Abstract
We describe a novel framework for specifying and monitoring Service Level Agreements (SLA) for Web Services. SLA monitoring and enforcement become increasingly important in a Web Service environment where enterprise applications and services rely on services that may be subscribed dynamically and on-demand. For economic and practical reasons, we want an automated provisioning process for both the service itself as well as the SLA managment system that measures and monitors the QoS parameters, checks the agreed-upon service levels, and reports violations to the authorized parties involved in the SLA management process. Our approach to these issues is presented in this paper. The Web Service Level Agreement (WSLA) framework is targeted at defining and monitoring SLAs for Web Services. Although WSLA has been designed for a Web Services environment, it is applicable as well to any inter-domain management scenario, such as business process and service management, or the management of networks, systems and applications in general. The WSLA framework consists of a flexible and extensible language based on XML Schema and a runtime architecture comprising several SLA monitoring services, which may be outsourced to third parties to ensure a maximum of objectivity. WSLA enables service customers and providers to unambiguously define a wide variety of SLAs, specify the SLA parameters and the way they are measured, and relate them to managed resource instrumentations. Upon receipt of an SLA specification, the WSLA monitoring services are automatically configured to enforce the SLA. An implementation of the WSLA framework, termed SLA Compliance Monitor, is publicly available as part of the IBM Web Services Toolkit.
Similar content being viewed by others
References
H. Kreger, Web Services Conceptual Architecture 1.0. IBM Software Group, May 2001.
UDDI Version 2.0 API Specification, Universal Description, Discovery and Integration, uddi.org, June 2001.
A. Keller, G. Kar, H. Ludwig, A. Dan, and J. L. Hellerstein, Managing dynamic services: A contract based approach to a conceptual architecture. In R. Stadler and M. Ulema, eds. Proceedings of the Eighth IEEE/IFIP Network Operations and Management Symposium (NOMS 2002), Florence, Italy, IEEE Publishing, pp. 513–528, April 2002.
D. Verma, Supporting Service Level Agreements on IP Networks, Macmillan Technical Publishing, 1999.
L. Lewis, Managing Business and Service Networks, Kluwer Academic Publishers, 2001.
G. Dreo Rodosek and L. Lewis, Dynamic service provisioning: A user-centric approach. In O. Festor and A. Pras, eds. Proceedings of the 12th Annual IFIP/IEEE International Workshop on Distributed Systems: Operations & Management (DSOM 2001), IFIP/IEEE, INRIA Press, Nancy, France, pp. 37–48, October 2001.
P. Bhoj, S. Singhal, and S. Chutani, SLA management in federated environments. In M. Sloman, S. Mazumdar, and E. Lupu, eds. Proceedings of the Sixth IFIP/IEEE Symposium on Integrated Network Management (IM'99), Boston, Massachusetts, IEEE Publishing. 293–308, May 1999.
K. White, Definition of Managed Objects for Service Level Agreements Performance Monitoring. RFC 2758, IETF, February 2000.
ASP Industry Consortium, White Paper on Service Level Agreements, 2000.
S. Field, C. Facciorusso, Y. Hoffner, A. Schade, and M. Stolze, Design criteria for a virtual marketplace (ViMP). In C. Nikolaou and C. Stephandis, eds., Research and Advanced Technology for Digital Libraries, Berlin, Springer-Verlag, 1998.
M. Bichler, The Future of e-Markets-Multidimentional Market Mechanisms, Cambridge University Press, Cambridge, United Kingdom, 2001.
M. Ströbel, A design and implementation framework for multi-attribute negotiation intermediation in electronic markets, Ph.D. thesis, Universität St. Gallen, St. Gallen, Switzerland, 2002.
M. Greunz, B. Schopp, and K. Stanoevska-Slabeva, Supporting market transactions through XML contracting container, Proceeding of the Sixth Americas Conference on Information Systems (AMCIS 2000), Long Beach, California, 2000.
ebXML-Creating a Single Global Electronic Market. http://www.ebxml.org.
