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Content for  TS 33.127  Word version:  16.4.0

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6.3  EPC

6.3.1  General |R16|

The present document specifies two options for EPC interception capabilities:
  1. Use TS 33.107 and TS 33.108 natively as defined in those documents;
  2. Use the capabilities specified below in the present document for stage 2 and in TS 33.128 for stage 3.
Detailed LI architecture and functional requirements for Control and User Plane Separation (CUPS) are outside the scope of the present document. They are specified in TS 33.107.
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6.3.2  LI at the MME |R16|

6.3.2.1  Architecture

In the EPC network, the MME handles the mobility management and connection management as specified in TS 23.401. The MME shall have LI capabilities to generate the target UE's network access, registration and connection management related xIRI. Extending the generic LI architecture presented in clause 5, figure 6.3-1 below gives a reference point representation of the LI architecture with MME as a CP Network Element providing the IRI-POI functions.
[not reproduced yet]
Figure 6.3-1: LI architecture for LI at MME
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The LICF present in the ADMF receives the warrant from an LEA, derives the intercept information from the warrant and provides the same to the LIPF.
The LIPF present in the ADMF provisions the IRI-POI (over LI_X1) present in the MME and the MDF2.
The IRI-POI present in the MME detects the target UE's access and mobility related functions (network access, registration and connection management), generates and delivers the xIRI to the MDF2 over LI_X2. The MDF2 delivers the IRI messages as part of the Interception Product to the LEMF over LI_HI2.
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6.3.2.2  Target identitiesWord‑p. 42
The target identities which the LIPF present in the ADMF provisions to the IRI-POI present in the MME are specified in TS 33.107.

6.3.2.3  IRI events

The IRI-POI present in the MME shall generate xIRI, when it detects the applicable events specified in TS 33.107.

6.3.2.4  Common IRI parameters

The list of xIRI parameters are specified in TS 33.128. All xIRI shall include the following:
  • Target identity.
  • Time stamp.
  • Location information.

6.3.2.5  Specific IRI parametersWord‑p. 43
The list of parameters in each xIRI are defined in TS 33.128.

6.3.2.6  Network topologies

The MME shall provide the IRI-POI functions in the following network topology cases:
  • Non-roaming case.
  • Roaming case, in VPLMN.

6.3.3  LI at SGW/PGW |R16|

6.3.3.1  Architecture

In the EPC network, the SGW is the gateway which terminates the user plane interface as specified in TS 23.401. The PGW is the gateway which terminates the SGi interface towards the PDN as specified in TS 23.401. Additionally, the PGW is the user plane anchor for mobility between 3GPP access and non-3GPP access as specified in TS 23.402.
The SGW and PGW shall include an IRI-POI that has the LI capabilities to generate the target UE's bearer related xIRI.
In addition, the SGW and PGW shall include a CC-POI that has the LI capabilities to duplicate the user plane packets from the EPS bearers related to a target UE. Figure 6.3-2 shows the LI architecture for SGW/PGW based interception.
[not reproduced yet]
Figure 6.3-2: LI architecture for LI at SGW/PGW
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The LICF present in the ADMF receives the warrant from an LEA, derives the intercept information from the warrant and provides the same to the LIPF.
The LIPF present in the ADMF provisions IRI-POI present in the SGW/PGW, MDF2 and MDF3 over the LI_X1 interfaces. To enable the interception of the target's user plane packets (e.g. when the warrant requires the interception of communication contents), the CC-POI present in the SMF is also considered to be provisioned with the intercept data.
The IRI-POI present in the SGW/PGW detects the target UE's bearer activation, modification and deactivation, generates and delivers the xIRI to the MDF2 over LI_X2. The MDF2 delivers the IRI messages to the LEMF over LI_HI2.
The CC-POI present in the SGW/PGW generates the xCC from the user plane packets and delivers the xCC (that includes the correlation number and the target identity) to the MDF3. The MDF3 delivers the CC to the LEMF over LI_HI3.
A warrant that does not require the interception of communication contents, may require IRI messages that have to be derived from the user plane packets. To support the generation of related xIRI (i.e. that requires access to the user plane packets), the present document supports two implementation approaches:
  • In approach 1, the IRI-POI responsible for the generation of such xIRI resides in the SGW/PGW. Such an IRI-POI requires a trigger to enable it to detect the user plane packets. The corresponding Triggering Function (IRI-TF) resides in the same SGW/PGW that has the IRI-POI for the generation of other xIRI.
  • The trigger sent by the IRI-TF to the IRI-POI includes the following:
    • User plane packet detection rules.
    • Target identity.
    • Correlation information.
    • MDF2 address.
  • The IRI-POI generates the xIRI (that includes the correlation number and the target identity) from the user plane packets and sends it to the MDF2. The MDF2 generates the IRI messages and send them to the LEMF.
  • In approach 2, xCC is generated by the CC-POI as if the warrant involves the interception of communication contents. To enable this, the CC-POI is presumed to be present in the SGW/PGW even when the warrant does not require the interception of communication contents. As explained before, the CC-POI generates the xCC and sends it to the MDF3. The MDF3 (based on the provisioned intercept information) does not generate and deliver the CC to the LEMF. Instead, the MDF3 forwards the xCC to the MDF2 over LI_MDF interface. The MDF2 then generates the IRI messages from xCC and delivers those IRI messages to the LEMF.
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6.3.3.2  Target identitiesWord‑p. 45
The target identities which the LIPF present in the ADMF provisions to the IRI-POI, CC-POI and IRI-TF present in the SGW/PGW are specified in TS 33.107.

