Sent between various nodes, for example between source and target MMEs or SGSNs as part of various handover or relocation processes.

Response to forward relocation requests to confirm that the relocation was successful or not.

Sent to the source MME/SGSN/AMF to indicate a handover was successful.

Response to a forward relocation complete notification.

Sent by the new MME/SGSN to the old MME/SGSN on S3/S16/S10 interface as a part of TAU/RAU procedure and UTRAN/GERAN to E-UTRAN/UTRAN (HSPA) SRVCC procedure to get the MM and EPS bearer contexts for the UE.

Response to a context request message.

Response to a context response message

Sent by a UE when it changes SGSN or MME. The request is sent to the UE's old SGSN/MME/AMF.

Sent by the old SGSN/MME/AMF to the new MME/SGSN/AMF in response to a identification request message.

Forward new RNC contexts to the new target system. Sent by the old SGSN to the new SGSN over the S16 interface.\

Can also forward RNC/eNodeB contexts to the new target system. Sent from the old MME to the new MME over the S10 interface.

Sent to the old MME/SGSN as a response to Forward access context notification.

Sent by various nodes as part of a detach procedure.

Response to a detach notification.

Used for reporting of changes of UE presence in presence reporting areas or user CSG information change reporting.

Response to a change notification request. Includes information about whether the change was successful or not.

Sent from the source MME/SGSN/AMF to the target MME/SGSN/AMF on S3/S10/S16/N26 interface during a handover or relocation cancel procedure.

Response to a relocation cancel request. Includes information about whether the cancel request was successful or not.

Set up a tunnel to securely transfer configuration transfer messages between source and target MMEs or between MMEs and AMFs.

Transfer the RAN information received by an SGSN from BSS or RNS (or GERAN Iu mode) or by an MME from eNodeB. Also to transfer the RAN information between GERAN or GERAN Iu mode or UTRAN.

Sent on the S3 interface by the MME/SGSN to the ISR associated SGSN/MME to:

• Restore PDN connections after an SGW failure for UEs.
• Begin the HSS Based P-CSCF restoration procedure for 3GPP access (for both basic and PCO extension).

Supports CS/PS coordination for shared UTRAN and GERAN access.