# The Next Generation Platform as A Service: Composition and Deployment of Platforms and Services
## 1 Introduction  
5G is expected to be the ubiquitous fabric to provide reliable, low-latency and high-speed connectivity for a wide variety of services (Internet of Things (IoT), mobile, Industry 4.0, automotive, etc.). However current network architectures are not yet able to provide these characteristics, mainly due to their monolithic nature which limits their flexibility, scalability, and programability. To facilitate the adoption of 5G, the consensus in the industry is to utilise technologies and workflows from the field of Information Technology (IT), such as the cloudification and virtualisation of services [1]. This way, network services that previously comprised dedicated and monolithic hardware appliances (e.g., Firewalls) will now be virtualised instances in commodity servers in the cloud. This shift is expected to offer a much higher degree of flexibility, scalability, and automation to service providers, as they will be able to modify the virtual setups dynamically and programmatically.  
To fully reap the benefits provided by virtualisation and cloudification, the deployment and management of services must be decoupled from the underlying computing and networking infrastructure. A paradigm that can facilitate this requirement is the Platform as a Service (PaaS), as it provides a centralised and reliable environment, with high degrees of agility and automation, on which services can be deployed and managed. The benefits provided by the PaaS model can be further enhanced by incorporating the paradigms of Software Defined Networking (SDN) and Network Function Virtualisation (NFV). The scope of SDN would be to facilitate the control and programmability of the network infrastructure while NFV would allow for the efficient virtualisation and management of services on commodity servers.  
In contrast with IT services, 5G services are more diverse and stringent in terms of their network and computing requirements. These requirements imply the need for a more flexible and customisable PaaS model [2] than the currently available non 5G oriented solutions. One such model is the Next Generation Platform as a Service (NGPaaS) [3,4], which is built around the principles of micro-services, modularity, and build-to-order. In short, NGPaaS allows for the deployment of custom-built platforms and services, on a diverse set of infrastructure technologies, using automated and technology agnostic workflows. Through the same workflow, any Vertical Service Provider (VSP) (e.g., a Telco provider or IoT provider) can deploy either a custom platform on the available infrastructure or services on top of an existing platform.  
The content of this paper is structured as follows. At first, a study of related work is presented in Section 2. Section 3 presents the implementation of the requirements and architecture of NGPaaS, as conceptualised in references [3,4]--specifically, it provides the NGPaaS architectural design, the concept of Reusable Functional Blocks (RFBs) and introduces the RFB Description and Composition Languages Design, Deploy and Direct (RDCL 3D) tool [5]. Later in Section 4, the NGPaaS workflow is practically validated through a use case. This use case (Telco PaaS) is based on the Central Office Re-architected as a Datacentre (CORD) [6] platform and provides Virtual Network Function (VNF) as a Service (VNFaaS) capabilities to a VSP. In addition to describing the use case and the components that comprise it, this paper also details the process of how these components were made NGPaaS-ready in Section 5. Later, in Section 6 a brief description of another use case targeted by NGPaaS (5G Public Safety) is provided. Finally, Section 7 provides a critical conclusion of the presented work.