Service level agreements (SLA) becomes the prevailing business model for delivery of a large number of products and services in telecommunication and IT arenas. Service Level Agreement (SLA) is a formal definition of the relationship that exists between two organizations, usually between a supplier of services and its customer. The, supplier organization may be an IT organization providing computing services to its customers. The SLA-based Service Allocation model ultimately aims to provide solutions to the above mentioned problems by proposing a framework for service allocation in a Multi- Cloud environment while taking into consideration the SLA management issues.
A service level agreement (SLA) is a contract between a provider and customer that guarantees specific levels of performance and reliability at certain cost. Usually cost is the underlying factor that drives quality of service that can be offered. A complete SLA is a legal document stating the parties involved; the terms of agreement, fees, arbitration policies, modification terms, reporting, responsibility of both parties, and so on .
Most often SLA takes the form of a negotiated contract made between a service provider and a customer and defines a price paid in exchange for an entitlement to a product or service to be delivered under certain terms, conditions, and with certain financial guarantees. Service level management is a method for a service provider to attract a customer and is applied to OSS application. So it is a hot research topic to design a framework of SLA driven OSS .
SLAs also specify what service providers can expect from their customers in terms of workload and resource usage. SLAs have included availability and customer Support guarantees, such as guarantee on helpdesk problem resolution time, or guarantees on service outages, etc. .
Cloud computing is a solution for addressing challenges such as licensing, distribution, configuration, and operation of enterprise applications associated with the traditional IT infrastructure, software sales and deployment models. Migrating from a traditional model to the Cloud model reduces the maintenance complexity and cost for enterprise customers, and provides on-going revenue for Software as a Service (SaaS) providers. Clients and SaaS providers need to establish a Service Level Agreement (SLA) to define the Quality of Service (QoS) .
Migrating from traditional software to Cloud enables on-going revenue for software providers. However, in order to deliver hosted services to customers, SaaS companies have to either maintain their own hardware or rent it from infrastructure providers .
The remainder of this paper is organized as follows. In Section 2, we describe some SLA concepts. In Section 3, we discuss each component and its function of the framework of service level agreements. In Section 4, SLA usage in Cloud-based Environments is described. In section 5, we discuss Adaptive SLA-based Management Algorithms. In section 6, SLA Based Scheduling Algorithms are explained. In section 7, we introduce a novel SLA Description Language. In section 8, we proposed an Interleaved Polling Algorithm with SLA. Finally in section 9, the discussion will be given.
2. Basic Concepts
In this section some basic concepts which are necessary to understand issues explained in this paper are described.
Service Level Agreement (SLA) is a contract between a user and its service provider. An SLA defines the service (QoS) requested by the user, the price that the user must pay for the service, the penalty if the agreement is violated, and etc. This paper considers SLA as the reference point between the network and the network users .
The Workflow Management Coalition (WfMC) defines workflow as the automation of a business process, in whole or part, during which documents, information or tasks are passed from one participant to another for action, according to a set of procedural rules. Workflow management system defines, create and manages the execution of workflows through the use of software, running on one or more workflow engines, which is able to interpret the process definition, interact with workflow participants and, where required, invoke the use of IT tools and applications .