4.1 General concepts

28.5303GPPConcepts, use cases and requirementsManagement and orchestrationRelease 17TS

4.1.1 Management of 5G networks and network slicing

5G system consists of 5G Access Network (AN), 5G Core Network and UE, see TS 23.501 [3].

5G system is expected to be able to provide optimized support for a variety of different communication services, different traffic loads, and different end user communities, see clause 4 of TS 22.261 [2]. For example, the communication services using network slicing may include:

– V2X services

The 5G system aims to enhance its capability to meet KPIs that emerging V2X applications require. For these advanced applications, the requirements, such as data rate, reliability, latency, communication range and speed, are made more stringent, see clause 4 of TS 22.261 [2].

– 5G seamless eMBB service with FMC

As one of the key technologies to enable network slicing, fixed mobile convergence (FMC) which includes wireless-to-the-everything (WTTx) and fibre-to-the-everything (FTTx), is expected to provide native support for network slicing. For optimization and resource efficiency, the 5G system will select the most appropriate 3GPP or non-3GPP access technology for a communication service, potentially allowing multiple access technologies to be used simultaneously for one or more services active on a UE, see clause 6.3 of TS 22.261 [2].

– massive IoT connections

Support for massive Internet of Things (mIoT) brings many new requirements in addition to MBB enhancements, see clause 4 of TS 22.261 [2]. Communication services with massive IoT connections such as smart households, smart grid, smart agriculture and smart meter will require the support of a large number and high density IoT devices to be efficient and cost effective, see TS 23.501 [3]. Operators can use one or more network slices to provide these communication services, which require similar network characteristics, to different vertical industries.

Services, e.g. like those described above, can be provided to customers (e.g. verticals) by the operator. The SLS may contain service requirements that should be used for performance monitoring, configuration and some service requirement attributes may influence the dimensioning of new network slices and network slice subnets.

The fulfilment of the performance requirements in the service profile and slice profile is monitored by KPIs.

Configured attributes in the service profile and slice profile may be enforced by the 3GPP system, or their fulfillment monitored by the management system, e.g. for charging reasons.

Network slice data may be exposed to the customer.

The next generation 3GPP management system is expected to support the management of 3GPP 5G system and 3GPP legacy systems.

3GPP management system directly manages 3GPP managed network components (e.g. 5G RAN, 5G CN). For non-3GPP domains (e.g. DCN, TN), 3GPP management system needs to coordinate with the corresponding management systems of the non-3GPP domains.

4.1.2 Types of communication services

Communication services offered by Communication Service Providers (CSPs) to Communication Service Customers (CSCs) are of various categories, among which:

– Business to consumer (B2C) services, e.g. mobile web browsing, 5G voice, Rich Communication Services, etc.

– Business to business (B2B) services, e.g. Internet access, LAN interconnection, etc.

– Business to household (B2H) services, e.g. Internet access, MBMS, VOIP, VPN, etc.

– Business to business to everything (B2B2X) services: e.g. services offered to other CSPs (e.g. international roaming, RAN sharing, etc.) offering themselves communication services to their own customers. B2B2X service type includes B2B2 applied recursively, i.e. B2B2B, B2B2B2B, etc.

NOTE: How to derive different network slice related requirements from different categories of communication services is not in the scope of the present document.

A communication service offered by CSPs can include a bundle of specific B2C, B2B, B2H or B2B2X type of services. Taking as an example the B2C type of services, a bundle could include: data (for mobile web browsing), voice (through 5G voice), and messaging (via Rich Communication Services). In this case, each one of the individual B2C may be fulfilled by different PDU connectivity services provided via corresponding PDU sessions.

4.1.3 Communication services using network slices

As an example, a variety of communication services provided by multiple network slice(s) are illustrated in the figure 4.1.3.1. Figure 4.1.3.1 is only for illustrative purposes to highlight the combination and relationship of communication services to network slices without depicting any UE. An actual network slice deployment offering communication services to UEs will need to comply with the 5G system architecture defined in TS 23.501 [3] and TS 38.401 [4].

Figure 4.1.3.1: A variety of communication services provided by multiple network slices

Figure 4.1.3.1 illustrates the relationship between communication services, network slices, and network slice subnets:

– network slice subnet AN-1 and network slice subnet AN-2 each contain distinct sets of AN NFs. network slice subnet CN-1, network slice subnet CN-2 and network slice subnet CN-3 each contain distinct sets of CN NFs. The TN supporting connectivity facilitates the communication between CN and AN NFs. network slice subnet A combines network slice subnet AN-1 with network slice subnet CN-1 and corresponding TN connectivity. network slice subnet B combines network slice subnet AN-2 and network slice subnet CN-2 and corresponding TN connectivity. network slice subnet C combines network slice subnet AN-2 with network slice subnet CN-3 and corresponding TN connectivity. The network slice subnet AN-2 is shared between network slice subnet B and network slice subnet C, while network slice subnet AN-1 is dedicated to network slice subnet A.

– NOP offers network slice subnet A as a network slice A, in this relationship network slice A represents network slice subnet A with associated Service Level Specification (SLS). NOP also offers network slice subnet B as network slice B and network slice subnet C as network slice C. The SLS of network slice A satisfies the service requirements of communication service 1 and communication service 2. The SLS of network slice B satisfies the service requirements of communication service 2. The SLS of network slice C satisfies the service requirements of communication service 3.

– The communication service 1 is supported by network slice A. The communication service 2 may be supported by either network slice A or network slice B. The communication service 3 is supported by network slice C.

