Cloud computing -- Best practices for cloud SLA metrics

In most cases, cloud service providers (CSPs) and cloud service customers (CSCs) negotiate service level agreements (SLAs) which include service level objectives (SLOs) and service qualitative objectives (SQOs) for which CSPs make commitments.. The commitments described in SLAs must be measured against actual performance of the service to ensure compliance with the SLA. How actual performance compares against commitments in SLAs, is explained in ISO/IEC 19086-2:2018[2] Metric model.  Cloud SLAs are covered in ISO/IEC 19086-1:2016[1] Service level agreement (SLA) framework Part 1:  Overview and concepts and in ISO/IEC 19086-4:2019[3] Security and privacy.
ISO/IEC 19086-2 Metric model establishes common terminology, defines a model for specifying metrics for cloud SLAs, and includes applications of the model with examples.  This document provides a primer on using the metrics model in 19086-2 to compose the calculation of a cloud service performance measure in order to compare against an SLA commitment. A few examples from the SLOs listed in ISO/IEC 19086-1 (Clause 10) are given in the document, such as Cloud Service Response Time Mean and Cloud Service Availability. As specific, measurable characteristics of a cloud service, SLOs are the basis for defining the metrics used to evaluate and compare agreements between parties.
In the second half of the document, a basic dissection of these examples is provided using a practical method based on a tabular format. This  format allows for a consistent usage of the model across practitioners such as:
- Extracting metric material from an SLA narrative and representing this content separately and unambiguously.
- Designing and representing a new metric definition.
Along with demonstrating this method on previous examples, some best practices are collected and reported.  These best practices also provide practical guidance on how to extend or complement the model when necessary, which is allowed by the 19086-2 Metric model standard but beyond its scope and non-normative.
The scope of this technical report is to describe a practical method for using ISO/IEC 19086-2 Metric Model.
 
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