An Overview Of Service Models Of Cloud Computing - IJMCR
International Journal of Multidisciplinary and Current ResearchResearch ArticleISSN: 2321-3124Available at: http://ijmcr.comAn Overview of Service Models of Cloud ComputingImran AshrafaaDepartment of Information Technology, University of The Punjab, Gujranwala Campus, PakistanAccepted 15 Aug 2014, Available online 27 Aug 2014, Vol.2 (July/Aug 2014 issue)AbstractSince its inception Cloud Computing is making a paradigm shift in the world of computing technology. Based on pay-peruse principle it provides a variety of services to both individual and industry. The services it provides include Platform-asa-Service (PaaS), Software-as-a-Service (SaaS) and Infrastructure-as-a-Service (IaaS) and it is still making its way toother similar services. These services models have certain requirements to be met and other security and design issues.This paper aims at discussing these three services models, important factors for these models and challenges currentlyfaced by these services models.Keywords: Cloud computing, SaaS, PaaS, IaaS, Security Challenges.1. IntroductionLast decade witnessed a huge paradigm shift in the fieldof computing world. This shift is from traditional standalone systems to Cloud Computing which is a shared poolof hardware and software resources combined to provideon demand services [9, 10]. The main idea is to utilizethese cheap resources in order to provide efficient and intime distributed computing whenever and wherever it isneeded. Cloud computing is being embraced by manyfields and is most adoptable field of informationtechnology at the moment. Due to its pay-per-useprinciple it is becoming very attractive and competitivesolutions for even small organizations who cannot affordto have their own hardware or software infrastructure.Moreover, it’s on demand changing scalability has made itvery viable solution for organizations who need to changetheir acquired services with the changing workload.Apart from being simple and easy to use it has otheradvantages over traditional framework. It works indistributed environment and serves the user according tohis needs. Users just need to have internet to connect tothe services and it is accessible from everywhere. It hasminimized cost, improved throughput, fast access ofsoftware and hardware resources and can scale readilyand easily as required [11].Cloud computing provides different services to itsusers as it works as service provider including IaaS, PaaSand SaaS and it is still making its way to other similarservices like network or database etc. this paper aims atdiscussing three mentioned service, their features andchallenges in brief.This paper is divided in two sections. Afterintroduction section two describes a comprehensiveoverview of cloud computing infrastructure in focus withtheir advantages and challenges. In the end conclusion isgiven.2. Cloud Services ModelsCloud computing is able to provide a variety of services atthe moment but main three services are InfrastructureAs-A-Service, Platform-As-A-Service and Software-As-AService also called as service model of Cloud computing[12].Figure 1: Cloud computing service model [1]2.1 Infrastructure-As-A-Service (IaaS)The core computing resources are hardware and softwarecomponents. They lay the foundations of everycomputing infrastructure. Infrastructure-as-a-Structureservice of cloud computing provides these services tocloud end users. In other words IaaS is making user freeof these services. End users can hire any of these servicesat the level they desire. User has to pay only for the usageof his resources. IaaS is to provide computing779 Int. J. of Multidisciplinary and Current research, July/Aug 2014
Imran Ashrafinfrastructure and operating middleware [2]. Grid/Clusterarchitectures provide high performance infrastructures tothe organizations on rent bases and make them free fromtheir own resources. So organizations can put theirattention on manufacturing and quality concerns [13].The main concept behind IaaS is the resourcevirtualisation. It allows the user to have his own guestoperating system on top of infrastructure provided by thecloud provider. This concept leads to automaticdeployment of infrastructure which is both distributedand scalable. The administration, deployment, andmaintenance is the responsibility of the service provider[13, 2].2.1.2 Components of IaaSInfrastructure of cloud has multiple components whichare used in infrastructure service model. They are theshared resources among the users, so they have multiplechallenges for service providers. Some components are:[14] Cloud Software Computer Hardware Network and Internet Connectivity Platform Virtualization Utility Computing Service Level Agreements2.1.2.1 Service Level AgreementsBefore deploying the service providing architecture ofcloud computing, one of the desired concerns of thecustomers is the reliability and quality of the offeredservices [3]. The expectations of these services changesfrom customer to customer so a consensus is neededbetween service provider and the