illllllllI 2 7AD-A81 756 UNCLASSIIED WESTERN UNION TELEGRAPH CO MCLEAN VA GOVERNMENT SYST-ETC F 6 17 2 COMPUTER PROGRAM DEVELOPMENT SPECIFICATION TRANSMISSION CONTRO--ETC U FEB 80 DCA200-C-637 SBIE-AD-EIOO 342 Nt I'MENNEN1 IiiiimE 'ME onmIII I ll on i i i _ 0oI BH- 12 2 2 0 1111 j140 I I2 4 jj MICROCOPY RESOLUTION TEST CHAT NATIONALBUREAU OF STANDARDS-1963- - A I mm or an mum Wmm M mu una- 1mm gkm_ I DISCLAIMER NOTICE THIS DOCUMENT IS BEST QUALITY PRACTICABLE THE COPY FURNISHED TO DDC CONTAINED A SIGNIFICANT NUMBER OF PAGES WHICH DO NOT REPRODUCE LEGIBLY # 4 7 UNCLASSIFIED 450 7 MAR 80 $ECURITY CLASSIFICATION OF THIS PAGE When Data Entered READ INSTRUCTIONS REPORT DOCUMENTATION PAGE 1 REPORT DCA 2bo M 19E 12 R BEFORE COMPLETING FORM GOVT ACCESSION NO RECIPIENT'S CATALOG NUMBER 3 7-PO05'_ TITLE sod Subtitle TYPE OF REPORT 6 PERIOD COVERED _ Computer Program Development SpecificationI Transmission Control Program TCP # MFINAL I A r ER a CONTRACT OR GRANT NUMBER 7 AUTHOR 9 PERFORMING ORGANIZATION NAME AND ADDRESS Government Systems Division 7916 Westpark Drive McLean Virginia PROGRAM ELEMENT PROJECT TASK 12 REPORT MATE AREA WORK UNIT NUMBERS 22102 CONTROLLING OFFICE NAME AND ADDRESS Defense Communications Agency Code 450 ATTN Washington D C 20305 8 Fe1 o 3a 14 MONITORING AGENCY NAME ADDRESS i diffetent from Controlling Office IS T 8f SECURITY CLASS of this report E '- Ic 10 Western Union Telegraph Company Defense Communications Agency ATTN Code 450 20305 Washington D C -C-637' CA Western Union Telegraph Company II J UNCLASSIFIED r Is 1 5 ' ECLASSIFICATION DOWNGRADING SCHEDULE N A IS DISTRIBUTION STATEMENT of this Report Approved for public release distribution unlimited 17 ti4b-E2 l DISTRIBUTION STATEMENT of the abstract enterod in Block 20 Ifdifferent from Report Approved for public release distribution unlimited IS SUPPLEMENTARY NOTES Review relevance five years from submission date 19 KEY WORDS Continue on reverse side it necessary and identify by block number Telecommunications Data Communications Protocol Switching Systems Telecommunications Systems Data Communications System AUTODIN II O ABSTRACT Continue an reverse eide If necessery and identify by block number This document provides the functional specification of the Transmission Control Protocol TCP as used in the AUTODIN II packet switched network TCP performs the mechanics of establishing maintaining and terminating a virtual connection through the AUTODIN II system TCP controls the flow of data so that the users on either end of the virtual connection appear to be communicating via a dedicated circuit This document also contains many examples of the TCP design and implementation in the AUTODIN II Multiple Channel Control Unit DD I 1473 EDITION OF 1INOV65 I OBSOLETE UNCLASSIFIED 7 MkR 80 rr 0 evv ru atef Wsr -rw r rove war-w n t w -ai lop AUTODIN II FINAL COMPUTER PROGRAM DEVELOPMENT S PECIFICAT ION TRANSMISSION CONTROL PROGRAM TCP CDRL ITEM NO B006 DOCUMENT CONTROL # DIN II-F-622 13B06-1124 PREPARED FOR DEFENSE COMMUNICATIONS AGENCY DCA CONTRACT 200-C-637 MARCH 5 1979 REVISION 1 -- JULY 4 1979 REVISION 2 - AUGUST 3 1979 REVISION 3 - FEBRUARY 8 1980 WESTERN UNION TELEGRAPH COMPANY GOVERNMENT SYSTEMS DIVISION 7916 WESTPARK DRIVE MCLEAN VIRGINIA 22102 MR 14 1980 I DIST IM ON STATEU _6-- AB Appiow fat publIC zlhaag DisUibuto Unlimtod TCP SPECIFICATION REVISION 1 JULY 4 1979 LIST OF cQWZGED PAGES Title A-10 ii C-I 9 D-1 10 D-2 18 D-3 32 D-14 37 D-20 A-I E-1 A-4 E-2 A-5 E-3 A-6 E-4 ACCESSION for W h SI weC Buff SWUM 13 UNANNrOUNCED 0l JUSTIFICATION NTIS MDt o 8_CW_ D0ist AVML aM aYILM% IAVA Attachment 1 TCP SPECIFICATION REVISION 2 AUGUST 3 1979 LIST OF CHANGED PAGES Title 12 13 14 15 17 18 19 20 34 35 A-I C-i D-7 Attachment 1 TCP SPECIFICATION REVISION 3 FEBRUARY 8 1980 LIST OF CHANGED PAGES Title 10 30 B-1 C-1 C-44 D-4 TCP SPECIFICATION MARCH 5 1979 TABLE OF CONTENTS Section I - General 2 1 1 Sinmary 1 2 References Section 2 - 2 Connection Processingt 4 2 1t Envirnent 2 1 1DataStructures 212TCP Processing 2 4 CPSequence Numbers 7 2 1 TCPTCPError Messages 2 1 TCPTCPControl Segments 2 1 VirualConnection Protocol Addressing 9 11 13 16 22 Establishing a Connection 2 2 1OpenRequest Processing 2 2 TCPTCPThree-Way Handshake CPWindow Determination 2 23 5 16 19 21 2 2 4 2 2 5 Connection Establishment Scenario Move Connection 2 3 Maintaining a Connection 26p 2 3 1 2 3 2 2 3 3 2 3 4 2 4 2 4 1 2 4 2 2 4 3 Flow Control Processing Data for a Connection Interrupt Flush Feature Processing Data from the Network Terminating a Connection Local Graceful Close Local Immediate Close Connection Preemption 22 24 26 28 31 32 36 37 37 38 Index 40 LIST OF APPENDICES Appendix Appendix Appendix Appendix Appendix A T-Segment Header B TCP MCCU Data Structure - C D E TCP Events for MCCU TCP State Tables AUTODIN II Transmission Units A-I 1 C-1 D-1 E-1 LIST OF TABLES AUTODIN 11 Traffic Category Matrix 17 Figure E-1 AUTODIN 11 Segment Format E-3 Figure E-2 AUTODIN 11 Segment Transmission Schematic E-4 Table 1 LIST OF FIGURES Revision 1 July 4 1979 2OoFES 79 T0636644 UNCLASSIFZEO ' P SPECIFICATION# MARCH So 1979a P N A L PAGE 1012 PACE 2 SECTION I a GENERAL III SUMMARY This document Opovjdes OuidelInes with which ea AUTOD Iestamdapd Tsoemlosion ComtPo9 Pporo m TCP can be imoleo menteS Included in this specification Pei 0 a • TCP Network Protocol TCPoTCP TC oTP TCPeSIP Imtepect ions TCO € Flow and Control Mechanism YC P Connection PPeoessima Mechanism$ Thepe are geptaim concepts which ape fundametal to the undepetandinm of this soecifieaeionl 1 AUTOO N I 2 TCP'o Pole in AUTOOIN It ends to a lessee euntot 3 THP s pole im AUTOOIN 1 AUTOOIN 11 SPOvIaee a eons by whiCh dive Ps and goearao 'h0ellv Seoarte hosts Computers and tepeinals may communicate Users hoets and tepmnals nod have AG komwlod 9 e of physical chapactepistlcs word site lime caged# link OpeOtOcols etc OP limitations of another uae to colmonicate with the Otop useeg network components compensate fop these diffecencese These JTODIN 11 comOOMonte fell into one of three genelOp cetegoPlesi 1o bockborie components e Switch Control Module Supervisory SCM $SCM i SCM i Stamdbv Processor SI 2 access components a Channel Control Unit CCU i Terminal Access Cotpollep TAC i note that using t is and related enecificatioms a uee may develop hs own access comnolent 3 Neteopk Conteal Contep NeCC The CCU and T C are the comoonents which provide generel ysees access to AUTODIN III User provided bomponentst also In the access component category could be a subscpibep host oF hoot fPontoeed which eupooPts the AUTOOIN I interface Protocols The AUTODIN 11 inefPiaeo potocols opel e e 0 310 Semoent Imteefoce Protocol fC Transmission Control Progeam TWO Termeialetoeost Protocol SIP iS PeouiPed by all usees IM oPdee to access the Packet Switch SCM o Users maV employ a SP to access the SCM and than develop any otheP levels of protocol CTCP and op TmP OF equivalent 9p useer delmed protocols to eommumceate vie AUTODIN 11 within th91P own commoeoapotecol user community NowevePt 2699F079 to communicete with usees connected to AUTODIN 11 T8M3ha UNCLASSITIED PAGE 66602l US P36S44 UCLASIFED ICP fP CP CAY ONo MARCH4 So 1979 PACE 99993 1 4 A L 'PAGE 3 via a TAC OP CCU# other users must supoort S Po TCP and TWP fully comoatible with these of AUTOD % Potocols that are TWP61 poeim AUTODIN 11 is to Provide Dept of the tafomes Service to users TNP# and other usoe soocific tory mecesseso such a Most Specific Interface H4S in a CCU or Terminal Wandler THI in a TAC know the snocific charseteimistics a# each user to be SU ooPted THP Two and 431 use this knowledaq to eocess date camin@ feom and going to theO user The concep t of WVT defines an AUTOOPJ Z-etwopk internal standard bidirsetiompl ehapacter-opiomted devices TWP is P99oomsible10or converting fpgm user's to NVT format date 2oing from his user to the mqtworko and fop conveptima frow NVT to usepis format data eopmifom the network to his user CS Neference 9 TCP Provides the mechanism by which a Drocess outh as T4Po Can Interface with the network Cvi SIP and subsquently other CCU TAC TCPs and THPs Essentially TCP pefopms the Mechanics of establiuhina maintaining and terminating an AUTODIN It Oviptual tommnetion ' It is TCP's Pesoonuibility to contr'ol the flow of data so that the users an either end of the virtual onnection aptear to be communicating Via a dedicated eipeuito maps The Peader should be 1familiaP With these coiceots baCkground infopmation is evoilable in the Pefepenced docuo Monts ose