1、PDISO/IECTR23951:2025BSIStandardsPublicationInformationtechnologyCloudcomputing一Bestpracticesforusingthecloudservicelevelagreement(SLA)metricmodelbsi.NationalforewordThisPublishedDocumentistheUKimplementationofISO/IECTR23951:2025.ItsupersedesPDISO/IECTR23951:2020,whichiswithdrawn.TheUKparticipationi
2、nitspreparationwasentrustedtoTechnicalCommitteeIST38,CloudComputingandDistributedPlatforms.Alistoforganizationsrepresentedonthiscommitteecanbeobtainedonrequesttoitscommitteemanager.ContractualandlegalconsiderationsThispublicationhasbeenpreparedingoodfaith,howevernorepresentation,warranty,assuranceor
3、undertaking(expressorimplied)isorwillbemade,andnoresponsibilityorliabilityisorwillbeacceptedbyBSIinrelationtotheadequacy,accuracy,completenessorreasonablenessofthispublication.Allandanysuchresponsibilityandliabilityisexpresslydisclaimedtothefullextentpermittedbythelaw.Thispublicationisprovidedasis,a
4、ndistobeusedattherecipientsownrisk.Therecipientisadvisedtoconsiderseekingprofessionalguidancewithrespecttoitsuseofthispublication.Thispublicationisnotintendedtoconstituteacontract.Usersareresponsibleforitscorrectapplication.ThispublicationisnottoberegardedasaBritishStandard.TheBritishStandardsInstit
5、ution2025PublishedbyBSIStandardsLimited2025ISBN9780539335460ICS35.210CompliancewithaPublishedDocumentcannotconferimmunityfromlegalobligations.ThisPublishedDocumentwaspublishedundertheauthorityoftheStandardsPolicyandStrategyCommitteeon30April2025.Amendments/corrigendaissuedsincepublicationDateTextaff
6、ectedPDISO/IECTR23951:2025TechnicalReportISO/IECTR23951Secondedition2025-04InformationtechnologyCloudcomputingBestpracticesforusingthecloudservicelevelagreement(SLA)metricmodelTechnologiesde!informationInformatiqueennuageBonnespratiquespour!utilisationdumodelemetriquedaccorddeniveaudeservice(SLA)dan
7、sIeCloudReferencenumberISO/IECTR23951:2025(en)COPYRIGHTPROTECTEDDOCUMENTISO/IEC2025Allrightsreserved.Unlessotherwisespecified,orrequiredinthecontextofitsimplementation,nopartofthispublicationmaybereproducedorutilizedotherwiseinanyformorbyanymeans,electronicormechanical,includingphotocopying,orpostin
8、gontheinternetoranintranet,withoutpriorwrittenpermission.PermissioncanberequestedfromeitherISOattheaddressbeloworISO,smemberbodyinthecountryoftherequester.ISOcopyrightofficeCP401Ch.deBlandonnet8CH-1214Vernier,GenevaPhone:+41227490111Email:copyrightiso.orgWebsite:www.iso.orgPublishedinSwitzerlandCont
9、entsPageForewordvIntroductionvi1 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 Cloudservicepartn
10、er(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 Examplesofscenari
11、osandrolesinvolvedinsharingmetricdefinitions57 Themetricmodelinpractice:templates67.1 Abriefreminderofthemetricmodel67.2 Atabularrepresentation.77.2.1 General.77.2.2 ThetabularrepresentationfortheMetricelement87.2.3 ThetabularrepresentationfortheExpressionelements97.2.4 Thetabularrepresentationforth
12、eRuleelements.107.2.5 ThetabularrepresentationfortheParameterelements108 Anexampleofmetricdefinition:thecloudservicemeanresponsetimemetric118.1 Thecloudservicemeanresponsetimemetric:informalvariant118.1.1 ExtractingmetricelementsfromanSLAnarrative118.1.2 Usingthetabularrepresentation128.1.3 Overalls
13、tructureofthemetric138.2 Thecloudservicemeanresponsetimemetric:moreformalvariant148.2.1 Amoreformalvariantofthemetric148.2.2 Addingaparameter148.2.3 Themetricrules158.2.4 Themetricexpressions158.2.5 Overallstructureofthemetric168.2.6 Usingconstants179 Guidelinesforusingthemetricmodelwiththetabularre