customer. Thisagreement about the quality and reliability of service iscalled Service level Agreement. It aims at defining,describing and negotiating on terms and conditions ofcontract between service provider and customers toreach a final verdict. QoS attribute is also part of SLA andit needs to be defined properly. QoS (Quality of Services)may include feature like response time, memory usageand throughput etc [4] and they need to be monitoredclosely. It is very critical part because if any term orcondition is skipped or not discussed, it will createproblems for the users and service providers. SLA includesother features like services measurement, servicecondition evaluation and management services [3].2.1.2.2 Utility ComputingCloud computing provides utility computing and itincludes computations, storage, connection bandwidthand other similar resources. The main focus of utilitycomputing is to reduce optimization cost and provideresources to the end user and charge them anAn Overview of Service Models of Cloud Computingappropriate cost for the usage. It also ensures that thescalability of infrastructure of cloud is managed properly.It allows the service provider to enhance the systemwithout quitting the services, as the number of users isincreased.2.1.2.3 Cloud SoftwareCloud software is used to integrate different componentsof cloud infrastructure and make them synchronized.There are many open source software available in themarket i.e. Eucalyptus and Nimbus, but they are not clearfrom bugs and vulnerabilities which can harm the cloudsystem. Furthermore cloud service provider develop anduse APIs (Application Programming Interfaces) i.e. SOAP,REST and HTTP with xml, for performing differentfunctions i.e. access control etc.2.1.2.4 Platform VirtualizationVirtualization is the basic task in cloud infrastructurebecause it provides multiple virtual systems on a singlesystem so that multiple tasks are performedsimultaneously. It reduces the hardware maintenancebecause it shared the hardware resources. In thedescribed way it reduces the complexity and enhancesthe scalability of cloud resources.2.1.2.5 Network and Internet ConnectivityCloud infrastructure is distributed on different locationsto minimize the delay and damage of resources. Thesecloud infrastructure components are locally connectedwith LANs and then these components are connectedwith each other via high speed internet. These individualcomponents construct the overall cloud infrastructure.2.1.2.6 Computer HardwareAn interface is provided by IaaS to its customers or usersto access the distributed resources of cloudinfrastructure. These resources are CPU, Storage andnetwork connecting components. These cloud resourcesneed a high level security measure; as if they arevulnerable then the whole cloud is under threat. Anydamage to of flaw in hardware will result in failure ofservices.2.2 Software-As-A-Service (SaaS)SaaS is the top layer of cloud computing services. It isdifferent than traditional software services, wheretraditional software need own hardware and softwarecomponents, Where SaaS makes users, independent oftheir own resources. Users use the integrated servicesprovided by cloud operator. One of the best examples ofSaaS is Google Docs [15, 16].2.2.1 Quality Model780 Int. J. of Multidisciplinary and Current research, July/Aug 2014
Imran AshrafTo evaluate and understand SaaS there is a need to definea quality model [17].An Overview of Service Models of Cloud Computingof lack of customizable SaaS service availability, serviceconsumers should simply avail the services. It will alsolimit the usage of SaaS services.2.2.1.4 AvailabilityFigure 1: Quality model of SaaS [18]2.2.1.1 ReusabilityReusability refers to using software elements to createdifferent other applications and it is an important featurein the context of cloud computing. To reuse differenttypes of internet-based services is the primaryfundamental of CC. while focusing the SaaS, over theinternet software that is to be reused, is supplied toservice consumers. Delivery of SaaS services often createsone –to-many relationships. For example, number ofcustomer uses services by Google map which provides anumber of operations to make use of shared informationlocally and on map.2.2.1.2 Data Managed by ProviderSaaS is and on demand service, that provides licenseapplication for the use of customers and is used as asoftware development model as well. It is theresponsibility of service providers to manage data andinstall services on their own servers. That is why; themost of data produced by service consumers is storedand managed in data centers by data providers. Thereforetwo things are not perceived by service customers, indetails: Where, their data is stored? How could be the data managed?That’s why if reliability functions and data security is notprovided by service providers, the services may bedoubted by the customers and the utilization of servicesbecomes lower.2.2.1.3 Service CustomizabilityCustomizability means that the consumers can changethe services based on their requirements. It is veryessential to