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Top1. Introduction
Cloud computing is an advanced technology that is built on utility computing, virtualization, service-oriented architecture and parallel computing. Distributed computing can be referred as a synonym of cloud computing over a network. The word “cloud” can be referred as a blend of networks, hardware, storage and interfaces to deliver a service. Currently, many information technology companies like Microsoft, Google, Yahoo, Amazon, etc., are providing different cloud services (Zhang et al., 2010).
In cloud computing, there are mainly three parties, namely CSP, Data Owner (DO) and users. The CSP provides the cloud infrastructure and services for both the DOs and users. The CSP records the profile of each and every user and DO, and controls all the tasks of the cloud server (Namasurdra et al., 2014; Devi et al., 2016; Namasurdra & Roy 2017). The CSP allows the DOs to store their data or files on the cloud server. The users can access these data from the cloud server. It has recently much attention from both industry and academia because of its profitability. Since CSP is the central authority that manages and controls all the tasks and services of a cloud server, the CSP should provide a good QoS and strong security of the user’s confidential or sensitive data. Due to the presence of a huge number of users and dynamic changing of number of user in the cloud environment (Breskovic et al., 2011; Namasurdra & Roy 2015; Namasurdra & Roy 2016; Breskovic et al., 2011; Namasurdra & Roy 2017; Majumder et al., 2014; Namasurdra et al., 2017), there is gradually increasing the service level agreement or SLA issues. SLA can be defined as a contract between both the CSP or service provider and users. It can also be an agreement attained out of negotiation among the CSPs or traders for availing any required service. SLA includes each and every terms and conditions about the services for assuring QoS to the recipient or user. It monitors or manages the services along with its assured elements, and terminates the services, if there is any kind of violation. Here, monitoring can be achieved by utilizing several SLA frameworks that monitors or manages different features. Monitoring of services helps to track many features, such as efficiency, availability, etc. SLA keeps the standard of a CSP to provide the recommended services as per the customers’ satisfactions.