點對點網路(Peer-to-Peer)之穩定性常被高度動態變化所影響，網路內的點高頻率的進出使得建立此分散式系統遭受挑戰。具體上來說，在大型的覆蓋性網路常發生訊息的遺失或延遲，如此對網路的信賴度將大受影響。目前存在之解決方法大多依靠冗餘的訊息來減少遺失或延遲，而卻造成大量頻寬的花費。
我們提出一個模型來分析並改進轉發反饋協議(Forward Feedback Protocol)，轉發反饋協議其傳輸訊息使用單一路徑且可以在傳輸路徑上偵測是否有點是故障或延遲。當完成一次服務傳輸(lookup)，反饋值將會被依照此次路徑再次傳輸以更新每個點之反饋值，如此一來，每個點可以獨立地學習並避免再次走到故障之點，降低下一次傳輸服務的錯誤率。經由此協議，網路上之所有點可以自組織地形成穩定狀態的網路，並適時地改變傳輸路徑。
我們將此協議放入Chord演算法當中並加以評估。並由實驗結果得知，其頻寬利用度比現今存在方法之利用冗餘訊息少約二到四倍，儘管頻寬利用度的減少可能導致容錯能力下降，但使用此協議下卻可高於25%的成功率。此協議是富有可擴充性且適用於其他遞迴式之路由網路。

herobustnessofPeer-to-Peersystemsischallengedbyitshighlydynamicnature.Highfre-quentpeerfailureanddepartureeventscauseuncertaintyforwhichisconsideredexceptionalintraditionaldistributedsystems.Specically,insucientlylargeheterogeneousoverlaysmessagelossanddelaysarelikelytooccur.Thishasaseriouslyimpactonoverlayrouting,especiallyonlongerpaths.Mostoftheexistingsolutionstothisproblemrelyonmessageredundancytodecreasethelossanddelays.Thisincursalargebandwidthcost.WeproposeamodeltoestimateandimprovetheForwardFeedbackProtocol(FFP).FFPusessinglepathtoroutemessageanddetectsthemessagelossandexcessivedelayswhilerouting.Afterpeersendsaservice,theoutcomeissignalledalongtheroutingpath.Basedonlyonthebinary(positiveandnegative)signals,eachoverlaypeerlocallyandindependentlylearnstoroutetoavoidfailures.Whentheoutcomeoflookupisfailure,theacknowledgementoffeedbackhelpspeertocheckthepositionofthefailedpeerthenbroadcastsawarninginformationtopeerswhicharoundthefailedpeerandavoidstomeetitinfuture.Thelocalpeerinteractionsleadtotheemergenceoffastreliableoverlayroutes.Thisisacontinuousprocess,thesystemconstantlyself-organizesinresponsetochangingdelayandlossconditions.WeevaluatetheprotocolandsimulateinChordPeer-to-Peersystem.Thebandwidthisused2-4timeslessinoursystemthantheexistingoverlayroutingapproachesthatdependentonhighmessageredundancyforfault-tolerance.Despitethelessbandwidthmighttocause owreliability,FFPachievesuptoa25%higherdeliverysuccessrateincomparisontotheexistingsolutions.TheprotocolisscalablewithlocalstatesizeofO(log2N)intermsoftheoverlaynetworksizeandisuniversallyapplicabletoallrecursivelyroutingoverlays.

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