UNIT 5

LECTURE 2

FEDERATED CLOUDS/INTER CLOUDS

Characterization and definition

The terms cloud federation and Inter Cloud; often used interchangeably, convey the general meaning of an aggregation of cloud computing providers that have separate administrative domains.

It is important to clarify what these two terms mean and how they apply to cloud computing.

The term federation implies the creation of an organization that supersedes the decisional and administrative power of the single entities and that acts as a whole.

 Within a cloud computing context, the word federation does not have such a strong connotation but implies that there are agreements between the various cloud providers, allowing them to leverage each other’s services in a privileged manner.

A definition of the term cloud federation was given by Reuven Cohen, founder and CTO of Enomaly Inc.

“Cloud federation manages consistency and access controls when two or more independent geographically distinct Clouds share either authentication, files, computing resources, command and control or access to storage resources.”

This definition is broad enough to include all the different expressions of cloud services aggregations that are governed by agreements between cloud providers, rather than composed by the user.

Inter Cloud is a term that is often used interchangeably to express the concept of Cloud federation. It was introduced by Cisco for expressing a composition of clouds that are interconnected by means of open standards to provide a universal environment that leverages cloud computing services. By mimicking the Internet term, often referred as the “network of networks,” Inter Cloud represents a “Cloud of Clouds” and therefore expresses the same concept of federating together clouds that belong to different administrative organizations. Whereas this is in many cases acceptable, some practitioners and experts—like Ellen Rubin, founder and VP of Products at Cloud Switch —prefer to give different connotations to the two terms:

The primary difference between the Inter Cloud and federation is that the Inter Cloud is based on future standards and open interfaces, while federation uses a vendor version of the control plane. With the Inter Cloud vision, all Clouds will have a common understanding of how applications should be deployed. Eventually workloads submitted to a Cloud will include enough of a definition (resources, security, service level, geo-location, etc.) that the Cloud is able to process the request and deploy the application. This will create the true utility model, where all the requirements are met by the definition and the application can execute “as is” in any Cloud with the resources to support it.

Therefore, the term Inter Cloud refers mostly to a global vision in which interoperability among different cloud providers is governed by standards, thus creating an open platform where applications can shift workloads and freely compose services from different sources. On the other hand, the concept of a cloud federation is more general and includes ad hoc aggregations between cloud providers on the basis of private agreements and proprietary interfaces.

WHY CLOUD FEDERATION?

CLOUD FEDERATION STACK

Creating a cloud federation involves research and development at different levels: conceptual, logical and operational, and infrastructural. 

Figure provides a comprehensive view of the challenges faced in designing and implementing an organizational structure that coordinates together cloud services that belong to different administrative domains and makes them operate within a context of a single unified service middleware.

Each cloud federation level presents different challenges and operates at a different layer of the IT stack. It then requires the use of different approaches and technologies. Taken together, the solutions to the challenges faced at each of these levels constitute a reference model for a cloud federation.

CONCEPTUAL LEVEL

The conceptual level addresses the challenges in presenting a cloud federation as a favourable solution with respect to the use of services leased by single cloud providers. In this level it is important to clearly identify the advantages for either service providers or service consumers in joining a federation and to delineate the new opportunities that a federated environment creates with respect to the single-provider solution. 

Elements of concern at this level are:

• ·         Motivations for cloud providers to join a federation.
• ·         Motivations for service consumers to leverage a federation.
• ·         Advantages for providers in leasing their services to other providers.
• ·         Obligations of providers once they have joined the federation.
• ·         Trust agreements between providers.
• ·         Transparency versus consumers.

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Among these aspects, the most relevant are the motivations of both service providers and consumers in joining a federation.

LOGICAL & OPERATIONAL LEVEL

The logical and operational level of a federated cloud identifies and addresses the challenges in devising a framework that enables the aggregation of providers that belong to different administrative domains within a context of a single overlay infrastructure, which is the cloud federation.

At this level, policies and rules for interoperation are defined. Moreover, this is the layer at which decisions are made as to how and when to lease a service to—or to leverage a service from— another provider.

The logical component defines a context in which agreements among providers are settled and services are negotiated, whereas the operational component characterizes and shapes the dynamic behaviour of the federation as a result of the single providers’ choices.

This is the level where MOCC is implemented and realized. It is important at this level to address the following challenges:

• How should a federation be represented?

• How should we model and represent a cloud service, a cloud provider, or an agreement?

• How should we define the rules and policies that allow providers to join a federation?

• What are the mechanisms in place for settling agreements among providers?

• What are provider’s responsibilities with respect to each other?

• When should providers and consumers take advantage of the federation?

• Which kinds of services are more likely to be leased or bought?

• How should we price resources that are leased, and which fraction of resources should we lease? The logical and operational level provides opportunities for both academia and industry.

INFRASTRUCTURE LEVEL

The infrastructural level addresses the technical challenges involved in enabling heterogeneous cloud computing systems to interoperate seamlessly.

It deals with the technology barriers that keep separate cloud computing systems belonging to different administrative domains. By having standardized protocols and interfaces, these barriers can be overcome.

At this level it is important to address the following issues:

• What kind of standards should be used?

• How should design interfaces and protocols be designed for interoperation?

• Which are the technologies to use for interoperation?

• How can we realize a software system, design platform components, and services enabling interoperability?

Interoperation and composition among different cloud computing vendors is possible only by means of open standards and interfaces. Moreover, interfaces and protocols change considerably at each layer of the Cloud Computing Reference Model.