10.1.7 Network-requested PDU session release

38.523-13GPP5GSPart 1: ProtocolRelease 17TSUser Equipment (UE) conformance specification

10.1.7.1 SNPN / Network-requested PDU session release / Accepted / Insufficient resources / T3396, Accepted / Insufficient resources for specific slice and DNN / T3584

10.1.7.1.1 Test Purpose (TP)

(1)

with { UE is in PDU SESSION ACTIVE state }

ensure that {
when { UE receives a PDU SESSION RELEASE COMMAND message including 5GSM cause #26 "insufficient resources" and the Back-off timer value that indicates deactivated }

then { UE does not send a PDU SESSION ESTABLISHMENT REQUEST message until the UE is switched off, the USIM is removed, the entry in the "list of subscriber data" for the current SNPN is updated }

}

(2)

with { UE is in PDU SESSION ACTIVE state }

ensure that {
when { UE receives a PDU SESSION RELEASE COMMAND message including 5GSM cause #67 "insufficient resources for specific slice and DNN" and the Back-off timer value that indicates deactivated }

then { UE does not send a PDU SESSION ESTABLISHMENT REQUEST message for the same [S-NSSAI, DNN] combination until the UE is switched off, the USIM is removed, the entry in the "list of subscriber data" for the current SNPN is updated }

}

10.1.7.1.2 Conformance requirements

References: The conformance requirements covered in the current TC are specified in: TS 24.501, clause 6.2.7, 6.4.3.3 and 6.4.3.5. Unless otherwise stated these are Rel-15 requirements.

[TS 24.501, clause 6.2.7]

The network may detect and start performing DNN based congestion control when one or more DNN congestion criteria as specified in 3GPP TS 23.501 [8] are met. If the UE does not provide a DNN for a non-emergency PDU session, then the network uses the selected DNN.

In the UE, 5GS session management timers T3396 for DNN based congestion control are started and stopped on a per DNN basis except for an LADN DNN in case of PLMN. For an LADN DNN, 5GS session management timers T3396 for DNN based congestion control is applied to the registered PLMN and its equivalent PLMNs. In the UE, 5GS session management timers T3396 for DNN based congestion control are started and stopped on a per DNN and SNPN basis in case of SNPN. Upon receipt of a 5GMM message or 5GSM message from the network for which the UE needs to stop the running timers T3396 associated with an LADN DNN as specified in subclause 5.5.2.3.2, 6.3.2.3, 6.3.3.3, 6.4.1.4.2 and 6.4.1.4.2, only the running timer T3396 associated with the LADN DNN for the current PLMN and equivalent PLMNs is stopped.

The DNN associated with T3396 is the DNN provided by the UE during the PDU session establishment. If no DNN is provided by the UE along the PDU SESSION ESTABLISHMENT REQUEST, then T3396 is associated with no DNN. For this purpose, the UE shall memorize the DNN provided to the network during the PDU session establishment. The timer T3396 associated with no DNN will never be started due to any 5GSM procedure related to an emergency PDU session. If the timer T3396 associated with no DNN is running, it does not affect the ability of the UE to request an emergency PDU session.

If T3396 is running or is deactivated, then the UE is neither allowed to initiate the PDU session establishment procedure nor the PDU session modification procedure for the respective DNN or without a DNN unless the UE is a UE configured for high priority access in selected PLMN or to report a change of 3GPP PS data off UE status.

[TS 24.501, clause 6.3.3.2]

In order to initiate the network-requested PDU session release procedure, the SMF shall create a PDU SESSION RELEASE COMMAND message.

The SMF shall set the 5GSM cause IE of the PDU SESSION RELEASE COMMAND message to indicate the reason for releasing the PDU session.

The 5GSM cause IE typically indicates one of the following 5GSM cause values:

#8 operator determined barring;

#26 insufficient resources;

#29 user authentication or authorization failed;

#36 regular deactivation;

#38 network failure;

#39 reactivation requested;

#46 out of LADN service area;

#67 insufficient resources for specific slice and DNN;

#69 insufficient resources for specific slice.

