Abstract-Cloudresources are provided to users on request and the bills are generated on thebasis of resources actually consumed. Therefore, during periods of low demand,the idle resources may cause financial loss toCloud Providers (CPs). While in peak load, user’s request may be rejected dueto insufficient resources.
To managethis issue of under or over provisioning of resources, different CPs mayvoluntarily unite and efficiently utilize the resources in accordance with someagreement among them, thus creating a Federation of Clouds. Accounting andBilling of resources in such an environment is an important issue as inappropriatecalculation of bills may either cause loss to CPs due to undercharging or to usersby overcharging them. Taking this into consideration, this paper aims: Toperform a literature review of the existing accounting and billing solutions insingle CP and Federated Cloud Environment and; Identify the requirements and limitationsof the existing accounting and billing methods so as to justify and support theneed of a new framework for Accounting and Billing of infrastructural resourcesin Federation of Clouds.Keywords: Cloud Computing, Federation,Accounting, Billing 1 IntroductionCloud Computing (CC) is an established paradigm which providesconvenient, on demand network access to a shared pool of configurable computingresources (e.g., networks, servers, storage, applications, and services) thatcan be rapidly provisioned and released with minimal management effort orservice provider interaction 1. Its features like no upfront investment, low operatingcost, high scalability, easy access, reduced business and maintenance risk etc.2 make it a much better option to use than traditional data centres 3.
In a standard CC model, resources of Cloud Providers (CPs) are sharedamong different customers. This introduces many challenges 4. In case ofshortage of resources, either customer’s requests are denied or low priority servicesthat were already running on the system, are cancelled. This results in loss ofrevenue from some services, apart from a loss of reputation and therefore aloss of future customers 5. Relying on a single Cloud’s data centres alsomakes it hard to implement adequate responsiveness and usability to clientsdistributed worldwide. All these problems generate the requirement ofinterconnecting Clouds i.e.
creating Federation of Clouds. Cloud Federationwill allow sharing of resources among different CPs and thus help achievebetter Quality of Service (QoS), reliability and flexibility 4. In afederated cloud environment, different Cloud Service Providers (CSPs) areinvolved, each having its own different mechanism to charge customers for theresources consumed.
Appropriate accounting and billing of cloud resources in suchan environment is essential for both CSPs as well as customers and is a major area of concern 6. Presence of resources of different CSPsmay cause one to bear the cost of another if accounting is not properly done.It may also cause the customer to pay more if bills are not calculated properly.
Sothere is a need to gain insight into the work done in this area of research. Tillnow, no systematic literature review has been performedfor accounting and billing of resources inCloud Federation or single CP environment that cansummarize the work done so far in this particular area of research. Taking thisinto consideration, this paper reviews the existing literature of accountingand billing in both Single CP and Federated Cloud environment and identifiesthe requirements and limitations of current solutions. The limitations arefurther analysed to identify the need of a new framework for accounting and billing in a Federation of Clouds.The paper is structured as follows. Section 2 gives thebackground and motivation for selecting accounting and billing for research.
Section3 highlights the review method. Accounting and Billing and its existingsolutions in CC and Cloud Federation are discussed inSection 4. Requirements of Accounting and Billing are mentioned in Section 5. Limitationsof existing solutions are discussed in Section 6. Section 7 concludesthe paper.2Background and MotivationIncurrent scenario, actual usage patterns of many real-world application servicesvary with time, most of the time in unpredictable ways e.g. Social networkssuch as Facebook and MySpace are popular Web 2.
0 based applications. They servedynamic content to millions of users, whose access and interaction patterns arehard to predict. Load spikes can take place at different locations at any time7. At present, no single hosting company can create a seemingly infiniteinfrastructure capable to serve such applications and the increasing number ofon-line services, each having massive amounts of users and access at all times,from all locations 8.
To cater to such needs, it is required that workloadsand data from one CP can be easily moved to another or between private andpublic Clouds 9 i.e. interconnection of Clouds is required. One way of doingthis is to create Federation of Clouds. 2.1 Cloud FederationIt isa concept of service aggregation characterized by interoperability features,which addresses the vendor lock-in and provider integration problem 9. Interoperability feature allows users to move easily to different CPs,if and when required. It also enables CPs to exchange and share resources in anefficient manner thus solving the problem of under or over provisioning ofresources.
As awhole, Cloud Federation provides following benefits:· It is acost-efficient alternative to over dimensioning the amount of servers in orderto cope with peak loads.· Underutilizedresources are made available to other sites during periods of lower load thusproviding an extra source of income to CPs.· It enablesinteroperability among different CPs thus solving vendor lock-in problem 1. Though Cloud Federation provides manybenefits but some problems are associated with it. In 11, different issuesrelated to Cloud Federation have been discussed:· Portability (Virtual Machine (VM) Mobility, VM and Data Portability)· Service Level Agreement (SLA) (Federated SLA Management, Federation LevelAgreement, SLA Monitoring and Dependency, Legal Issues)· Security (Trust, Authorization and Identity Management,Federated Policy and Semantic Interoperability)· Economy (Market, Pricing, Accounting and Billing) etc. In thispaper, the focus is on accounting and billing issue. 2.2MotivationAccounting systems are responsible for trackingservice consumptions, charging customers for their usage and generatingrevenues for their providers 12.
Currently, lack of a fair and transparentprocess of accounting and billing is one of the main reasons for hindering organizationsfrom embracing Cloud.The process of accounting and billing of cloud resources also involvessome issues which are discussed below. Theseissues create the requirement of studying and exploring this area of research indetail.2.2.1Issues:Related to customers· It is difficult for customersto reason about the expenses of their application due to the black-box and dynamic nature of the cloudinfrastructure.
They have little or no visibility into the infrastructure. · CPs resources are shared. This may cause providers to incorrectly attributeresource consumption to customers. · There aremany shared resources that cannot be perfectly isolated and this can result inunforeseen externalities that may inflate an application’s resource footprint 13.Related to CPs· The profitabilityof CPs is not clear. This is because; it is difficult for CPs to preciselymonitor their own resource consumption and bill their customers’.
As a result, some resources that aredifficult to monitor and attribute to client computations are not accountedfor, resulting in low revenue generation. · Sharing ofresources imposes costs that are challenging to measure. Consequently,providers may incorrectly account for these costs, thereby, implicitly bearingadditional costs and increasing their own operating expenses and thus, reducingtheir cost-effectiveness 22.214.171.124 Benefits:These issues can be solved with the help of appropriate accounting andbilling mechanisms that will provide following benefits with respect to the abovementioned issues:Customers related benefits· Helpcustomers in making sense of the cost footprint of their outsourced computation13.· Preventovercharging.
CP related benefits· Helps inestimating their Return on Investment.· PreventsCPs from losing revenue due to undercharging 6. As a whole, availability of appropriate accounting andbilling mechanisms will encourage more customers to adoptclouds thereby reducing their infrastructural investment cost and enabling themto avail Cloud environment related other benefits. It will also be beneficialfor CPs as their infrastructure utilization will be increased and their profitmargins will improve 13.Fromthe above discussion, accountingand billing of cloud resources may be justified as asuitable area for further research.