In the developing scenarios of 5G software networks and network service management, several actors have emerged with their proposed implementation of ETSI MANO (Network Functions Virtualization Management and Orchestration) framework, able to manage, orchestrate, and operate multiple instances of complex virtual network services, optimise the physical and virtual resources allocated to different actors and users, and resolve conflicts that may arise among such actors during service operation. These different implementations can bring with them several interworking challenges and deal with the different problems related to end-to-end network service management in different ways.
As an example, consider a scenario of a company composed of one or more local offices scattered across Europe, or divided into different business units, such as a head office and multiple telecom service provision offices for mobile services, streaming services, etc. In this scenario, one of the business units wants to deploy network services composed of several VNFs (Network Functions Virtualization), but the structure of this network service is complex and needs to leverage resources or has specific requirements that a local office cannot offer on its own dedicated NFVi (Network Function Virtualisation infrastructure). Nonetheless, local offices are able to offer to their users a MANO and a Service Platform to operate and orchestrate their service instances, which is able to meet their day-to-day requirements. For this reason, the local office orchestrator has to interact with other partitions of the company that can meet these complex requirements. The service deployment requests need to be sent to the head office or to other local offices, which may have a dedicated NFVi, so that the request can be completed.
The NFVi which is able to meet the requirements of the local office would be orchestrated by one or more service provider orchestrators in the company. The communication between different orchestrators could be realised by considering a north-south interface between them, where each north-bound orchestrator interacts with its south-bound counterpart, as it would do with a VIM. In the SONATA project , this interaction is facilitated and mediated by the SONATA abstraction layer  that allows exposing the orchestrator capabilities in a compliant way with a VIM (Virtual Infrastructure Manager) interface.
By means of this orchestrator to orchestrator abstraction, this simple scenario can be extended and generalised by considering a generic tree model where each orchestrator can leverage other orchestrators to access resources it cannot directly orchestrate, or to leverage software and services provided by other segments of the company.
In order to support service provisioning, we have built a mechanism to support the slicing of the resources. To manifest this slice approach, we have designed a built a Slice Controller which is able to allocate a slice of a network Data Centre (DC) and create a per-slice VIM in an on-demand fashion. The DC slice and the VIM are provisioned solely for use with the service. Each slice and its associated VIM are independent of the other slices and VIMs.
Along with partners BT, ATOS, Altice Labs, iMEC, NEC, NOKIA, Optare, Synelexis and UPB, UCL has specified the Service Platform to Service Platform (SP2SP)  use-case to serve different MANO interworking operations. As an example of proof of concept of this scenario, UCL has combined the efforts of the partners in SONATA and in 5GEx , and has designed and developed an implementation of a Service Platform to Service Platform demonstrator that provides a 5G PPP cross-projects interaction. The SP2SP demonstrator is described below and has the following aspects:
As a proof of concept, we at University College London, as part of the SONATA project, designed and developed an implementation of a Service Platform to Service Platform (SP2SP)  that is described in the following aspects:
- Two Service Platforms co-operate for rapid and dynamic service provisioning in an NFV environment.
- The company has segmented its NFVi in order to meet the demands of separate organisations/departments/business units. Therefore, the company has deployed a hierarchy of service platforms that collaborate in order to deploy NFV-based end-to-end services across the network.
- A generic SP/orchestrator can leverage on a segment of NFVi or on other SPs to instantiate functions and services.
- We selected the 5GEx SP  as the orchestrator at the higher level, as it was designed and built to be a multi-domain orchestrator. It operates over a lightweight VIM domain (VLSP)  with slicing capabilities and over a SONATA SP  which was designed and built to be a single domain orchestrator, through a new developed adaptation layer (“SONATA domain adapter”).
- A REST interface between the 5GEx domain adapter and the remote SONATA Gatekeeper facilitates the communication.
- The SONATA SP operates on top of another partition of the NFVi, again using the slicing capabilities and the VLSP VIM to manage it.
- The SONATA Infrastructure Adapter drives the creation of slices with an on-demand VIM interacting with the Slice Manager and offers to the MANO the interface to interact with the VIM.
- End-to-end service and its composing VNFs, on-boarded as services in SONATA Service Platform and exposed as Domain Capabilities to the 5GEx orchestrator through the “SONATA domain adapter” together with the available abstracted resource view.
The specification and the open source software can be download at http://clayfour.ee.ucl.ac.uk/5g-integration/index.html
We are currently working on a 3-way SP to SP multi-domain interworking proof on concept demonstrator.
Overall, the richness and flexibility of both the SONATA APIs and the 5GEx APIs has been clearly demonstrated in our proof of concept.
- 5G SONATA project – 5G Virtualized Networks - http://www.sonata-nfv.eu
- 5GEx project – 5G Exchange - https://www.5gex.eu/wp/
- VLSP – Very Lightweight Network & Service Platform for SDN Environments - http://clayfour.ee.ucl.ac.uk/usr/index.html
- University College London – 5G Integration Components and Testbeds - http://clayfour.ee.ucl.ac.uk/5g-integration/index.html
- SONATA Infrastructure Abstraction Document - https://github.com/sonata-nfv/son-sp-infrabstract/wiki