praach 1 should be Poted that this document contains Mmy ezamoles OM0402470 the MCCU deuign enyironment' These are Protocol Merely emamplos of ome impllemfientation of the TCP it is ssumepd that the reader is aware that many design des cisions wepe based on the socifie reauipremts for a CCU op TAC# and tnat the discussion Of the TCP aratOol itself cone sists of thosp captions of this datunent which palate to The THP TCP and TCP-SP imtopo communication CPtoGTCP #@cgs shown here sa seecifie to the CCU TAC TCP Imolements tian It which 28uPEI q41 4 NLSSFE PACE 69603 136644 26OPE8079 UNCLASSIFIED _TCp pEC P CA7 ONe O RCN 1979 jeCtoam 1 General e Rgfqp Aces 1 2 1 N A L PAGE 98884 o PACE 4 REFER1E'CS Imformatiom The following documemts opovids addtional detail am AUTOD N 11 it3s cofpcommts ad oredogeSooPse anid 1 rmfOerntIOR TILNET Ppgtogal Saee9fiCatiOme NetwoPk issue Cimcluded iA latest 18639# NIC Comte mumber 20 below 2 ARPA iET Protocol M4amdbooke MIC 7194# latest Issue 3 Stsmiqpd ROBO rch Imetitute SRI Termmaleto-Host pr'otocol S09eificatioa 1S July 1976 4 341 Tranqsisson Control Ppotagal Sooc111 1cati@A 1S July 197b S Doeteme Comffu mCatiams Aoemey System Type A for AUTODIN veciffeation laes t issue Pgrfop'msmge 11 Phae If 6 WUa391I Preoel Western' Umf@A WU Phase Is koell 1976 latest issue AUTOOP4 7 wU AUVODIN 11 Desion Plaim latest issue 8e AIJYODIN It 00s9qvM Plan 90 hIJTODTN Necutqve summary# 11 latest It TI4P Trasaotble Specifieatio9 latest 10 AUTOOIN 11 SIP Tpemsoeetable Soecifieationp latest issue issue 28OsrS 9 P336644 UNCLA3S FIED t PAGE 99004 aseres- ' T9036644 -TCP SPECIFICAYZON# ection 2 UNCLASS 3 IO M0ss MARCH So 1979 F I N A L co Connection Ppocesssin SECTON 2 cinmee mm eMa 2 1 PAGE PAGE S Enviponment CONNECTION PROCE33ING C mcam a em an e ENVIRONMENT Fop the CC'J TAC# TNP is PeSoonseble ioP oovidimg ceptain seevices to the useP humin or apoctos These sepvies ime elude NVT conveesion as discussed briefly in PapOaopsh lot ee Refesenet 9 However# the mechanics of establshimat maintaining end tePmlnating Virtual Connection bpe the resoosibillty of TCPe TIP peauests TCP's services on behalf of the usep TCP uses the services of SIP to send data to the 3C4 sn ultimaeteiy to the TCP at the remote end of the virtual Connection TCP does all demultIolexing of the data tPee egoming from the SCM That Ie# TCP determines to which Connection the Inout segment is destined The oubseaueRt OfpQeraohs will describe TCPOs enviponment In the MCCUo ioecifleallyo as well 4s In the AUTODIN 11 note work# In senepal These arpeapoho are imooptamt fo the understanding of the Pemainder of the documenot end the TCP opotOCole In Odd4tion ApOendix E defines the basic unite of transmission fop AUTODIN 11 The tepminology defired In Aooemdix 6 Is also fimoetent fop the undepstending of the Pemaindep Of this document 21 1 Data Stpuctupes AlthouGh date structures could be comsideped to be imolementation deoenent the maJor TCP data structure is discussed hepe to voint out the basic informetion about each comnection Peouleed to oeefopm TCP opOcessing Thee is only one maloe data stpucture which is used bv TCP In the mCCUI the Tensmission Contpol Block CTCB Thee In one TC8 Pr connection n it Cqntains most of the information pequiped to oepfopm comnectien opoc'essi The TCe Is sceated when a valid ooen liten Peuest Is Peceived from THP Csee Pare Geoch 2 2 1 and Is deleted when Close opoesslng fe comoleted see Prersopah 2 Thepe are other data stpuctupes used by CCUITAC TCPso which my ybe pefe4poced In this docuMent These howeveP are more Imolemensatioeoeiented and are# jheefope not discussed In detail The MCCU TCB Is shown in its entirety in Aooenoix R The SCCU and TAC TCSs ape not shOwn# but el@o Peltysemi t9 that fop the CCU That Is similep Infopmation is maitaimed fop the eonnection althouGh the struCtUes may d4ffeP ae Es v7 T0036644 UNCLA3$IIED PACE s5 280FEB- 9 U036644 C UNCLA3SFEO o oeoo PAGE 69946 -CP 8PECIFICATION# MARCN St 1q 9 0o F I N A 1 Connection Ppocessing E vromoent PAGE b ectiOn 2 2 1 2 TCP Processing TCP is driveN ov the occurrence of sigi4icant etvetso Uch as# data comima in fpom the netwopk recuests Coming from TWP ermote el9 si@a of the connection and so foPth These uignificant sjtuations ae conveyed to TCP by either TmP op SIP via intep i9'tra-oaceg Communications kmown as nevemts in the CCU end TACs Events are processed in turn Cf1Pasin irpstwouto by oreesdeme and Carry enough imform moti 9 n to comoTete the took eauired Ooe the significant s4i tuation Pop examole the situation of data arriving from the network is conveyed in the MCCU by a SIP-to-TCP Receive Oat event TCP events deined fop the MC U ore described Im Acoendim C These ape caceptually similar to those used by the SCCU and TAC imolelmonttions although the event fo p mat and the mechomics Of inter intrpoeopoess communicatlon may differ Amy eferemne to an event im this document refers to am CCU event In addition to the event mechanism TCP is driven by the information in the Tusegmemt header received from the remote TCP see Aicondix A This informatiom may be on acknowledment fop date #eto notice of a remote Closing# or other TCPeTCP control information te Pareapaohs 2019 24t 6# and 2 3o4 2 1 3 TCO Stotts Sesed on TCPwTCP Control informatiom or events from TNP and SIP TCP chmaes the state of the virtusl Connection This TCP states is reflt ted in the TCR for each connection are d0efimad here based an the MCCU imoleentation It is conceivable that other imolementations of TCP may not reGuipe as manv or may reauire mope statees These states are oeod to keeo track 'of one end of the virtuel connectio4n its @ they reflect the $tate of the local TCS more esteme sive informetion as to the Peletionshio between each state and the varieus Dossible stimuli local close reauest pemote ClOse Peouest date from the network etc is given in Aooendli 0 2OeFE90 9 1 omen THP has issued a fully soeci#ied ODen event but the thpecaway handshake has not begun 2e lIsten TMP hes issued a aePtielly s5 cii4d Opon evemt security orpcdenee TCC or destination address were not l0ecified 30 SYN sent a SYN segment PeOuest to synchronize seln seouenee numbeps has been sent beginning the Y993664a UNCLASSPr0E PAGE 00006 oSS6644 26-FE8079 UNCLAS$I3FIEO PAGE 81007 eaeae eeeee -TCP SPECIFICATION MARCM 5# 1979 ection 2 Connection Ppeeessinm F I N A L ' PAGE 7 Enviponment thjoewway hoAdshake 4 SY% sent pece4ved a TCP has sent end received a SYN the acknowledgment has not been Pe nsgment t but ctived fop the SYN segment that wee sent So established w the thPeeoway handshake is Complete od Poceoved a SYN soamOnto and has TCP has sent received an acknowledgment for the SYN segment that was sent b has received a Close local close received % TCP the local THPO Peouestlg a deforred event from has mot but gepceiul close of the conectiono sent the FIN' soegentl network data will not be Receive events for THP deliveped to the local this connection once this state has bee entered 7 remote clase received e TCP hos received a Istatusw control Seament from the remote TCP# idJ eatimg that the pemote TCP has begun close processing for TCP will continue to acceot nete the connections but work date and pass it to THP Receive events accept no are THP letters destined for the will Metwopk Send events 8 begimirig segment FIN sent a TCP has sent A FIN no fupthep data will be ace connection closures to Receivo oP given ceoted fPom Send events events the local THP on this connection 9 FIN received e TCP hes received F14 segment but Is un sle to Send a FIN segment because all octets sent have not beeo sccounted foP a yet 10 FIN set received - TCP has sent and received a FIN segment but has not peceived am acknowledgment for tme FIN Segment that wae sent a FIN segment lit Closed - TCP has sent grd rceiaved and hag received am acknowledgment op the FIN soon its PSnt that was seot but TCP is Waiting fop all oueuoes to cloe before deleting the rC8 2 1 4 TCP Se$ uenc NymbeoP o# TCP TCP The use of seauonqe numbers isan intogpel part every segment sent between ome is carried in opotocoll TCPe conteol 28-FE'74 text Eqe4 actoynteble octet CG bits of uee infopmatiom Is assigned a seuence number 03664 UNCLASS FIEO e or TCP The se- PAGE seON 28-F99e 9 TS36644 -TCP OPECIFICATIONt MARCW So lection 2 UNCLASSFIEO 1979 PAGE 6888 F I N A L o PAGE I Comectiom Ppocesuime EnviPonment ouomee umbop iv te send eauew e number field of toe T-oaeamt header it that of the fisPt Octet in the Segment@ Im segeonts eontaining dots end