6.3.3.3  IRI events

The IRI-POI present in the SGW/PGW shall generate xIRI, when it detects the applicable events specified in TS 33.107.

6.3.3.4  Common IRI parameters

The list of xIRI parameters are specified in TS 33.128. All xIRI shall include the following:
  • Target identity.
  • Time stamp.
  • Location information.

6.3.3.5  Specific IRI parameters

The parameters in each xIRI are defined in TS 33.128.

6.3.3.6  Network topologies

The SGW shall provide the IRI-POI, CC-POI and IRI-TF functions in the following network topology cases:
  • Optionally in non-roaming case for E-UTRAN.
  • Roaming case, in VPLMN.
The PGW shall provide the IRI-POI, CC-POI and IRI-TF functions in the following network topology cases:
  • Optionally in non-roaming case for E-UTRAN.
  • Roaming case, in HPLMN.
  • Non-3GPP access case, in the HPLMN.
For the case of access to EPC via E-UTRAN, in case of non-roaming, at least one between SGW and PGW shall provide IRI-POI, CC-POI and IRI-TF.
When the target UE has multiple bearers active, the generation and delivery of xCC for each bearer shall be done independently, each with separate correlation information.
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6.3.4  LI at ePDG |R16|Word‑p. 46

6.3.4.1  Architecture

In the EPC network, the ePDG is the gateway which allows interworking between non-3GPP access and 3GPP network. The ePDG functionalities are specified in TS 23.402.
The ePDG shall include an IRI-POI that has the LI capabilities to generate the target UE's bearer related xIRI.
In addition, the ePDG shall include a CC-POI that has the LI capabilities to duplicate the user plane packets from the EPS bearers related to a target UE. Figure 6.3-3 shows the LI architecture for ePDG based interception.
[not reproduced yet]
Figure 6.3-3: LI architecture for LI at ePDG
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The LICF present in the ADMF receives the warrant from an LEA, derives the intercept information from the warrant and provides the same to the LIPF.
The LIPF present in the ADMF provisions IRI-POI present in the ePDG, MDF2 and MDF3 over the LI_X1 interfaces. To enable the interception of the target's user plane packets (e.g. when the warrant requires the interception of communication contents), the CC-POI present in the ePDG is also considered to be provisioned with the intercept data.
The IRI-POI present in the ePDG detects the target UE's bearer activation, modification and deactivation, generates and delivers the xIRI to the MDF2 over LI_X2. The MDF2 delivers the IRI messages to the LEMF over LI_HI2.
The CC-POI present in the ePDG generates the xCC from the user plane packets and delivers the xCC (that includes the correlation number and the target identity) to the MDF3. The MDF3 delivers the CC to the LEMF over LI_HI3.
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6.3.4.2  Target identitiesWord‑p. 47
The target identities which the LIPF present in the ADMF provisions to the IRI-POI and CC-POI present in the ePDG are specified in TS 33.107.

6.3.4.3  IRI events

The IRI-POI present in the ePDG shall generate xIRI, when it detects the applicable events specified in TS 33.107.

6.3.4.4  Common IRI parametersWord‑p. 48
The list of xIRI parameters are specified in TS 33.128. Each xIRI shall include at the minimum the following information:
  • Target identity.
  • Time stamp.
  • Correlation information.
  • Location information.
  • Bearer related information.

6.3.4.5  Specific IRI parameters

The parameters in each xIRI are defined in TS 33.128.

6.3.4.6  Network topologies

The ePDG shall provide the IRI-POI and CC-POI functions in the following network topology cases:
  • Roaming case, in VPLMN.

6.4  3G

For virtualised 4G implemenations from Release 15 onwards (including combined 4G / 5G scenarios), 4G shall be virtualised based on the architecture in clause 5.6. For such implementations the LI architecture for 4G / LTE shall be implemented using an ADMF as defined in the present document (including LIPF and LICF split). However, equivalent reference points as specified in TS 33.107 shall be used where appropriate (e.g. X2 is equivalent to LI_X2 in the present document and MDF is equivalent to MF/DF). Security and audit requirements as defined in clause 8 of the present document shall be applied to such 4G scenarios.
The present document does not specify further LI functionality for 3G / UMTS. LI capabilities for 3G / UMTS for this release are specified in TS 33.107.
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6.5  VoNR

Voice over NR as defined in TS 23.501 and TS 23.502 is intended to provide equivalent functionality to VoLTE in 4G.
LI requirements for VoNR based on IMS are defined in clause 7.4 of the present document.

6.6  4G/5G Interworking |R16|Word‑p. 49
Figure 6.6-1 depicts interworking between EPC and the 5G architecture. The network functions are depicted in grey, while the LI elements are depicted in blue.
[not reproduced yet]
Figure 6.6-1: EPC/5G Interworking LI architecture
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