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Transpo rt Protocols in. Wireless Sensor Networks. Kevin Mendes Lakehead University. Topics to be Covered. Trans p ort Protocol O bjectives Draw b acks of TCP in W SNs Design Guid e li n es ( Performa n ce Metrics ) Cong e stion Control & its Causes Loss Recove r y.

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slide1

TransportProtocolsin

WirelessSensorNetworks

Kevin Mendes

Lakehead University

topics to be covered
Topics to be Covered
  • TransportProtocol Objectives
  • Drawbacksof TCPin WSNs
  • DesignGuidelines (PerformanceMetrics)
  • CongestionControl & its Causes
  • LossRecovery
trans p ort protocol o bjectives
TransportProtocol Objectives
  • Transportprotocolsare usedto:
    • Mitigatecongestion,
    • Reducepacketloss,
    • Providefairnessin bandwidthallocation,
    • Guaranteeend-to-endreliability.
  • Thetraditionaltransport protocols (i.e.,UDPandTCP) cannot be directlyimplementedfor WSNs
    • UDPdoesnotprovidedeliveryreliabilitythatisoftenneeded formanysensorapplications,
    • Nordoesitofferflow andcongestioncontrolthatcanlead to packetlossandunnecessaryenergyconsumption.
draw b acks of tcp in w sns
Drawbacksof TCPin WSNs
  • Overheadassociatedwith TCP connection
  • establishment
  • Flow andcongestioncontrol mechanismsinTCP
    • Resultin unfairbandwidthallocationanddatacollections.
    • TCPassumesthatpacketlossisduetocongestion
    • TCPhasadegradedthroughputin wirelesssystems
  • TCPrelieson end-to-endretransmission
    • Consumesmoreenergyandbandwidththanhop-by-hop
  • retransmission.
  • TCPguaranteessuccessfultransmissionof packets
    • Isnotalwaysnecessaryforevent-drivenapplicationsin
  • sensornetworks.
design guid e li n es
DesignGuidelines
  • In WSNsseveralnewfactors,canresultin congestion:
    • Convergentnature ofupstreamtraffic
    • Limited wirelessbandwidth
  • TworeasonsofpacketlossinWSNs:
    • Packet loss dueto congestioninintermediate nodes
    • Packet loss dueto bit-error rate(number of bit errors divided by the total number of transferred bits during a studied time interval)inwirelesschannel
  • TwomajorproblemsthatWSNtransport protocolsneedtocopewith:
    • Congestion
    • Packet loss.
performa n ce metrics
PerformanceMetrics
  • TransportprotocolsforWSNsshouldprovide:
    • End-to-endreliability
    • End-to-endQoS
  • Performancemetrics:
    • Energy efficiency,
    • Reliability,
    • QoS
      • Packet-lossratio,
      • Packet-delivery
      • Latency
    • Fairness.
slide7

PerformanceMetrics: EnergyEfficiency

  • Sensornodeshave limitedenergy.
  • Transportprotocolsshouldmaintainhighenergy efficiency
    • Tomaximizesystemlifetime.
  • Forloss-sensitiveapplications,
    • Packetlossleadstoretransmission
    • Inevitableconsumptionofadditional batterypower
  • Therefore,severalfactorsneedtobecarefully
  • considered,
    • Numberofpacketretransmissions,
    • Distance(e.g.,hop)foreachretransmission,
    • Overheadassociatedwithcontrolmessages.
slide8

PerformanceMetrics: Reliability

  • ReliabilityinWSNscanbeclassifiedintothe
  • following categories:
    • Packet reliability:
      • Applicationsareloss-sensitiveandrequiresuccessful transmissionofall packetsorata certainsuccessratio.
    • Event reliability:
      • Applicationsrequireonly successfuleventdetection,but
  • notsuccessfultransmissionofallpackets.
    • Destination-relatedreliability:
      • Messagesmightneedtobe deliveredtosensornodes:
        • Thatarein aspecificsubarea
        • Thatareequippedwithaparticularsensortype.
slide9