accountable TCP control in fopmation too TCP control Is Pposmnted by the first goauence number of that seoment seouence numbers ope assigned by the sondo TCP and used by the receiving TCP for the following oupooese 1 palishility a With the segment seoueneg number and othop Tseomtot header information TCP ean ensure that the SeGQmet received ip a valid one fo the indieated virtual connection This is always ims oratant for date imtegrity and eeoeclellv imoortant in regard to erorp oe mos e see PaG rONph 2 o15 and other connection topmination segments FIN sea- 2 acCOunjab4litV - TCP acknowl gs to toe emdfdg i ost segenats received The Means by which this is accomolishel is the sequence number Of the Segment eommunicatino the number of acknowledged oetstoe TCP 3 foe order a Seouence numbers are uood to order data beimg accumulated or transmission to the destinetion use Each Segment sent between source and destination TCPS may take 9 different oath throua% the network# ossibly arriving at the destination TCP before a segment which should logically oeeceda it TCP uses the sequence number of each 8semOnt 1 to Order the dats befope it is sent to T1P or M to oorfopm a requested functfon Cegov flush In the same relative order to the data as upon entry by the Source user 4 dualicate detection a TCP is able to detect an discard retransmitted segments based on the segment eoueneo number and the sequence numbope ousiv Fe¢covod ackmowledged segmenteo of moevis The sed sevuenee number Is a 31abit value which Is initialo Ited fop either Side Of the connectIon Coach TCPs oon side duripg the thr eoway handshake Of oven Op oeeaig see Papesorsg h 2 2o4 CCU TAC TCPs use tho eupromt value of the clock for tho initial Seouenee numbio This value repreSenta the number 9f l0the of a mi lie C5md mimes the System The initial valuo is# therefoPe uniouo 31abit value foe each onmneetion within the CCU TAC was iitiolised 8 CCU TAC o The Siouonee number is fincpmOeted based on the amount of date number of octets or accountable control infoermation sent on a aonnection 280PER 9 TON36644 There ape cartain UNCLASSPIED TCPwTCP control PACE 66608 110JUL079 T644'4936 UNCLAS31IEDO PAGE 9969 TCP SPECIFICATION# MARCH4 St 1979 F 1 N A L Section 2 Connection Processing a Environment PAGE 9 segmmts Whig%# whom e to will not caseS the next Send son @u@e numbeo value to be Imcpementeod ACK Segments not carrying user test# WACK Segments aCoknobledgment for window open segments status segmme tse Paragraph 284 v outeofeban@ Interrupt segment$ Csee Paragraph 20383 f and oerop message gments see Paragraph 2 1 5 a These are not subject to accountability other gment types have unique sequence numberst segments carrying user text# SYN segmfents FINd segments flush request segments and WOPEN window Open Segments When a sequence number is assigned to one of these segment$# the nUM t Send seQUence number V6lue If incre0mted by the number of octets being sent for date segments Including one fop the control or by one fop controloonly segments All Sequence number values for a Virtual connection will Wrap around eventually That IS at some point In time whon the next send Sequence number is incremented the value will go from a Very large number 2 147#483 647 to tero Therefore although moet of the time lower' Sequence numbers will be transmitted first and delivered first to the destination user the possibility of wrPOPOSPund is there TCP will take this possibility Into account at all times whom assigning validating and ordering Sequence numbers e Neither the osuibilitv mor the Contingency procedure will Any discussion of be Mentioned further In this document sequsee numbers and their relative position to one another lower or higher Should be pead assuming that wrPooaround is being consideroe CP-tCP Error Message 2 1'5 There ape five TCP error messages that may be sent received which Cause the receiving TCP to immediately consider the connection to be terminstedo The normal Connection tormIna tion procedures Csee Paragraph 2 4 will not take place # in this case There will be no acknowledgment sent to the TCP generating these messages There will however be a yell dation of the receive Segment seguence number to ensure that the error notice is legitimate$ It the segment is valid the connection will be Closed and the local THP notified The error messages are$ 1 Connection does not exit a This message is Sent if tneme Is no associated connection for a received segment# so determined during demultiplexing Of the network data stream see Pararaph 2 3 6 security Violation a This message IS 2 sent if the Revision It July 4# 1979 Tw 4a4936 11eJULe79 - - UNVCLASSIFIED PACE 0S009 A L Tec SPECIPICATOd ARCH so tT9 ee F 1 seetion a Connection PPe66 gime a 1 vIpoAemnt PA9 13 of my 4noming segment to deters ima eoofate for the connoetiono There or thsPOe uiepupteneos whem this e014ee is listen# the looel uooP did 1 eonmetion setae security amed level to be Soeeupity level in his listen Fee not toe4fV the ouoste and the Security level of the ineoming seas Meont is higher then that authoried foP use by the listen# local usedp Connection state is 60omp Or IYN Sent the loeal user did ooeify tho seocupi ty level In tis ooen#'ietom Peuoet and the eun Pity level of the ifeomino Segment does not match the logified Beeuetvi or 33 eo neet4on State 4e established end the security level of the ineoeming segment dos not Mote% the connection se ueity Th TCP geneptinO the OPPOP meO@ae will level eonto or established remain In oven# listen SYN State# as 3 spopeistee TCC violation This osee is sent 1 if the TCC n ming SYN seogmot does not Mote the TCC SeO ied b a user In his oomenlgten oeguest Or# C2 f the local user did not sooeify a TCC In %4 l4sten eouest and the CC of an incoming SYN $eo mont is not outhocived 4oe use by the local User The TC' Generatino the OPPOP message will pome n 4 state oF Peturn to the e 4llistef of 4e an connetion opOmoted a This message Is If sent the established Connection is Doing oPeemoted se Poe The Teo0 e 4netimo the OPPgP Mean 1 8 3 GPOOD will cantimue ges opoceduoes for the sage oreemotod connection pde SubseOuntlvp Ofatolie0 the new connection twit% iiOthe destination S umseceotable SYN e This message i8 sent if a SY4 from Same source as Initial Segment is Poee4ved initi l of the SYN that is not a petdono 9isiom oYN mt# peeoIvod or SYN segment when the statoeis message the epo The TCP genoetinq eoto140ai0he notifying the local will also close the eennoetiome THP via Cloe Netupo event In CCU o enouce that the o'op A TCP doeeiving an epee messes@ will If the befoeo tePem4atino the eonneetoe is 'molieveblo dISeed Semuonge number believability saeek failo TCP will The volidOtion consist$ of the the epeeo message segmOnto iol lowimgg 1 the Is eoneetiom opoo ooeted # the otifiation the aeknowledmeont sontained In soeueneo number fied of the Oeror Messes@ segment must be the the mUmbee Po eond seeUO¢ mout TCeo oeeoting Passive volue theme must De within the ¢upp nt 4evisiom 3V FV eupv o 1ge o T91366a4 as F19-79 PAGE 66611 UNCLASS F ED eeeteeeeeee PAGE it CP OPECIFICATON MARCH St 19T9 at F I N A L ' action 20 Connection Processing Evironment window ioe Mont 2 the C erop message $ a- eeeivig the X pv ether error mot4ileetion Is received the seauence number of the Orpor O segment Oog p the SYN segment must be in the acknowledoment field of the error meesage sement That value must of CouPSe be a seoauence number fop a segment Sant by the TCP receiving the erpor message segments TCP TCP Coetrol Segments 2 i TCP control seamoents oe orOtocol suboeeauet exchanged in GuO0OPt of It should be noted that those Control segments whiCh reauire acknowledgeents always consume soauence Pareagrh 2 1 4 1 the TCP-TCP These ae defined below# as well as discussed in Tables opapaoohs and in Aooen#dx D TCP State number soace see SYN soamOnt a This control is used during ODM VreOcessinia so¢cifically h9 thee-rwv handshake see Parearsoh 2 2 23 to initialize the seod seouence TCP The SYN segment must be number for eat aexnowledoed end may not Carry User text seament carries informatfon The 3YN in the control data extension field about the source user which is re OulPed to calculate the destination TCP's receive window see Pasaroh window and THPwTCP soer The aooroimate letter size# hest-CCU or 2 2 3l tspminaleTAC line sooed and CCU- or TACeSCm line If a segment In the $YN Included oases are les nO CCU T C TCP does not USe this Opocedurep Includ tS9 user informetion in the cadoes Mot Cero