This Annex describes an optional architecture configuration that centralizes all services, including emergency calls and SMS, within the IMS domain for all users roaming in that network independent of access used, i.e. it replaces service execution of the CS service domain with service logic execution in IMS only. The service profile for all users is soley provided by the IMS domain. For inbound roamers not supporting IMS or ICS in HPLMN therefore a temporary IMS subscription is created and service is handled locally in the VPLMN. The architecture configuration utilizes the "Registration and Authentication procedure utilizing IMS Authorization", which enables the option to remove subscriber related data from the VLR and use data of the IMS domain instead, e.g. the HSS. An interworking function provides the support for inbound and outbound roaming in networks not supporting IMS or ICS. This architecture configuration has no impact to UEs, no impact to interconnection interfaces of the roaming partner, no impact access networks (e.g. CS access) and does not require changes of specifications (e.g. TS 24.008). The basic principles of this solution are that CS access is mapped to IMS and PS access uses "native" IMS (VoLTE) but there is a single service domain for both accesses in IMS. The user profile is solely provided by IMS domain. For the migration phase the SeDoC enabled network operator is required to provide legacy support for inbound roamers. Long term target is that the service for inbound roamer be provided by the HPLMN, i.e. the VPLMN IMS-GWs (IBCFs) would relay towards home IMS service infrastructure.