CNTT Reference Architectures
Available Reference Architectures
CNTT develops a limited number of NFVI reference architectures. While technology and deployment aspects may differ between them, each of the CNTT reference architectures is based on a common CNTT Reference Model.
There are a number of key architectural principles that apply to all Reference Architectures produced by CNTT. These principles are enumerated below. They are meant to be general and at a high level, and limited in number. Some of the chapters of this document will include more specific principles to provide the implementation guidelines for a particular function or a specific component. Note that the Architectural Principles discussed in this Chapter follow the over-arching principles provided in CNTT Reference Model:Introduction:Principles
We need to distinguish between architectural principles and architectural requirements elaborated later in this document. The principles are here to guide our architectural thinking, while requirements should be understood as a check list used to gauge a level of compliance of a NFVI implementation to the CNTT reference architecture.
Open source preference: To ensure, by building on technology available in open source projects, that suppliers’ and operators’ investment have a tangible pathway towards a standard and production ready NFVI solution portfolio.
Open APIs: To enable interoperability and component substitution, and minimize integration efforts by using openly published API definitions.
Separation of concerns: To promote lifecycle independence of different architectural layers and modules (e.g. disagregation of software from hardware).
Automated lifecycle management: To minimize costs of the end-to-end lifecycle, maintenance downtime (target zero downtime), avoid errors and discrepancies resulting from manual processes.
Automated scalability: To minimize costs and operational impacts through automated policy-driven scaling of workloads by enabling automated horizontal scalability of workloads.
Automated closed loop assurance: To minimize operational costs and simplify NFVI platform operations by using automated fault resolution and performance optimization.
Cloud nativeness: To optimise the utilization of resources and enable operational efficiencies.
Security compliance: To ensure the architecture follows the industry best security practices and is at all levels compliant to relevant security regulations.
Resilience and Availability: To allow High Availability and Resilience for hosted VNFs, and to avoid Single Point of Failure.
Reference Architectures Relationships and Scope
Figure 1: Relationships between and scope of the CNTT Reference Architectures
RA1 is focussing on an OpenStack Reference Architecture that will support VM-based VNFs only (i.e. no containerised workloads), whilst delivering the NFVI and VIM requirements as outlined in the Reference Model.
The scope of RA2 will be to enable support for containerised and VM-based workloads (i.e. VMs managed by Kubernetes). A thorough gap analysis will need performing to understand the level to which Kubernetes might support traditional VNFs (i.e. to what level can Kubernetes conform to the VIM specification from ETSI NFV v3, or the Vi-Vnfm interface, for example).
RA2 is delivering a Kubernetes Reference Architecture that will be standalone, meaning that a Reference Implementation for RA2 can be established solely on the content and requirements present in the RA2 documentation.
Kubernetes can be executed on top of different types of underlying infrastrucutre. Examples of those underlying infrastructures are:
- Infrastructure as a Service based on virtual machines such as OpenStack in general or a Reference Implementation of RA1
- Physical servers. (This is often referred to as “baremetal Kubernetes”)
Kubernetes expects certain capabilities or resources provided by the underlying infrastructure. Examples for resources or capabilities of the underlying infrastructure consumed by Kubernetes are, but are not limited to:
- storage (ephemeral/persistent)
RA2 contains concrete provisions on the type of infrastructure resources consumed by Kubernetes.
If the underlying infrastructure provides a dynamic way to allocate resources, Kubernetes can integrate directly with the underlying infrastructure and use it as a infrastructure resource provider. Kubernetes uses a plugin-based mechanism for integration with any type of infrastructure resource providers. Most prominently Kubernetes Cloud Provider collect various integrations towards a particular infrastructure platform e.g. to create volumes or additional worker nodes. The Kubernetes cluster api harmonizes some of the k8s cluster management related integrations with different infrastructure platforms under a common API. With the Container Network Interface (CNI) and the Container Storage Interface (CSI) specifications Kubernetes also provides additional means to integrate with the underlying infrastructure. (Note: the use of CNIs or CSIs does not imply the use of specific platform resources.)
Figure 2 depicts the relationship between RA2 and an arbitrary underlying infrastructure.
Figure 2: RA2 relation to underlying infrastructure