Page 138 - ITU-T Focus Group IMT-2020 Deliverables

3 ITU-T Focus Group IMT-2020 Deliverables

6.4.5 5GPPP H2020 5GEx project

6.4.5.1 Introduction
NFV does not define orchestration explicitly. Its meaning may be inferred from the NFVO definition Network
Functions Virtualisation Orchestrator (NFVO): functional block that manages the Network Service (NS)
lifecycle and coordinates the management of NS lifecycle, VNF lifecycle (supported by the VNFM) and NFVI
resources (supported by the VIM) to ensure an optimized allocation of the necessary resources and
connectivity. Where lifecycle management is defined as: a set of functions required to manage the
instantiation, maintenance and termination of a VNF or NS. NFV orchestration is seen as a single
concentrated functional block, without delegation. The NFV orchestrator may consider resource availability
and load when it responds to a new demand, and may rebalance capacity as needed, including creating,
deleting, scaling and migrating VNFs.
Although SDN does not formally define orchestration, the meaning of the concept is apparent from the SDN
controller that is expected to coordinate a number of interrelated resources, often distributed across a
number of subordinate platforms, and sometimes to assure transactional integrity as part of the process.
This is commonly called orchestration. An orchestrator is sometimes considered to be an SDN controller in
its own right, but the reduced scope of a lower level controller does not eliminate the need for the lower
level SDN controller to perform orchestration across its own domain of control. A provisional definition of
(SDN) orchestration might be: the continuing process of allocating resources to satisfy contending demands
in an optimal manner. The idea of optimal would include at least prioritized customer SLA commitments, and
factors such as customer endpoint location, geographic or topological proximity, delay, aggregate or fine-
grained load, monetary cost, fate-sharing or affinity. The word continuing incorporates recognition that the
environment and the service demands constantly change over the course of time, so that orchestration is a
continuous, multi-dimensional optimization feedback loop. The orchestration process is often discussed as
having an inherent intelligence and implicitly autonomic control. Orchestration is also guaranteeing the
adequate service performance during the service delivery despite concurrent resource usage among users
and service outages.
6.4.5.2 Development Focus and Research Challenges of 5GEx Project

The followings are representing the main expected developments in the 5GEx [Ref.6.4.5-1]:
• Resource Orchestration: automated management of resources in one or multiple Resource Domains
to host an NF or a topology of NFs. A resource orchestrator only deals with resource level abstraction
and does not understand the service that the NF or topology of NFs deliver.

• Service Orchestration: automated management of a service slice that form a service requested by a
customer (network service, cloud service, online service…); a service orchestrator understands the
service that the service slice delivers.
• Multi-domain orchestration: automated management of services and resources in multi-technology
(multiple domains involving different cloud and networking technology) and multi-operator
(multiple administrative domains) environments.
6.4.5.3 5GEx architecture

Figure 6.4.5-1 presents the reference architectural framework [Ref.6.4.5-2] [Ref.6.4.5-3] for organizing the
components and interworking interfaces involved in end-to-end management and orchestration in multi-
domain environments.

132