Compression Format for IPv6 Datagrams in 6LoWPAN N

NetworkWorkingGroupJ.Hui,Ed.Internet-DraftArchRockCorporationUpdates:4944(ifapproved)P.ThubertIntendedstatus:StandardsTrackCiscoExpires:April8,2010October5,2009CompressionFormatforIPv6Datagramsin6LoWPANNetworksdraft-ietf-6lowpan-hc-06StatusofthisMemoThisInternet-DraftissubmittedtoIETFinfullconformancewiththeprovisionsofBCP78andBCP79.Internet-DraftsareworkingdocumentsoftheInternetEngineeringTaskForce(IETF),itsareas,anditsworkinggroups.NotethatothergroupsmayalsodistributeworkingdocumentsasInternet-Drafts.Internet-Draftsaredraftdocumentsvalidforamaximumofsixmonthsandmaybeupdated,replaced,orobsoletedbyotherdocumentsatanytime.ItisinappropriatetouseInternet-Draftsasreferencematerialortocitethemotherthanasworkinprogress.ThelistofcurrentInternet-Draftscanbeaccessedat://(c)2009IETFTrustandthepersonsidentifiedasthedocumentauthors.Allrightsreserved.ThisdocumentissubjecttoBCP78andtheIETFTrust’sLegalProvisionsRelatingtoIETFDocumentsineffectonthedateofpublicationofthisdocument().Pleasereviewthesedocumentscarefully,astheydescribeyourrightsandrestrictionswithrespecttothisdocument.AbstractThisdocumentspecifiesanIPv6headercompressionformatforIPv6packetdeliveryin6LoWPANnetworks.ThecompressionformatreliesHui&ThubertExpiresApril8,2010[Page1]Internet-Draft6LoWPANCompressionofIPv6DatagramsOctober2009onsharedcontexttoallowcompressionofarbitraryprefixes.Howtheinformationismaintainedinthatsharedcontextisoutofscope.Thisdocumentspecifiescompressionofmulticastaddressesandaframeworkforcompressingnextheaders.ThisframeworkspecifiesUDPcompression.TableofContents1.Introduction.........................31.1.RequirementsLanguage..................42.SpecificUpdatestoRFC4944.................43.IPv6HeaderCompression...................53.1.LOWPAN_IPHCEncodingFormat...............53.1.1.BaseFormat.....................63.1.2.ContextIdentifierExtension.............83.2.IPv6HeaderEncoding...................93.2.1.TrafficClassandFlowLabelCompression.......93.2.2.StatelessMulticastAddressesCompression......103.2.3.StatefulMulticastAddressesCompression.......114.IPv6NextHeaderCompression.................124.1.LOWPAN_NHCFormat....................124.2.IPv6ExtensionHeaderCompression............124.3.UDPHeaderCompression..................144.3.1.CompressingUDPports................144.3.2.CompressingUDPchecksum...............154.3.3.UDPLOWPAN_NHCFormat................155.IANAConsiderations.....................166.SecurityConsiderations...................177.Acknowledgements.......................178.Changes...........................179.References..........................189.1.NormativeReferences...................189.2.InformativeReferences..................19Authors’Addresses........................20Hui&ThubertExpiresApril8,2010[Page2]Internet-Draft6LoWPANCompressionofIPv6DatagramsOctober20091.IntroductionThe[IEEE802.15.4]standardspecifiesanMTUof128bytes,yieldingabout80octetsofactualMACpayloadwithsecurityenabled,onawirelesslinkwithalinkthroughputof250kbpsorless.The6LoWPANadaptationformat[RFC4944]wasspecifiedtocarryIPv6datagramsoversuchconstrainedlinks,takingintoaccountlimitedbandwidth,memory,orenergyresourcesthatareexpectedinapplicationssuchaswirelesssensornetworks.[RFC4944]definesaMeshAddressingheadertosupportsub-IPforwarding,aFragmentationheadertosupporttheIPv6minimumMTUrequirement[RFC2460],andstatelessheadercompressionforIPv6datagrams(LOWPAN_HC1andLOWPAN_HC2)toreducetherelativelylargeIPv6andUDPheadersdownto(inthebestcase)severalbytes.LOWPAN_HC1andLOWPAN_HC2areinsufficientformostpracticalusesof6LoWPANnetworks.LOWPAN_HC1ismosteffectiveforlink-localunicastcommunication,whereIPv6addressescarrythelink-localprefixandanInterfaceIdentifier(IID)directlyderivedfromIEEE802.15.4addresses.Inthiscase,bothaddressesmaybecompletelyelided.However,thoughlink-localaddressesarecommonlyusedforlocalprotocolinteractionssuchasIPv6ND[RFC4861],DHCPv6[RFC3315]orroutingprotocols,theyareusuallynotusedforapplication-layerdatatraffic,sotheactualvalueofthiscompressionmechanismislimited.RoutableaddressesmustbeusedwhencommunicatingwithdevicesexternaltotheLoWPANorinaroute-overconfigurationwhereIPforwardingoccurswithintheLoWPAN.Forroutableaddresses,LOWPAN_HC1requiresbothIPv6sourceanddestinationaddressestocarrytheprefixin-line.IncaseswheretheMeshAddressingheaderisnotused,theIIDofaroutableaddressmustbecarriedin-line.However,LOWPAN_HC1requires64-bitsfortheIIDwhencarriedin-lineandcannotbeshortenedevenwhenitisderivedfromtheIEEE802.15.416-bitshortaddress.WhenthedestinationisanIPv6multicastaddress,LOWPAN_HC1requiresthefull128-bitaddresstobecarriedin-line.Asaresult,thisdocumentdefinesanencodingformat,LOWPAN_IPHC,foreffectivecompressionofUniqueLocal,Global,andmulticastIPv6Addressesbasedonsharedstatewithincontexts.Inaddition,thisdocumentalsointroducesanumberofadditionalimp