ensure customizability as service providersare able to satisfy varying requirements of multifarioususer by having customizability.The customers, who use internet, can easily use thesecloud services and can become potential users of it. Onlybecause of this characteristic, for many serviceconsumers, service providers can never modify theircloud services. So service consumer can easily change ormodify their services according to their own need. In caseUsing a web browser and internet service consumer caneasily access SaaS services in Cloud Computing. Provider’sserver which runs and deploys SaaS services does not giveownership to customers for SaaS. Due to this reason, toachieve best availability of services is the main focus ofmost of venders. If SaaS services are not available anyfunctionality of SaaS cannot be accessed by customers.Gmail service is one of the examples of this statement,stwhich was completely down at September 1 , 2009.Which caused unavailability of read and writes service ofemail for Gmail users. In cloud computing, customersexpect 24/7 availability from SaaS which means thereshould not be single source of failure [5]. Service shouldbe available at all times in spite of failures, maintenance,upgrading or any attack.2.2.1.5 ScalabilityIt is a pivotal requirement of cloud to be scalable becauseit decides how a system or software is flexible anddynamic. It is also indicate the growing ratio of softwareusage. As the resources of cloud are controlled by serviceprovider and the customer could not controlled resourcesused by services. So it is the responsibility of serviceprovider to enhancing the capacity of resources so thecustomer requests are fulfilled without interruption andinforming the customer.2.2.1.6 Pay par UseWhile using the software services, it is important thatcustomers have not paid cost as they are the owner ofthe service. But they should pay according to the serviceusage. This is about; when a customer wants to use theservice he will connect with the cloud and leave theservices after use of it. And then, he will pay for that timeof service usage.2.3 Platform-As-A-Service (PaaS)Platform as a service provides a development platform toits users so that they can develop and maintain theirapplications and cloud specific utilities. It is different fromSaaS because SaaS is a developed and deployedapplication and PaaS provides a platform or ground todevelop those applications. PaaS provides developmentenvironment and platform, so all supporting material i.e.programming environment, development tools andinfrastructure etc. must be provided by cloud provider[20].2.3.1 Stakeholders of Platform-As-A-Service781 Int. J. of Multidisciplinary and Current research, July/Aug 2014
Imran AshrafAn Overview of Service Models of Cloud ComputingTable 1 Features and challenges of cloud computing services models [5-8, 13, 18-19]Attribute g the risksReduced operational tabilityDisaster recoveryCost minimizationHigh throughputTime savingAvailability of high techservicesHigh availabilityReduced administrationcostAccess of high levelinfrastructureFlexibilityReady to use servicesScalabilityLess administration costAccording to usage of resources and control ofinfrastructure, there are three types of PaaS stakeholders[21].2.3.1.1 PaaS HosterPaaS hoster is responsible for deploying hardwareinfrastructure through IaaS, Which are necessary foraccomplishing user demands.2.3.1.2 PaaS ProviderPaaS provider is responsible for providing developmentplatform to developers so they can work on their webapplication development without having knowledgeabout servers and front end applications.2.3.1.3 PaaS UserPaaS user is the developer, who will develop applications.They must have browser based utility to work on thatplatform. They will pay for services as much they use3. Opportunities and Challenges of Services Models ofCloud ComputingThis section provides the detail about the challenges andissues faced by IaaS, PaaS and SaaS as well as the featuresand opportunities these models provide.1.Temperature of cloud places need to bemaintained2. System should be power failure tolerant3. Selection of infrastructure hardware is veryimportant4. Connection between cloud and hardwareshould be a high bandwidth channel5. Storage of cloud should be able to fulfill thechanging demands of large data size6. Loss of control1. Data security is highly preferred feature2. High availability requirement3. Authentication and authorization4. Data integrity5. Data privacy6. Network security7. Cloud standardization8. Deployment of cloud resources in differentcountries results in conflict of rules9. Data backup10. Web application security11. Data confidentiality12. Virtualization1. Limited APIs2. Data Lock-in3. Auditability4. Performance is unpredictable5. Lack of control over low level security6. Data inaccessibility between applications7. Vulnerabilities of web applications and SOAConclusionCloud computing is an emerging technology whichintroduced itself as a service oriented technology. It isworking on the principle of on demand service andscalability. It is providing services in many ways includingsoftware, platform and infrastructure and making theusers free of installing and administering these services.In spite the fact that cloud computing provide highperformance, high available, fault tolerant services; theissues it comes with are also very serious in nature. Of theworth mentioning are data and network security, dataauthenticity and audit ability, lack of user control overdata and security polices and virtualization problem. Inorder to attract the organizations and build theconfidence of customer, these issues need to be wellresearched and resolved.References[1]W. Voorsluys, J. Broberg, and R. Buyya, "Introduction to cloudcomputing," Cloud Computing, pp. 1-41, 2011.