7.4 CS Fallback and SRVCC related messages

29.2743GPP3GPP Evolved Packet System (EPS)Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control plane (GTPv2-C)Release 16Stage 3TS

7.4.1 Suspend Notification

The Suspend Notification message shall be sent on the S11 interface by the MME to the SGW and on the S5/S8 interface by the SGW to the PGW as part of the 1xRTT CS fallback procedures in 3GPP TS 23.272 [21].

The Suspend Notification message shall be sent on the S3 interface by the SGSN to the MME, on the S11 interface by the MME to the SGW, and on the S5/S8 interface by the SGW to the PGW as part of the SRVCC procedures in 3GPP TS 23.216 [43] or the CS fallback from E-UTRAN access to UTRAN/GERAN CS domain access related procedures in 3GPP TS 23.272 [21].

The Suspend Notification message shall be sent on the S16 interface as per the inter-SGSN suspend procedures in 3GPP TS 23.060 [35].

The Suspend Notification message shall be sent on the S16, the S4 and the S5/S8 interfaces as part of the SRVCC from UTRAN (HSPA) to GERAN without DTM support procedure in 3GPP TS 23.216 [43].

The Suspend Notification message shall be sent on the S4 and the S5/S8 interfaces as part of the CS fallback from E-UTRAN to GERAN CS domain related procedures in 3GPP TS 23.272 [21].

After receiving a Suspend Notification message, the SGW/PGW marks all the non-GBR bearers as suspended status. The PGW should discard packets it receives for the suspended UE.

Table 7.4.1-1 specifies the presence requirements and conditions of the IEs in the message.

Table 7.4.1-1: Information Element in Suspend Notification

Information elements

P

Condition / Comment

IE Type

Ins.

IMSI

C

This IE shall be included only on the S11 interface.

See NOTE 2.

IMSI

0

Routeing Area Identity(RAI)

C

This IE shall be included only on the S3 interface.

See NOTE 1.

ULI (NOTE 3)

0

CO

This IE shall be included on the S16 interface.

Linked EPS Bearer ID (LBI)

CO

This IE shall be included on the S11/S4 interface to indicate the default bearer associated with the PDN connection.

EBI

0

Packet TMSI(P-TMSI)

C

This IE shall be included only on the S3 interface.

See NOTE 1.

P-TMSI

0

CO

This IE shall be included on the S16 interface.

Originating Node

CO

This IE shall be sent on S11 interface, if before MME initiates a Detach procedure (a) ISR was active in the MME and (b) the MME was in EMM-Connected state (see also 8.65).

This IE shall be sent on S4 interface, if before S4-SGSN initiates a Detach procedure (a) ISR was active in the SGSN and (b) the SGSN was in PMM-Connected state (see also 8.65).

Node Type

0

Address for Control Plane

CO

If an SGSN within the same SGSN pool with the old SGSN receives this message, the SGSN shall include the source IP address of the received message in this optional parameter if this IE is not present and relay the message to the old SGSN.

IP Address

0

UDP Source Port Number

CO

If an SGSN within the same SGSN pool as the old SGSN receives this message, the SGSN shall include the UDP Source Port number of the received message in this parameter if this IE is not present and relay the message to the old SGSN. The old SGSN shall use this UDP port as the UDP destination port of the Suspend Acknowledge message.

Port Number

0

Hop Counter

O

If an SGSN within the same SGSN pool with the old SGSN receives this message, the SGSN shall decrement the Hop Counter if this IE is present in the received message; otherwise, the SGSN may include a Hop Counter with a value of max-1, and may relay the message to the old SGSN.

Hop Counter

0

Sender F-TEID for Control Plane

CO

The MME/SGSN and SGW shall include this IE on the S11/S4 and S5/S8 interfaces respectively and set it to the last value sent to the peer.

If the Sender F-TEID for Control Plane is received, the receiver shall only handle the message if the Sender F-TEID for Control Plane in this message is the same as the last Sender F-TEID for Control Plane received on the given interface.

F-TEID

0

Private Extension

O

Private Extension

VS

NOTE 1: If the ISR is not active, the MME can not suspend the bearers after receving the Suspend Notification message from the SGSN, the GUTI can not be derived from the P-TMSI and RAI pair as the P-TMSI Signature is not included in the message. The MME shall still reply the Suspend Acknowledge to the SGSN. Suspend procedure on MME, SGW and PGW are triggered by the S1 UE Context Release message sent from the eNodeB to the MME. Refer to clause 6.3 and clause 7.4 in 3GPP TS 23.272 [21] for detail.

NOTE 2: The IMSI is present only for backward compatibility reasons since the SGW can derive the context from the TEID in the header. In scenarios where IMSI is not present (e.g. UICCless UE during an Emergency call) a dummy IMSI shall be provided.

NOTE 3: Only RAI field in the ULI IE type shall be present in the Routeing Area Identity (RAI) IE.