volute tPol data extension field default foe the letter silo and line soed codes will be used in the lndow calculations 2 FIN segment e This control is used ti O termination tsee Parop during connec- eeoh 2s4 to ensure a Fimal sesuence the connection acknowledoment takes elece at that times oPderly close of number The FIN seoment must be acknowledoeod and represents the acknowledgment fop all octets which have bee accounted fop by the destination TCP sender of the Although the TCP opotoeol allows acknowledoment o data to be sent in a FIN goomento CCU TAC TCPs will never penod user text In this segment but will ace coot text sent In a FIN segment by a non CCU TAC The FIN echanoe Is not always used to close TCPo pros the connectiOn# as 19 the case of some TCP 2e8e9ta 3e e9 e 6 TP63 8 a eelel CCUNCLASSIF EOae PC PAGE 66311 2-AUT-q -rib93o UJCLASSIFIEO bA4CW TCP SPICPICATZONp Section 2 197Q S V I F ' £ 1 PAGE F0012 PAGE 12 Connection Ppocessinq - Environment oP oreemvtion Error conditiO s such as those rea varted in Sent Data Return events or encountered in time out situations see Aocenoiu cause the comnectiom to fe closeo usinq the FIN exchange Other errors such as security violition or oreem-o tion see Aoomedi 0 cause the error message to a sent aon the connection to oe closed without fa ral TCPeTCP orotocol In these cases the TCP error messaqe is sent see Paagreaoh 2 15 is £CK segment a This control Is useo to acknowleaqe all accountable segments imcluning date segmets am sray control segment requiring accoutability The acknowledgment sequence numoer Is comta'e1e In the seoment ano imoicates thp sequence numeer of tne newt octet expected on the commection Tnis ioc14os thet all octets with lower Sequence nuombers than the sequence nulhoer in the acknowledgment fiela have been accounted for Mv the TCP senoing the ACX segment A TCP receivinq the ACK seqment will ensure that the ocknowledqenet sequence numoer is imnoed for octets sent he value must be witho in a range from and including the oldest' unackno-leaqed octet too end excluainq the next semi seouence numoer The ACK seqment itself is mot acknowledged However# if it carries data whiCh is aer-ittedo the oats is subject to accountobili- d wPE 4 seament - This control is useo to notifv source TCP that iestimation TCPs seoer of OPEN seq-tent rreviously zero receive wtnoaw Is now mnn Zero The segment must be sent to open the receive h in1owo if the Window is ever decreaseo to zero and it may ce sent Into a zero window That is tne TCP receiving a OPEN will always process it A -3PE% segment must be ackowltedQeo My a ACK Seg ment and may never carry dates tIn addition it siog1d be noted that once the OPEN is received and a tACK is sent to acknowledge it oats and or other control segments may be sent on the Connection The oestination TCP will be reaoy to ecceot seaoients once it has sent the 0OPENo The acknowleaqnent of the OPEN is exoecteo and the OPEN will be Petransmittei as eolained In Paragreaoh 2 3 2t however# this neeO not have taen place In order for the destination TCP to comsider Its receive w4ndow to be open S AC4 segment - This control is useo to acknowleaqe Tine WACK - control and mav not carry data a itself is not subject tO accountability 4evisiom 2o 2-AUG-79 -- • i 1 34h96e 1 JNCLASSIFIE l a a mm m m1 August 3 1979 PAGE 0012 _ e T 1 4a 2-AUG-79 6 UhCLA$STFIEO TCP SPECIFICATION# mARCm 5# 1979 Section 2 Connection Processing - ' AGE e13 PAGE 13 F 1 4 A L Environment 6 Status segment - This control is Used to inform the remote TCP that a local close is in process and to canProvide aCcountability for data received that be aelivered to T4P due to te previous close not The segment is sent to remote TCP after a reauest request has been Peceived but before close local see Paragraph it is ti e to send a FIN segment status segment is not acknowledged and The 2 seauence numbep The segment May not carry data$ field will Contain the sequence number plus one of The the last octet successfully oeliverea to TnP field will contain the see acknowledgment segment ouence number of the next octet expected 79 Error Message segments - The error message seoment# as discussed in Paragraph 2 1 5 is use to notify the remote TCP that an error was detected in a seaconnection preemption 1%s received or' that ment acknowledged and The Seg-ent is not taken place The TCP receiving such a segnOt carry data may meat will unser most circumstances close the Connaction see Appenmix D 89 reFlush segment - This control requests that the TCP perform a flush function for the virtual mote segThe flus connection see Paragraph 2 303 to but is subject data# never carries ment accountability 9 re segment - This control Interrupt Outeof-aman that the remote TCP perform the out-of-eana guests The 2 5 3 see Paragraph function intterr ot outeofe-band interrupt segment may not carry data end Is not subject to accountability 291 7 Virtual Connection Protocol anO in e Aedressinq 0e i Woo e cc Virtual connection addressing is accomolishen by TCP through a $Chene based on sockets In general a socket is the identifconCatnnation of an internetwork identifier a tCP This Socket defines one eng of end a port loentifier for# A pair of sockets one describing a TCP virtual connection the source and one describing the destination fully soeci- fit$ a TCP virtual Connection when a host Process or terminal user makes a request to open a connection all Information required to fully specify the sockets must 0e local destination foreign and source %hen a destination TCP receives a request fop a congiven Nevision 2-AUGO79 TAA46936 UNCLASSFPIEO 00 PAGE August 13 3 1q9Q 2-AU6079 Tea 15 UNCL SSIP PAGE 1 S 1979 F 1 N A L TCP SPECIFICATION# ICq' Connection Processinq Environment Section 2 PAGE 1' two contain will header T-segment sectiont the receivea For a connectio to 0e addresses socket specified fully one match exactly must establishea a destinatiOn socket fop a connection via a previously issued listen or waiting is connection the Once even reaueSt t the destinationS two socket ad resseso source and destinatoe estahlishec tion will uniouely identify a TCP virtual connection reParoaraoh 2 2 discusses in more detail the Procedures dose 2 3 Paragraph for establishing a connection puired data network the in detaile the demultiolexig o cribest feiCh TCP uses the socket adoresses to determine I street # deis meant to This oaragqroo the aporecriate connection of socket ano the two categories of outconcept fine the CCU adoressinq and TAC addressing scriber oapessin9t CCLI Aadres ina asubscriber network Since the CCJ is identified by one can route oats to only the CCU switch Docket the dress The CCU must oeterfrmne to which host user host-CCU channel toe connection refers when a host user enters the oven listen reouest he rust include the complete local user This includes both the local subscriber saidentification the the subscriber address is dress and the local Dort ID the Dort 1D is designed for all users of any one CCul sa'e the ov entered ID The Port a specific user to loet4iv associated with the oarticuelar host-CCU Chanoecoes user snoula It This is the concern of T4P Reference 4 nel every channel between a host and CCU can be that noted oe The desired is it lo if associated with the same ort unlOue adaress reouirea to associate a connection to a soecific user channel is provided by the fully soec fiea sockwhon TNP submitS an open or listen re escrioed apove et# to assigned L C'e is aome guest to TCPe a local connection This is a shorthand notation for the fully connection the TCP and specified socket pair end provides a reans for THP TCP To summarfrel to the connection internally refop to receives a se aent which contains hoth the source and destie socket specified fully the joentification user nation TCQ associates the segment with a particular connecvoair TCP relays the information pair socket this usinq tion which descrioe to LCN the usino TSP Gate or control to correlates the LCN and the TAP concerned 4s connection specific host-CCU channel 1 oaptst The port 10 is actually broken down into three user ID anc 3 static dynamic Dort 2 quffix function To the CCLU TMP or TC0 the various portions of ioentifier TCP e are recognized fop only one ouroosel 11 port the tracts the user TO to perform a security opeceoence TCC vale to ensure trat the oarticular user ID is aucneck idetion and opecedence thorizec to Vse those values for socurity Revision i-AUGP7q ytwsb b ccc a cc c 0 ii cUNCLASSITIED I' 2P August PAGE