PerformanceMetrics: QoSMetrics

  • QoSmetricsinclude:
    • Bandwidth,
    • Latencyor delay,
    • Packet-loss ratio.
  • Dependingontheapplication,thesemetricsor theirvariantscouldbeused forWSNs.
    • TargettrackingApplication:
      • Generatehigh-speeddatastreams
      • Requirehigherbandwidth
    • Fora delay-sensitiveapplication:
      • Mayalsorequiretimelydeliverydata.
slide10

PerformanceMetrics: Fairness

  • What if Sensornodesarescatteredinageographical
  • Area?
  • Many-to-oneconvergentnatureofupstream
  • traffic:
    • Itis difficult forsensornodesthatare farawayfrom thesinkto transmitdata.
  • Transportprotocolsneedtoallocate
  • bandwidthfairlyamongallsensornodes
    • Sink can obtaina fairamount of data fromall the sensor nodes.
cong e stion control
CongestionControl

Closed-loopcontrol

feedback

Feedbackshouldbefrequent,butnottoomuchotherwisetherewillbeoscillations Cannotcontrolthebehaviorwith atimegranularitylessthanthefeedbackperiod

ef f ect of cong e stion
EffectofCongestion
  • Packetloss
  • Retransmission
  • Reducedthroughput
  • Congestioncollapsedue to
    • Unnecessarilyretransmittedpackets
    • Undeliveredorunusablepackets
con g estion control in the int e rnet
CongestionControlintheInternet

improving the efficiency of TCP/IP networks by reducing the number of packets that need to be sent over the network.

ActiveQueue Management(AQM)

