Today’s model of networking primarily concentrates intelligence at the end hosts with the network itself offering a simple“best-effort”,“data agnostic ” communication medium. However, this paradigm has proven to be insufficient to meet todays needs co
Peer-to-Peeroverlaytoallowforkeylookupswillbeneededforthisoption.Inthisapproach,beforeaclientstartsa owthroughanetwork,itregistersitscontentmetadatawiththe rsthoprouterandgeneratesakey.ThiskeyiscarriedintheIPpacketsandisavailabletoanyintermediaryrouter.Atanypointalongthedata ow,thiskeycanbeusedbyintermediaryrouterstofetchthemetadatathroughanoutofbandmechanism.Theinformationconveyedinthemetadataisreallyleftuptotheapplication.Forexample,anMP3streammayhavethefollowingdescriptionwhichcanbeusedbytheexam-pleenterprisedescribedintheearliersectiontodeterminewhethertodropornot(inthiscase,thestreamisallowedtopasssinceitispartofof cialbusiness).
<?xmlversion="1.0"?><rdf:RDFxmlns:rdf=
"/1999/
02/22-rdf-syntax-ns#"
xmlns:mmschema=
"/mms#"><rdf:Descriptionrdf:about=
"/SalesReport.mp3">
<rdf:typerdf:resource=
"/mms#audio"/><mms:LengthInMin>5</mms:LengthInMin><mms:LengthInMB>4</<mms:LenghtInMB><mms:technicalType>
/mms#MP3</mms:technicalType><mms:semanticType>
/mms#Lecture</mms:semanticType></rdf:Description>
Asimilarframeworkisproposedin[22]specifyingameta-dataarchitectureforapolicybasedcontentdeliverynet-work.Here,theauthorsenvisionusingametadatagate-waycapableofextractingnetworkdeliveryrelatedmeta-datafromcontentmetadata.ThisdeliveryrelatedmetadataisusedtoimplementnetworkservicessuchasQoSandcon-tentcachingcontrol.Ourapproachisdifferentmainlyinthatweencodethecontentmetadataontothestreamsthem-selves(in-bandorout-of-band).Theintermediaryrouters(andnotjusttheedgeasin[22])cantheninferbasedonlocalknowledgebaseandcontext,whatpoliciesareapplica-bleandtakelocalaction.Thisallowsforon-demandcon-tentadaptationbasedontransientconditionsasopposedtoend-to-endadaptations.Furthermore,providingcontentin-formationsothataroutercandifferentiatebetween,forex-ample,videostreamingfromasurveillancecameraanda
7
streamingmovieallowsthenetworktomakesmartdeci-sionsonroutingdatastreamsacrosslinkswithdifferentre-liabilitycharacteristics.Also,forourarchitecture,weareusingRDFwhichprovidesagenericmechanismtoconveymetadatawhichcanbereasonedover.
4PreliminaryResults
Toinvestigatesomeofthepotentialbene tsthatcon-tentawarenesswithinthenetworkcanbring,wesimulatedacrosslayerapproachwheretheroutinglayerproactivelymaintainsalternateroutesthatcanbeusedimmediatelyuponfailureoftheprimaryroute.Weconsideredawire-lessnetworkrunningtheDSR[20]routingprotocoloverwhicha2000frameMPEG-4videoisstreamed.DSRisareactiveprotocolie.routesarediscoveredwhenneededbyanapplicationordatapacket.Dataisthentransmittedthroughsourceroutingandwhentheroutebreaks,thenodeupstreamfromthebreaksignalsarouteerrortothesourceandcanoptionallytrytosalvagethecurrentpacketthroughre-routing.Routesarediscoveredtoadestinationonde-mandbythesourcebybroadcastingarouterequestmes-sage.Onekeybene twithDSRisthefactthatasourcecan,inonerequest,potentiallyreceivemultiplerouteresponsesindicatingdifferentpathsthatcanbeusedforroutingdatafromsourcetodestination.DSRthenreliesonsourcerout-ingtotransferdata.Inourwork,weexploittheinher-entmultipathcapabilityofDSRbymaintainingalternateroutes.WeassumethattheapplicationmarkspacketsasIntracodedFrames(IFrames),Predictive-codedFrames(PFrames)orBidirectionally-interpolatedFrames(BFrames).The“marking”inoursimulationissimple;theapplicationinterfacetothetransportlayerhasbeenextendedtocarryalongwitheachsegmentofdata,agloballyknownidenti errepresentingtheframetype.OurextensiontoDSRutilizesthe“lessimportantdata”(BFramesinthiscase)astracerstocheckfortheviabilityofanalternateroute.Therationalhereisthatevenifwelosethisframe,theuserisnotgoingtoseeabigdropinthequalityofthereceivedsignalsincethesearethemostcompressedframes.WeusedNS2foroursimulationsandconsideredanareaof1000mx1000mwithvaryingnumberofnodesrangingfrom25to100withspeedsbetween0and20m/susingthe802.11MAC.ThetwoapproachescomparedwereregularDSRandourcon-tentawareenhancement.FortheregularDSR,theonlymodi cationmadewastoturnoff owstateanddisabledrouterequestsfromintermediarynodesforthepurposeofsalvaging.Withourenhancement,thesourcenodecontin-uestousetheprimarypathforbulkofthedatatransfer.Periodically,thesourcewillpickaBFrame(theapplica-tionspeci edmarkingisusedtodetectattheroutinglayer,whichframesareBFrames)toberoutedalongalternateroutesthatwereobtainedthroughtheinitial(andsnooped)