports
the integrated LI functions of market leading
switch and router vendors, and where none is
available, offers a range of Data Collectors to
filter and capture the desired data.
The Data Collectors directly offer Ethernet and
ATM interfaces and bandwidths ranging from
small ISPs to peering points in the Internet.
Other interfaces are supported using adapters.
IPIS can also manage ETSI LI sources.
A well conceived security architecture ensures
access to targets and data only by authorized
persons. Security of both data and
management transmissions is always offered
with IPIS but customer specific solutions can be
easily implemented.

IPIS Applications
The IPIS is capable of intercepting data in the
Internet, in other IP based networks and VoIP in
Next Generation Networks (NGN). It can be
configured to intercept and deliver a range of
data using very granular triggers to select the
types of data or the targets to be intercepted.
The IPIS is used in several application scenarios
including the following:
Email only interception and delivery
VoIP interception in NGN
General Internet interception
All IP data received into the IPIS can be
distributed to LEAs according to ETSI standards.
The LEA can extract IP data based on triggers
set in the IPIS. The following trigger types can
be set in the IPIS:
Email, such as SMTP, POP3, IMAP4 &
Keyword/String Search
IP Address
Instant Messaging

Figure 1. LI Network, Mediation and LEMF environment

IP Interception System

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Background to IP Interception
Most modern Circuit Switched networks have
an integrated Lawful Interception (LI) function.
The Lawful Interception function intercepts the
targeted calls and forwards them to Law
Enforcement Agencies (LEA), as directed by an
Interception Management System (IMS). Metadata about the call (Intercept Related
Information) is sent to the IMS which forwards
it to the appropriate LEA.
In contrast to this mature standards
environment, the Internet is still in the process
of LI standardisation. Most IP interception is
performed by Data Collectors that are located
near or inside the Internet nodes and
essentially filter it for desired data.
There are a few IP Switch and Router vendors
that have started to implement LI functions
and these will become more common in
networks over time.
The varied mixture of Switch or Router
integrated LI function and Data Collectors from
different vendors needs a Mediation and
Delivery application to mediate between the
Internet and the LEA.

Siemens IP Interception System
Siemens offers the IP Interception System to
address the needs of Lawful Interception in the
Internet. There are several components in the
solutions as well as flexible configurations to
suit the needs of the customer. This application
note looks more closely at these solutions from

The Networks
There is an ever-increasing array of networks
that use IP as their data transmission protocol.
The Internet is the first that comes to mind, but
it also includes GPRS, UMTS, VoIP networks –
Next Generation Networks (NGN) and many
Wireless Networks. Where there is a mandate
to perform Lawful Interception in any or all of
these networks, the first questions are how and
where to access the data.
IPIS offers a wide variety of possibilities to gain
access to and manage the flow of the
intercepted data from the networks.

IP Interception System

These include:
SPAN Ports
Devices with integrated LI functions
Data Collectors
Load balancing techniques, including IP
Application and Aggregation switching
Interface/Protocol Mediation

Network Taps are used to connect to different
physical signals in an unobtrusive manner.
They are available for electrical and optical
lines for different transmission speeds.

Figure 2. IP Tap

SPAN Ports

In most network switches, a SPAN or mirroring
Port can be configured to copy the traffic of a
single or of multiple switch ports. Also
complete VLANs can be mirrored. However,
over-subscription of SPAN Ports can lead to a
loss of data.

Figure 3. SPAN Port

Integrated LI Function

Due to the evolving requirements of Lawful
Interception in IP networks, leading Internet
Switch and Router manufacturers have started
development to integrate an LI Function
directly into their devices.

Figure 4. Integrated LI function

More security as only the targeted data
leaves the network
No additional components within the

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Data Collectors

A Data Collector is a device used to intercept
data from IP based networks, most notably the
They come in many forms but generally
operate by passively tapping the traffic on a
communications link and filtering an
unobtrusive copy of the data for desired
content. Only the filtered data is forwarded to
the LEA.

Figure 5. Data Collector

Independence from other network
High data output rates

Its purpose is to mediate requests for
intercepted content by authorised entities and
convert them into commands that are
understood by the various Data Collector
implementations and integrated LI functions in
the networks. It must also understand the
delivery protocols and mechanisms of the Data
Collectors and the integrated LI functions and
convert the intercepted data into a form
suitable for delivery to one or more Law
Enforcement Agencies.

Marking Terminals
Marking Terminals connect to the Mediation
Device and are used by Operators to mark parts
of the Internet traffic for interception by setting
or defining targets/triggers.

Load Balancing Techniques

Load Balancers can aggregate Ethernet based
signals and distribute them to multiple Data
Collectors based on load balancing and/or
traffic filtering schemes. The Load Balancer
ensures that data, which belongs to a unique
session, is forwarded to the same connected
Data Collector. In addition to aggregation and
load balancing, pre-filtering of traffic can be
performed based on an IP protocol and port
qualifier (e.g. protocol TCP with port 25).

Interface/Protocol Mediation

With special components like Routers,
transport protocols (e.g. Frame Relay, HDLC,
ATM) can be removed. In addition, the IP traffic
can be mediated from various electrical or
optical transmission media (e.g. E3/T3, STM1/OC-3, STM-4/OC-12) to Ethernet connections.

Mediation Device
The Mediation Device sits between the Data
Collectors and/or the integrated LI functions on
the network side and the LEMFs or Monitoring
Centers on the Law Enforcement Agencies’

Figure 6. Mediation Device

IP Interception System

Figure 7. IMS – Marking Terminal

The marking process specifies identifying
aspects of Internet Traffic such as an IP
address, an email address, etc. The
targets/triggers are placed by the Mediation
Device into the Data Collectors or integrated LI
functions of the networks.