e0014J 1979 T 'wb69 2-AUG 19 6 arE 015 UNCLASSIFIED TCP SPECIFICATIONP ARCO- Se 1979 Connection Ppocessing Section 2 F I N A L 0 F Environwent PAGE Is Umne p that were soecified in his ooen listen Peauest all othep circumstances the cort ID is not important as an enity Of courser it is cart of the unique fully soecifled host to the The Port 10 is uselp rathep by socket pair determine to which Process the Connection refers TCC TAC Addressing by a unique Each terminal attached to a TAC is represente tre fu tly soeclto the packet suitceh address subscriber unique only the fled socket fop each user will consist of subscriber aOdreSs no eOitional information cOrt ID is network data the still emultiolex TCP must reouireo the acororieate comnectiom Osseo on the oete ining stream socket pair in the received segment 4evislon 2v 2 AUG NCLASSIFIV p Auaust 3 Iq7q 71036644 2S 7E8079 UNCLASS1IED c PACE 9I016 TCP PEC F CAT ONP MARCHd St 19 9 F I N A L coPACE Section 2 Connection Ppoegesifte a Establishing a Conneaction 2 2 16 ESTABLISHING A CONNECTION There art gevepal stoe in establishing a virtual connection peoess or terminal user between two CCU TAC user's Chest The stoe summarized hope and detailed in Subseguent 0prgot t ase taken by an MCCU TI4P TCP# howevep they aP5Phas are logicatllv similar to those taken In an SCC'J or TAC TCP becomes involved In oven oeessino upon receiot of A Cooen event from THP This event may have boom generated as a pesult oi a user Pemuest THP oven op listen command op In ny an automopenbautoelisten function see Refep ee 9 0 Ims case TCP must validate the cooen roauest and notify THP The eonnece mediatelv of the result Om Return even tion will not be established however until the TCPinTCP thpe mway handshake has taken DISC At that time TCP will notify notify THP vie the Coen Complete ovet t and 'TNR will the user as reculpede Paearaphs 2 2 1 and 2 2@2 will- describe these two proces du 'Cst Scam rveoest PrOCusino and the thP emway henduhaka comdentpatina on what is reouired to successfully establish a virtual connection as walt as tole various conditions that cam make am ocm attemot unoecesul Paragraph 2@2 3 des- Cribiss the calculation of the THPaTCP send window and TCP PTCP receive window Paragoaph 2 2 4 providess a comalete Oar ovening a connection Ammendix Do TCP State sconapio Tables will aid In umdeestandina and euDmnd uon this diseussi on Open% Reaueot Processina 2 2 1 The Ocm event hpom THP to TCP defines the oapameteps Pem a virtual connection oulped to establish amd maintain These prs ttes aret 1 2S VE9679 precedence a A value ipom zero to fifteen Peopem sentino the eateqory and type of data to be sent by There ape V e local usep on the new connection four categoriest Is It# III and IV# with I being high most expeditiously handled Foe each eaten cory there are ioup subclsss The retationshim botwen Coen evant saeametep values category and suhelasso as well as a bpief description of the type a dot9 is shown In Table 1 The terminology used in this table 4@ the sme as that used In the A'JT flIN It System Performane Soecification Type A # 0eferene So 803664a UNCLA3S PIfOc PAGE U9016 'a - e 2-AJG-79 UNCL6SSIFIEC P AGE Zt417 TCP SPECIFICAION M qCN So Section 2 1q99 f ' IA L Connection Processing - tstablisnnQ TAiLE 1 AUTUOIJ value cateeorv criticality Is m 141 I 13 12 11 1 11 PAGE 17 a Connection TQAFFIC CATEGORY subclass traffic MATqIX tyce Yi #Z I Y2Z a AUTCO II control messaQes suoscrivinq network control essaages 1 Y e Z S Critlc ECP messages 1 Y Z a subclasses A1 II II 0 0 8 interactive traffic cuery resoonse traffic 9 8 7 II II IlI 0 0 P C1 C2 A narrative aata bulk data interactive traffic b lit 0 8 ouery resoonse traffic 5 g 11 III P C1 C2 narrative cata A 2 1 IV IV IV lv I interactive traffic uerv resnose traffic narrative data bulk data 8 C1 C2 p R ocriticelitvi B CI and C2 bulk data Yon - flash oveeride Z - flash 0 - immediate P - Priority - routime cateQory It values 14 ano 15s are for network use only ando as such# are not available to tSe sutscrib r Nevisiom 2-AU -Tq qiLUq3b UNCLS$IFIEC 2p AUQqgt PAGE O-VO17 3 1979 TCP SPECIFCATTO0 MA RCN s 979 a P N A t PACE IS Section 2 Connection Ppocessing a Establishimg a Connection 2 securitV a A value from Rope to 15 Peoposentimn the Security level fop all dote to be Sent by the local uep oan the now connogtiono Seeurity levels Peoes seonted ope unclassified# £FTO restricted# seofle dentioal SCeePot too seceet and NMMh 1 to b room oetively and PROG 15 a not available fof uSe by ub6PeibeGs o 3 SeVon through 14 are met assiaed teamemisson Control code TCC o A value the eofuni'ty of Interest to which both defining the Souce and deetinetion subecroee oelong There are 512 TCC eooe fop AUTODTN 11o Jeep Should contact OCA Code 530 fop assienents f'e destination subscpibee addreess the with The value has a Penoa So A value defiming netwoPk address of the destination subseriber w ich the connection is to be established destination oot tional TD a A addeessing subseciber subcpibop fpon Repo to 6553S volue peoeenting The value Is reo if is a addle information for the destination the eostntifo4 te inel conneted to a TACO and IS thecefoce oo1496le only to CCU subaeifboPe The Dort ID define9 the hostoCCJ chonnel fop THP'e use end also contain user Cooces identifias tion fOP use In the hosts This lt-ait value is actually divided into thee fieldel bit a leapt soigiicant bit is the state ie dye ec noot indicator bits 1-l1 peopeset the user 1l1 and bits 12 1S Peoesent the function suffoi See Paeagoaoh 2 1 7 6 source Doet 10 a A 7 ePeenotebility a A value lsee or one indietima Whether the new connection ey be oreemotee one or not zero Ii this value is epo TCP w411 not Consider the connection to be a Candidate #oP Con value Peopesenti a elditional The iop the loeli ree Information addrssinot value is eoe If the local uee is a teen4nl Cone nected to a TACO and is# thepefsepe sooeloble onlv to CC' subscribeprs The ouoose eAd forest ae Identical to the destination Port ID nection peemotien aPO 2o6 3 ftOweveps is oYeoOee not Opeomition see Popes effected by this Indicateeo To Teo the DOom event aV PeopOset a oom or listen eGuest If all the above mapraetePs ace soecified In the OnM evot TCP consideps it to be a eaueset fee an Den connection and oloees the connection In the ooen states If Revision 3 Febpuary So 190 2WAUG079 TCP SPECIFICATION Section 2 '36 UCASL 'ARC 5s 1979 Connection Processing - t a F I It A L OG 010j 19 tPAGE EstabliskinQ a Connect4on any parameters are unsoecifiey in the Open event# TCP comeider$ it to oe a listen reouest ano places the connection in the listem state The only aifferemce is that lop a lise tening comnertion TCP will olock any attemrpt oy TI4P to send osa Senco evpnts on the connection see Paragraoh 2 2 3 It should to notec that if a user were to enter a T IP listen comman id viitc a I parame'ters sp'ec ifiedc the Open event would be fully soeeiiied and 1CP would consider the connection ooem 0 TH4O however consicers the connection to be Mlistenino 684a would not seno data to the network see Reference 9 TCP will ess're that the security orececenCep amo TCC if specified# 4re within the bounds autraorizein for this user TCP has no way however to valicate the destination sube scriber adaress or oestimatiorm port ID values TCP also emsures that resources buffer space permits the establishwent of amot %er connection If resources are critical iee space fop oata structures ena date buffers does mot exist TC 2 -ay oeny tae poen Peouest or may preempt lower precedence connections to acouire space for the mew open Pea Quest 4 9 jraen Peturm event will be sent to TmP Inoicatimg accep tamce or rpjection of the ovenflistem reouest If the reoucit 4Ss valid TCP will set the connection state to reflect the open or listen statet as appropriate 2 2 2 TCOaTCP Tmreem ay W -M --- - --- andshake lfb TCP's 'three ay handsha ke is the -nechanism used to esteblish the network virtual connection The three-way handshake# fro'r the viewpoint of each TCPp consists of sending a reauest for synchronization of the semi seauence numters roceiving tine similar reauest from the remote TCP semeling an acknowlediment for the reauest that was received# amo receivin an acknoti Jeogment for the reouest that was sent The Peouest for synchronization is calleo a SY'N segment The above onening oroceoures Paragraph 2 2 1 are Prelimi-l mary steps hich leave the suoscriber in a TCP state ooen or listen roady for a virtual connmection The thrteway handshake