Service level agreement in cloud computing
- 2. Contents 1. Introduction 2. SLA definition 3. SLA Components and Categories 4. Customer and service provider definition 5. Qualities determined by SLA 6. SLA parameters and metrics
- 3. What is Service Level Agreement A formal contract between a service provider (SP) and a service consumer (SC) SLA: foundation of the consumers trust in the provider Purpose: to define a formal basis for performance and availability the SP guarantees to deliver SLA contains service level objectives (SLOs) Objectively measurable condition s for the service SLA and SLO:: basis of selection of cloud provider
- 4. What is Service Level Agreement Describes a set of non functional requirements of the service. Example : RTO time – Return to Operation Time if case of failure SLO – Service Level Objective. That is, the objective to be achieved. KPI – Key Performance Indicators Service Level Objective: Objective of service quality that has to be achieved. Set of measurable KPIs with thresholds to decide if the objective is fulfilled or not.
- 5. SLA Contents A set of services which the provider will deliver A complete, specific definition of each service The responsibilities of the provider and the consumer A set of metrics to measure whether the provider is offering the services as guaranteed An auditing mechanism to monitor the services The remedies available to the consumer and provider if the terms are not satisfied How the SLA will change over time
- 6. Web Service SLA WS-Agreement ◦ Xml-based language and protocol for negotiating, establishing, and managing service agreements at runtime ◦ Specify the nature of agreement template ◦ Facilitates in discovering compatible providers ◦ Interaction: request-response WSLA (web service level agreement framework) ◦ Formal XML-schema based language to express SLA and a runtime interpreter ◦ Measure and monitor QoS parameters and report violations
- 7. Difference between cloud SLA and web service SLA Qos parameters: ◦ Traditional web service: response time, SLA violation rate for reliability, availability, cost of service, ETC ◦ Cloud computing: Qos related to security, privacy, trust, management, etc Automation: ◦ Traditional web service: SLA negotiation, provisioning. Service delivery, monitoring are no automated ◦ Cloud computing: SLA automation is required for highly dynamic and scalable service consumption Resource allocation: ◦ Traditional web service: UDDI(universal description discovery and integration) for advertising and discovering between web services ◦ Cloud computing: resource are allocated and distributed globally without any central directory
- 8. Types of SLA 1- Service Level SLA A service based SLA covers one service for all customers. Let’s consider that the IT service provider provides customer query service for many customers. In a service based service level agreement, the service level of the customer query service will be same for all customers that will be using this service. For instance, if the finance department and the human resources department are two customers which will be using this service, the same SLA will be valid between the IT service provider and these two departments since it is a service based SLA.
- 9. Types of SLA 2- Customer based SLA A customer based SLA is an agreement with one customer, covering all the services used by this customer. For example: the relationship between you and your telecom operator. You use the voice services, SMS services, data services, and several other services of the telecom operator. For all these services, you have only one contract between you and the telecom operator. Similarly, if the IT service provider provides several services for the business and the customers, and if all the service levels are documented in one service level agreement for the provided services, it will be a customer based SLA.
- 10. Types of SLA 3- Multi-level SLA In multi-level SLA, aspects of SLA are defined according to the organization of the customer using some kind of inheritance with overall definitions with relevance for all subordinate levels. This SLA focuses on the organization of the customer. All services and their interrelationships with secondary services are used when defining the multi-level service level agreement structure.
- 11. Service level objective(SLOs) The service levels that are approved by the customer and the providers. It contains a group of service level indicators such as; availability, performance, and reliability. Each part of the service level, like availability will have a target level to complete. Objectively measurable conditions for the service Example: ◦ Availability of a service x is 99.9% ◦ Response time of a database query is between 3 to 5 seconds ◦ Throughput of a server at peak load time is 0.875
- 12. Service level management Monitoring and measuring performance of service based on SLOs Provider perspective: ◦ Make decisions based on business objectives and technical realties Consumer perspective: ◦ Decisions about how to use cloud services
- 13. Considerations for SLA Business level objectives: Consumers should know why they are using cloud services before they decide how to use cloud computing. Responsibilities of the provider and consumer: The balance of responsibilities between providers and consumers will vary according to the type of service. Business continuity and disaster recovery: Consumers should ensure their cloud providers have adequate protections case of a disaster. System redundancy: Many cloud providers deliver their services via massively redundant systems. Those systems are designed so that even if hard drives or network connections or servers fail, consumer will not experience and outages.
- 14. Considerations for SLA (cont..) Maintenance: maintenance of cloud infrastructure affects any kind of cloud offers (applicable to both software and hardware) Location of data: if a cloud service provider promises to enforce data location regulations, the consumer must be able to audit the provider to prove that regulations are being followed Seizure of data: if law enforcement targets the data and applications associated with a particular consumer, the multi-tenant nature of cloud commuting makes it likely that other consumers will be affected. Therefore, the consumer should consider using a third-party to keep backups of their data Failure of the provider: consumers should consider the financial health of their provider and make contingency plans. The providers policies of handling data and applications of a consumer whose account is delinquent or under dispute are to be considered. Jurisdiction: consumers should understand the law that apply to any cloud providers they consider.
- 15. SLA Requirements Security: cloud consumer must understand the controls and federation patterns necessary to meet the security requirements. Providers must understand what they should deliver to enable the appropriate controls and federation patterns. Data encryption: details of encryption and access control policies. Privacy: isolation of customer data in a multi-tenant environment. Data retention and deletion: some cloud providers have legal requirements of retaining data even of it has been deleted by the consumer. Hence, they must be able to prove their compliance with these policies. Hardware erasure and destructions: provider requires to zero out the memory if a consumer powers off the VM or even zero out the platters of a disk, if it is to be disposed or recycled.
- 16. SLA Requirements (cont..) Regulatory compliance: if regulation are enforced on data and applications, the providers should be able to prove compliance. Transparency: for critical data and applications, providers must be proactive in notifying consumers when the terms of the SLA are breached. Certification: the provider should be responsible in proving the certification of any kind of data or applications and keeping its up to date. Monitoring: to eliminate the conflict of interest between the provider and the consumer, a neural third party organization is the best solution to monitor performance. Auditability: An SLA should make it clear how and when those audits take place. Because audits are disruptive and expensive, the provider will most likely place limits and charges on them.
- 17. Key performance indicators Low level resource metrics Multiple KPLS are composed, aggregated, or converted to for high level SLOs. Example: Downtime, uptime, packet size and so on..
- 18. Industry defined KPLs Monitoring: ◦ Natural questions: ◦ Who should monitor the performance of the provider? ◦ Does the consumer meet its responsibilities? ◦ Solution: neutral third party organization to perform monitoring ◦ Eliminates conflicts of interest if: ◦ Provider reports outage at its sole discretion ◦ Consumer is responsible for an outage Auditability: ◦ Consumer regiments: ◦ Is the provider adhering to legal regulations or industry standard ◦ SLA should make it clear how and when to conduct audits
- 19. Metrics for Monitoring and Auditing Throughput- how quickly the service responds Availability- represented as a percentage of uptime for a service in a given observation period. Reliability- how often the service is available Durability- how likely the data is to be lost
- 20. Cont.. Agility- how quickly the provider responds as the consumers resource load scales up and down Automation- what percentage of requests to the provider are handled without and human interaction Customer service response time- how quickly the provider responds to a service request Resolution time- time period between detection of a service problem and its resolution