14、presentation199.1 General199.2 Guideline1aboutdefiningexpressionandrulelanguages199.3 Guideline2aboutassociatingruleswithexpressions199.4 Guideline3aboutrelatingexpressionstoeachother209.5 Guideline4abouttheidentifiersofmetricelements209.6 Guideline5aboutrulesspecificallydesignedtosupportanexpressio
15、n209.7 Guideline6abouttheroleofparameters219.8 Guideline7aboutrepresentingconstants2110 Thesimplecloudserviceavailabilitymetric2210.1 Measuringcloudserviceavailability2210.1.1 General2210.1.2 Overalldesignapproach2210.1.3 SLArulesandmetricrules2210.2 ThesimplecloudserviceavailabilitymetricvariantSim
16、ple_SAM_l2310.2.1 TheMetricelement2310.2.2 Themetricrules2410.2.3 Themetricexpressions2510.2.4 Themetricparameters2610.2.5 Overallstructureofthemetric2610.3 ThesimplecloudserviceavailabilitymetricvariantSimple_SAM_22710.3.1 Differencesinmetricdesignandassumptions2710.3.2 TheMetricelement2810.3.3 The
17、metricrules2810.3.4 Themetricparameters2910.3.5 Themetricexpressions3010.3.6 Overallstructureofthemetric3110.3.7 AnalternativemetricdesignusingtheConfigurationelementoption32Bibliography33ForewordISO(theInternationalOrganizationforStandardization)andIEC(theInternationalElectrotechnicalCommission)for
18、mthespecializedsystemforworldwidestandardization.NationalbodiesthataremembersofISOorIECparticipateinthedevelopmentofInternationalStandardsthroughtechnicalcommitteesestablishedbytherespectiveorganizationtodealwithparticularfieldsoftechnicalactivity.ISOandIECtechnicalcommitteescollaborateinfieldsofmut
19、ualinterest.Otherinternationalorganizations,governmentalandnon-governmental,inliaisonwithISOandIEC,alsotakepartinthework.TheproceduresusedtodevelopthisdocumentandthoseintendedforitsfurthermaintenancearedescribedintheISO/IECDirectives,Part1.Inparticular,thedifferentapprovalcriterianeededforthediffere
20、nttypesofdocumentshouldbenoted.ThisdocumentwasdraftedinaccordancewiththeeditorialrulesoftheISO/IECDirectives,Part2(seeWWW.iso.org/directivesorwww.iec.ch/membersexpvrtsrefdocs).ISOandIECdrawattentiontothepossibilitythattheimplementationofthisdocumentmayinvolvetheuseof（八）patent(三),ISOandIECtakenoposit
21、ionconcerningtheevidence,validityorapplicabilityofanyclaimedpatentrightsinrespectthereof.Asofthedateofpublicationofthisdocument,ISOandIEChadnotreceivednoticeof（八）patent(三)whichmayberequiredtoimplementthisdocument.However,implementersarecautionedthatthismaynotrepresentthelatestinformation,whichmaybeo
22、btainedfromthepatentdatabaseavailableatWWW.isoQrg/PatentSandhttps:/PatentS.iec.ch.ISOandIECshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.Anytradenameusedinthisdocumentisinformationgivenfortheconvenienceofusersanddoesnotconstituteanendorsement.Foranexplanationofthevoluntarynatureofs
23、tandards,themeaningofISOspecifictermsandexpressionsrelatedtoconformityassessment,aswellasinformationaboutISOsadherencetotheWorldTradeOrganization(WTO)principlesintheTechnicalBarrierstoTrade(TBT)seeWWW.iso.org/iso/foreword.html.IntheEC,seeWWW.iec.ch/UnderStanding-standards.ThisdocumentwaspreparedbyJo
24、intTechnicalCommitteeISO/IECJTC1,Informationtechnology,SubcommitteeSC38,Cloudcomputinganddistributedplatforms.Thissecondeditioncancelsandreplacesthefirstedition(ISO/IECTR23951:2020),whichhasbeentechnicallyrevised.Themainchangesareasfollows:alignmentwithISO/IEC22123;referencestoISO/IEC17788andISO/IEC
25、17789havebeenchangedtoISO/IEC22123.Anyfeedbackorquestionsonthisdocumentshouldbedirectedtotheusersnationalstandardsbody.AcompletelistingofthesebodiescanbefoundatWWW.iso.org/members.htmlandwww.iec.ch/national-committees.IntroductionInmostcases,cloudserviceproviders(CSPs)andcloudservicecustomers(CSCS)n
