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wo 2005/025133 PCT/SE2003/001392 , 

MONITORING IN A TELECOMMDNICATION NETWORK 

TECHNICAL FIELD OF THE INVENTION 

The present invention relates to methods and arrangements 
for monitoring media flow in a telecommunication network 
that comprises a control domain that handles session 
5 control, and a bearer domain that handles the media flow. 



DESCRIPTION OF RELATED ART 

Three major trends currently occurs in telecommunication, 
i^e. 1) increasing amount of data traffic, 2) real-time 

10 communication goes from circuit switching to packet 
switching, and 3) new focus of real-time in packet switching, 
for example video and multimedia. The ever increasing amount 
of data traffic as well as real-time communication in packet 
switched networks leads to a demand for monitoring of this 

15 data traffic with the same level of security and 
confidentiality as known from circuit switched networks 
monitoring. In circuit switched networks,, e.g. telephony 
networks, it is customary to monitor communication 
connections from a remote operation centre so that a network 

20 operator wishing to operate real time traffic can constantly 
receive information on the quality of the communication 
lines. Another application of monitoring is lawful 
interception, i.e. the act of intercepting a communication 
on behalf of a law enforcement agency. 

25 From the above, it is only natural that network operators 
will want to continue such monitoring approaches in other 
types of networks for example in packet switched networks. 

One approach is described in the international application 
WO 02/102111. It is proposed to provide an interception unit 
30 to store an identification of a communication connection to 
be monitored. A copying unit hereby copy selected cells to a 
monitoring connection. The solution according to the 



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wo 2005/025133 PCT/SE2003/001392 

international application implies isolation of cells to be 
intercepted. According to the international application, a 
predefined session is monitored by listen to the session via 
an extra port. There is a possibility with the solution in 
5 the international application, for the end-user, to find out 
with which IP address he is communicating, i.e. to find out 
that interception is going on. This possibility is 
considered as a drawback. 

Requirements for lawful interception in 3GPP ( S'^ Generation 
10 Partnership Project) networks are being standardised within 
3GPP and ETSI. So far requirements on IMS (IP Multimedia 
Subsystem) for multimedia communication are only concerned 
with IRI (Intercept Related Inf orrmation) and not with CC 
(Content of Communication), i.e. the media flow. The 
15 solutions specified so far within the standardisation work 
foresee interception only of IRI from IMS. This is a natural 
consequence of the fact that CC is, for normal two-party 
sessions, not processed within IMS. This means that CC will 
have to be intercepted by involving the backbone or access 
20 network. However, some of sessions in 3GPP require special 
media nodes in the IP-based network in order to handle the 
media flow. The following are examples of such cases: 

- Multi-party sessions within the IP-based network which 
requires a multi-party node. 

25 - Interworking with the legacy telephone network which 
requires a media gateway for the media flow. 

- Interworking with other types of IP-based networks (e.g. 
between a SIP-based (Session Initiation Protocol) and 
H.323-based network) which also requires a gateway for the 

30 media flow. 



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PCT/SE2003/001392 



The invention that now will be presented refers to this type 
of sessions and it proposes a principle for intercepting the 
content of a session for these cases* 



5 SXJMMARY OF THE IMVEKTION 

The present invention relates to problems how to conceal^ to 
involved parties, monitoring of media flow when the flow is 
monitored via an extra port in a media-handling node. 
Assigning an extra port to a media-handling node is a 
10 visible measures to an involved party. 

The problem is solved by the invention by, for each media 
flow session that is transported through the media-handling 
node, assigning an extra port to the node and by connect 
assigned ports only for those sessions that are of interest 
15 to monitor. While assigning an extra port to a media- 
handling node is a visible measure to involved parties, the 
connecting of the port is not. Monitoring of a session is 
difficult to detect for an involved party when extra ports 
always are assigned for each session. 

20 More in detail, the problem is solved by a method for 
monitoring media session flow in a telecommunication network 
that comprises a media-handling node through which session 
flows. The session is hereby transported via inports and 
outports in the node. An extra port is assigned to the 

25 media-handling node for each new session that is transported 
through the node. The method comprises the following further 
steps : 

- Storing in a database LI-DB, identification of a first 
subscriber A for which monitoring is desired. 

30 - Setting up a connection between the first subscriber A and 
a second subscriber B. 

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- Assigning an extra port (XPl) that is adherent to the 
session between the first and second subscriber (A, B) . 

