Page 177 - ITU-T Focus Group IMT-2020 Deliverables

ITU-T Focus Group IMT-2020 Deliverables 3

8.2.7 Control plane considerations for transport network slicing

8.2.7.1 Hybrid control plane for transport network slicing
In order to create an End-to-End network slice for 5G services, the control plane needs to obtain the network
topology information, and be able to compute paths which meet both the policies and service performance
requirements of the slice. The control plane also needs OAM mechanisms to monitor the real-time network
status and performance of the paths it has created for the given slices. This performance information is then
used as an important input for reoptimization and protection computations.

When an End-to-End network slice is initiated, different parts of the End-to-End network would respectively
use the appropriate technology to realize the mapping from network slice to the physical infrastructure and
resources. In addition, the stringent performance requirement of some 5G services requires that many
innovative technologies be used in the transport, most notably FlexE, Detnet, etc.
When a service is provisioned in a specific network slice, it is necessary to monitor the performance of the
service to ensure that network SLA is always guaranteed (this is especially true of statistically multiplexed
connections), and trigger optimization, protection or restoration of the network slice when needed.

A logically centralized controller can be used to create E2E network slices according to specific service
requirements. In real network deployments, this logically centralized controller is usually realized with the
combination of a distributed control plane and some centralized control functions (in SDN this is referred to
as an in-direct model). This is not only because distributed control planes already exists and can’t be replaced
immediately, but also due to fact that the distributed control plane has lots of advantages, such as scalability,
short response time and robustness against network failure and insensitivity to a central controller failure.
Therefore, a hybrid control plane (in-direct model) should be considered for 5G network slicing especially
with respect to the transport and packet portions of the end to end slice
8.2.7.2 Layered architecture for transport network slicing

The E2E communication infrastructure consists of UE, RAN, transport network, core network, mobile edge
computing network, etc. Each segment will choose suitable slicing technologies to achieve several slices, and
the slices in each segment are combined together to achieve E2E slicing. For example, one UE slice can match
one application or some applications which have similar requirements in the terminal. RAN slicing refers to
slice software and hardware resources to meet different service requirements. Meanwhile, RAN slicing could
coordinate with different core network slice to provide differentiated services. Transport network slicing can
obtain separated transport network slices in the same physical network, and each network slice provides the
service with the required characteristics, such as delay, bandwidth, packet loss rate, etc. The core network
slices that deal with authentication and mobility etc., and mobile edge computing network slices that offer
users cloud-computing capabilities and various applications at the edge of the mobile network can be
provided with combination of network functions which run on partitioned computing, storage and network
resources to meet the requirements of particular services.

This section describes the proposed control plane architecture for transport network slicing. Essentially it is
a layered architecture:

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