rfc822

RFC#822Obsoletes:RFC#733(NIC#41952)STANDARDFORTHEFORMATOFARPAINTERNETTEXTMESSAGESAugust13,1982RevisedbyDavidH.CrockerDept.ofElectricalEngineeringUniversityofDelaware,Newark,DE19711Network:DCrocker@UDel-RelayStandardforARPAInternetTextMessagesTABLEOFCONTENTSPREFACE....................................................ii1.INTRODUCTION...........................................11.1.Scope............................................11.2.CommunicationFramework..........................22.NOTATIONALCONVENTIONS.................................33.LEXICALANALYSISOFMESSAGES...........................53.1.GeneralDescription..............................53.2.HeaderFieldDefinitions.........................93.3.LexicalTokens...................................103.4.Clarifications...................................114.MESSAGESPECIFICATION..................................174.1.Syntax...........................................174.2.Forwarding.......................................194.3.TraceFields.....................................204.4.OriginatorFields................................214.5.ReceiverFields..................................234.6.ReferenceFields.................................234.7.OtherFields.....................................245.DATEANDTIMESPECIFICATION............................265.1.Syntax...........................................265.2.Semantics........................................266.ADDRESSSPECIFICATION..................................276.1.Syntax...........................................276.2.Semantics........................................276.3.ReservedAddress.................................337.BIBLIOGRAPHY...........................................34APPENDIXA.EXAMPLES...............................................36B.SIMPLEFIELDPARSING...................................40C.DIFFERENCESFROMRFC#733..............................41D.ALPHABETICALLISTINGOFSYNTAXRULES...................44August13,1982-i-RFC#822StandardforARPAInternetTextMessagesPREFACEBy1977,theArpanetemployedseveralinformalstandardsforthetextmessages(mail)sentamongitshostcomputers.Itwasfeltnecessarytocodifythesepracticesandprovideforthosefeaturesthatseemedimminent.TheresultofthateffortwasRequestforComments(RFC)#733,StandardfortheFormatofARPANetworkTextMessage,byCrocker,Vittal,Pogran,andHenderson.Thespecificationattemptedtoavoidmajorchangesinexistingsoftware,whilepermittingseveralnewfeatures.ThisdocumentrevisesthespecificationsinRFC#733,inordertoservetheneedsofthelargerandmorecomplexARPAInternet.SomeofRFC#733’sfeaturesfailedtogainadequateacceptance.Inordertosimplifythestandardandthesoftwarethatfollowsit,thesefeatureshavebeenremoved.Adifferentaddressingschemeisused,tohandlethecaseofinter-networkmail;andtheconceptofre-transmissionhasbeenintroduced.ThisspecificationisintendedforuseintheARPAInternet.However,anattempthasbeenmadetofreeitofanydependenceonthatenvironment,sothatitcanbeappliedtoothernetworktextmessagesystems.ThespecificationofRFC#733tookplaceoverthecourseofoneyear,usingtheARPANETmailenvironment,itself,toprovideanon-goingforumfordiscussingthecapabilitiestobeincluded.Morethantwentyindividuals,fromacrossthecountry,partici-patedintheoriginaldiscussion.Thedevelopmentofthisrevisedspecificationhas,similarly,utilizednetworkmail-basedgroupdiscussion.Bothspecificationeffortsgreatlybenefitedfromthecommentsandideasoftheparticipants.Thesyntaxofthestandard,inRFC#733,wasoriginallyspecifiedintheBackus-NaurForm(BNF)meta-language.KenL.Harrenstien,ofSRIInternational,wasresponsibleforre-codingtheBNFintoanaugmentedBNFthatmakestherepresentationsmallerandeasiertounderstand.August13,1982-ii-RFC#822StandardforARPAInternetTextMessages1.INTRODUCTION1.1.SCOPEThisstandardspecifiesasyntaxfortextmessagesthataresentamongcomputerusers,withintheframeworkofelectronicmail.ThestandardsupersedestheonespecifiedinARPANETRequestforComments#733,StandardfortheFormatofARPANet-workTextMessages.Inthiscontext,messagesareviewedashavinganenvelopeandcontents.Theenvelopecontainswhateverinformationisneededtoaccomplishtransmissionanddelivery.Thecontentscomposetheobjecttobedeliveredtotherecipient.Thisstan-dardappliesonlytotheformatandsomeofthesemanticsofmes-sagecontents.Itcontainsnospecificationoftheinformationintheenvelope.However,somemessagesystemsmayuseinformationfromthecontentstocreatetheenvelope.Itisintendedthatthisstan-dardfacilitatetheacquisitionofsuchinformationbyprograms.Somemessagesystemsmaystoremessagesinformatsthatdifferfromtheonespecifiedinthisstandard.Thisspecifica-tionisintendedstrictlyasadefinitionofwhatmessagecontentformatistobepassedBETWEENhosts.Note:ThisstandardisNOTintendedtodictatetheinternalfor-matsusedbysites,thespecificmessagesystemfeaturesthattheyareexpectedtosupport,oranyofthecharac-teristicsofuserinterfaceprogramsthatcreateorreadmessages.AdistinctionshouldbemadebetweenwhatthespecificationREQUIRESandwhatitALLOWS.Messagescanbemadecomplexandrichwithformally-structuredcomponentsofinformationorcanbekeptsmallandsimple,withaminimumofsuchinformation.Also,thest