- Connecting the assigned extra port XPl that is adherent to 
the session between the first and second subscriber A^ B. 

5 - Monitoring the session between the first and second 
subscriber via the extra port XPl. 



An arrangement according to the invention comprises means 
for performing the above mentioned method steps. 

10 

The object of the present invention is to make it possible 
to perform real-time monitoring of Content of Communication 
flow and to conceal the monitoring to involved subscriber - 

Another advantage is that a minimum of adaptations of the 
15 normal Jietwork functions is required. 

Another advantage is that the invention makes it possible to 
perform real-time interception of the session initiated by 
the control network. 

Another advantage is that the invention does not require any 
20 re-routing of the media session. Since the session is routed 
and treated exactly in the same manner as if the call was 
not . intercepted it is impossible for the end user to find 
out whether the call is intercepted or not. 

Yet another advantage is the possibility to conceal 
25 interception to other networks and to personnel that is 
involved in the operation and maintenance of the network. 



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The invention will now be described more in detail with the 
aid of preferred embodiments in connection with the enclosed 
drawings . 



5 BRIEF DESCRIPTION OF THE DRAWINGS 

. Figure 1 belongs to prior art and discloses a block 
schematic illustration of two subscribers located in 
separate access networks. Control of the media flow is 
handled in a control domain and the media flow is handled in 
10 a bearer domain. 

Figure 2 shows a block schematic illustration of two 
subscribers located in different access networks. The figure 
discloses interception according to the invention. 

Figure 3 shows a block schematic illustration of a Media- 
15 handling Node. 

Figure 4 shows a flow chart illustrating a method used to 
initiate interception according to the invention. 



DETAILED DESCRIPTION OF EMBODIMENTS 

20 At first, interception of Intercept Related Information IRI 
according to current standardisation will be briefly 
discussed together with figure 1. Intercept Related 
Information IRI is defined as signalling information related 
to subscribers. Figure 1 belongs to prior art and discloses 

25 a first mobile subscriber A and a second mobile subscriber 
B. The subscriber A is located in a first access network 
ACNW-A, which network is subscriber A's home location. 
Subscriber B is located in a second access network ACNW-B. 
Media flow MF, for example speech, is communicated between 

30 the subscribers A and B via a backbone network BBNW. The 



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media flow is transported in a path in the bearer domain BD. 
The control of the media flow takes place in the control 
domain CD. Control information can for example be, 
signalling during set-up of a call. The control information 
5 related to the A subscriber is handled in the IP multimedia 
subsystem domain IMS-A and the control information related 
to the B subscriber is handled in the IP multimedia 
subsystem domain IMS-B. The control information passes 
several Call/Session Control Functions CSCF in both IMS-A 

10 and IMS-B. Requirements for interception of control 
information, also called Intercept related information IRI, 
are being standardised within the 3GPP and ETSI. Figure 1 
discloses interception of IRI according to prior art. The 
control information is hereby copied into a lawful 

15 interception database LI-DB located in relation to a serving 
CSCF in IMS-A, i.e. S-CSCF-A. The information is then 
forwarded from the LI-DB to a lawful interception monitoring 
facility LEMF, where the IRI is monitored. Information that 
is of interest to monitor can for example be if a certain 

20 subscriber has made a call, to whom the call was made and 
for how long time. After a call has been set-up between the 
subscriber A and B, the media flow MF between the 
subscribers is routed via an edge-node EDGE-A in the access 
network ACNW-A, the backbone network BBNW and via an edge- 

25 node EDGE-B in the access network ACNW-B. 

According to the present invention, which now will be 
discussed, it is the content of communication that is of 
particular interest to monitor and furthermore to conceal 
the monitoring to involved parties. 

30 Figure 2 discloses interception according to the invention. 
The figure shows the same network as was disclosed in figure 
1. The IP multimedia subsystem domain IMS-A in figure 2 
comprises a media-handling node MHN. MHN is a collective 
term for different types of gateways. The media-handling 

35 node MHN is disclosed more in detail and will be further 



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explained in figure 3. A database, for example the lawful 
interception database LI-DB contains identification of what 
subscribers that are to be intercepted. In this first 
embodiment, the first subscriber A is to be intercepted and 
consequently an identification of A is stored in LI-DB. When 
a call is set-up between the subscriber A and the subscriber 
B, monitoring according to the invention takes place. Before 
this monitoring is explained, the media-handling node MHN 
will be explained together with figure 3. 



