Vertical extension of slicing (Data plane enhancement)

6.6.5 End-to-end reference model for scalable operation

The main constraints for scalability of softwarized systems would be the dynamic behaviour of each slice and the control granularity of physical resources. The communication session established by mobile core, however, would be beyond the scope of this activity, because it requires a dedicated system for such an extraordinary multiple-state and real-time control, especially for the mobility handling. The coordination and isolation between these systems should be clearly defined.

Nevertheless, scalability for other types of sessions would be the issues of architectural modelling, including application services, system operation, or advanced network services.

In addition to the dimensions and dynamics of the softwarized systems, investigations would be required from the viewpoints of resiliency and inter-system coordination.

For resiliency, some new aspects might be considered other than traditional MTBF type faulty conditions. In case of disaster, for example, the fault localization, analysis, and recovery could be more complicated for such virtual systems with network softwarization. Miss-behaviors caused by human factors are also difficult to cope with the traditional operation architecture, because of the indirectness of virtual system operation.

The inter-system coordination architecture should be clearly structured and modelled for efficient standardization and for scalability evaluation of the softwarized networking systems. There might be two categories of the coordination, namely horizontal and vertical. The horizontal coordination is for between slice, cloud systems, and UE, the end-to-end system coordination in other word. Two types of vertical coordination could be distinguished. One is for slice and service provider through APIs and another is for virtual and physical resource coordination aimed to efficient resource handling through policy and analytics.

In summary, the softwarized network systems should have sufficient levels of scalability in the components;

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  The number of instances/service slices to be supported
  
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  Series of capabilities provided by service slices
  
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  The number of service sessions to be handled concurrently
  
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  Dynamic behaviour of the instances and slices
  
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  Granularity of resource management, especially for policy control and/or analytics
  
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  Resiliency for various faulty conditions
  
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  Intra-slice coordination among the end-to-end resources
  
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  Inter-slice coordination, specifically with various external systems.
  

Intensive studies are required on both the dimension and the dynamic behavior of softwarized networks, since such highly virtualized systems will have an enormous number of instances and reactions are not easy to extrapolate from the current physical systems.

The virtualized resource handling must be the essential part of the scalable and novel operation architecture, which potentially improves conventional network operations and possibly even up to the level of supporting disaster recovery by using softwarized network resiliency and recovery of/with the virtualized systems both in a single domain and in multiple domains.

One of the benefits of 5G systems should be the end-to-end QoE management, however, this capability will be established on the complex interaction between the virtualized systems including UEs, Cloud Systems, Applications, and the softwarized network systems. The softwarized network system itself will be composed of various virtualized subsystems. An appropriate end-to-end reference model and architecture should be intensively investigated for such complex systems.