# The Next Generation Platform as A Service: Composition and Deployment of Platforms and Services
## 4 Virtual Network Function as A Service, Overview
### The Telco PaaS Use Case: Virtual Network Function as A Service (VNFaaS)  
In the Telco PaaS use case, the NGPaaS operator (e.g., a Tier 1 Telco operator) hosts VNFs on behalf of a Service Provider (the VSP). These VNFs could be virtual Routers and Firewalls, which the Service Provider can configure accordingly depending on the desired service (business VPNs, Internet access, etc.). In a \"pre-NGPaaS\" NFV architecture, the on-boarding of VNFs, to be made available in the service catalogue, is done by the Telco operator (based on the preferences of the Service Provider).  
Using the NGPaaS workflow, the Telco operator instead utilises a PaaS-oriented approach instead. While the Telco provider still deploys the platforms, the Service Providers can onboard and administer specific VNFs on their own (e.g., vRouter, vFirewall) and also enable Value-added Service (VAS) capabilities. These VASs could be Telco-grade enhancements to the basic service (e.g., monitoring, healing, policy-based network control, etc.). This way, a pre-existing \"VNF App Store\" can be supplemented by allowing the Service Provider to onboard new VNFs via direct interactions with preferred vendors, resulting in a more diverse set of capabilities than could be obtainable with the  
\begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline \hline
**NGPaaS Process** & **Details** \\ \hline Infrastructure registration & A generic provisioning process to support the broad spectrum of available infrastructure technologies. According to the use-case and the required services, the appropriate infrastructure nodes are leased and registered in the OSS. \\ \hline PaaS orchestration & Refers to the deployment of selected PaaS components on the appropriate IaaS. The PaaS could be Kubernetes, CORD, or any other platform. The PaaS components can be aggregated flexibly and modelled as RFBs. This capability could not be implemented using ETSI MANO, which is focused only on VNFs and assumes the platform is already deployed. \\ \hline Service orchestration & A service is provided by deploying VNFs as sets of RFBs. The target execution environment of each VNF is included in the metadata of the related RFBs, which also specify the runtime aspect: VM, container, Unikernel, FPGA Bitstream, etc. The execution environment of a service component is a pre-deployed PaaS which supports the runtime aspects of the RFB. \\ \hline Onboarding new components & The design rule in NGPaaS is “everything is an RFB” (VNF, ancillary services like orchestration, SDN controller, etc.). Therefore, all the components could be updated, upgraded, set. This can be done through the usage of the Dev-for-Operations processes. \\ \hline \hline \end{tabular}
\end{table}
Table 2: Processes of the NGPaaS architecture.  
pre-NGPaaS model. There many benefits associated with the adoption of the VNFaaS use case for both the VSP and its end customers. Most of these benefits are due to the nature of the VNFaaS use case, for example, the Service Provider does not need to ship hardware to the premises of its end customer, allowing for a more flexible and scalable business and service model.  
Figure 6 illustrates the VNFaaS use case in more detail. There, a VSP has deployed two service graphs through the RDCL 3D tool, each comprising of two VNFs. Deploying these two graphs has resulted in the deployment of two service chains onto the CORD platform. Both service chains comprise an interconnected virtual router and firewall and are associated with a unique end user. The figure also illustrates the possibility to onboard and deploy VNFs of different vendors, thus providing flexibility to the end user.