[2]R. Prodan and S. Ostermann, "A survey and taxonomy ofinfrastructure as a service and web hosting cloud providers," inGrid Computing, 2009 10th IEEE/ACM International Conferenceon, 2009, pp. 17-25.782 Int. J. of Multidisciplinary and Current research, July/Aug 2014
Imran Ashraf[3]P. Patel, A. H. Ranabahu, and A. P. Sheth, "Service levelagreement in cloud computing," 2009.[4]A. Keller and H. Ludwig, "The WSLA framework: Specifyingand monitoring service level agreements for web services,"Journal of Network and Systems Management, vol. 11, pp. 5781, 2003.[5]M. Armbrust, O. Fox, R. Griffith, A. D. Joseph, Y. Katz, A.Konwinski, et al., "M.: Above the clouds: A Berkeley view ofcloud computing," 2009.[6]S. Kaur and G. S. Bhathal, "OVERVIEW OF SAAS IN CLOUDCOMPUTING," 2013.[7]W. Yuan, "Infrastructure as a Service."[8]S. Subashini and V. Kavitha, "A survey on security issues inservice delivery models of cloud computing," Journal of Networkand Computer Applications, vol. 34, pp. 1-11, 2011.*9 Shyam Patidar, Dheeraj Rane, “A Survey Paper on CloudComputing,” Second International Conference on AdvancedComputing & Communication Technologies, 2012.[10] Mohiuddin Ahmed, Abu Sina Md. Raju Chowdhury, MustaqAhmed, Md. Mahmudul Hasan Rafee, ” An Advanced Survey onCloud Computing and State-of-the-art Research Issues,” IJCSIInternational Journal of Computer Science Issues, Vol. 9, Issue 1,No 1, January 2012.*11 Rahul Bhoyar, Prof. Nitin Chopde, “Cloud Computing:Service, models, Types, Database and issues,”InternationalJournal of Advanced Research in Computer Science andSoftware Engineering, Volume 3, Issue 3, March 2013.*12 Ms. Disha H. Parekh, Dr. R. Sridaran, “An Analysis ofSecurity Challenges in Cloud Computing,” (IJACSA) InternationalJournal of Advanced Computer Science and Applications, Vol. 4,No.1, 2013.[13] Aniruddha S. Rumale, D.N.Chaudhari, ” Cloud Computing:Infrastructure as a Service,” International Journal of InventiveEngineering and Sciences (IJIES) ISSN: 2319–9598, Volume-1,Issue-3, February 2013.An Overview of Service Models of Cloud Computing[14] Wesam Dawoud, Ibrahim Takouna, Christoph Meinel, ”Infrastructure as a Service Security: Challenges andSolutions,”Hasso Plattner Institute Potsdam, Germany, Ministryof Education & Higher Education Palestine.[15] Zhengxiong Hou, Xingshe Zhou, Jianhua Gu,YunlanWang,Tianhai Zhao, “ASAAS: Application Software as a Servicefor High Performance Cloud Computing,” 12th IEEE InternationalConference on High Performance Computing andCommunications, 2010.[16] Wei-Tek Tsai, Xin Sun, Janaka Balasooriya, “ServiceOriented Cloud Computing Architecture,” Seventh InternationalConference on Information Technology, 2010.*17 Jae Yoo Lee, Jung Woo Lee, Du Wan Cheun†, and Soo DongKim, “A Quality Model for Evaluating Software-as-a-Service inCloud Computing,” Seventh ACIS International Conference onSoftware Engineering Research, Management and Applications,2009.*18 Choudhary V, “Software as a service: implications forinvestment in software development,” International conferenceon system sciences, 2007, p. 209.[19] Rashmi, Dr.G.Sahoo, Dr.S.Mehfuz, “Securing Software as aService Model of CloudComputing: Issues and Solutions,” International Journal onCloud Computing: Services and Architecture (IJCCSA) ,Vol.3,No.4, August 2013.*20 Santosh Kumar and R. H. Goudar, “Cloud Computing –Research Issues, Challenges, Architecture, Platforms andApplications: A Survey,” International Journal of FutureComputer and Communication, Vol. 1, No. 4, December 2012.[21] Michael Boniface, Bassem Nasser, Juri Papay, Stephen C.Phillips, Arturo Servin, Xiaoyu Yang, Zlatko Zlatev, Spyridon V.Gogouvitis, Gregory Katsaros, Kleopatra Konstanteli, GeorgeKousiouris, Andreas Menychtas, Dimosthenis Kyriazis,“Platform-as-a-Service Architecture for Real-time Quality ofService Management in Clouds,” Fifth International Conferenceon Internet and Web Applications and Services, 2010.783 Int. J. of Multidisciplinary and Current research, July/Aug 2014
2. Cloud Services Models Cloud computing is able to provide a variety of services at the moment but main three services are Infrastructure-As-A-Service, Platform-As-A-Service and Software-As-A-Service also called as service model of Cloud computing [12]. Figure 1: Cloud computing service model [1] 2.1 Infrastructure-As-A-Service (IaaS)
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