TCPCongestionControl

causes for congestion in w s ns
CausesFor Congestion in WSNs
  • Duetothepacket-arrivalrateexceeding
  • thepacket-servicerate.
    • Thisismorelikelytooccuratsensornodes
  • closeto thesink
  • Link-levelperformanceaspectssuchas:
    • Contention,
    • Interference,
    • Bit-errorrate.
    • Thistypeof congestionoccursonthelink.
types of congestion in wsns
Typesof Congestionin WSNs
  • NodeLevel Congestion:
    • It isduetothepacket-arrival rateexceedingthepacket- servicerate.
    • Thisis morelikelytooccur at sensornodesclosetothe sink.
  • LinkLevel Congestion:
  • It aspects suchas contention,interference,and bit-errorrate.
ef f ects of cong e stion in w sns
EffectsofCongestion in WSNs
  • Energy:
    • Wastethelimitednodeenergy
  • ApplicationQoS:
    • Degrade reliabilityandapplicationQoS
  • Buffer overflow
    • Larger queuingdelays
    • Higherpacket loss.
  • Degrade linkutilization.
  • ItresultsintransmissioncollisionsifCSMA,is
  • used
    • increases packet-servicetime
    • wastes energy.
cong e stion control approac h es
CongestionControlApproaches
  • Therearetwogeneralapproachesto
  • controlcongestion:
    • Networkresourcemanagement:
      • triesto increasenetwork resource to mitigate congestion
    • Trafficcontrol:
      • impliesto control congestionthroughadjusting trafficrate atsource nodesor intermediates nodes
traffic control metho d s
TrafficControlMethods
  • End-to-end:
    • Can imposeexact rate adjustment at each source node
    • Simplify the designat intermediatenodes
    • Itresults inslowresponseandrelieshighlyonthe
  • round-triptime (RTT).
  • Hop-by-hop:
    • Ithas fasterresponse.
    • Difficultto adjust thepacket forwardingrate at intermediate nodes
      • BecausepacketforwardingrateisdependentonMAC
  • protocolandcouldbe variable.
cong e stion control parts
CongestionControlParts
  • Congestiondetection
    • Monitor buffer/queue size
    • Monitor channelbusy time, estimatechannel’sload
    • Monitor theinter-packet arrivaltime (data,ctrl)
  • Congestionnotification
    • Explicitcongestionnotificationinpacketheader,then broadcast (but then energy-consuming!)
  • RateAdjustment
    • Dynamic reportingrate dependingon congestionlevel
    • In-networkdatareductiontechniques(agressive
  • aggregation)oncongestion
cong e stion detection
CongestionDetection
  • In TCP:
    • Congestionis observedat theendnodesbasedon atimeoutor redundantAcknowledgments.
  • In WSNs:
    • Proactivemethods are preferred.
  • Congestion indicators:
    • Queuelength
    • Packet service time
    • Theratioof packet servicetimeover packet
  • interarrivaltime
cong e stion notification
CongestionNotification
  • Propagationofcongestioninformationfromthe
  • congested node
    • Totheupstreamsensornodes
    • Tothesourcenodesthatcontributetocongestion
  • Congestioninformation
    • CongestionNotification(CN)bit,
    • Ormoreinformationsuchasallowable datarate,orthe congestiondegree.
  • Disseminatingcongestioninformation:
    • Explicit
      • Usesspecialcontrol messagesto notifytheinvolvedsensor nodes of congestion
    • Implicit
      • Piggybackscongestioninformationin normaldata packets.
rate adjustment
RateAdjustment
  • Uponreceivingacongestion indication,a
  • sensornodecanadjustitstransmissionrate.
  • If a singleCNbitisused:
    • AdditiveIncreaseMultiplicativeDecrease(AIMD)
  • If additionalcongestion informationis available:
    • Accuraterate adjustmentcanbe implemented
loss recove r y
LossRecovery
  • Reasonsofpacket loss in wirelessenvironments:
    • Congestion
    • Biterror
    • nodefailure,
    • wrongoroutdatedroutinginformation,
    • Energydepletion.
  • How to overcomethisproblem:
    • Increasethesourcesendingrate
      • Workswellforguaranteeingevent reliability
      • Isnotenergyefficient
    • Introduceretransmission-basedlossrecovery.
      • Ismoreactiveandenergyefficient
      • Can be implementedat both thelinkand transportlayers.
        • Link-layerloss recoveryis hop-by-hop,whilethetransportlayer recoveryis usuallydoneend-to-end.
loss detection and notification
LossDetection andNotification
  • Acommonmechanismis toincludea sequencenumberineachpacket header.
  • Thecontinuityofsequencenumbers can beusedtodetectpacketloss.
  • Lossdetectionandnotificationcanbe:
    • End-to-end
    • Hop-by-hop.
en d to end ap p roaches
End-to-EndApproaches
  • End-points(destinationorsource)are
  • responsibleforlossdetectionandnotification.
  • Drawbacks
    • Isnotenergy efficient.
      • Thecontrolmessageswould utilize areturnpath consistingofseveralhops
    • Control messagestravelthroughmultiplehops
      • Couldbe lostwitha highprobabilityduetoeitherlinkerror orcongestion.
    • Leads toend-to-endretransmissionsfor loss
  • recovery.
ho p b y hop loss detection and notif i cation
Hop-by-hopLossDetectionand Notification
  • Intermediatenodesdetectandnotifypacket
  • loss.
  • Apairofneighboringnodesareresponsible
  • for lossdetection.
  • Is moreenergyefficient.
  • Twocategories:
    • Receiver-based
      • Receiverinferspacketlosswhenitobservesout-of- sequencepacketarrivals.
    • Senderbased
      • Senderdetectspacketlossoneitheratimer-basedor overhearingmechanism.
metho d s to notify the sender
MethodstoNotify theSender
  • Specialcontrolmessages:
    • ACK(Acknowledgment)
    • NACK(NegativeACK)
  • PiggybackingACKinthepacket header
    • IACK(ImplicitACK) usingoverhearing
      • Avoids control messageoverhead
      • Moreenergyefficient.
      • Sensor nodesmusthavethecapabilitytooverhearthephysical
  • channel.
      • Isnotfeasiblewhen:
        • Transmissionis corrupt
        • Channelisnotbidirectional
        • Sensornodesaccess thephysicalchannelusingTimeDivision MultipleAccess(TDMA)-basedprotocols
slide28