26、egotiateservicelevelagreements(SLAs)whichincludeservicelevelobjectives(SLOs)andservicequalitativeobjectives(SQOs)forwhichCSPsmakecommitments.ThecommitmentsdescribedinSLAsareexpectedtobemeasuredagainstactualperformanceoftheservicetoensurecompliancewiththeSLA.Howactualperformancecomparesagainstcommitm
27、entsinSLAsisexplainedinISO/IEC19086-2.CloudSLAsarecoveredinISO/IEC19086-1andinISO/IEC19086-4.ThemetricmodelinISO/IEC19086-2establishescommonterminology,definesamodelforspecifyingmetricsforcloudSLAs,andincludesapplicationsofthemodelwithexamples.Thisdocumentprovidesguidanceandexamplesonusingthemetricm
28、odeltocomposethecalculationofacloudserviceperformancemeasureinordertocompareagainstanSLAcommitment.AfewexamplesfromtheSLOslistedinISO/IEC19086-1:2016,Clause10aregiveninthedocument,suchasCloudServiceMeanResponseTimeandSimpleCloudServiceAvailability.Asspecific,measurablecharacteristicsofacloudservice,
29、SLOsarethebasisfordefiningthemetricsusedtoevaluateandcompareagreementsbetweenparties.InClauses8,9and10ofthisdocument,abasicexplanationoftheseexamplesisprovidedusingapracticalmethodbasedonatabularformatthatisarefinementoftheinformativetablesprovidedinISO/IEC19086-2:2018,AnnexB.Thetabularrepresentatio
30、ndescribedinthisdocumentservesastemplatesfordesigningmetrics.Guidanceinusingthemetricmodelwiththesetemplatesisprovidedwhiledevelopingmetricexamples.InformationtechnologyCloudcomputingBestpracticesforusingthecloudservicelevelagreement(SLA)metricmodel1 ScopeThisdocumentprovidesbestpracticesforusingthe
31、ISO/IEC19086-2metricmodel,illustratedwithexamples.2 NormativereferencesThefollowingdocumentsarereferredtointhetextinsuchawaythatsomeoralloftheircontentconstitutesrequirementsofthisdocument.Fordatedreferences,onlytheeditioncitedapplies.Forundatedreferences,thelatesteditionofthereferenceddocument(incl
32、udinganyamendments)applies.ISO/IEC22123-1,InformationtechnologyCloudcomputingPart1:VocabularyISO/IEC19086-LInformationtechnologyCloudcomputingServicelevelagreement(SLA)frameworkPart1:OverviewandconceptsISO/IEC19086-2,CloudcomputingServicelevelagreement(SLA)frameworkPart2:Metricmodel3 Termsanddefinit
33、ionsForthepurposesofthisdocument,thetermsanddefinitionsgiveninISO/IEC22123-1,ISO/IEC19086-1and,ISO/IEC19086-2apply.ISOandIECmaintainterminologydatabasesforuseinstandardizationatthefollowingaddresses: ISOOnlinebrowsingplatform:availableathttps:/www.iso.org/ObP IECElectropedia:availableathttps:WWW.ele
34、ctropedia.org/4 SymbolsandabbreviatedtermsCCRAcloudcomputingreferencearchitectureCSCcloudservicecustomerCSNcloudservicepartnerCSPcloudserviceproviderSLAservicelevelagreementSLOservicelevelobjectiveSQOservicequalityobjective5 StructureofthisdocumentInsupportingthescopepresentedinClause1,thisdocumentd
35、evelopstherationaleforapracticalmetricrepresentationtocomplementthemetricmodelinISO/IEC19086-2inthefollowingclauses:ClaUSe6statestherationaleforcomplementingthemetricmodelasdefinedinISO/IEC19086-2withapracticalrepresentationandforprovidingrelatedusageguidanceasintroducedbythisdocument.Itidentifiesso
36、meusagepatternsandhighlightssomeusagescenarioswheremetricdefinitionsaresharedacrossvariousparties.TheuserswhobenefitfromthisdocumentincludepartieswithrolesdefinedinISO/IEC22123-3(CloudcomputingReferencearchitecture). ClaUSe7introducesthetabularmetricrepresentationsupportiveofthemetricmodelandderived
37、fromtheinformativetableslistedinISO/IEC19086-2:2018,AnnexB.Thisrepresentationisbasedontablesintendedtoserveastemplatesformetricdefinitions.Thisclauserepresentsinitialguidanceinusingthemetricmodel,whichisthenillustratedanddiscussedthroughouttheexamplesdevelopedlaterinthedocument. ClaUSe8introducesasi
