Specifications

Flex-Edge Overview
December 02, 2010 Page 2 of 5
Flex-Edge Overview
AllS‐SeriesswitchessupporttheFlex‐Edgefeature,whichprovidesauniquemechanismforthe
classificationoftrafficasitenterstheswitch.
Figure 1onpage 2providesahighlevelviewofFlex‐Edgeprocessing.TheadvancedMACchip
appliespacketclassificationandbandwidthcontroltotheingressingpackets.If
required,the
MACchipsendsaMACpausedownstreamtotemporarilystopthetrafficcomingattheport.
Packetsclassifiedwiththehighestpriorityareforwardedtothepacketprocessorbeforepackets
withalowerpriority.Packetbufferingprovidesreliefforcongestionattheegress.Ifpacketsmust
bedropped,
lowestprioritypacketsaredroppedinthepacketbufferbaseduponQoS
configuration.Finally,packetsegressthedevicebaseduponpacketscheduling.
Figure 1 Flex-Edge Processing
TheFlex‐Edgefeatureassignsoneoffourtrafficcategoriestoeachpacketasitenterstheswitch.
Flex‐Edge,usingtheMA Cchipcapabilityontheswitch,
queueseachoffourtrafficcategoriesinto
itsownprioritizedqueue.Eachqueuewillnotpassanytrafficontothepacketprocessoruntilall
higherpriorityqueuesareempty.
Ifflowcontrolisenabledontheport,eithermanuallyorusingauto‐negotiation,Flex‐Edgeapplies
backpressuretofrontand
aggregatorportstoavoiddiscard.TheMACcapabilitymonitorstraffic
onallports,bycategoryandpriority,andmakesintelligentdecisionsconcerningwhichfront
panelportstoinitiateflowcontrolon,bysendingaMACPAUSEframetothesending deviceout
theportcausingthecongestion.
Note: The Flex-Edge feature and the port priority (IEEE 802.1D) configuration are functionally
separate and have no affect on each other.