or 3GPP and non-3GPP accesses (see 3GPP TS 23.401 (2019) and 3GPP TS 23.402 (2019) for details). A common NAS protocol for mobility and session management is used between the UE or 5G Residential Gateway and the core network for both 3GPP accesses and non-3GPP accesses (e.g. WLAN or wireline access technologies). This is a significant simplifica- tion compared with EPS where e.g. different session management protocols were used between UE and core network for 3GPP access and non-3GPP technologies. 3.2.5 Enablers for Concurrent and Efficient Access to Local and Centralized Services 3.2.5.1 Overview There has been an increasing demand to host services closer to the user (an approach also known as MEC) to reduce end-to-end latency, for example, for virtual and augmented real- ity applications. Another driver to host services at least partially closer to the user is to reduce traffic volume across backbone links by caching content within the RAN aggregation network. At the same time, many services will continue to be hosted in central locations, for example, IMS voice and many internet services. Therefore, it is important to support concurrent access to both local and centralized services. This raises the following questions: 1. How can an efficient data-forwarding path be enabled between the UE and local services as well as centralized services? 3.2 5G Core Network 2. How can the data-forwarding path be updated when the UE changes its location? 3. How can it be determined when to update the data-forwarding path and where to for- ward data to depending on the locations where a given service is hosted? 4. How can the operator or applications be enabled to influence which traffic should be routed locally and which traffic should be forwarded to a central location? The 5GC mechanisms that have been specified (3GPP TS 23.501) to address these questions can be classified based on whether they operate within a single PDU session or across mul- tiple PDU sessions and subsequently whether the UE is aware of and involved in t