Specifications

Quality of Service Overview
May 09, 2011 Page 5 of 38
Figure 1 Assigning and Marking Traffic with a Priority
TheICMPprotocol,usedforerrormessaging,hasalowbandwidthrequirement,withahigh
tolerancefordelayandjitter,andisappropriateforalowprioritysetting.HTTPandFTP
protocols,usedrespectivelyforbrowser‐generatedandfiletransfertraffic,haveamediumtohigh
bandwidthrequirement,witha
mediumtohigh tolerancefordelayandjitter,andareappropriate
foramediumprioritylevel.Voice(VoIP),usedforvoicecalls,hasalowbandwidthrequirement,
butisverysensitivetodelayandjitterandisappropriateforahighprioritylevel.
SeeRFC1349forfurtherdetailsonToS.
SeeRFCs2474and2475forfurtherdetailsonDSCP.
Drop-Precedence
Drop‐Precedenceindicatesapreferencefordroppingpackets,oftenusedinassociationwith
weightedfairqueuing.ThisS‐Seriesonlyfeatureusestheconfiguredvaluetoprioritizepackets
onthequeue.Drop‐precedencecansetthepacketprioritytofavored,best‐effort,orunfavored.
Dropprecedencehasaspecialmeaningwithin
aFlex‐Edgecontext.Packetsassigneda
drop‐precedencevalueareassigneda4thlevelofpriorityintheFlex‐Edgemechanism,andare
limitedtorulesappliedtoasingleport.SeetheFlex‐EdgefeatureguideforadetailedFlex‐Edge
drop‐precedencediscussion.TheFlex‐Edgefeature
guidecanbefoundat
https://extranet.enterasys.com/downloads.
CoS Reference
UsetheCoSreferenceconfigurationifyouneedto:
•Mapatransmitqueuereferencetoanysupportedtransmitqueueontheport.
•MapaCoSsettingIRLorORLreferencetoanIRLorORLportresourceratelimiter.
TheCoSreferenceconfigurationissetbyspecifyingthetypeofhardwareresource
forthe
reference(TxQ,IRL,ORL),theportgroupthereferenceisbeingappliedto,andthehardware