Understanding Decentralized and Dynamic Brokerage in Federated Cloud Environments

Understanding Decentralized and Dynamic Brokerage in Federated Cloud Environments

Nicolò Maria Calcavecchia (Politecnico di Milano, Italy), Antonio Celesti (Universit Degli Studi di Messina, Italy) and Elisabetta Di Nitto (Politecnico di Milano, Italy)
DOI: 10.4018/978-1-4666-1631-8.ch003
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Abstract

The advent of the cloud computing paradigm offers different ways both to sell services and to exploit external computational resources according to a pay-per-use economic model. Nowadays, cloud computing clients can buy various form of IaaS, PaaS, and SaaS from cloud providers. Besides this form of pay-per-use, the perspective of cloud federation offers further business opportunities for small/medium providers which hold physical datacenters. Considering the cloud computing ecosystem, besides large cloud providers, smaller ones are also becoming popular even though their own virtualization infrastructures (i.e., deployed in their datacenters) cannot directly compete with the bigger market leaders. The result is that often small/medium clouds have to exploit the services of mega-providers in order to develop their business logic and their cloud-based services. To this regard, a possible future alternative scenario is represented by the promotion of cooperation among small/medium cloud providers, thus enabling the sharing of computational and storage resources. However, in order to achieve such an environment, several issues have to be addressed. One of these challenges is how to plan brokerage strategies allowing cloud providers to discover other providers for partnership establishment. This chapter focuses on different possible centralized and decentralized approaches in designing a brokerage strategy for cloud federation, analyzing their features, advantages and disadvantages.
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Introduction

The advent of the cloud computing paradigm offers different ways for buying/selling services by exploiting computational resources offered by third parties according to a pay-per-use economic model. Nowadays, cloud computing clients can buy services at various levels of abstraction from cloud providers. Examples include: IaaS, that is, VMs and storage, PaaS that is, the possibility of deploying applications fulfilling specific architectural and programming models, and SaaS, that is, pure application services.

Considering the cloud computing ecosystem, besides large cloud providers, smaller/medium providers are also becoming popular even though the virtualization infrastructures they have deployed in their datacenters cannot directly compete with the bigger counterparts including mega-providers such as: Amazon, Rackspace, Google, and Salesforce. A way to overcome these resource limitations is represented by the promotion of federation and cooperation mechanisms among small/medium cloud providers, thus enabling the sharing of computational and storage resources. This allows another form of pay-per-use economic model for ICT societies, universities, research centers, and organizations that commonly do not fully exploit the resources of their own physical infrastructure.

Federation brings new business opportunities for clouds. In fact besides, the traditional market where cloud providers offer cloud-based services to their clients, federation triggers a new market where cloud providers can buy and/or sell computing/storage capabilities and services to other clouds. For example, a cloud might need to buy resources from other clouds for the following reasons:

  • The cloud runs out of its storage/computing resources. In order to continue providing cloud-based service to its clients, it decides to buy resources from other clouds.

  • The cloud needs to deploy a distributed cloud-based service in different geographical locations; hence, it acquires resources placed in those target locations.

  • The cloud needs to migrate cloud-based service instances in other clouds in order to accomplish service relocation, power saving, backup, etc.

At the same time, a cloud can decide to provide resources to other clouds when it realizes that its datacenter is under-utilized at given times. Typically, datacenters are under-utilized during the night and over-utilized during the morning. Therefore, as the datacenter cannot be turned off, the cloud provider may decide to turn the problem into a business opportunity. This case may be applied to many different organizations, such as, universities, public administrations, and enterprises.

Hence, the advantage of transforming a physical datacenter in a cloud virtualization infrastructure, in the perspective of cloud federation, is twofold. On the one hand, small/medium cloud providers that rent resources to other providers can optimize the use of their infrastructure, which are often underutilized. On the other hand, external small/medium cloud providers can elastically scale up/down their logical virtualization infrastructure borrowing resources and paying them to other providers.

The federation partnership establishment process can be schematized according to the following three main phases: (i) discovery, the cloud looks for other available clouds for federation; (ii) match-making, the cloud selects between the discovered clouds the ones that fit as much as possible its requirements; (iii) authentication, the cloud establishes a trust context with the selected clouds.

When the federation is established, a new phase becomes very relevant, that is, the “management” of the federated resources. All above phases can be executed in various ways and are complicated by the fact that the involved cloud platforms can be heterogeneous in the technology they use and in the level of abstraction (IaaS, PaaS, SaaS) at which they offer their services.

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