6.6 Miscellaneous procedures

24.3013GPPNon-Access-Stratum (NAS) protocol for Evolved Packet System (EPS)Release 18Stage 3TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

6.6.1 Exchange of protocol configuration options

6.6.1.1 General

The UE and the PDN GW can exchange protocol configuration options via the dedicated ESM information request procedure or via other ESM procedures.

If supported by the network and UE end-to-end for a PDN connection, protocol configuration options shall be exchanged via the extended protocol configuration options IE. Otherwise the protocol configuration options IE is used.

NOTE 1: In this version of the protocol inter-system mobility to and from NB-S1 mode is supported. During inter-system-mobility from NB-S1 mode to WB-S1 mode the end-to-end support of the extended protocol configuration options IE can be lost, e.g. if the new MME does not support the extended protocol configuration options IE.

For the UE, the extended protocol configuration options is supported by the network and the UE end-to-end for a PDN connection if

– the UE is in NB-S1 mode;

– the APN requested for the PDN connection is for UAS services;

– the PDN Type requested for the PDN connection is non-IP or Ethernet; or

– the network has indicated support of the extended protocol configuration options IE in the last ATTACH ACCEPT or TRACKING AREA UPDATING ACCEPT message and the network has included the extended protocol configuration options IE in at least one EPS session management message received by the UE for this PDN connection.

For the MME, the extended protocol configuration options is supported by the network and the UE end-to-end for a PDN connection if

– the UE is in NB-S1 mode;

– the APN requested for the PDN connection is for UAS services;

– the PDN Type requested for the PDN connection is non-IP or Ethernet; or

– the UE has indicated support of the extended protocol configuration options IE in the last ATTACH REQUEST or TRACKING AREA UPDATING REQUEST message, and the MME has received the extended protocol configuration options IE in at least one message sent by the PDN GW towards the UE for this PDN connection (for details see 3GPP TS 29.274 [16D]).

NOTE 2: For the PDN GW, the extended protocol configuration options is supported by the network and the UE end-to-end for a PDN connection if the last support indication received from the MME or S-GW indicates that extended protocol configuration options is supported for this PDN connection (for details see 3GPP TS 29.274 [16D]).

6.6.1.2 ESM information request procedure

6.6.1.2.1 General

The ESM information request procedure is used by the network to retrieve ESM information, i.e. protocol configuration options, APN, or both from the UE during the attach procedure if the UE indicated in the PDN CONNECTIVITY REQUEST message that it has ESM information that needs to be sent security protected. The purpose of this procedure is to provide privacy for the ESM information if ciphering is enabled in the network.

6.6.1.2.2 ESM information request initiated by the network

The network initiates the ESM information request procedure by sending an ESM INFORMATION REQUEST message to the UE, starting timer T3489 and entering the state PROCEDURE TRANSACTION PENDING (see example in figure 6.6.1.2.2.1). This message shall be sent only after the security context has been setup, and if the ESM information transfer flag has been set in the PDN CONNECTIVITY REQUEST message. The MME shall set the EPS bearer identity of the ESM INFORMATION REQUEST message to the value "no EPS bearer identity assigned" and include the PTI from the associated PDN CONNECTIVITY REQUEST message.

Figure 6.6.1.2.2.1: ESM information request procedure

6.6.1.2.3 ESM information request completion by the UE

Upon receipt of the ESM INFORMATION REQUEST message, the UE shall send an ESM INFORMATION RESPONSE message to the network. The UE shall include all the protocol configuration options that need to be transferred security protected, and APN if required, to the network in the ESM INFORMATION RESPONSE message. The UE shall set the EPS bearer identity of the ESM INFORMATION RESPONSE message to the value "no EPS bearer identity assigned" and include the PTI from the ESM INFORMATION REQUEST message.

6.6.1.2.4 ESM information request completion by the network

Upon receipt of the ESM INFORMATION RESPONSE message, the network shall stop timer T3489 and enter the state PROCEDURE TRANSACTION INACTIVE. A protocol configuration options IE or extended protocol configuration options IE included in the ESM INFORMATION RESPONSE message replaces any protocol configuration options IE or extended protocol configuration options IE that the network previously may have received during the attach procedure execution.

6.6.1.2.5 Abnormal cases in the UE

Apart from the case described in clause 6.3.3, no abnormal cases have been identified.

6.6.1.2.6 Abnormal cases on the network side

The following abnormal cases can be identified:

a) Expiry of timer T3489:

On the first expiry of the timer T3489, the MME shall resend the ESM INFORMATION REQUEST message and shall reset and restart timer T3489. This retransmission is repeated two times, i.e. on the third expiry of timer T3489, the MME shall abort the procedure, release any resources for this procedure and reject the associated PDN connectivity procedure including the ESM cause #53 "ESM information not received", in the PDN CONNECTIVITY REJECT message.