Figure 3 discloses the media-handling node MHN shown in 
figure 2. The media-handling node can for example be a PSTN 
gateway used in public switching networks, a video gateway 
for video applications or a conference bridge used in 
15 multiple party conferences. The MHN in figure 3 comprises 
so-called first ports PI1-PI5 and second ports P01-P05. 
A media session flow between two subscribers is transported 
bi-directional in the media-handling node MHN between a 
first and second port. In the example in figure 3, five 
20 media session flows are transported in the MHN. According to 
the invention every session that is set up in the node MHN 
is assigned an extra port XP1-XP5 in the MHN. A media 
session between PIl and POl for example is the cause of an 
extra port XPl. Media multiparty sessions between more than 
25 two ports in the MHN are treated in a similar way. If a 
session is set up between one first port PIl and a number of 
second ports, POl-POn, an extra port PXl is always assigned 
to this session. 

30 The invention will now be further explained together with 
figure 2 and 3. The first subscriber A is, as mentioned, the 
subscriber for which monitoring is requested. An 
identification of the first subscriber A is stored in the 
database LI-DB. Monitoring starts when a connection is set- 

35 up between the first subscriber A and a second subscriber, 
in this example the subscriber B. Media flow session is 



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wo 2005/025133 PCT/SE2003/001392 

hereby transported through the media-handling node MHN via 
the ports PI3 and P03. Extra ports are set up in the node 
MHN for each session that is set up in the node independent 
of if monitoring is requested or not. An extra port XP3 is 
5 in this case set up adherent to the session between the 
first and second subscriber A and B. An indicator FLAG is 
sent from the database LI-DB to the edge node EDGE-A 
indicating that this session is to be monitored. Since the 
session is to be monitored the edge node initiates 

10 connecting of the extra port XP3, for example via a router 
RO, see figure 2. The media flow session between the ports 
PI3 and P03 is hereby forwarded from the media-handling node 
MHN to the lawful interception monitoring facility LEMF, via 
the extra port XP3 and the router RO^ see figure 2 and 3. As 

15 an alternative, the indicator can be forwarded to the media 
handling node MHN whereby the extra port is connected. The 
indicator is added to the normal signalling associated with 
the session. 

20 In figure 4 some essential steps of the invention is 
disclosed in a flowchart. The flowchart is to be read 
together with the earlier shown figure 2 and 3. The method 
for monitoring media session according to the invention 
comprises the following steps: 

25 - An extra port XP1-XP5 is assigned to the media-handling 
node MHN for each new session that is transported through 
the node. This step is shown in figure 4 by a block 101. 

- An identification of the first subscriber A for which 
monitoring is desired is stored in the database LI-DB. 

30 This step is shown in figure 4 by a block 102. 

- A connection between the first subscriber A and a second 
subscriber B is set up. This step is shown in figure 4 by 
a block 103. 



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- An extra port XPl that is adherent to the session between 
the first and second subscriber B is connected. This 
step is shown in figure 4 by a block 104. 

- The session between the first and second subscriber is 
5 monitored via the extra port XPl. This step is shown in 

figure 4 by a block 105. 



Different variations are of course possible within the 
scope of the invention. The two subscribers A and B can be 

10 situated in the same access network or in different access 
networks in different countries. The subscriber unit for 
which interception is desired may have roamed to an access 
network in another country than the country of the 
subscribers home access network. In the embodiments, the 

15 subscriber A is the monitored subscriber and if using 
standard telecommunication terminology it can be assumed 
that the subscriber A also is the calling subscriber while 
sxabscriber B is the called subscriber. It is to be noted 
that the claimed invention also covers cases when the 

20 monitored subscriber is the called subscriber. Also 
conference calls involving more than two parties is covered 
by the claimed invention and of course also when more than 
one subscriber in the conference is monitored. It is 
important to observe that interception only is one type of 

25 monitoring for which the invention is applicable. Other 
types of monitoring might for example be monitoring of the 
type of media flow or quality measurements monitoring. The 
flag indicator is in the example sent during the call set- 
up session but can of course also be sent after the call 

30 set-up has finished in which case the media flow is re- 
routed via the lawful interception server. 



The invention is not limited to the above described and in 
the drawings shown embodiments but can be modified within 
35 the scope of the enclosed claims. 



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