Page 321 - 5G Basics - Core Network Aspects
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Core network aspects                                            1


            6.2.1   FSC capability discovery/negotiation requirement

            A  mechanism  is  defined  for  the  MUE  and  the  network  to  discover  whether  the  network  and  the  MUE
            respectively support FSC and to decide whether FSC is applied for multi-connection. The MUE and the access
            control functional entity (AC-FE) shall always be aware of which access Internet protocol (IP) flows are used
            in multi-connection.
            During initial multi-connection establishment over the first connection, the MUE triggers a FSC request. The
            intermediate network nodes indicate to the AC-FE whether they support FSC for the corresponding request.
            If an MPC-FE is deployed, the AC-FE communicates to the MPC-FE indicating whether or not the MUE and
            the network support FSC. The MPC-FE then takes the decision of whether or not FSC may apply to the multi-
            connection and communicates this decision to the AC-FE.
            If the network supports FSC and is willing to accept FSC for the multi-connection, the AC-FE confirms the FSC
            support in an "FSC accepted" indication sent back to the MUE in the multi-connection establishment accept
            message.
            6.2.2   Routing rules

            It is recommended that a routing rule contains the following parameters:
            –       Routing filter
            –       Routing access information
            –       Routing rule priority

            –       Routing rule identifier
            A routing filter consists of IP header parameter values and/or ranges used to identify one or more IP flows.
            The routing access information identifies the access type where the IP flow shall be routed.

            For the purpose of matching user traffic against routing rules, filters are applied in the order designated by
            the routing rule priority.

            The routing rule identifier uniquely identifies a routing rule for one connection. The routing rule identifier is
            allocated by the entity creating the routing rule; i.e., by the MUE in MUE-initiated FSC mode and by the AC-
            FE in network-initiated FSC mode.

            6.2.3   Delivery of routing rules
            Routing rules are exchanged between the MUE and the AC-FE via control plane signalling.

            For the MUE-initiated FSC procedure, the routing rules are provided by the MUE to the network. The MUE
            does not apply new routing rules until the AC-FE has acknowledged them.
            For the network-initiated FSC procedure, the MPC-FE makes the decision on when and which flows should
            be  moved  to  which  connections.  The  MPC-FE  learns  about  the  multiple  accesses  supporting  a
            multi-connection via event triggers from the AC-FE.


            7       Flow-based service continuity mechanisms

            7.1     Overview

            Both, the MUE-initiated FSC mode and the network-initiated mode are supported. The FSC mode applicable
            to multi-connection is determined during connection establishment. Routing rule installation is possible at
            any time during the lifetime of the multi-connection sessions. The routing rules can even be installed if there
            is no IP flow currently matching the routing filter in the routing rule.
            The AC-FE performs IP flow routing for downlink traffic. The MUE performs IP flow routing for uplink traffic.

            During the multi-connection sessions and when the policies determine that the IP flows should be moved
            and the target access is available for the MUE, it is possible to move individual IP flows from one access
            network to another.


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