Section: Suspend Acknowledge
Content: 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[ Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2 ]  [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[ Single Radio Voice Call Continuity (SRVCC); Stage 2 ]  [43] or the CS fallback from E-UTRAN access to UTRAN/GERAN CS domain access related procedures in 3GPP TS 23.272[ Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2 ]  [21]. The Suspend Acknowledge message shall be sent on the S16 interface as per the inter-SGSN suspend procedures in 3GPP TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [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[ Single Radio Voice Call Continuity (SRVCC); Stage 2 ]  [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[ Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2 ]  [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 -1: Information Element in Suspend Acknowledge