SLA Negotiation

SLA negotiation is an important mechanism to guarantee the cloud service performance and enhance the trust between cloud service customers and cloud service providers. It has already attracted a lot of attention from academic communities that have proposed several important works.

Web Service Agreement (WSLA [1]) is proposed in the form of the standard protocol and dedicated formatted language, which aims to facilitate service providers in generating a formal copy of web service agreements and achieve real time monitoring on its compliance. It can create a formal contract with corresponding obligations both for service customers and service providers during the entire life cycle as creation, termination and state monitoring are carried out by two main types of services as Agreement Service and Agreement Factory Service. The former service aims to access established agreement content, real-time monitoring on the life cycle management. The later service is for creating agreements for both parties and then instantiating relevant services with corresponding QoS. It is also the base of WS-Agreement negotiation specification that is equipped with enhanced capabilities such as the support of more than one round of negotiation processes, including a language and protocol to negotiate the agreement offer and counter offer.

NextGrid [2] offers a business-objectives oriented service layer agreement and a specific flexible negotiation approach. It supports creating SLA dynamically in order to meet the requirements both from service providers and customers after bilateral consent. Additionally, it also offers a uniform framework to operate and manage the quality of all running services. The mapping mechanism of the uniform framework supports translating business-level objects defined in SLA into resource management policies and translating technical-level monitoring details into business-level consequences for comparing the SLA compliance as well as sending feedback to customers.

HPC4U [3] developed a reliable and predictable SLA-aware Grid middleware to offer several attractive features to the end users. This includes guaranteeing the quality of a critical project independent from underlay IT infrastructure; supporting both commercial and open source software components; organizing components in various groups of modular, implementing features in a transparent manner, etc. The SLA-aware and Gridenabled Resource Management System (RMS) of HPC4U supports SLA negotiation, multisite SLA-awareness scheduling, security and interfaces for storage, check-pointing and networking support. A cluster middleware system will be developed to negotiate service level agreement with customers and assure the run-time SLA compliance.

Finally, BREIN [ref] created a dynamic, intelligent and adaptable infrastructure to increase the level and dynamism of collaborations among companies. It can create SLAs for improving the discovery capabilities of services providers based on its own template of "Semantic Annotated Service Level Agreements" (SA-SLA). The annotation carries a reference to a concept in a semantic model (BREIN Business Ontology) that provides a high level description of a specific terminology which can be translated by the Negotiation Broker and the Contract Net Protocol. Meanwhile, BREIN also improves the dynamic negotiation capability on architectural level, which can apply different kinds of negotiation protocols ranging from discrete offer negotiation to multi-round/phase negotiation.

[1] A. Keller and H. Ludwig. "The WSLA framework: Specifying and monitoring service level agreements for web services," Journal of Network and Systems Management, vol. 11, no. 1 pp. 57-81, 2003.

[2] D. Snelling, A. Ali, F. Wray, A. Basermann, M. Fisher, M. Surridge, and P. Wieder, "NextGRID Architectural Concepts," In Towards Next Generation Grids, pp. 3-13, Springer US, 2007.

[3] F. Heine, M. Hovestadt, and O. Kao, "HPC4U: Providing highly predictable and SLA-aware clusters for the next generation grid," In 4th Cracow Grid Workshop, Cracow, Poland. 2004.