7.4.2 Suspend Acknowledge

The Suspend Acknowledge message shall be sent on the S11 interface by the SGW to the MME and on the S5/S8 interface by the PGW to the SGW as part of the 1xRTT CS fallback procedures in 3GPP TS 23.272 [21].

The Suspend Acknowledge message shall be sent on the S3 interface by the MME to the SGSN, on the S11 interface by the SGW to the MME and on the S5/S8 interface by the PGW to SGW as part of the SRVCC procedures in 3GPP TS 23.216 [43] or the CS fallback from E-UTRAN access to UTRAN/GERAN CS domain access related procedures in 3GPP TS 23.272 [21].

The Suspend Acknowledge message shall be sent on the S16 interface as per the inter-SGSN suspend procedures in 3GPP TS 23.060 [35].

The Suspend Acknowledge message shall be sent on the S16, the S4 and the S5/S8 interfaces as part of the SRVCC from UTRAN (HSPA) to GERAN without DTM support procedure in 3GPP TS 23.216 [43].

The Suspend Acknowledge message shall be sent on the S4 and the S5/S8 interfaces as part of the CS fallback from E-UTRAN to GERAN CS domain related procedures in 3GPP TS 23.272 [21].

Possible Cause values are specified in Table 8.4-1.

For backward compatibility, if the IMSI IE is missing in the Suspend Notification message that is received on the S11 interface, the cause value "Mandatory IE missing" shall be used.

Table 7.4.2-1 specifies the presence requirements and conditions of the IEs in the message.

Table 7.4.2-1: Information Element in Suspend Acknowledge

Information elements

P

Condition / Comment

IE Type

Ins.

Cause

M

Cause

0

Private Extension

O

Private Extension

VS

7.4.3 Resume Notification

The Resume Notification message should be sent on the S11 interface by the MME to the SGW and forwarded on the S5/S8 interface by the SGW to the PGW as part of the resume procedure returning back to E-UTRAN in the case of CS fallback or SRVCC.

The Resume Notification message should also be sent on the S4 interface by the SGSN to the SGW and forwarded on the S5/S8 interface by the SGW to the PGW as part of the resume procedure returning from SRVCC to HSPA if there is no Modify Bearer Request message sent to the SGW and PGW as specified in 3GPP TS 23.216 [43].

The SGW may also send a Resume Notification message to the PGW on the S5/S8 interface upon receipt from the MME/S4-SGSN of a (non-empty) Modify Bearer Request used as an implicit resume of the suspended bearers in the SGW and in the PGW (see 3GPP TS 23.216 [43] clauses 6.2.2.1 and 6.3.2.1, 3GPP TS 23.272 [21] clauses 6.3, 6.5 and 7.4) if the conditions of presence of the IEs in the Modify Bearer Request specified in table 7.2.7-1 do not require any IE to be sent over S5/S8 to the PGW.

NOTE: This is an alternative to sending over S5/S8 a Modify Bearer Request used as an implicit resume with zero IE(s), see clause 7.2.7.

After receiving a Resume Notification message or a Modify Bearer Request used as an implicit resume of the suspended bearers, the SGW/PGW clears suspended status for all the non-GBR bearers. The PGW shall forward packets it receives for the UE. If the suspended bearers are of the type S4-U GTP-U, the SGW shall forward over the S4-U interface, packets it receives for the UE, upon receipt of Resume Notification.

Table 7.4.3-1 specifies the presence requirements and conditions of the IEs in the message.

Table 7.4.3-1: Information Element in Resume Notification

Information elements

P

Condition / Comment

IE Type

Ins.

IMSI

M

See NOTE1.

IMSI

0

Linked EPS Bearer ID (LBI)

CO

This IE shall be included on the S11/S4 interface to indicate the default bearer associated with the PDN connection.

EBI

0

Originating Node

CO

This IE shall be sent on S11 interface, if before MME initiates a Detach procedure (a) ISR was active in the MME and (b) the MME was in EMM-Connected state (see also 8.65).

This IE shall be sent on S4 interface, if before S4-SGSN initiates a Detach procedure (a) ISR was active in the SGSN and (b) the SGSN was in PMM-Connected state (see also 8.65).

Node Type

0

Sender F-TEID for Control Plane

CO

The MME/SGSN and SGW shall include this IE on the S11/S4 and S5/S8 interfaces respectively and set it to the last value sent to the peer

If the Sender F-TEID for Control Plane is received, the receiver shall only handle the message if the Sender F-TEID for Control Plane in this message is the same as the last Sender F-TEID for Control Plane received on the given interface.

F-TEID

0

Private Extension

O

Private Extension

VS

NOTE 1: The IMSI is present only for backward compatibility reasons since the receiver can derive the context from the TEID in the header. In scenarios where IMSI is not present (e.g. UICCless UE during an Emergency call) a dummy IMSI shall be provided.

