GTP access supports X2 handover and Tracking Area Update (TAU) without SGW relocation procedures as defined in TS 23.401.
GTP also supports subscriptions to location reporting. The required level of location reporting (for example, ECGI, TAI, ECGI+TAI) can be configured and overridden by AAA. Location reporting is only enabled if support is signaled by an MME. If an MME changes as part of a TAU procedure, change reporting is disabled unless the new MME also explicitly signals support.
Updated ULI can be learned in any regular procedure such as X2 handover, TAU, and UE-triggered service request. Additionally, the Location Change Reporting procedure, as defined in TS 23.401, is supported to signal location changes in absence of any other change.
Any AAA messages sent by the router always contain the latest ULI for the related GTP session. Additionally, RADIUS Accounting and Gx support triggered updates whenever the ULI changes. For RADIUS, this support is configured locally in the radius-accounting-policy. For Gx, the PCRF needs to subscribe to the USER_LOCATION_CHANGE, RAT_CHANGE, or ECGI_CHANGE event as specified in TS 29.214. In case of RAT/ECGI event subscription, this is directly reflected in GTP Change Reporting Action, overriding any local configuration. If only a generic USER_LOCATION_CHANGE subscription is requested, the GTP signaled action depends on the local configuration, requiring change-reporting-action to be configured in the applicable peer-profile.