Law Enforcement Monitoring Facility (LEMF)
LEMF is the term used by ETSI to denote the
application used by the Law Enforcement
Agency to receive, analyse and archive
intercepted data. The Monitoring Center (MC)
from Siemens is such a LEMF and it is a typical
representative of a system that receives
intercepted data from the Mediation Device of
the IPIS.

Figure 8. Law Enforcement Monitoring Facility

The MC is designed with a flexible architecture
and can also be used to play the role of the
Marking Terminal where this is allowed under a
country’s LI laws. It can receive and process
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intercepted data from the Internet as well as
from PSTN, Mobile, 3G and NGN networks.
GPRS and UMTS networks
In GPRS and UMTS networks, subscribers can
be marked for monitoring of IP traffic by IMS
systems. The Intercept Related Information
(HI2) is transmitted via the IMS system to the
LEMF while the Call Content (HI3) is
transmitted directly from the appropriate
network element to the LEMF. These
transmissions are IP connections which can be
based on various transport networks (e.g.
Ethernet, ISDN, X.25).
For marked GPRS and UMTS subscribers, the
whole IP traffic is intercepted and forwarded to
the LEMF, regardless of the IP application used
(Web, Mail, Chat, etc.). This traffic does not
need to pass through the Mediation Device.

IP Interception System

The Challenge of Rapid Evolution
No network has evolved as far and as fast as
the Internet. Its constant change presents
continuous challenges to the LI technology
communications applications being used in the
Internet. As an example, the use of VoIP is
spreading rapidly and presented its own
challenges to LI technology. VoIP interception
is now supported in the IPIS and MC.
Another evolution of the Internet is towards
broadband and the consequent increase in
amounts of data that the LEA must manage.
The Siemens VDR group is proactive and
anticipatory in its analysis and development of
technologies and architectures to address the
constant change in Internet applications and
mass data management. This is reflected in the
range of protocols supported and the various
load-balancing and data segregation techniques employed in the Siemens solutions.

Page 5



Direct Access


100 Mbps and 1 Gbps Ethernet electromagnetic taps
1, 2.5, 10 Gbps Ethernet optical taps
E3 electromagnetic taps
STM-1/OC-3 and STM-4/OC-12 optical taps



E3 with HDLC to Ethernet
E3 with Frame Relay to Ethernet
E3 with PPP to Ethernet
STM-1/OC-3 Packet-over-SONET with HDLC to Ethernet
STM-1/OC-3 Packet-over-SONET with Frame Relay to Ethernet
STM-1/OC-3 Packet-over-SONET with PPP to Ethernet
STM-1/OC-3 ATM with AAL5 to Ethernet
STM-4/OC-12 Packet-over-SONET with HDLC to Ethernet
STM-4/OC-12 Packet-over-SONET with Frame Relay to Ethernet
STM-4/OC-12 Packet-over-SONET with PPP to Ethernet
STM-4/OC-12 ATM with AAL5 to Ethernet

Data Collectors


Filtering of IP-based traffic according to various trigger criteria
High throughput rates

Interfaces to
Integrated LI


Various, dependent on the vendor


E- mail (SMTP, POP3, IMAP4, Webmail)
Keyword/String Search
IP Address
Instant Messaging

Mediation Device


Supports numerous Data Collectors
Load Balancing
Supports multiple LEMF for delivery
Marking terminal
Access and marking security

Marking Terminal


Remote locations
GUI for Trigger creations

VPN Devices


Secures the connection between Data Collector and Mediation Device when they are
deployed in different locations as well as the connection between the Mediation Device
and the LEMF.


Appropriate models can be supplied by Siemens but also dedicated customer equipment
can be integrated on request if required by national legislation.

IP Interception System

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Third Generation
ATM Application Layer 5
America OnLine
Asynchronous Transfer Mode
34.368Mbps ITU standard - Europe
European Telecommunications
Standards Institute
File Transfer Protocol
General Packet Radio Service
Global System for Mobile
Graphical User Interface
ITU H series standard
Handover Interface
High level Data Link Control
Lawful Interception
Chat protocol
(Pronounced “I seek you”)
Internet Message Access Protocol
version 4
Interception Management System
Internet Protocol
Internet Relay Chat
Integrated Services Digital Network
International Telecommunications
Law Enforcement Agency

IP Interception System


Law Enforcement Monitoring Facility
Monitoring Center
Management Station
Microsoft Network
Next Generation Network
Network News Transfer Protocol
Optical Carrier - x
Post Office Protocol version 3
Point To Point Protocol
Public Switched Telecommunications
Session Initiation Protocol
Simple Mail Transfer Protocol
Synchronous Optical Network
Switched Port Analyser
Synchronous Transport Module - x
44.736Mbps ITU standard - US
Transmission Control Protocol
Universal Mobile Telecommunications
Unified User Station
Virtual Local Area Network
Voice over IP
Virtual Private Network
ITU-T standardisation for wide area

Page 7

Siemens Voice and Data Recording (VDR)
Sales Office Fax: +49 89 722 49801

Siemens Networks GmbH & Co. KG 2007
Voice & Data Recording
Hofmannstr. 51
D – 81379 Munich

Monitoring Center – Internet – Application Note
Copyright Siemens AG 2002, Dezember 2002

The information provided in this flyer contains merely
general descriptions or characteristics of performance
which in case of actual use do not always apply as
described or which may change as a result of further
development of the products. An obligation to provide the
respective characteristics shall only exist if expressly agreed
in the terms of contract. Availability and technical
specifications are subject to change without notice.
Document number S41045-N691-B018-03-7629

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