If the selected SSC mode of the PDU session is "SSC mode 2" and the SMF requests the relocation of SSC mode 2 PDU session anchor with different PDU sessions as specified in 3GPP TS 23.502 [9], the SMF shall include 5GSM cause #39 "reactivation requested".

If the network-requested PDU session release procedure is triggered by a UE-requested PDU session release procedure, the SMF shall set the PTI IE of the PDU SESSION RELEASE COMMAND message to the PTI of the PDU SESSION RELEASE REQUEST message received as part of the UE-requested PDU session release procedure.

If the network-requested PDU session release procedure is not triggered by a UE-requested PDU session release procedure, the SMF shall set the PTI IE of the PDU SESSION RELEASE COMMAND message to "No procedure transaction identity assigned".

Based on the local policy and user’s subscription data, if the SMF decides to release the PDU session after determining:

a) the UE has moved between a tracking area in NB-N1 mode and a tracking area in WB-N1 mode;

b) the UE has moved between a tracking area in NB-S1 mode and a tracking area in WB-N1 mode;

c) the UE has moved between a tracking area in WB-S1 mode and a tracking area in NB-N1 mode; or

d) a PDU session is not only for control plane CIoT 5GS optimization any more,

the SMF shall:

a) include the 5GSM cause value #39 "reactivation requested" in the 5GSM cause IE of the PDU SESSION RELEASE COMMAND message; or

b) include a 5GSM cause value other than #39 "reactivation requested" in the 5GSM cause IE of the PDU SESSION RELEASE COMMAND message.

NOTE: The included 5GSM cause value is up to the network implementation.

If the SMF receives UE presence in LADN service area from the AMF indicating that the UE is out of the LADN service area and the SMF decides to release the PDU session, the SMF shall include the 5GSM cause value #46 "out of LADN service area" in the 5GSM cause IE of the PDU SESSION RELEASE COMMAND message. Upon receipt of the 5GSM cause value #46 "out of LADN service area" in the 5GSM cause IE of the PDU SESSION RELEASE COMMAND message, the UE shall release the PDU session.

The SMF may include a Back-off timer value IE in the PDU SESSION RELEASE COMMAND message when the 5GSM cause value #26 "insufficient resources" is included in the PDU SESSION RELEASE COMMAND message. If the 5GSM cause value is #26 "insufficient resources" and the PDU SESSION RELEASE COMMAND message is sent to a UE configured for high priority access in selected PLMN or the request type was set to "initial emergency request" or "existing emergency PDU session" for the establishment of the PDU session, the network shall not include a Back-off timer value IE.

The SMF may include a Back-off timer value IE in the PDU SESSION RELEASE COMMAND message when the 5GSM cause value #67 "insufficient resources for specific slice and DNN" is included in the PDU SESSION RELEASE COMMAND message. If the 5GSM cause value is #67 "insufficient resources for specific slice and DNN" and the PDU SESSION RELEASE COMMAND message is sent to a UE configured for high priority access in selected PLMN or the request type was set to "initial emergency request" or "existing emergency PDU session" for the establishment of the PDU session, the network shall not include a Back-off timer value IE.

The SMF may include a Back-off timer value IE in the PDU SESSION RELEASE COMMAND message when the 5GSM cause #69 "insufficient resources for specific slice" is included in the PDU SESSION RELEASE COMMAND message. If the 5GSM cause value is #69 "insufficient resources for specific slice" and the PDU SESSION RELEASE COMMAND message is sent to a UE configured for high priority access in selected PLMN or the request type was set to "initial emergency request" or "existing emergency PDU session" for the establishment of the PDU session, the network shall not include a Back-off timer value IE.

The SMF shall send:

a) the PDU SESSION RELEASE COMMAND message; and

b) the N1 SM delivery skip allowed indication:

1) if the SMF allows the AMF to skip sending the N1 SM container to the UE and the 5GSM cause IE is not set to #39 "reactivation requested"; or

2) if the SMF allows the AMF to skip sending the N1 SM container to the UE and the Access type IE is not included

towards the AMF, and the SMF shall start timer T3592 (see example in figure 6.3.3.2.1).

