10  Interception of Multimedia Broadcast/MultiCast Service (MBMS) |R7|  Word‑p. 98

10.0  General |R12|

MBMS provides video or similar streamed services via either point to point multicast or cell broadcast mechanisms between an operator content server (BM-SC) and UEs as defined in TS 23.246. This section details the stage 2 Lawful Interception requirements for MBMS.

Figure 10.1 shows the extract from the reference configuration which is relevant for the invocation of the Lawful Interception of the MBMS Services.

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Figure 10.1: Functional model for invocation of Lawful Interception for MBMS Services

10.1  Provision of Content of Communications

Interception of the content of communications for MBMS services if available, may be provided by the underlying transport bearer interception functionality (e.g. GSN, PDG or NGN network) and is therefore subject to the current transport bearer interception functionality detailed in other parts of this specification.

10.2  Provision of Intercept Related Information

10.2.0  General |R12|

Figure 10.2 shows the transfer of intercept related information to the DF2. If an event for / from a mobile subscriber occurs, the BM-SC shall send the relevant data to the DF2.

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Figure 10.2: Provision of Intercept Related Information

10.2.1  X2-interface  Word‑p. 99

The following information needs to be transferred from the BM-SC to the DF2 in order to allow a DF2 to perform its functionality:

• target identity;
• events and associated parameters as defined in clauses 10.3.2 may be provided;
• For Further Study:- Encryption parameters (keys and associated parameters for decrypting CC), if available and necessary.

The IRI should be sent to DF2 using a reliable transport mechanism.

10.2.2  MBMS LI Events and Event Information

Intercept Related Information (Events) are necessary are necessary for the following;

• Service Joining.
• Service Leaving.
• Start of Interception with Service Active.
• Subscription Activation.
• Subscription Modification.
• Subscription Termination.

Events shall include changes resulting from direct communication between the UE and BM-SC and off-line subscription changes (e.g. changes made by operator customer services on behalf of the subscriber).

A set of possible elements as shown in Table 10.2.2 are used to generate the events.

Table 10.2.2: Information Events for MBMS Event Records

Element

Description

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Observed IMSI

IMSI of the target.

Observed Other Identity

Other Identity of the target.

Event type

Description which type of event is delivered:- Service Joining; Service Leaving; Subscription Activation; Subscription Modification; Subscription Termination.

Event date

Date of the event generation in the BM-SC.

Event time

Time of the event generation in the BM-SC. Timestamp shall be generated relative to the BM-SC server internal clock.

MBMS Subscribed Service

Details of the MBMS Service to which the target has subscribed.

MBMS Service Joining Time

Requested MBMS Service Joining Time

MBMS Service Subscription List

List of all users subscribed to MBMS Service to which target has requested Joining.

Correlation Number

The correlation number is used to correlate CC and IRI. The correlation number is also used to allow the correlation of IRI records.

Network Element Identifier

Unique identifier for the element reporting the ICE.

Initiator

The initiator of the request either the UE or Off-line BM-SC access (eg customer services agent or internet).

Visited PLMN ID

Identity of the visited PLMN to which the user is registered

APN

Access Point Name on which this IP multicast address is defined.

Multicast/Broadcast Mode

MBMS bearer service in broadcast or multicast mode

IP IP/IPv6 multicast address(multicast mode only)

IP or IPv6 multicast address identifying the MBMS bearer described by this MBMS Bearer Context.

List of Downstream Nodes

List of downstream nodes that have requested the MBMS bearer service and to which notifications and MBMS data have to be forwarded.

MBMS Leaving Reason

Indicates whether UE initiated/requested leaving, or whether BM-SC/network terminated the Service to the UE (e.g. GSN session dropped or BM-SC subscription expired etc).

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10.3  Structure of MBMS Events  Word‑p. 101

10.3.1  Service Joining

For MBMS Service Joining, a Service Joining event is generated. The elements, shown in Table 10.,3.1 will be delivered to the DF2, if available, by the BM-SC. A new Service Joining Event shall be generated for each individual service joined.

