UPF-initiated Detach Procedure
The following call flow illustrates an E-UTRAN network (UPF) initiated detach.

Step | Description | ||
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1 |
UPF sends N4 Session Report Request (ERIR[default bearer]/UPIR) to SMF. |
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2 |
SMF sends N4 Session Report Response to UPF. |
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3 |
SMF sends N4 PFCP Session Modification Request to UPF with FARs having apply action set to drop |
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4 |
UPF sends N4 PFCP Session Modification Response to SMF. |
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5 |
SMF sends Delete Bearer Request to S-GW. |
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6 |
S-GW sends Delete Bearer Request to MME. |
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7 |
MME sends Delete Bearer Response to S-GW. |
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8 |
S-GW sends Delete Bearer Response to SMF. |
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9 |
SMF sends N4 PFCP Session Deletion Request to UPF to release N4 session. |
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10 |
UPF sends N4 PFCP Session Deletion Response to SMF. |
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11 |
SMF sends Radius Accounting Request Stop to AAA server to release the accounting session. |
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12 |
AAA server sends Radius Accounting Response to SMF. |
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13 |
SMF sends Gy Credit Control Request Terminate to OCS to release the Gy session. |
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14 |
OCS sends Gy Credit Control Answer Terminate to SMF. |
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15 |
SMF sends Gx Credit Control Request Terminate to PCRF to release the Gx session. |
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16 |
PCRF sends Gx Credit Control Answer Terminate to SMF. |