P. J. Grefen, K. Aberer, H. Ludwig, and Y. Hoffner, Crossflow: Cross-organizational workflow management for service outsourcing in dynamic virtual enterprises, IEEE Data Engineering Bulletin, Vol. 24, No. 1, pp. 52–57, 2001.
H. Ludwig and Y. Hoffner, The role of contract and component semantics in dynamic E-contract enactment configuration, Proceedings of the Ninth IFIP Workshop on Data Semantics (DS9), pp. 26–40, Hong Kong, 2001.
enhanced Telecom Operations Map: The Business Process Framework. Member Evaluation Version 2.7 GB 921, TeleManagement Forum, April 2002.
FORM Consortium, Final Inter-Enterprise Management System Model. Deliverable 11, IST Project FORM: Engineering a Co-operative Inter-Enterprise Framework Supporting Dynamic Federated Organizations Management, February 2002. http://www.ist-form.org.
B. Bhushan, M. Tschichholz, E. Leray, and W. Donnelly, Federated accounting: Service charging and billing in a business-to-business environment. In N. Anerousis, G. Pavlou, and A. Liotta, eds., Proceedings of the seventh IFIP/IEEE International Symposium on Integrated Network Management, Seattle, Washington IEEE Publishing, pp. 107–121, May 2001.
Keynote—The Internet Performance Authority. http://www.keynote.com.
C. Overton and E. Siegel, Experiences with Internet measurements and statistics, Computer Measurement Group, Journal of Computer Resource Measurement, Vol. 106, pp. 4–14, April 2002.
C. Overton, On the theory and practice of Internet SLAs, Computer Measurement Group, Journal of Computer Resource Measurement, Vol. 106, pp. 32–45, April 2002.
SLA and QoS Management Team, Service Provider to Customer Performance Reporting: Information Agreement. Member Draft Version 1.5 TMF 602, TeleManagement Forum, June 1999.
SLA Management Team, SLA Management Handbook, Public Evaluation Version 1.5 GB 917, TeleManagement Forum, June 2001.
R. Gopal, Unifying network configuration and service assurance with a service modeling language. In R. Stadler and M. Ulema, eds., Proceedings of the Eighth IEEE/IFIP Network Operations and Management Symposium (NOMS 2002), Florence, Italy, IEEE Publishing. pp. 711–725, April 2002.
B. Moore, E. Ellesson, J. Strassner, and A. Westerinen, Policy Core Information Model-Version 1 Specification. RFC 3060, IETF, February 2001.
F. Griffel, M. Boger, H. Weinreich, W. Lamersdorf, and M. Merz, Electronic contracting with COS-MOS—How to establish, negotiate and execute electronic contracts on the Internet, Proceedings of the Second International Enterprise Distributed Object Computing Workshop (EDOC '98), La Jolla, California, October 1998.
Y. Hoffner, S. Field, P. Grefen, and H. Ludwig, Contract-driven creation and operation of virtual enterprises, Computer Networks Vol. 37, pp. 111–136, 2001.
V. Tosic, B. Pagurek, B. Esfandiari, and K. Patel, Management of compositions of E-and M-business web services with multiple classes of service. In R. Stadler and M. Ulema, eds., Proceedings of the Eighth IEEE/IFIP Network Operations and Management Symposium (NOMS 2002), IEEE Publishing, Florence, Italy, pp. 935–937, April 2002.
H. Ludwig, A. Keller, A. Dan, R. Franck, and R.P. King, Web Service Level Agreement (WSLA) Language Specification, IBM Corporation, July 2002.
XML Schema Part 1: Structures. W3C Recommendation, W3 Consortium, May 2001.
XML Schema Part 2: Datatypes. W3C Recommendation, W3 Consortium, May 2001.
F. Leymann, Web Services Flow Language (WSFL) 1.0. IBM Software Group, May 2001.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Keller, A., Ludwig, H. The WSLA Framework: Specifying and Monitoring Service Level Agreements for Web Services. Journal of Network and Systems Management 11, 57–81 (2003). https://doi.org/10.1023/A:1022445108617
Issue Date:
DOI: https://doi.org/10.1023/A:1022445108617