6.6.1.3 Exchange of protocol configuration options in other messages

The UE may include a protocol configuration options IE or extended protocol configuration options IE on EPS bearer context activation, EPS bearer context deactivation, EPS bearer context modification, PDN connectivity request, PDN disconnect request, bearer resource allocation request and bearer resource modification request if the UE wishes to transmit (protocol) data (e.g. configuration parameters, error codes or messages/events) to the PDN GW or the SCEF. In particular, the UE may use this procedure on EPS bearer context activation to perform the MSISDN notification procedure as specified in 3GPP TS 24.008 [13], clause 6.4.

The PDN GW or the SCEF may include a protocol configuration options IE or extended protocol configuration options IE on EPS bearer context activation, EPS bearer context deactivation, EPS bearer context modification, PDN connectivity reject, PDN disconnect reject, bearer resource allocation reject and bearer resource modification reject if the PDN GW or the SCEF wishes to transmit (protocol) data (e.g. configuration parameters, error codes or messages/events) to the UE. In particular, the PDN GW may use this procedure on EPS bearer context activation to perform the MSISDN notification procedure as specified in 3GPP TS 24.008 [13], clause 6.4.

6.6.2 Notification procedure

6.6.2.1 General

The network can use the notification procedure to inform the UE about events which are relevant for the upper layer which is using an EPS bearer context or has requested a procedure transaction.

If the UE has indicated that it supports the notification procedure, the network may initiate the procedure at any time while a PDN connection exists or a procedure transaction is ongoing.

6.6.2.2 Notification procedure initiation by the network

The network initiates the notification procedure by sending a NOTIFICATION message to the UE (see example in figure 6.6.2.2.1).

Figure 6.6.2.2.1: Notification procedure

6.6.2.3 Notification procedure in the UE

When the UE receives a NOTIFICATION message, the ESM protocol entity in the UE shall provide the notification indicator to the upper layer.

The notification indicator can have the following value:

#1: SRVCC handover cancelled, IMS session re-establishment required.

6.6.2.4 Abnormal cases on the network side

The following abnormal case can be identified:

a) Lower layer indication of non-delivered NAS PDU due to handover

If the NOTIFICATION message could not be delivered due to an intra MME handover, then upon successful completion of the intra MME handover the MME shall retransmit the NOTIFICATION message. If a failure of the handover procedure is reported by the lower layer and the S1 signalling connection exists, the MME shall retransmit the NOTIFICATION message.

6.6.3 Remote UE Report procedure

6.6.3.1 General

The purpose of the Remote UE Report procedure is for a UE acting as ProSe UE-to-network relay to notify the network that a remote UE is connected to the ProSe UE-to-network relay or disconnected from the ProSe UE-to-network relay as specified in 3GPP TS 23.303 [31].

6.6.3.2 Remote UE Report initiated by the UE

The UE initiates the Remote UE Report procedure by sending a REMOTE UE REPORT message to the network, starting timer T3493 and entering the state PROCEDURE TRANSACTION PENDING (see example in figure 6.6.3.2.1). The UE shall include information of newly connected or disconnected remote UEs to the network in the REMOTE UE REPORT message. If any encrypted IMSI remote UE identity is included in the REMOTE UE REPORT message, the UE shall include the corresponding ProSe Key Management Function address. The UE shall include the default EPS bearer identity of the PDN connection associated with the remote UE connected to the ProSe UE-to-network relay or disconnected from the ProSe UE-to-network relay. If the UE allocated an IPv4 address to a remote UE and enabled UDP usage to the remote UE, the UE shall include in the REMOTE UE REPORT message the UDP port range assigned to the remote UE in the NAT function of ProSe layer-3 UE-to-network relay. If the UE allocated an IPv4 address to a remote UE and enabled TCP usage to the remote UE, the UE shall include in the REMOTE UE REPORT message the TCP port range assigned to the remote UE in the NAT function of ProSe layer-3 UE-to-network relay.

NOTE: Encrypted IMSI remote UE identities corresponding to different ProSe Key Management Function addresses need to be reported using separate REMOTE UE REPORT messages.

Figure 6.6.3.2.1: Remote UE Report procedure

6.6.3.3 Remote UE Report completion by the network

Upon receipt of the REMOTE UE REPORT message, the MME shall send a REMOTE UE REPORT RESPONSE message to the UE. The MME shall include the PTI from the REMOTE UE REPORT message.

6.6.3.4 Remote UE Report completion by the UE

Upon receipt of the REMOTE UE REPORT RESPONSE message, the UE shall stop timer T3493 and enter the state PROCEDURE TRANSACTION INACTIVE.

6.6.3.5 Abnormal cases in the UE

The following abnormal cases can be identified:

a) Expiry of timer T3493:

On the first expiry of the timer T3493, the UE shall resend the REMOTE UE REPORT message and shall reset and restart timer T3493. This retransmission is repeated two times, i.e. on the third expiry of timer T3493, the UE shall abort the procedure and release any resources for this procedure.

NOTE: After the abortion of the Remote UE Report procedure, the Remote UE Report procedure for the remote UE(s) can be restarted and how to restart the procedure is left to UE implementation.

6.6.3.6 Abnormal cases on the network side

No abnormal cases have been identified.

6.6.4 Transport of user data via the control plane procedure

6.6.4.1 General

The purpose of the transport of user data via the control plane procedure is to transfer user data via the control plane in an encapsulated form between the UE and the MME.