38、mplecaseofmetricdefinitionthatillustratestheuseofthetabletemplatesintroducedinCIaUSe7.ThisexamplestartswiththedescriptionofametricasitwouldappearinthenarrativeofanexistingSLAandillustratestheextractionofthisdescriptiontowardamorestructuredanddistinctrepresentationusingtheproposedtabularrepresentatio
39、n.Theexampleshowspracticalaspectswhendesigninganddevelopingmetrics,suchashowmetricrulesrelatetoexpressions,andhowtoparameterizerulesandexpressions. ClaUSe9isasetofguidelinesonhowtousethemetricmodelwiththetabulartemplates(Clause7).Thisguidanceismotivatedandillustratedbytheexamplesthroughoutthedocumen
40、t.Theseguidelinesarebestunderstoodafterdevelopingapreliminaryexample(Clause8).Theyexplainhowtousethemetricmodelwiththetabulartemplatesformetricusecasesposingsimilarchallengesorusingsimilarfeatures. ClaUSe10developsamoreelaboratemetricexampleforcloudserviceavailability.Itdescribestwovariantsofthesame
41、metricthatillustratetwodifferentapproachesinusingthemetricmodelelements.SinceitcomesaftertheguidelineitemslistedinClaUSe9,itiseasiertorelatethedevelopmentofthissecondexampletotheseguidelines.6 Motivation6.1 PreambleThisclausefirstidentifiestheaudienceofthisdocumentandforthetabularmetricrepresentatio
42、ndescribedinthisdocument.Thisclausethendescribessomemetricusagepatternsandthenidentifiesscenariosandrolesforthesemetricusagepatterns.Sharingcommonguidelinesandconventionsinusingthemetricmodelimprovestheabilitytoreuseandcomparemetrics.Thesecommonguidelinesextendtotheaspectsofametricthatarepartoftheme
43、tricmodelbutthedetailsofwhichareoutofscopeofthemetricmodelinISO/IEC19086-2,suchastheuseofruleandexpressionlanguagesandhowtheseconstructsrelatetoeachother.Supportiveofthegoalofharmonizingtheusageofthemetricmodelacrossusers,thisdocumentproposesatabularrepresentationformetricdefinitionsthatisderivedfro
44、mandaugmentsthetablesprovidedinAnnexBofthemetricmodelinISO/IEC19086-2:2018,asexplainedin7.2.2.6.2 Audienceandsomeusercategories6.2.1 GeneralTheaudienceforthisdocumentisexpectedtobediverse,asthemetricrepresentationproposedinthisdocumentisintendedfordifferentpartiesinvolvedinprovidingorusingcloudservi
45、ces.Howevernoteveryclauseisofinteresttoall.Thosewhoread,negotiateorcreateSLAcontent,suchasbusinessusersandadministrators,areexpectedtobeinterestedinClaUSnStto7andintheinitialapproachtothefirstmetricexample(see8.1).Inadditiontotheseclauses,metricdesignersanddevelopersareexpectedtobeinterestedintherem
46、ainingclausesincludingmoreelaborateexamplesofmetrics(startingfrom82andbeyond).ThepartiesinterestedinthisdocumentincluderepresentativesofthefollowingrolesdefinedinISO/IEC22123-2.6.2.2 Cloudservicecustomer(CSC)ThisdocumenthelpstheCSCtounderstandthemetricsusedforservicequalityandotherassurancesdescribe
47、dinSLAs.WhenblendedintothenarrativeoftheSLAmetricsareoftenambiguousorincomplete.Astructureddefinitionasdescribedinthemetricmodelandmadepracticalwithatabularrepresentationhelpstoavoidoratleastdetectsuchissues.Specifictypesofcustomersareinterestedinunderstandinghowaserviceismeasuredwithouthavingtoread
48、theentireSLAorpriortoestablishinganSLA.ThesecustomersaredefinedintheCCRAasacloudserviceusers(whousesacloudservicetofulfilher/hisrole),aserviceadministrator(whooverseesalltheoperationalprocessesrelatingtotheuseofcloudservices,servingasintermediarybetweentheuserandtheprovider)andabusinessmanager(whohasoverallresponsibilityforthebusinessaspectsofusingcloudservices,includingthepurchaseoftheserviceu
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