Cloud Computing - The Cloud Reference Model

This article was totally based on a research paper called Defining a Cloud Reference Model by Teresa Tung (teresa.tung@accenture.com). In this paper they introduce a new reference model for cloud computing. As OSI model for networking. So I thought sharing this will be good.

A general meaning of “cloud” in computer world is a collection of network-hosted services accessible from anywhere with the following attributes: elastically scalable, illusion of infinite capacity, available on-demand, and consumption based charges.

Throughout the past several years cloud computing is a buzzword. But its meaning is confusing for most of the people. Also cloud has conflicts on policy issues including legal, indemnity, and compliance, and on technology issues around security, reliability, and performance. Reasons for these are cloud-based application architecture is confusing. First the term “cloud” is overloaded and used by many vendors also cloud’s on-demand and scalability features are new and architects are still working to understand how to leverage these capabilities.

The Cloud Reference Model brings order to this cloud confusing cloud computing model. The Model divides cloud-based application architecture into seven layers: Application, Transformation, Control, Instantiation, Appliance, Virtual, and Physical. In this model each layer has its own IT functionality on supporting a specific area of concern and abstracts details of other layers. So having this reference model we can think application architecture as the process of determining the necessary functionality at each layer and assessing attributes like performance, security, and reliability is decoupled. So though out this discussion we talk about that.

Using this new reference model for cloud computing it becomes easy to evaluate the benefit of cloud. Anyone can use the Model to breakdown technology and policies to layers. Also model is defined so that per-layer solutions interface with adjacent layers. So each layer is reusable, and people can properly combining the solutions to create an overall architecture for applications like portals, batch, and distributed file systems.

The major layers of the Cloud Model are,

1. Application Layer
2. Transformation Layer
3. Control Layer
4. Instantiation Layer
5. Appliance Layer
6. Virtualization Layer
7. Physical Layer

Application Layer: This layer specifies the overall application functionality and end-user experience. Also this layer is responsible for sets up the application program. User-generated content like code, data, static files, and executables specifies the application program. The content format and representation determine the required application architecture.

Transformation Layer: This layer transforms application program for execution on the specific compute environment. It converts content and metadata from the Application Layer to the required format for storage or execution on the specific platform. It do things like encrypting, encoding for error correction, segmenting large data objects into smaller units, reformatting data structures into XML, or applying business logic to structure data etc.

Control Layer: Generally Control Layer algorithms ultimately determine how the platform is created. It prescribes the optimized set of virtual machine appliances required to form the desired compute platform. Controller logic determines the quantity, type, and location of virtual appliances to create the desired compute platform. So controller logic assigns the formatted content from the Transformation Layer across the prescribed deployment.

The Instantiation Layer: Instantiation Layer decides how provisioning and configuration occurs specific to the infrastructure provider. It executes the specification of the Control Layer. For example it applies the IP address and updates the DNS.

The Appliance Layer: In a single sentence The Appliance Layer functions create the images and templates of the specific appliance used in the compute platform. This layer adds middleware to a virtual machine to create a virtual machine appliance. For example we can think Linux operating system, Apache HTTP server, MySQL database, and Python scripting language forms an appliance with the LAMP solution stack.

The Virtualization Layer: This is responsible for produces the virtualized representation of the compute resources. There are Management software in this layer to handle the virtualization management of server images, generic storage volumes, and logical network connections.

The Physical Layer: This layer maintains the physical devices that perform the compute operations. This layer includes the IT hardware for compute platform.

The Cloud Reference Model can be used to evaluate vendors and design attributes. Each layer of the model focuses concerns on one aspect of overall design making it easier to characterize capability.

After carefully looking at the current situation in the world, we can see two major points. First the need to characterize offerings and not service providers.

Second how this new reference model expands the functionality of today’s “as –a –service” characterization. IaaS offerings provide virtualized compute resources at the Virtual Layer. Then Platform-as-a-Service (PaaS) offerings provide the Control Layer’s compute platform for execution of user-generated program. And then Software-as-a-Service (SaaS) supplies programs at the Application Layer like for Customer Relationship Management, E-mail, or SharePoint.

Revived by Andun S.L. Gunawardana –andunslg@gamil.com