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Core network aspects                                            1


            •       processing location registration messages sent from or on behalf of the UE;

            •
                    assigned to the UE;
            •       management of the binding between the persistent address assigned to the UE and its temporary
                    address, in the case of host-based mobility, or the address of the lower tunnel end point, in the case
                    of network-based mobility;
            •       optionally, holding two location bindings for the mobile UE by marking the binding for the serving
                    network as active state and marking the binding for target network as standby state;
            •       supporting  separation  of  control  and  data  plane  by  allowing  the  MLM-FE  address  and  data
                    forwarding end point address (i.e., tunnelling end point address) to be different;

            •       indication of a new mobility location binding and distribution of binding information to the HDC-FE.
            The MLM-FE has two roles, as proxy (MLM-FE(P)) and as the central instance (MLM-FE(C)). The MLM-FE(P)
            and MLM-FE(C) roles may be co-located in specific deployments providing only host-based mobility. The
            MLM-FE(C) provides a central point of contact for correspondent nodes (e.g., the SCF). The MLM-FE(P) and
            MLM-FE(C)  together  provide  hierarchical  location  management.  The  MLM-FE(P)  holds  and  updates  the
            binding between mobile user ID, persistent address, and temporary/lower tunnel end point address. The
            MLM-FE(C) holds the binding between mobile user ID, persistent address, and address of the MLM-FE(P). The
            MLM-FE(P) may identify the corresponding MLM-FE(C) by extracting the home domain from the mobile user
            ID.
            The MLM-FE(P) consists of the following functions:
            •       in the host-based case, it provides the first point of contact for location registration for mobile users.
                    As such, it appears as a proxy for the MLM-FE(C) from the point of view of the UE, while appearing
                    as a proxy for the UE from the point of view of the MLM-FE(C). The mobile UE obtains the address
                    of the MLM-FE(P) in the attachment procedure;

            •       in the network-based mobility case, the MLM-FE(P) acts as a proxy for the UE from the point of view
                    of the network side;
            •       the MLM-FE(P) supports IP-based paging to locate the mobile UE;

            •       in  the  host-based  case,  the  MLM-FE(P)  may  interwork  between  different  mobility  signalling
                    protocols (e.g., due to a difference in IP versions supported) at the UE and at the MLM-FE(C);
            •       signalling for location registration in the host-based case is secured through the security association
                    between the UE and the MLM-FE(P). The security association is dynamically created based on the
                    keying materials generated in the attachment procedure;
            •       the  MLM-FE(P)  is  responsible  for  requesting  the  HDC-FE  to  perform  handover  control  as  a
                    consequence of mobile location registration or update;
            •       the MLM-FE(P) may be the proxy of the UE for initiating route optimization, especially in the case of
                    interworking between signalling protocols;
            •       if there is a second anchor point between the UE and the anchor point to which the MLM-FE(C)
                    corresponds, the MLM-FE(P) carries the additional address binding;
            •       the MLM-FE(P) may be used to transform addresses within the signalling because of intervening
                    NATs;

            •       the MLM-FE(P) may be used to provide address anonymity to the UE.
            6.4.2   Handover decision and control functional entity (HDC-FE)

            The handover decision and control functional entity (HDC-FE) has three sub-functions: handover decision
            (HDF), layer 2 handover control (L2HCF), and layer 3 handover control (L3HCF). Their relationship is shown in
            Figure 2.






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