W ill Oegin when the ooeninig user enters data oestinea for the listening user It is assumed for the nurvose 04 this psiscussion that pine user will enter a T4P open commamcp Ausimo a fuly specified open state in TCP and that the other user connected to AUJTODIN 11 through another access area CCU TkC p will enter a TmP listen command creatino a partially snecified orem state in TCP ahen TCP receives a valid Seno event from TmP for a connection in tine open states TCP cegins the tinree-why handshake sendino A Sy'J seg-ent to the remote TCP The remote TCP 2A4- T-'i46936 Uf CLASSIFIED - PAGE 0000 2 AUG-79 TeA B 1JNCLASSTFJEn TCP SPECIFICATION# 4n C %p 1qq Section 2 Conectiom Processinq PAGE 002 F I L Establishin a Connection 2AZj will determpne the comnection or local subscrirer assoc4I comim segment see ParagraoP 2 3 4 ani will make the following adootioal checks before acknowledoIng the SYv segment ana retur nm a SYa'N segment of its own it should be moteo that oreemotton is comsicere in deterMining the subscriber to be essociated with the incoming seoment The security oreceience and TCC of the SYk segwent are extoactea from the @SL oy SIP ano oassed to TCP for analysis i e these are mot In the TCP header ated with the 1 connection has been security - If the soecifieO by the user connection in the Oven security reouesto the security level of the SY - selment must match If the security was not scecified the security level of the SYN segment will ne used tut it must be euthorizeo for 2 use by the user connectiom orecedence - If a orecedence is soecffiem in the opemimo listenina reauest it will he tme crecedence level for that local user's seni side of the virtual connection Ise orececemce sneclfied in the SY segment will be the orecedemce level for the local user's receive side If the precedence was not soecitfe in tne local user's listen eeouestp the local user's send oprecedence level will be set to that of the SY4 segment or to the meuimum authorized for use ov t is user wmienever is lo-er There may be# therefore# two orecocences associated with this conmectiomt user's seni orecedence ant user's receive orececemce If the connectiom becomes a canlidate for oree'mctio see Paragrao h be used 3 In 2 a 3 the determininq If hianer of opeemotion the I two will allowed TCC - If the user specifie a TCC in his open reQuest# the SYr segmemt TCc must match If the TCC was not soecifieo the SvY seqnent TCC will be used as lonq as it is authorized for use rv the user all foreign address - If the user scecified a foreigm subscriber aooress ano foreign oort 10t the SYN segment addresses must -etch If the amdress was not onecifiec tme SYN senment aqdress is used If the above criteria are mot satisf eav e 99 an associated connection can mot be foundr a local user scecifieo carameter is not ratched in the SYN segment p or# for a parameter that was not snecifird vy the local user the SYN segment value is not authopireo for use 'v thie user TCP w111 will the will not coiolete the three-wav handshake Ise SvN seqment be discarded amd TCP will return an error iessape to TCP that sent the uaccoeotable SV segnemt That TCP notify T qP that the connection is closed Send 4eturn 4evisiom 2oAUG-79 To- a6q3e UNCLASSIFTEC4 PACi 2f AQuuSt V IeP S tq q TCP SPECIFICATION MARCH S PAGE 90121 soUNCLASUIP FD T9630644 2S FES- 9 1979 F I N A L PAGE 21 0 Connection Ppoeessima e Establishing Connection section 2 and Clos Retu events handshake threoeway the i ell the ho eke oe g$uecesosful continue Omce the remote TCP sands am acknowledogment will ior the SYN that wgs preoived ard initiates a SYN segment of eknowledgoe the remote SYN own and the Initiating TCP its Comolete Am ODeM segment the conneetion Is established ven is sent to TwP# In the MCCU# to imdicafe that the eon- nectiom has boen established the motOficetion 2 203 4 the $CCU A similar vehicle Is used for and TAC TC P WidOOw DoetermiatIon by Each TCP must determine two sand wimdowso one to be used evets the local TWO in sending dote to the local TCP CSend the and one to be used by the remote TCP In sendiog date to The first window is called the THP-TCP send wine local TCP dow and is evortseed In number of letteps which THP may have In the mCCU this Peopeoento the numbOP to TCP outstandimn receoivig of Send vents which maV be aueued to TCP without The Sema event oueued a Send Rqtupr vent for the woldtot TCP's the remote window TCP s receive is this second window send window The value to conveyed In the Tesegment header the remote TCP A in every ement sent to see Aopendiom of octets which mav be sent to the numbep and reopreoets this TCP before waiting fop acknowledoment For subclase A and 6 Of Precedence categories Ile II and 2 of oreeedence category I see I and and subclasses TV simple The are ouito Table I the window detemoimatio tyoes Deprit certain assumotions tPaffic of these mature In orecedence a with about date exchange em a conmectiom dots flow will be omeewav at a aPOu Fesetiolly this tome rather then im a $teady stream fop either or both sides of the connection In addition the amount of data In each teaotsmission will be within one THP letter Thaerefore TCP will establish each window with a value Ouivaent to One Fop the local TMP send window the value will letter buffer Send evoet may be sent at a that ofe be aoe# Indicating time For tme remote TCPs pend window the value w41 be the letter Sire Ccomveyed 4M the SYN segment to Gufvalent from the remote TCP fop that TCPO yseer This window is In every segment sent by the Toseomeot heoadepr conveyed Im winreceive the destination TCP as the deptinatiom TCPee be uoressiod in the number of oetets Sebit and will dowe Toe bytes that the destination TCP is willing to reoeive will not ehange thPoughout the value sand window TP-TCP The life of a eonmection having a arecodemce In this grouo window may go to tero in the normal Dpec reeoive TCP-TCP cesing of a connection but will not be imceseed to mae 28oPED7O T9936b44 UNCLASSIFIED PAGE 68621 2S FE6679 T843644 e 0 UNCLASS P ED PAGE sgg22 TCP PEC FICATIONg MARCH 5e 1979 F I N A L Section 2e COnnection Processim e Establishing a ConnectiOn PAGE 22 then the eauivylemt of one TwP lotter so The TCPwTCP rei eeivq window will go to Zero only if oeSou'eae are needed to service a higher opeoedenee connection The window determinatione for the narrative and bulk data Subclasses s9e Table 1 ore more complex The THP mend window Is initially calculated during ooen Peauet Dope eant orocessing if the open request is partially specified listen reouesto e Pareogp oA 2 2 1 the window value will be zero@ blocking date from the user until a cone section is established If the oon reueet is fully mmccifl9d the window value will be one allowing one Send event This wend reuelt will actually beatm the three-way handlhakt see Parpprsoh 2 2 The THP mend window and TCP receive window will be recalculated duPing the three-way handshake amd @ay time another connection terminates in the some CCU TAC Both windowe ape calculated uling the infOr motion conveyed in the YN seoment duping the threwovey handshake as well as informetion about the local subscriber #n CCU TAC resourcese The followia Items are cone sideped in t e windOw computatiOns fouPce user's aDpmoufi mete letter sizes soed of the line between source user hOst 9r terminal and access comoonent CCU TAC P smed of the line eetween source access component and the Source SCM access line speed access line soeed between destination SCm and destinetion access comoonent lime speed between destinetiom acceps comoOnent and destination user and local resource availability 2 2 Conect In Establishment Sceneria For cl0iiceation in reading this sceerio certain terms must be defined An openag user' is one hoot process or teeminal usep which rGauests that a connection be opened to another aper A Plitemning userp is one which indicates that he Is ready for a connectio to be established Opeoing TMP and TCPare the 0cess area Comoonent protocols which serve the opening user Listening TMP and TCP are those that Serve the listening user This scenerae will provide the overall view pf the ooening oi a connection Only the moter participants are noted here That Is M31 TM and SIP are not Considered as they provide only I Odriver link oprotoeol suooorto The scenaro Is also not esolicit as to which access comoonents ape being used althouoh the events mentioned are thee9 of the MCCU The scenapio opreents a typical TIP TCP interface ne TCPwTCP srotoeol It should also be noted