Page 481 - 5G Basics - Core Network Aspects
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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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