Figure 6.3.3.2.1: Network-requested PDU session release procedure

[TS 24.501, clause 6.3.3.3]

If the PDU SESSION RELEASE COMMAND message includes 5GSM cause #26 "insufficient resources" and the Back-off timer value IE, the UE shall ignore the 5GSM congestion re-attempt indicator IE provided by the network, if any, and the UE shall take different actions depending on the timer value received for timer T3396 in the Back-off timer value:

…

b) if the timer value indicates that this timer is deactivated and a DNN was provided during the PDU session establishment, the UE shall stop timer T3396 associated with the corresponding DNN, if it is running. If the timer value indicates that this timer is deactivated and no DNN was provided during the PDU session establishment and the request type was different from "initial emergency request" and different from "existing emergency PDU session", the UE shall stop timer T3396 associated with no DNN if it is running. The UE:

1) shall not send a PDU SESSION ESTABLISHMENT REQUEST message or PDU SESSION MODIFICATION REQUEST message with exception of those identified in subclause 6.4.2.1, for the same DNN until the UE is switched off, the USIM is removed, the entry in the "list of subscriber data" for the current SNPN is updated, or the UE receives a PDU SESSION MODIFICATION COMMAND message for the same DNN from the network, or a PDU SESSION RELEASE COMMAND message without the Back-off timer value IE or including 5GSM cause #39 "reactivation requested" for the same DNN from the network; and

2) shall not send a PDU SESSION ESTABLISHMENT REQUEST message without an DNN and with request type different from "initial emergency request" and different from "existing emergency PDU session", or a PDU SESSION MODIFICATION REQUEST message with exception of those identified in subclause 6.4.2.1, for a non-emergency PDU session established without an DNN provided by the UE, if no DNN was provided during the PDU session establishment and the request type was different from "initial emergency request" and different from "existing emergency PDU session", until the UE is switched off, the USIM is removed, the entry in the "list of subscriber data" for the current SNPN is updated, or the UE receives a PDU SESSION MODIFICATION COMMAND message for a non-emergency PDU session established without an DNN provided by the UE, or a PDU SESSION RELEASE COMMAND message without the Back-off timer value IE or including 5GSM cause #39 "reactivation requested" for a non-emergency PDU session established without an DNN provided by the UE.

The timer T3396 remains deactivated upon a PLMN change or inter-system change; and

…

If the 5GSM cause value is #69 "insufficient resources for specific slice" and the Back-off timer value IE is included, the UE shall take different actions depending on the timer value received for timer T3585 in the Back-off timer value:

…

b) if the timer value indicates that this timer is deactivated and an S-NSSAI was provided during the PDU session establishment, the UE shall stop timer T3585 associated with the S-NSSAI of the PDU session, if it is running. If the timer value indicates that this timer is deactivated and no S-NSSAI was provided during the PDU session establishment and the request type was different from "initial emergency request" and different from "existing emergency PDU session", the UE shall stop timer T3585 associated with no S-NSSAI if it is running. In addition:

1) if an S-NSSAI was provided by the UE during the PDU session establishment, the UE shall not send another PDU SESSION ESTABLISHMENT REQUEST, or PDU SESSION MODIFICATION REQUEST with exception of those identified in subclause 6.4.2.1, for the S-NSSAI of the PDU session until the UE is switched off, the USIM is removed, the entry in the "list of subscriber data" for the current SNPN is updated, or a PDU SESSION RELEASE COMMAND message without the Back-off timer value IE or including 5GSM cause #39 "reactivation requested" for the S-NSSAI of the PDU session from the network; and

2) if the request type was different from "initial emergency request" and from "existing emergency PDU session", and an S-NSSAI was not provided by the UE during the PDU session establishment, the UE shall not send another PDU SESSION ESTABLISHMENT REQUEST message without an S-NSSAI and with request type different from "initial emergency request" and different from "existing emergency PDU session", or another PDU SESSION MODIFICATION REQUEST message with exception of those identified in subclause 6.4.2.1, for a non-emergency PDU session established without an S-NSSAI provided by the UE, , until the UE is switched off, the USIM is removed, the entry in the "list of subscriber data" for the current SNPN is updated, or a PDU SESSION RELEASE COMMAND message without the Back-off timer value IE or including 5GSM cause #39 "reactivation requested" for a non-emergency PDU session established without an S-NSSAI provided by the UE.