Table 10.3.1: Service Joining

Information Element

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Observed IMSI

Event Type

Event Time

Event Date

MBMS Subscribed Service

MBMS Service Joining Time

Network Element Identifier

Initiator

IP/IPv6 Multicast Address (If Applicable)

Visited PLMN ID (If Applicable)

Multicast/Broadcast Mode

APN (If Available)

List of Downstream Nodes (If Available)

MBMS Service Subscription List (Optional)

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10.3.2  Service Leaving

For MBMS Service Leaving, a Service Leaving event is generated. The elements, shown in Table 10.3.2 will be delivered to the DF2, if available, by the BM-SC. A new Service Leaving Event shall be generated for each individual service leaving.

Table 10.3.2: Service Leaving

Information Element

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Observed IMSI

Event Type

Event Time

Event Date

MBMS Subscribed Service

Network Element Identifier

Initiator

IP/IPv6 Multicast Address (If Applicable)

Visited PLMN ID (If Applicable)

MBMS Service Subscription List (Optional)

MBMS Service Leaving Reason

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10.3.3  Start of Interception with Service Active  Word‑p. 102

For Start of Interception where MBMS Service Joining has already occurred prior to start of interception, a Start of Interception with Service Active event is generated. The elements, shown in Table 10.3.3 will be delivered to the DF2, if available, by the BM-SC. A new Start of Interception with Service Active Event shall be generated for each individual service the target is subscribed to.

Table 10.3.3: Start of Interception with Service Active

Information Element

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Observed IMSI

Event Type

Event Time

Event Date

MBMS Subscribed Service

MBMS Service Joining Time

Network Element Identifier

Initiator

IP/IPv6 Multicast Address (If Applicable)

Visited PLMN ID (If Applicable)

Multicast/Broadcast Mode

APN (If Available)

List of Downstream Nodes (If Available)

MBMS Service Subscription List (Optional)

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10.3.4  Subscription Activation

For MBMS Subscription Activation, a Subscription Activation event is generated. The elements, shown in Table 10.3.4 will be delivered to the DF2, if available, by the BM-SC. If Subscription Activation is performed simultaneously for more than one service, a separate event shall be generated for each service activated.

Table 10.3.4: Subscription Activation

Information Element

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Observed IMSI

Event Type

Event Time

Event Date

MBMS Subscribed Service

Network Element Identifier

Initiator

IP/IPv6 Address (If Applicable)

Visited PLMN ID (If Applicable)

MBMS Service Subscription List (Optional)

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10.3.5  Subscription Modification

For MBMS Subscription Modification, a Subscription Modification event is generated. The elements, shown in Table 10.3.5, will be delivered to the DF2, if available, by the BM-SC. If Subscription Modification is performed simultaneously for more than one service, a separate event shall be generated for each service modified.

Table 10.3.5: Subscription Modification

Information Element

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Observed IMSI

Event Type

Event Time

Event Date

MBMS Subscribed Service

Network Element Identifier

Initiator

IP/IPv6 Address (If Applicable)

Visited PLMN ID (If Applicable)

MBMS Service Subscription List (Optional)

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10.3.6  Subscription Termination  Word‑p. 103

For MBMS Subscription Termination, a Subscription Termination event is generated. The elements, shown in Table 10.3.6 will be delivered to the DF2, if available, by the BM-SC. If Subscription Termination is performed simultaneously for more than one service, a separate event shall be generated for each service performed.

Table 10.3.6: Subscription Modification

Information Element

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Observed IMSI

Event Type

Event Time

Event Date

MBMS Subscribed Service

Network Element Identifier

Initiator

IP/IPv6 Address (If Applicable)

Visited PLMN ID (If Applicable)

MBMS Service Subscription List (Optional)

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