4.1.4 Communication services requirements

eMBB service type aims at supporting high data rates and high traffic densities as outlined in TS 22.261 [2], Table 7.1-1 "Performance requirements for high data rate and traffic density scenarios". URLLC service type aims at supporting the requirements in TS 22.261 [2], Table 7.2.2-1 "Performance requirements for low-latency and high-reliability services." related to high reliability and low latency scenarios. mIoT service type aims at supporting a large number and high density of IoT devices efficiently and cost effectively, see TS 23.501 [3].

Depending on the service type (eMBB, URLLC, mIoT), different service types may include different network slice related requirements, for example:

– Area traffic capacity requirement

– Charging requirement

– Coverage area requirement

– Degree of isolation requirement

– End-to-end latency requirement

– Mobility requirement

– Overall user density requirement

– Priority requirement

– Service availability requirement

– Service reliability requirement

– UE speed requirement

4.1.5 NetworkSlice instance Lifecycle and relationship to service instances

An NetworkSlice instance may support multiple service instances if it satisfies their service level requirements or has been modified to support these requirements. When a service instance is to be supported, it may trigger an operation phase of the NetworkSlice instance lifecycle for activation or modification(s) of an existing NetworkSlice instance, or it may trigger a commissioning phase of the NetworkSlice instance lifecycle for creation of a new NetworkSlice instance. When a service instance no longer needs to be supported by an NetworkSlice instance, it may trigger an operation phase of the NetworkSlice instance lifecycle for de-activation or modification(s) of an existing NetworkSlice instance, or it may trigger a decommissioning phase of the NetworkSlice instance lifecycle for termination of an existing NetworkSlice instance.

4.1.6 Network Slice as a Service (NSaaS)

Network Slice as a Service (NSaaS) can be offered by a CSP to its CSC in the form of a service. This service allows CSC to use the network slice as the end user or optionally allows CSC to manage the network slice as manager via management interface exposed by the CSP. In turn, these CSC can play the role of CSP and offer their own services (e.g. communication services) on top of the network slice obtained from the CSP. For example, a network slice customer can also play the role of NOP and could build their own network containing the network slice obtained from the CSP as a "building block". In this model, both CSP offering NSaaS and CSC consuming NSaaS have the knowledge of the existence of network slices. Depending on service offering, CSP offering NSaaS may impose limits on the NSaaS management capabilities exposure to the CSC, and the CSC can manage the network slice according to NSaaS management capabilities exposed and agreed upon limited level of management by the CSP.

The NSaaS offered by the CSP could be characterized by certain properties (capabilities to satisfy service level requirements), e.g.

– radio access technology,

– bandwidth,

– end-to-end latency,

– reliability,

– guaranteed / non-guaranteed QoS,

– security level, etc.

Figure 4.1.6.1 illustrates some examples on how network slices can be utilized to deliver communication services, including network slice as a Service. For simplicity this figure omits the details of how NFs are being managed and does not show their groupings into network slice subnet:

a) A Network Slice as a Service (NSaaS) is provided to CSC-A by CSP-A. Unlike the communication service delivered to end customers, in NSaaS, the offered service is the actual network slice.

b) CSC-A can use the network slice obtained from CSP-A to support own Communication Services or may add additional network functions to the obtained NSaaS and offer the resulting combination as a new network slice to CSP-B. In this case, CSC-A plays the role of NOP-B and builds his own network. The network slice obtained by CSC-A from CSP-A becomes a "building block" or a network slice subnet of CSC-A in its role of NOP-B. The NOP-B (a.k.a. CSC-A) combines this network slice subnet with other network slice subnets and offers the new network slice subnet as network slice to CSP-B.

c) CSP-B can use the network slice obtained from CSC-A / NOP-B to deliver communication services to its end customers (as CSC-B).

Figure 4.1.6.1: Examples of Network Slice as a Service (NSaaS) being utilized to deliver communication services to end customers

NOTE: In Figure 4.1.6.1, NS represents network slice, CS represents communication service

4.1.7 Network slices as NOP internals

In the "network slices as NOP internals" model, network slices are not part of the NOP service offering and hence are not visible to its customers. However, the NOP, to provide support to communication services, may decide to deploy network slices, e.g. for internal network optimization purposes. This model allows CSC to use the network as the end user or optionally allows CSC to monitor the service status (assurance of the SLA associated with the internally offered network slice).

The CSP should be able to provide the service status information (e.g. service performance, fault information, traffic data, etc) to CSC via the management exposure interface.

Figure 4.1.7.1 illustrates an example on how network slices can be utilized to deliver communication services:

a) A network slice is used as NOP internal, and CSP delivers communication services to end customers (CSC).

b) The CSC should be able to monitor the network and service status information (e.g. service performance, fault information, traffic data, etc.) provided by CSP.

Figure 4.1.7.1: Examples of network slice as NOP internals

NOTE: In Figure 4.1.7.1, NS represents network slice, CS represents communication service

4.1.8 Network slice delivery concepts

Network slices are provided in different compositions to the customer which may include access to different management capabilities and network slice provisioning procedures for the customer.

For example, a network slice may be delivered

a) to meet customer’s communication service requirements without any exposure of internal network slice structures (applicable to both individual subscribers and NSaaS); or

b) to meet the network slice requirements, with some exposure of the internal network slice structures (e.g. NFs, topology, etc.) and with some network monitoring capability as enabled by the provider; or

c) to meet the network slice requirements with some exposure of the internal network slice structures (e.g. NFs) with some management capabilities as enabled by the provider.

4.1.9 Tenant information concept

The purpose of tenant information concept is to support multiple tenant environment in 5G network management. The 3GPP management system may use tenant information for the following:

– Associating service(s) provided by 3GPP system, e.g. network slice(s), with the tenant.

– Controlling access of the tenant in relation to management capabilities.