that the first three Steop of the Scenario may be completed Say time before te opening TCP mende the aYN segment to the network Ctep 26eFES 79 TIRA1b44 UNCLASSIFIED PAGE 30622 eleleeeoeeee 26-V 8079 T9936644 PAGE @1323 UNCLASSIFZED tCP SPECIF CAT ON MARCH 5 1979 F I N A L see ection 2 Connection PPoeassino a Establishing a Connection 9 0 op mop speeiselve beoe'e that SYN segment the listenimg TCP PAGE 23 reee4ves A nteee a valid TMP lieten command seauence idicatino that a connection may be established with ev PeQuestimg Pmot usee Usee A will now be eerred to as the 'listenino VoP ' and the THP and TCP serving usep A will be refepped to s ilea tonin TMP and 'l istenine TCP ' pesectively 1 yse 2 Listening TMP validates uipee listen command se auence determines that it is a valid Peauest ana aueues a Detillv soeeified Omen event to TCP 3 Listeoin TC8 for TCP Validates the Oon event eeates a this user # uts the TCB In the listen state ad aueues am Open Retupn event to THPe 4 Listening TMP deoueues the Oeen Retupn event notes that the eceuest was OuecesofulT but takes no fuethee action as the user Is in the THP state S listening us e a 9nters a valid THP opne Command sequence recuoetine that a connection be established with usee A User B will now be pefee to as the o pening user and the THP and will be PefeePed to as TCP0 PesoectivelV ocomnin TCP serving usee 8 THPO and 'openisg 6 O Mnin TOP validetes usep S's open commend see Cuenca letpminee that it is a veld Peauesto and aueues a fully soeified Open event to TCPe 7 ooe iaTcP validates the Ooen event creates a TCB fo this users puts the TCR in the omen states and oueues an Open Retupn event to THP 0 Omenimna TP deeueuem the Oven Return event build$ a therecteristies eotiom pecord see Refeence 9 In a tommetwork letter bufferP end oucues a Send event to TCP Peuestimn that the lettep be $et to the nstwork The useep is in the TOP ovening states waitine foe chepcteisties opeocessiog to be come oleted 9 6-FES 79 Oenlne TCP deeusues the Send event eOM T#P dee teomines that the send Peoueet is valid@ and begins the theeeway handshake to esteblish the senneew ton TCP enide a SYN segment to the networko ads dee9ed to user A and Changes the TiC state to SYN sent 7e13b644 UNCLASSI3FEOE PAGE 36923 2S PS 9- TV836644 UNCLASSIFIOe 'CP $PEC FICAT ONP MARCH So 179 F I N A 4celoM 29 PACE 16314 PAGE 24 CC Connection PPOCessi's a Establishing a Connection 1@9 Listeing TCP Peeives the SYN seOmermt makes 6ev Pal checks to veripf that the SYN seqe t is sce centabl9 50ee Pareapaph 2 1 10 builds a SYN seament with a aeCknowledamert ACK foP the pegeived SYN ••smerts transmits te geoment to the and chemoes the TC9 state Its Ooemima TCP receives top the SYN segment metworik to 3YN •emt pecoiveodoi the SYN segment wit% am ACX oeViousiv sento TCP builds a date 8e0moat to be sent 'to the listernig TCP which Contains the Initial TMP lettep and an ACK for the received SYN semerto The TC state is eharoed to established ad an OMen Comolete vent era 3end Window event Inee aun TMPeTCP send witm dew Is oueued to T1P 12 Istenimg TCP receives tie ACK fop the listening useP segment determines with date that the ACK 48 fOr the SYN segment opoviouolv sent chamges the TC8 state to establigded aueues an Open Comlete event to TNPo and deliver the received data to TMP Receive event 13 Listen ng TOP dequeues tie Oean Complete event notifi e user A that the connection has bee tstablished builds a CheaecteriStics cotion record iA a to-network letter buffer and Queues a Send event to TCP as son so the CP lend window oDenM Seo Windew event The TwP state is active waiting for characteristics processian to be COm oleted 14 Ooeoino TwP deoueues the Open Comolete event notle fee user 9 that the connection has been et blilhedo but takes no further action as It is waite in fop the cheracteristies Pecord 15 2 9S TwP Will complete characteristics orocessing see Reference 9 and them beaIn to euceaoe user date but the virtual qonnectfon has been established from TCPs'v4ewooimt at this time move Comnectio The move coeeection featrepis Primarily a THP function and 4s available In the wCCU only It mvolves the relocation of am established viptWal connection from ome CCU user to anothep es tially from onse MCCUfoet channel to amotheP TCP'I role In skis opocess is minor amd 4volves oepformin a function similar to that for the ODen event thus the feem I8-FEB 19 T9336644 eretit ree 9UNCLAS31P 0e a 4 a A PAGE 66620 19936644 28 F S 9 UNCLASSIFIEO PAGE 0025 CP SPECIFICATION MARC 5 t979 F I N A L ace ection 2 Connection Ppeoee ing 0 Esteblishing a Connectiom tupe PAGE 25 is discussed hepeo It is eoneivable that on am mCCU thepe would be one MCCUwhost chanMel PeePved for use by 4 host logoon POCeSSOo AM AUTODIN t VSee Would PeoUOt to be connected to that loc-on subscreip oopt ID in order to 0842M onp the host One the loqon orocedure is Comoleted the user would be tPensfeppeo to another host DpOees on snother MCCUuhost chenelo The transfep would oiCur whem the log-on mPOCess use the THP gve eommnd Because of the neture of this ieature there are Ceetein PestPictiomse The reader Should consult Refeceme 9 for deteils TCP would be asked vie the move Co Meetion event to verify that the Rew user is uthopized to peceive the established fomectioin The secupftyo opecedoemce end TCC 9heck popformed dupieg ooen opocessin would be 0ePfopmed fop the new user The Ov Co nect ion Retupe event conveys the result of the velfidtioM From TCPsa viewoint the eoneetiom will not have chenaed iesi TMP will do all Omeoing of data to the new usee The log-on chenele will thef be evailable fop a virtual conmection with anothop subecr'ibeepiot ID It should be neted that the #bave desepiotion epolies to the MCCU iffiolema#tstien Othep imolemetstiang of this function may handle tle move differentlv as PeguiPed by soecific user chaepaeepistiese BeTe3ee 2eoPES 9 tgdebbo etee UNCLASSI IEC Pee 66625 PAGE 26-FE5679 78434644 UNCLASSIFIED 'CP 3PECIFIChTIONe MARCH S 1979 'e F I N A L dection 2 connection OProessino 0 Waintelninoa 2 3 PACE 9692b PAGE 26 Comnection MAINTAINING A CONNECTION 2 3 1 Flow Central a 00mmeem w handshake is Cameot@ and the virtual boom established the TCS state will be set to establilkhed until close processlno begins for some POGO Onc e th Connection eee Nag TCPsq melee goa1 while Maintaining a virtual comncsome tiOR is to sustain a rate of date transfer so as to facili a tat a constant date flow from user to users To accomoliss this# a flow Centrael mechanism has boen Implemented which Involves met only th two TCPs but else ether com0mpoets In the two access areas CCU VP TAC # i e NSI T Md TWO The access area comonent inely ded in this discussion is the MCCU similar mochan 4 sms Daovida the $CCU and TAC flow comtrol TCP-TcP flew control is inherent In the PotOCOl and does met vary across access areas The reader Can refer to AvooePdix E Yalu @ VII of the AUTOOP4IN 11 0ign1 Pian Reference 7 for details and the mathematical eNorISgioR Of the flow COmtrgl lgopithm The terms source and destination indicate which access area is being discussed That Is@ 9souree refers to the CCUJ serving to Originator of the dates Odestination Wres to the CCU serving the receiver of the data eetoonotwoek path 1 Source 145 will have un to a mauimum number Oi From user events Outstanding From User Return averts met received to source TWOP for any ore channelo The mauimum number wilt be Constant and will be besed 9m the eseed of the Imout line and other user secific informfation When the Maximum number Is reac %ed 481 will b0gIn holding Off tIha host# 0s a00 Speorliato foP the link Drotocol For examole a binary synchronous Communications 83C Orotocol has a wait before transmission feature which would allow HSI1 to acknowledge for a tranmisson while aakiml the host not to start another transmission 9 at this time 2 260FEB-79 Source TWO will haVe u0 to a PeuIMUIR number Oi Send events outstanding Send Return events not Pecalved to source TCP for any one gonnection The 0024mum Aumbere called the TMP-TCP send window# will be dynamic and will be Initialized Coon Rea turn event aMd Changed Send Window event by TCP see Pararaph 2 2 3 The initial value fop on oeni 91 user in the WCCU will be one A listsning user will hove a taeo send windOwv initially Source TCP will refine $nd increment the windOw 0s T0036644 UNCLASSIFIED PAGE 89626 2SoFE- 9 73636644 UNCLASSTIIED PACE 96627 -P 9PECIFICATION MARCM qq 1979 F 1 N A L action 2 Connection Ppoessing 0 Maintai i e PAGE 27 