UNIT 5

LECTURE 1

INTRODUCTION

Cloud computing is a rapidly moving target. New technological advances and application services are regularly introduced.

There are many open challenges, especially in the context of energy- efficient management of datacenters and the marketplace for cloud computing. 

This lecture notes presents an overview of various open issues in cloud computing that need long- term investigation.It discusses market models needed for realizing an open market for cloud computing systems from the perspective of federations of clouds and agreements between clouds. 

A general overview of some of the existing standards that enable interoperation between clouds and a brief look at third-party cloud services are presented.

MARKET BASED MANAGEMENT OF CLOUDS`

Cloud computing is still in its infancy, and its prominent use is twofold: First complete replacement of in-house IT infrastructure and services with the same capabilities rented by service providers and Second elastic scaling of existing computing systems in order to address peak workloads.

The efforts in research and industry have been mostly oriented to design and implement systems that actually enable business vendors and enterprises to achieve these goals. The real potential of cloud computing resides in the fact that it actually facilitates the establishment of a market for trading IT utilities. This opportunity until now has been mildly explored and falls in the domain of what it is called market-oriented cloud computing.

MARKET ORIENTED CLOUD COMPUTING

Cloud computing already embodies the concept of providing IT assets as utilities. Then, what makes cloud computing different from market-oriented cloud computing?

First, it is important to understand what we intend by the term market.

The Oxford English Dictionary (OED) defines a market as a “place where a trade is conducted”.

More precisely, market refers to a meeting or a gathering together of people for the purchase and sale of goods.

A broader characterization defines the term market as the action of buying and selling, a commercial transaction, a purchase, or a bargain.

Therefore, essentially the word market is the act of trading mostly performed in an environment—either physical or virtual—that is specifically dedicated to such activity.

WHY MARKET?

If we consider the way IT as sets and services are consumed as utilities, it is evident that there is a trade-off between the service provider and the consumer; this enables the use of the service by the user under a given SLA. Therefore, cloud computing already expresses the concept of trade, even though the interaction between consumer and provider is not as sophisticated as happens in real markets: Users generally select one cloud computing vendor from among a group of competing providers and leverage its services as long as they need them. Moreover, at present, most service provider shave inflexible pricing, generally limited to flat rates or tariffs based on usage thresholds. In addition, many providers have proprietary interfaces to their services, thus restricting the ability of consumers to quickly move—and with minimal conversion costs—from one vendor to another. This rigidity, known as vendor lock-in, under mines the potential of cloud computing to be an open market where services are freely traded. Therefore, to remove such restrictions, it is required that vendors expose services through standard interfaces. This enables full accommodation and thus would pave the way for the creation of a market infrastructure for trading services.

DIFFRENCE BETWEEN CLOUD COMPUTING & MOCC

What differentiates market-oriented cloud computing (MOCC) from cloud computing is the presence of a virtual market place where IT services are traded and brokered dynamically. This is something that still has to be achieved and that will significantly evolve the way cloud computing services are eventually delivered to the consumer. More precisely, what is missing is the availability of a market where desired services are published and then automatically bid on by matching the requirements of customers and providers. 

REFERENCE MODEL FOR MOCC

Market-oriented cloud computing originated from the coordination of several components: service consumers, service providers, and other entities that make trading between these two groups possible.

GLOBAL VIEW

Several components and entities contribute to the definition of a global market-oriented architecture.

The fundamental component is the virtual marketplace—represented by the

Cloud Exchange (CEx)—which acts as a market maker, bringing service producers and consumers together.

The principal players in the virtual market place are the

Cloud coordinators and the Cloud Brokers. The cloud coordinators represent the cloud vendors and publish the services that vendors offer. 

The cloud brokers operate on behalf of the consumers and identify the subset of services that match customers’ requirements in terms of service profiles and quality of service.

Brokers perform the same function as they would in the real world: They mediate between coordinators and consumers by acquiring services from the first and subleasing them to the latter.

Brokers can accept requests from many users. At the same time, users can leverage different brokers. A similar relationship can be considered between coordinators and cloud computing services vendors. Coordinator stake responsibility for publishing and advertising services on behalf of vendors and can gain benefits from reselling services to brokers. Every single participant has its own utility function that they all want to optimize rewards. Negotiation s and trades are carried out in a secure and dependable environment and are mostly driven by SLAs, which each party has to fulfil. There might be different models for negotiation among entities, even though the auction model seems to be the more appropriate in the current scenario. The same consideration can be made for the pricing models: Prices can be fixed, but it is expected that they will most likely change according to market conditions.

Several components contribute to the realization of the Cloud Exchange and implement its features.

In the reference model depicted in above Figure, it is possible to identify three major components:

Directory: The market directory contains a listing of all the published services that are available in the cloud market place. The directory not only contains a simple mapping between service names and the corresponding vendor (or cloud coordinators) offering them. It also provides additional metadata that can help the brokers or the end users in filtering from among the services of interest those that can really meet the expected quality of service. Moreover, several indexing methods can be provided to optimize the discovery of services according to various criteria. This component is modified in its content by service providers and queried by service consumers.

Auctioneer: The auctioneer is in charge of keeping track of the running auctions in the market place and of verifying that the auctions for services are properly conducted and that malicious market players are prevented from performing illegal activities.

Bank: The bank is the component that takes care of the financial aspect of all the operations happening in the virtual market place. It also ensures that all the financial transactions are carried out in a secure and dependable environment. Consumers and providers may register with the bank and have one or multiple accounts that can be used to perform the transactions in the virtual marketplace.

This organization, as described, constitutes only a reference model that is used to guide system architects and designers in laying out the foundations of a Cloud Exchange system.

In reality, the architecture of such a system is more complex and articulated since other elements have to be taken into account. For instance, since the cloud marketplace supports trading, which ultimately involves financial transactions between different parties, security becomes of fundamental importance. It is then important to put in place all the mechanisms that enable secure electronic transactions. These and other aspects are not unique to the design and implementation of MOCC systems but are of concern for any distributed computing system; therefore, they have been only mentioned here.