The timer T3585 remains deactivated upon a PLMN change or inter-system change; and

10.1.7.1.3 Test description

10.1.7.1.3.1 Pre-test conditions

System Simulator:

– NGC Cell A.

UE:

– The UE is provisioned with a “list of subscriber data” to allow access to SNPN identified by NGC Cell A.

Preamble:

The UE is in state 3N-A on NGC Cell A according to TS 38.508-1 [4].

10.1.7.1.3.2 Test procedure sequence

Table 10.1.7.1.3.2-1: Main behaviour

St

Procedure

Message Sequence

TP

Verdict

U – S

Message

1

Check: Does the UE perform PDU session release procedure defined in clause 4.9.21 of TS 38.508-1 [4]?

–

–

–

–

2

SS releases the RRC connection

–

–

–

–

3

Cause the UE to request the PDU Session establishment on the DNN of the released PDU session in Step 1(Note 1)

–

–

–

–

4

Check: Does the UE transmit an RRCSetupRequest message for PDU Session Establishment procedure within the next 30 seconds?

–>

NR RRC: RRCSetupRequest

1

F

5

The UE is provisioned with a “list of subscriber data” to allow access to SNPN identified by NGC Cell A (Note 2)

–

–

–

–

6

Cause the UE to request the PDU Session establishment on the DNN of the released PDU session in Step 1(Note 1)

–

–

–

–

7

The PDU session establishment procedure as specified in TS 38.508-1 [4] subclause 4.5A.2 takes place .

–

–

1

P

8

Check: Does the UE perform PDU session release procedure defined in clause 4.9.21 of TS 38.508-1 [4]?

–

–

–

–

9

SS releases the RRC connection

–

–

–

–

10

Cause the UE to request the PDU Session establishment on the DNN of the released PDU session in Step 8 (Note 1)

–

–

–

–

11

Check: Does the UE transmit an RRCSetupRequest message for PDU Session Establishment procedure within the next 30 seconds?

–>

NR RRC: RRCSetupRequest

2

F

12

The UE is provisioned with a “list of subscriber data” to allow access to SNPN identified by NGC Cell A (Note 2)

–

–

–

–

13

Cause the UE to request the PDU Session establishment on the DNN of the released PDU session in Step 1(Note 1)

–

–

–

–

14

The PDU session establishment procedure as specified in TS 38.508-1 [4] subclause 4.5A.2 takes place .

–

–

2

P

Note 1: The request of PDU session establishment may be performed by MMI or AT command.

Note 2: The request to provision with a “list of subscriber data” may be performed by MMI or AT command.

10.1.7.1.3.3 Specific message contents

Table 10.1.7.1.3.3-1: PDU SESSION RELEASE COMMAND (step 1, Table 10.1.7.1.3.2-1; step 1, TS 36.508 [4] Table 4.9.21.2.2-1)

Derivation Path: TS 38.508-1 [4] Table 4.7.2-14

Information Element

Value/remark

Comment

Condition

5GSM cause

‘0001 1010’B

#26 "insufficient resources"

Back-off timer value

Deactivated

Set to deactivated

Table 10.1.7.1.3.3-2: PDU SESSION RELEASE COMPLETE (step 1, 8, Table 10.1.7.1.3.2-1; step 2, TS 36.508 [4] Table 4.9.21.2.2-1)

Derivation Path: TS 38.508-1 [4] Table 4.7.2-15

Information Element

Value/remark

Comment

Condition

PDU session ID

The value indicated in PDU SESSION RELEASE REQUEST

PTI

The value indicated in PDU SESSION RELEASE REQUEST

Table 10.1.7.1.3.3-3: PDU SESSION RELEASE COMMAND (step 8, Table 10.1.7.1.3.2-1; step 1, TS 36.508 [4] Table 4.9.21.2.2-1)

Derivation Path: TS 38.508-1 [4] Table 4.7.2-14

Information Element

Value/remark

Comment

Condition

5GSM cause

‘0100 0011’B

#67 "insufficient resources for specific slice and DNN"

Back-off timer value

Deactivated

Set to deactivated