PD ISO-IEC TR 23951 2025.docx

PDISO/IECTR23951:2025BSIStandardsPublicationInformationtechnologyCloudcomputing一Bestpracticesforusingthecloudservicelevelagreement(SLA)metricmodelbsi.NationalforewordThisPublishedDocumentistheUKimplementationofISO/IECTR23951:2025.ItsupersedesPDISO/IECTR23951:2020,whichiswithdrawn.TheUKparticipationinitspreparationwasentrustedtoTechnicalCommitteeIST38,CloudComputingandDistributedPlatforms.Alistoforganizationsrepresentedonthiscommitteecanbeobtainedonrequesttoitscommitteemanager.ContractualandlegalconsiderationsThispublicationhasbeenpreparedingoodfaith,howevernorepresentation,warranty,assuranceorundertaking(expressorimplied)isorwillbemade,andnoresponsibilityorliabilityisorwillbeacceptedbyBSIinrelationtotheadequacy,accuracy,completenessorreasonablenessofthispublication.Allandanysuchresponsibilityandliabilityisexpresslydisclaimedtothefullextentpermittedbythelaw.Thispublicationisprovidedasis,andistobeusedattherecipientsownrisk.Therecipientisadvisedtoconsiderseekingprofessionalguidancewithrespecttoitsuseofthispublication.Thispublicationisnotintendedtoconstituteacontract.Usersareresponsibleforitscorrectapplication.ThispublicationisnottoberegardedasaBritishStandard.©TheBritishStandardsInstitution2025PublishedbyBSIStandardsLimited2025ISBN9780539335460ICS35.210CompliancewithaPublishedDocumentcannotconferimmunityfromlegalobligations.ThisPublishedDocumentwaspublishedundertheauthorityoftheStandardsPolicyandStrategyCommitteeon30April2025.Amendments/corrigendaissuedsincepublicationDateTextaffectedPDISO/IECTR23951:2025TechnicalReportISO/IECTR23951Secondedition2025-04InformationtechnologyCloudcomputingBestpracticesforusingthecloudservicelevelagreement(SLA)metricmodelTechnologiesde!'informationInformatiqueennuageBonnespratiquespour!'utilisationdumodelemetriqued'accorddeniveaudeservice(SLA)dansIeCloudReferencenumberISO/IECTR23951:2025(en)COPYRIGHTPROTECTEDDOCUMENT©ISO/IEC2025Allrightsreserved.Unlessotherwisespecified,orrequiredinthecontextofitsimplementation,nopartofthispublicationmaybereproducedorutilizedotherwiseinanyformorbyanymeans,electronicormechanical,includingphotocopying,orpostingontheinternetoranintranet,withoutpriorwrittenpermission.PermissioncanberequestedfromeitherISOattheaddressbeloworISO,smemberbodyinthecountryoftherequester.ISOcopyrightofficeCP401Ch.deBlandonnet8CH-1214Vernier,GenevaPhone:+41227490111Email:copyrightiso.orgWebsite:www.iso.orgPublishedinSwitzerlandContentsPageForewordvIntroductionvi1 Scope12 Normativereferences13 Termsanddefinitions14 Symbolsandabbreviatedterms15 Structureofthisdocument26 Motivation26.1 Preamble26.2 Audienceandsomeusercategories26.2.1 General.26.2.2 Cloudservicecustomer(CSC)36.2.3 Cloudserviceprovider(CSPl36.2.4 Cloudservicepartner(CSN)36.2.5 Regulatorsandpolicymakers36.3 Usagepatterns46.3.1 General.46.3.2 ExtractandclarifyanexistingmetricdescriptionfromanSLA46.3.3 Createandshareametricdescription.46.3.4 Comparemetricdescriptions46.3.5 Shareacommonfoundationforasetofmetrics56.3.6 Buildametricscatalogue56.4 Examplesofscenariosandrolesinvolvedinsharingmetricdefinitions57 Themetricmodelinpractice:templates67.1 Abriefreminderofthemetricmodel67.2 Atabularrepresentation.77.2.1 General.77.2.2 ThetabularrepresentationfortheMetricelement87.2.3 ThetabularrepresentationfortheExpressionelements97.2.4 ThetabularrepresentationfortheRuleelements.107.2.5 ThetabularrepresentationfortheParameterelements108 Anexampleofmetricdefinition:thecloudservicemeanresponsetimemetric118.1 Thecloudservicemeanresponsetimemetric:informalvariant118.1.1 ExtractingmetricelementsfromanSLAnarrative118.1.2 Usingthetabularrepresentation128.1.3 Overallstructureofthemetric138.2 Thecloudservicemeanresponsetimemetric:moreformalvariant148.2.1 Amoreformalvariantofthemetric148.2.2 Addingaparameter148.2.3 Themetricrules158.2.4 Themetricexpressions158.2.5 Overallstructureofthemetric168.2.6 Usingconstants179 Guidelinesforusingthemetricmodelwiththetabularrepresentation199.1 General199.2 Guideline1aboutdefiningexpressionandrulelanguages199.3 Guideline2aboutassociatingruleswithexpressions199.4 Guideline3aboutrelatingexpressionstoeachother209.5 Guideline4abouttheidentifiersofmetricelements209.6 Guideline5aboutrulesspecificallydesignedtosupportanexpression209.7 Guideline6abouttheroleofparameters219.8 Guideline7aboutrepresentingconstants2110 Thesimplecloudserviceavailabilitymetric2210.1 Measuringcloudserviceavailability2210.1.1 General2210.1.2 Overalldesignapproach2210.1.3 SLArulesandmetricrules2210.2 ThesimplecloudserviceavailabilitymetricvariantSimple_SAM_l2310.2.1 TheMetricelement2310.2.2 Themetricrules2410.2.3 Themetricexpressions2510.2.4 Themetricparameters2610.2.5 Overallstructureofthemetric2610.3 Thesimp