Page 90 - ITU-T Focus Group IMT-2020 Deliverables

3 ITU-T Focus Group IMT-2020 Deliverables

Figure 6.1.1-10 – Message flow to establish session between two Network Functions

1) The Network Function A decides to establish a new session with Network Function B. It sends
Function Discovery Request message to Network Function Repository Function, including the
Requested Network Function Type.
2) The Network Function Repository Function determines if a local Network Function B should be
selected or not. If local Network function B is selected it sends Function Discovery Response message
including a routable IP address of Network Function B. If the Network Function Repository Function
decides not to select a local Network Function B it sends Function Discovery Response message
including a routable IP address of Interconnection Function A.
3) If the Network Function Repository Function response with a routable IP address of the Network
Function B, it sends Session Establishment Request message to Network Function B directly,
including necessary information for session establishment.
4) The Network Function B establishes the session context per request and sends Session
Establishment Response to Network Function A directly.

6.1.1.2.3 Key issue: 3GPP architecture impacts to support network capability exposure
The network capability exposure function is to allow 3rd party/UE to access information regarding services
provided by the network (e.g., connectivity information, QoS, mobility, etc.) and to dynamically customize
the network capability for different diverse use cases within the limits set of functions by the operator. The
next generation system should provide suitable access/exchange of network/connectivity information
(e.g., via APIs) to the 3rd party/UE.
Please refer to Clauses 5.9 in NextGen TR 23.799 for the detailed non-exhaustive list of solutions for this key
issue. One thing that may need to keep tracking of is that the network capability exposure function itself does
not seem to include control capabilities differently from our discussion in Focus Group.
6.1.1.2.4 Key issue: Architecture impacts when using virtual environments

The NextGen system is expected to support deployments in virtualized environments. This key issue will
determine the need for and architecture impacts due to load rebalancing and load migration in the context
of:
– scaling of a network function instance, and
– dynamic addition or removal of a network function instance.

An agreement is as follows:
1) The architecture should support mechanisms to avoid issues caused by the persistence ("stickiness")
of UE-specific associations on at least NG2.
NOTE 1 – Solutions should be developed during normative phase.

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