7.4.4 Resume Acknowledge

The Resume Acknowledge message should be sent on the S11 interface by the SGW to the MME and on the S5/S8 by the PGW to the SGW as part of the resume procedure returning back to E-UTRAN in the case of CS fallback or SRVCC.

The Resume Acknowledge message should also be sent on the S4 interface by the SGW to the SGSN and on the S5/S8 interface by the PGW to the SGW as part of the resume procedure returning from SRVCC to HSPA if there is no Modify Bearer Request message sent to the SGW and PGW as specified in 3GPP TS 23.216 [43].

The PGW shall also send a Resume Acknowledge message to the SGW on the S5/S8 interface as a response to a Resume Notification message sent by the SGW upon receipt from the MME/S4-SGSN of a (non-empty) Modify Bearer Request used as an implicit resume of the suspended bearers in the SGW and in the PGW (see 3GPP TS 23.216 [43] clauses 6.2.2.1 and 6.3.2.1, 3GPP TS 23.272 [21] clauses 6.3, 6.5 and 7.4) if the conditions of presence of the IEs in the Modify Bearer Request specified in table 7.2.7-1 do not require any IE to be sent to the PGW.

Possible Cause values are specified in Table 8.4-1.

Table 7.4.4-1 specifies the presence requirements and conditions of the IEs in the message.

Table 7.4.4-1: Information Element in Resume Acknowledge

Information elements

P

Condition / Comment

IE Type

Ins.

Cause

M

Cause

0

Private Extension

O

Private Extension

VS

7.4.5 CS Paging Indication

The CS Paging Indication shall be sent on the S3 interface by the MME to the associated SGSN when ISR is activated as part of mobile terminated CS services. The MME gets the related information from SGsAP-PAGING-REQUEST message as specified in 3GPP TS29.118 [21].Table 7.4.5-1 specifies the presence requirements and the conditions of the IEs in the message.

NOTE: The SS code received on the SGs interface is not transferred to the SGSN because it is not used by the SGSN.

Table 7.4.5-1: Information Element in CS Paging Indication

Information elements

P

Condition / Comment

IE Type

Ins.

IMSI

M

IMSI

0

VLR Name

M

FQDN

0

TMSI

O

TMSI

0

Location area identifier

O

ULI

0

Global CN-Id

O

Global CN-Id

0

Channel needed

O

Channel needed

0

eMLPP Priority

O

eMLPP Priority

0

Service Indicator

CO

This IE shall be sent if the service type for the paging is available.

Service Indicator

0

Private Extension

O

Private Extension

VS

7.4.6 Alert MME Notification

An Alert MME Notification message shall be sent on the S3 interface by the MME to the associated SGSN as part of an SGs Non-EPS alert procedure (see 3GPP TS 29.118 [22]) when ISR is activated, except under the conditions specified in 3GPP TS 23.272 [21], to request to receive a notification when any activity from the UE is detected.

Table 7.4.6-1 specifies the presence requirements and the conditions of the IEs in the message.

Table 7.4.6-1: Information Element in Alert MME Notification

Information elements

P

Condition / Comment

IE Type

Ins.

Private Extension

O

Private Extension

VS

7.4.7 Alert MME Acknowledge

An Alert MME Acknowledge message shall be sent as a response to an Alert MME Notification message.

Possible Cause values are specified in Table 8.4-1.

NOTE: An SGSN implemented according to an earlier version of the specification will silently discard the Alert MME Notification message. An MME which does not receive an Alert MME Acknowledge message may not send further Alert MME Notification message to this SGSN.

Table 7.4.7-1 specifies the presence requirements and the conditions of the IEs in the message.

Table 7.4.7-1: Information Elements in Alert MME Acknowledge

Information elements

P

Condition / Comment

IE Type

Ins.

Cause

M

Cause

0

Private Extension

O

Private Extension

VS

7.4.8 UE Activity Notification

A UE Activity Notification message shall be sent on the S3 interface by the SGSN to the associated MME as part of an SGs Non-EPS alert procedure (see 3GPP TS 29.118 [22]) when ISR is activated, except under the conditions specified in 3GPP TS 23.272 [21], to indicate that activity from a UE has been detected. Table 7.4.8-1 specifies the presence requirements and the conditions of the IEs in the message.

Table 7.4.8-1: Information Element in UE Activity Notification

Information elements

P

Condition / Comment

IE Type

Ins.

Private Extension

O

Private Extension

VS

7.4.9 UE Activity Acknowledge

A UE Activity Acknowledge message shall be sent as a response to a UE Activity Notification message.

Possible Cause values are specified in Table 8.4-1.

Table 7.4.9-1 specifics the presence requirements and the conditions of the IEs in the message.

Table 7.4.z-1: Information Elements in UE Activity Acknowledge

Information elements

P

Condition / Comment

IE Type

Ins.

Cause

M

Cause

0

Private Extension

O

Private Extension

VS