Cisco has developed the depiction, shown in Figure 2, of a cloud reference architecture model, which portrays the
architectural layers, connected via APIs and repositories. If we study the framework more closely, the following
aspects can be articulated. At the foundation of this framework is the data center technology architecture, which
consists of three salient blocks of network, compute, and storage. This layer hosts all the services that are delivered
to a cloud consumer or subscriber. This layer will be discussed in more detail in later sections of this paper. The next
important layer is the security layer. The key takeaway in this layer is that security is blanketed as an end-to-end
architecture across all aspects of the framework. Security is considered as one of the key challenges to be solved in
a cloud framework; hence, it has to be accounted for in a comprehensive sense. This layer will be discussed in more
detail in later sections of this paper. Following the technology and security layer is the Service Orchestration layer,
which is implemented with configuration repository enablers. The configuration repository stores key information such
as service catalogue, asset inventory, and resource-to-service mappings. This layer is an important layer because it
maps the technology components to the service components and serves as a reference point during service
provisioning. The service orchestration layer is the “glue” that integrates the lower layers to create a service for
delivery. The next layer is also where infrastructure and service management function take place. The topmost layer
is the consumer-facing layer, usually exposed via a portal-like solution. This is the layer where service is defined,
requested, and managed by the consumer.