The procedure may be initiated by the UE or the network when the UE is in EMM-CONNECTED mode.

The procedure may also be initiated by the UE in EMM-IDLE mode by including the ESM DATA TRANSPORT message in a CONTROL PLANE SERVICE REQUEST message.

6.6.4.2 UE initiated transport of user data via the control plane

Upon receipt of a request to transfer user data via the control plane, if the UE is in EMM-CONNECTED mode, the UE initiates the procedure by sending the ESM DATA TRANSPORT message including the user data to be sent in the User data container IE (see example in figure 6.6.4.2.1). The length of the value part of the User data container IE should not exceed the link MTU size for the respective type of user data (IPv4, IPv6 or Non-IP). If the user data in the value part of the User data container IE is an Ethernet frame, then the length of the Ethernet frame payload should not exceed the Ethernet frame payload MTU size.

NOTE: The recommended maximum size for link MTU is 1358 octets to prevent fragmentation in the backbone network (see 3GPP TS 23.060 [74]). Depending on the network configuration, setting link MTU size to a value larger than 1358 octets could lead to inefficient core network implementation due to fragmentation.

If the UE is in EMM-IDLE mode, the UE initiates the procedure by sending the ESM DATA TRANSPORT message included in a CONTROL PLANE SERVICE REQUEST message.

Based on information provided by the upper layers, the UE may include a Release assistance indication IE in the ESM DATA TRANSPORT message to inform the network that

1) subsequent to the current uplink data transmission no further uplink or downlink data transmission (e.g. an acknowledgement or response) is expected; i.e. the upper layers indicated that data exchanges have completed with the current UL data transfer; or

2) subsequent to the current uplink data transmission only a single downlink data transmission and no further uplink data transmission is expected; i.e. the upper layers indicated that data exchanges will have completed with the next downlink data transmission.

When receiving the ESM DATA TRANSPORT message, the MME shall identify the PDN connection to the SCEF or to the PDN GW, based on the EPS bearer identity included in message, and forward the contents of the User data container IE accordingly. If the ESM DATA TRANSPORT message includes a Release assistance indication IE, then ESM layer indicates to the EMM layer to initiate release of the NAS signalling connection,

1) if the release assistance indication indicates that no further uplink and no further downlink data transmission subsequent to the uplink data transmission is expected; or

2) upon subsequent delivery of the next received downlink data transmission to the UE if the release assistance indication indicates that only a single downlink data transmission and no further uplink data transmission subsequent to the uplink data transmission is expected.

Figure 6.6.4.2.1: UE initiated transport of user data via the control plane procedure

6.6.4.3 Network initiated transport of user data via the control plane

The network initiates the procedure by sending the ESM DATA TRANSPORT message (see example in figure 6.6.4.3.1). Upon receiving the ESM DATA TRANSPORT message, the UE shall:

– forward the contents of the User data container IE to the upper layers.

Figure 6.6.4.3.1: Network initiated transport of user data via the control plane procedure

6.6.4.4 Abnormal cases in the UE

The following abnormal case can be identified:

a) T3396 is running

The UE shall not send an ESM DATA TRANSPORT message unless

– the UE is a UE configured to use AC11 – 15 in selected PLMN; or

– the ESM DATA TRANSPORT message is used for an exception data reporting and the UE is allowed to use exception data reporting (see the ExceptionDataReportingAllowed leaf of the NAS configuration MO in 3GPP TS 24.368 [15A] or the USIM file EF_NASCONFIG in 3GPP TS 31.102 [17]).

The ESM DATA TRANSPORT message can be sent, if still necessary, when timer T3396 expires or is stopped.

b) Transmission failure of the ESM DATA TRANSPORT message indication from lower layers

If lower layers indicate a TAI change and the current TAI is not in the TAI list, the transport of user data via the control plane procedure shall be aborted and re-initiated after successfully performing a tracking area updating procedure if the control plane CIoT EPS optimisation is still used and the user data exists. The "signalling active" flag shall be set in the TRACKING AREA UPDATE REQUEST message.

If lower layers indicate a TAI change, but the current TAI is still part of the TAI list, or the TAI has not changed, the transport of user data via the control plane procedure shall be re-initiated immediately if the user data still exists by including the ESM DATA TRANSPORT message in a CONTROL PLANE SERVICE REQUEST message.

NOTE: How the ESM sublayer handles the retransmission of user data via the control plane is up to the UE implementation.

c) NAS MAC calculation indication from lower layers

If lower layers indicate to calculate an NAS MAC, the UE shall calculate an NAS MAC as specified in 3GPP TS 33.401 [19] and then provide the calculated NAS MAC and 5 least significant bits of the uplink NAS COUNT used to calculate the NAS MAC to lower layers (see 3GPP TS 36.331 [22]). The UE shall increase the uplink NAS COUNT by one after the calculation of the NAS MAC.

6.6.4.5 Abnormal cases on the network side

a) ESM DATA TRANSPORT message received from a UE which is in a location where the PLMN is not allowed to operate

If the MME determines that the UE is in a location where the PLMN is not allowed to operate, the MME discards the message.