Understanding QoS Configuration on the Matrix N-Series
February 22, 2008 Page 9 of 29
discardingtrafficimposedbyratelimiting,delaysareinducedintoitstransmissionbyretaining
thedataforfuturetransmission.However,thedelaysmustalsobeboundedtothedegreethatthe
trafficissensitivetodelays.
Understanding QoS Configuration on the Matrix N-Series
ThissectiondiscussesthesixcomponentsforconfiguringQoSanddisplayingQoSstatusonan
N‐Seriesswitchrouter:
CoSPort‐Type:Determinesthetransmitqueue(TxQ)andInboundRateLimiting(IRL)resource
capabilitiesoftheportsinyoursystem.Knowledgeofthesecapabilitiesisimportantwhen
configuringqueuebehaviors.Portgroupmembershipandtheportresourcesavailableare
determinedbyporttype.
CoSPortGroups:Provideforthegroupingofportsbythesameclassofservicefeaturesandport
type.
CoSPortResourceTable:Enablestheassociationofratelimiterandrateshapervaluestoaport.
CoSReferenceMappingTable:MapsyourdefinedTxQandIRLindexreferences,usedbythe
CoSsettingstable,tothephysicalqueueandratelimitersettingscreatedintheport‐resource
table.
CoSSettingsTable:UsedforCoSparameterassignmentandcontainsthecurrentsettingsforeach
classofservicefeature.Eachclassofserviceentryconsistsofanentryindex,an802.1ppriority,an
optionalToSvalue,atransmitqueuereference,andanoptionalIRLreference.
CoSState:AglobalsettingthatmustbeenabledforaconfiguredCoStoaffectportbehavior.
Whenenabled,CoSstateassociatedwithaportsupersedescurrentdefaultormodifiedport‐level
controlsforpriorityqueuemapping,portratelimiting,andtransmitqueue.Whendisabledthe
portsettingsapply.
NumerousQoSvaluesareassociatedwitheachotherthroughreference.Withtheexceptionof
802.1ppriorityandToS,CoSvaluesarefirstmappedtoaportgroup,whichassociatesaCoS
configurationwithaporttype.AportgrouphasthefollowingCoSparametersassociatedwithit:
•Physicalport(s)
•Strictorweightedfairqueuingbehavior
• Rate‐limitsetting(s)
• Rate‐shapingsetting(s)
•Aportqueue
•Aportreference
UnderstandinghowtheseparametersarefirstmappedtotheportgroupandthentoaTxQorIRL
referenceisthekeytounderstandingQoSconfiguration.Whereappropriate,thetaskcolumnin
Procedure 1onpage 21identifiesthesemappingrelationships.
See“DeterminingCoSPort‐Type”onpage 10and“ConfiguringCoSPortGroups”onpage 11for
aportgroupdiscussion.
Note: It is recommended that you use Enterasys NetSight Policy Manager as an alternative to CLI
for configuring policy-based CoS on the Enterasys Matrix Series devices.
A policy discussion is outside the scope of this document and will be limited to the relevant
configuration example commands.
