6LoWPAN-教程

©ArchRockCorporation6LoWPANTutorialIPonIEEE802.15.4Low-PowerWirelessNetworks6LoWPANTutorialIPonIEEE802.15.4Low-PowerWirelessNetworksDavidE.CullerJonathanHuiDavidE.CullerJonathanHui2©ArchRockCorporationIEEE802.15.4–TheNewIPLink•–Pleaserefertotheinternetdraft/RFCsfordefinitivereference•1%of802.11power,easiertoembed,aseasytouse.3©ArchRockCorporationTHEQuestionIfWirelessSensorNetworksrepresentafutureof“billionsofinformationdevicesembeddedinthephysicalworld,”whydon’ttheyrunTHEstandardinternetworkingprotocol?4©ArchRockCorporationTheAnswerTheyshould•Substantiallyadvancesthestate-of-the-artinbothdomains.•ImplementingIPrequirestacklingthegeneralcase,notjustaspecificoperationalslice–InteroperabilitywithallotherpotentialIPnetworklinks–PotentialtonameandroutetoanyIP-enableddevicewithinsecuritydomain–Robustoperationdespiteexternalfactors•Coexistence,interference,errantdevices,...•Whilemeetingthecriticalembeddedwirelessrequirements–Highreliabilityandadaptability–Longlifetimeonlimitedenergy–Manageabilityofmanydevices–Withinhighlyconstrainedresources5©ArchRockCorporationManyAdvantagesofIP•Extensiveinteroperability–Otherwirelessembedded802.15.4networkdevices–DevicesonanyotherIPnetworklink(WiFi,Ethernet,GPRS,Seriallines,…)•Establishedsecurity–Authentication,accesscontrol,andfirewallmechanisms–Networkdesignandpolicydeterminesaccess,notthetechnology•Establishednaming,addressing,translation,lookup,discovery•Establishedproxyarchitecturesforhigher-levelservices–NAT,loadbalancing,caching,mobility•Establishedapplicationleveldatamodelandservices–HTTP/HTML/XML/SOAP/REST,Applicationprofiles•Establishednetworkmanagementtools–Ping,Traceroute,SNMP,…OpenView,NetManager,Ganglia,…•Transportprotocols–End-to-endreliabilityinadditiontolinkreliability•Most“industrial”(wiredandwireless)standardssupportanIPoption6©ArchRockCorporationLeverageexistingstandards,ratherthan“reinventingthewheel”•RFC768UDP-UserDatagramProtocol[1980]•RFC791IPv4–InternetProtocol[1981]•RFC792ICMPv4–InternetControlMessageProtocol[1981]•RFC793TCP–TransmissionControlProtocol[1981]•RFC862EchoProtocol[1983]•RFC1101DNSEncodingofNetworkNamesandOtherTypes[1989]•RFC1191IPv4PathMTUDiscovery[1990]•RFC1981IPv6PathMTUDiscovery[1996]•RFC2131DHCPv4-DynamicHostConfigurationProtocol[1997]•RFC2375IPv6MulticastAddressAssignments[1998]•RFC2460IPv6[1998]•RFC2463ICMPv6-InternetControlMessageProtocolforIPv6[1998]•RFC2765StatelessIP/ICMPTranslationAlgorithm(SIIT)[2000]•RFC3068AnAnycastPrefixfor6to4RelayRouters[2001]•RFC3307AllocationGuidelinesforIPv6MulticastAddresses[2002]•RFC3315DHCPv6-DynamicHostConfigurationProtocolforIPv6[2003]•RFC3484DefaultAddressSelectionforIPv6[2003]•RFC3587IPv6GlobalUnicastAddressFormat[2003]•RFC3819AdviceforInternetSubnetworkDesigners[2004]•RFC4007IPv6ScopedAddressArchitecture[2005]•RFC4193UniqueLocalIPv6UnicastAddresses[2005]•RFC4291IPv6AddressingArchitecture[2006]•ProposedStandard-TransmissionofIPv6PacketsoverIEEE802.15.4Networks7©ArchRockCorporationKeyFactorsforIPover802.15.4•Header–StandardIPv6headeris40bytes[RFC2460]–Entire802.15.4MTUis127bytes[IEEE]–Oftendatapayloadissmall•Fragmentation–Interoperabilitymeansthatapplicationsneednotknowtheconstraintsofphysicallinksthatmightcarrytheirpackets–IPpacketsmaybelarge,comparedto802.15.4maxframesize–IPv6requiresalllinkssupport1280bytepackets[RFC2460]•Allowlink-layermeshroutingunderIPtopology–802.15.4subnetsmayutilizemultipleradiohopsperIPhop–SimilartoLANswitchingwithinIProutingdomaininEthernet•AllowIProutingoverameshof802.15.4nodes–Optionsandcapabilitiesalreadywell-defines–Variousprotocolstoestablishroutingtables•Energycalculationsand6LoWPANimpact8©ArchRockCorporationIEEE802.15.4FrameFormat•LowBandwidth(250kbps),lowpower(1mW)radio•Moderatelyspreadspectrum(QPSK)providesrobustness•SimpleMACallowsforgeneraluse–ManyTinyOS-basedprotocols(MintRoute,LQI,BVR,…),TinyAODV,Zigbee,SP100.11,WirelessHART,…–6LoWPAN=IP•Choiceamongmanysemiconductorsuppliers•SmallPacketstokeeppacketerrorratelowandpermitmediasharingpreambleSFDLenFCFDSNDst16Src16DpanDstEUID64SpanSrcEUID64FchkNetworkHeaderApplicationDataMax127bytes9©ArchRockCorporationRFC3189–AdviceforInternetSub-NetworkDesigners•Totalend-to-endinteractiveresponsetimeshouldnotexceedhumanperceivabledelays•Lackofbroadcastcapabilityimpedesor,insomecases,renderssomeprotocolsinoperable(e.g.DHCP).Broadcastmediacanalsoallowefficientoperationofmulticast,acoremechanismofIPv6•Link-layererrorrecoveryoftenincreasesend-to-endperformance.However,itshouldbelightweightandneednotbeperfect,onlygoodenough•Sub-networkdesignersshouldminimizedelay,delayvariance,andpacketlossasmuchaspossible•Sub-networksoperatingatlowspeedsorwithsmallMTUsshouldcompressIPandtransport-levelheaders(TCPandUDP)10©ArchRockCorporationdspmhopHC1frag6LoWPANFormatDesign•Orthogonalstackableheaderformat•Almostnooverheadfortheabilitytointeroperateandscale.•PayforonlywhatyouuseIEEE802.15.4FrameFormatIETF6LoWPANFormatIPUDPHC1HeadercompressiondspDispatch:coexistencepreambleSFDLenFC