Radwin 2000 - Page 289

RADWIN2000UserManual Release2.8.30 16‐3
RADWINEthernetRing
ThestepsbelowfollowthenumberinginFigure16‐1:
1. Normaloperation
Ethernettrafficrunsinthering , butdoesnotpassthroughtheRPL,whichisblocked.The
RPLdoeshowever,broadcastRPMpacketsthroughthering.
2. RingLinkdown,RPLnotified
TheRPLdetectsalink‐downconditionbythenon‐arrivalofanRPMpacket.Itremains
blockedfortheMinimumtimeforfailuredetectionwhichisconfigurableusingtheRAD‐
WINManager(seepage16‐11).
3. RingLinkdown,RPLunblockedfortraffic
TheRPLunblocksforEthernettrafficaftertheMinimumtimeforfailuredetectionexpires
andnoRPMmessagehasbeenreceived.
4. RingLinkrestoredbutstillblockedfortraffic
TheRingLinkisrestored,butremainsblockedfortheMinimumtimeforrecovery,set
usingtheRADWINManager,toavoidrapidfluctuationsleadingtopotentialshortterm
loops(seepage16‐11).
5. RingLinkrestored,RPLblockedfortraffic
TheRPLblockstoEthernettrafficaftertheMinimumtimeforrecoveryexpiresand
restoresEthernettraffictothe RingLink(withaspecialRPMpacket).
6. Returnto1.)RingLinkrestored,RPLblockedfortraffic
Theringisbacktonormaloperation.
WithRADWINlinks,RADWIN’sRingProtectionsolutionpreventsEthernetloopsintheringat
alltimes.Theringisalwaysbrokensomewhere.
• UnderaringconfigurationaRADWINRingLinkthatwasdownandcommencesrecov‐
ery,keepsblockingEthernettraffic.TheRPLidentifiesthissituation,blocksitselfand
thenunblockstheotherRingLink.Thisisthetransitionfromstep4to5inFigure16‐1.
• IfthefailedhopisnotaRADWIN linkthentherearetwopossibi lities:
• IfthehopRingLinkcansignalthatitisdownbyissuingaLossofSignal(LOS)atthe
Ethernetport,thentheRPLwillcontroltheRADWINlinkconnectedtothatportin
thesamemannerasdescribedabove,topreventanEthernetloop.
• Otherwise,theremaybeashortloopperiodwhentheRPLisstillopenfortrafficand
theRingLinkisalsounblockedduringtheMinimumtimeforrecovery.