Retransmission-BasedLoss Recovery

  • End-to-end
    • The source performsretransmission.
  • Hop-byhop.
    • Anintermediatenodethat interceptsloss notification searchesitslocalbuffer.
    • Ifitfinds a copy of thelostpacket, it retransmits the packet.
    • Otherwiseitrelayslossinformation upstreamto
  • otherintermediatenodes.
comp a riso n s
Comparisons
  • End-to-end retransmission:
    • Thecachepointis thesourcenode.
    • Hasalongerretransmissiondistance
    • Allowsforapplication-dependentvariablereliabilitylevels
  • Hop-by-hopretransmission:
    • Thecachepointcouldbethepredecessornodeoftheloss point.
    • Ismoreenergy-efficient
    • Requiresintermediatenodestocachepackets.
    • Ispreferredif100percentpacketreliabilityis required
    • Cannotassuremessagedeliveryin thepresenceofnode
  • failure
issues relat e d to hop b y hop retransmission
IssuesRelated toHop-by-hop Retransmission
  • Immediateretransmission
    • Retransmissioncanbe triggeredimmediatelyuponthe detectionofa packetloss.
    • Resultsin shorterdelay
    • Ifpacketlossiscausedbycongestionitcouldaggravatethe
  • congestionsituationandcausemorepacketlosses.
  • Distributed TCP Cache(DTC)
    • Giventhelimited memoryin sensornodes,packetsmayonly
  • needtobecachedatselectednodes.
    • Howtodistributecachedpacketsamongasetofnodes?
    • Itbalancethebufferconstraintsandretransmissionefficiency byusingprobability-basedselectionforcachepoints.
design guidel i nes
DesignGuidelines
  • Severalfactorsmustbetaken into consideration:
    • Topology
    • Diversityofapplications
    • Trafficcharacteristics
    • Resourceconstraints
  • Transportprotocolscomponents
    • Congestioncontrol
    • Lossrecovery
  • Twoapproaches
    • Designseparateprotocolsoralgorithms,respectively,for congestioncontrolandlossrecovery.
    • Providescongestionandlosscontrolin an integratedway
    • Thejointuseofthesetwoprotocolsmayprovidethefull
  • functionalityrequiredbythetransportprotocolsforWSNs.
the existing transport protocols for wsns
TheExisting TransportProtocolsfor WSNS
  • ProtocolsforCongestionControl
    • CongestionDetectionandAvoidance(CODA)
    • Control andFairness (CCF)
    • PumpSlowlyFetch Quickly(PSFQ)
    • Priority-basedCongestionControlProtocol(PCCP)
    • Siphon
    • Adaptive Rate Control(ARC)
    • Trickle
  • ProtocolsforReliability
    • ReliableMulti-Segment Transport(RMST)
    • ReliableBurstyConvergecast(RBC)
    • Event-to-Sink ReliableTransport (ESRT)
    • GARUDA
  • ProtocolsforCongestionControlandReliability
    • Sensor TransmissionControlProtocol(STCP)
w s n con g estion con t rol prot o cols
WSNCongestionControlProtocols
  • CCF :
  • Packetservicetime
  • Implicit
  • Exact hop-by-hoprate adjustment
  • STCP:
    • Queuelength,
    • Implicitcongestionnotification,
    • AIMD-like end-to-endrate adjustment
  • Fusion:
    • Queuelength,
    • Implicitcongestionnotification,
    • Stop-and-starthop-by-hoprate
  • adjustment
  • CODA:
    • Queuelengthand channel status,
    • Explicitcongestionnotification,
    • AIMD-likeend-to-endrate
  • adjustment
  • PCCP:
  • Packetinterarrivaltime and packetservicetime,
  • Implicitcongestionnotification,
  • Exact hop-by-hoprate
  • adjustment
  • ARC:
  • Theevent if thepackets are successfully forwardedor not,
  • Implicitcongestionnotification,
  • AIMD-like hop-by-hoprate adjustment
references
References

A Survey of Transport Protocols for

Wireless Sensor Networks: Chong gang Wang and KazemSohraby, University of Arkansas

Link:http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=01637930

thank you
Thank You
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