Connection Onviectiomo the lifOtime of a pecuiPed duping When the cupreqt m ximym send window Is Peoeehdo TMW will Oe43n holding off 431 because FrOm User mot be oroCOssed and# thPOfOre FPeom evewt w4lt to source be ououed User Retum evoets will not op lack toepeof will cause Hsi This action as described sOups HSI holdeff 04 th host# above 3 ocTCP will have uo to a maximum number of to destination unackmowledged Outstndi 4g TCP The maximum mumbert callod the TCP-TCP win dew# will be dynamic amd will be conePtloed by the be Conveyed om The window will destination TCP evocv segment tPeRsmittod by the destination TCP as Soupce TCP the destination TCPOs Pocivo window will send uo to that many octets befae waiting for Whe the mex Ockmowledomemt 40oo destination TCP imum outstanding is leached end the destination TCP TCPr Source has stooed eckmowledoimg for octet as a pesult# will be unable to s d an acknowledge In This mont to source TMP Send Return event o hold off source THP because the numb•p turn will Peach the will of TmOgIs outstandia Send events peach 8 avid will then The holduoff maximum eventually the host Source tets notwoPketanoeP oath 14 ReOestination TCP will hove a maximum numbep of Receive Return events not ceive eve tS OutIsteAvid The maximum mumbo rsceiyed to destiatiom TMPo two in the MCCU will mot very thrPOuhat the conTCP destimetion 6ag 4 on this maximum nection Will peculate the source access opts date flow if Receive Return events are not sent fePoi deitiation TWP to TCPs destimotiom TCP Is unebe to send fpom Peceved TCP TCP acknowledgments for octots This Situation will eve tually $too TCPe source and so additiomal octets source TCP fpom seodiGn fOeth oe numba 3 aove 5 Destination TMP will have we to a maximum number of To User events outsteodime To Usee R tuv events maximum The H1 iO ec4ved to desti mot mymnep will be Conetant amd w411 e based onoutout infopmetion user soecific lina soed and other the maximum is ceahod TMP will discontinue whe will This queueina eceive Retuern evets to TCP Cause the acknowledgment eate by detimation TCP to soure TCPso slow In tupple will# stoo whigh transmission POate 6 E 79 7 33 4 4 UNCLASSIFIED PACE M6 P SPECIFZCATION MACM g action as 97o e F I N A PAGE 28 cL maintaining a Connect4on Connection Processino bo PAGE 96028 UNCLASSIFO T963664 260F99079 ooed of Desttmatomo HSI will be regulated by the To 14e as well as the 1ink petoeolo the outout utfil will oet oe Guoued to TNP User Rotupn ove acknowledOments are rece4ved fOP coprespeotoeol acknowlm @i'ndo date If there is not a DPOtool such as for dgCfOt Used Wa the DePticulap ohoae the until am evsckponous oPatOgOit HSi will wa4t teeamitted am the i k Z O eomoleo dote has beoo the To User Retup event to ti@0 befoPe outuelm TWPo Ppocess4mg Dot 2 3 2 for a Co'nqction fore Ote CoP4i' fpoR the user goino to t0e network must be TCP is eoeulpd by the oacket switch SCm matted as a TCP header to user data To4P peaoe0ible fop add4ig sPo@PatiOn foP the letters 1n the ease oi a CCU or TAC# im This addltion CIv SiPi of the binaPy e ommt leader SL op Tseamento foPmat is a PeQIulperot fop all TCP sogmeett mon AUTOO N losta dad TCPs segmemts beinq echangied i AoendO l E Th Tosogmene Toseavoem is lDCeUPed he header wh ch carries TCPoTCP co tpol infoemaetomp iroed In detail Is Oeoloo in Aooedix A ior the data TCP aeefores severe 1 fumctions In vroceelsng summarized below as they These basic functiome ape networks hanal4ng the fumce avly to the MCU Simi le methods of as tney t4os exist in the SCCU and TAC Imolef omettiaOns to the AUTOD' sho uld in anY TCP Imolemomtotfon conominoi coocopotoc ol The seemapeo assumes that 1It9sanddpo tion has boe establish 1 v¥l daTIAlp THP $end Peauest the TwP will Peaueet that TCP send a TmP lottoe to In the MCCU this pfouest will be dost4oA4en ueep whatevep the veh4clo im the fopm O a Send event that the peauest Is a valid ome TCP muset vepify the cucpeet that the data can be sont in A Spi so° the curpent state is not If $tote cOmP' CtiO t4blise1o Or OtPo7 TCP will Polect tho sed rem Guests 2 9ogne4IAtjg4Ing thi date The maJ0 TCP function in usecetooiotwork oeocess 4Im is dotopm44mg whe the date OP comtpol imfope edop a Tesoegment motion can be etne buildime end fopmetting the segmen$toe etwokew l8oFEI- 9 T103be44 The first @eo is 9ee903644 L UNCLASSF E0e be transmitted to the the eiop one PACE 99 PAGE S6I 8 TCP T9036644 IasFED79 P SPECIF CATIONo MARCH S e4ction as PAGE 96629 OUNCLASSIFIED 1979 Connci¢on Procesling a F AL Maimtaimima cc PAGE 29 a Connection toe number of octets which may be sent on The available the c neqtio available wimdow window will be based on the teed window destiatio TCPs peceive window and Sow many octets have boeo sent top but not sgkmowledoed by# the destimes That Is# the available window equals the TCP tio window mimus the diffepe ce between the most tend 89aueRCe lost amd the seauemge mumba to assiaR If the TCP@ destinatio by numoep ackowledoed the to satisfy available window is laoe enouag the Teeegment %ede is built Peaueets send newt SIP via the networks and the segment 48 sent to If the available In the MCCU event S nd Date pe the eo send to enough lapae windOW is mot letter end thepe ape alpeady sememts on TCPOs Pe- eomoutee toe-seiSion oueue TCP will mot send the segment ape mo segments oR the peotpeemission 14 there the oueue TCP will sOnd the seament regardless of a@m window ea eeknowledgent CACK inmormation begments not ceePpving ueep text outeof-boad Imtep ContPol and status segments wACK egoment8 Puot 9eamentos ee Aooendix A and Paea segments error message oPaohs 2 104 and 2 1 b do not consume seauomee therefope# Can be sent at any eoase ando RumOeP time even 4f the available windOw is zero 3 acknowledaments for Segments aoet Thepe are two tvoes of acknowledgmento which are of The fiet Is the acknowledgment TCP to Interest has Data event fom SIP Indicating that the Send been opocessed In the mCCu this Is conveyed by a tqat Send Date Return event and Poroceesed meoea has been sent to and acknowledged by te seament AOCCO am If at tse 14mk level the source 3C4 notice I Rmdoelivepy netwopk Or occurPed eoPPe destiatiOn 8ubsecibre dOwn # UpOn tcanmeism go the segment to the $CW the Send Date Reof si@ TCP will tuen event will be meked aceordimqlv attemot to peotnpemit 8eamenti falliRg Into this her e w 1 1 be a fixed numbep eqteaorv Csee below coRR9etiOm will be temimatthe before petpees of Return Other OPPOPS returned In the Send Data edo TCC or opecedence ecuriv imvelid ape eveot and fetal Thee earors are destinetie addrpes Cause immediate Connetion loeuP9 Is Te second acknowledgment of imooetence to TCP that gent by the oeetiatio TCP fop octets doliv aekowle Thie eped to the destinetioR user CTOV o comes iR the Tseoement header of a segment odoqemt 2S 9 eS-7 6J3 eoO e eee cc 2ece c UNCLASSIPIED PAGE PO02 Co $PECPF CATON Section 2 ACM 5 t197 9 e Connection Processing received fPom the doetinmtipn ie adament TCP wi1l a TCP 1f th9 eekmgwle Preeived In a opedoterminod time# not the retransmit Only Again PAGE 36 F t A 6 M ointaininO a Connection segment number of lot below e lO so ate Ptpies will temoted before the Connection Is Closed destio 4hom an aeknowledgmont is PrCoived fPom the nation lCP source TCP validates It# ensuring that the aCknOwledgmOnt oldest the give between sequence nUmbOp veluoe4i unoeknowledged $ouoneo number inelus and the next sosunem e Snd CoNulum number It Is not@ the AC9 control Is ignored If live It the value Is valid# TCP will remove all ackmowle The the rotponsmisoiom ausueo fPo edged octets rotransmission Queue contains information Concerns Ing all segamts that hove OeeR tent to the network does but have not been acknowledgOed by the remote a septial segment Is acknowle If TCe tination edged i e the lower is numbep the Sknewledgment eGeOVneC the soauenee number of the loot octet TCP included in the segmont will Pecomoute the in the segment so that only uneeks date of start A come PetPnsmittede mewledoel octets will Ds Dloto TWO letters arS seknowledgOde TCP GuOuea Send foF eOrraooodim@ Send eVentse qeturn events to T4i '4 Petponemittin@ segments As discussed above TCP will potpomemit seommts 1 when notified via Send conditional two umder netwopk Date Return event that tranemission to the C2 when a OpodeterpineO and unoucceseful was tpranqsmn sucessful amount of time @lioses after $ion to the source SC with nO acknowledgment fro- The CUPPent destination TCP fop the octets sent 40 the time PetPanamiasio TCP send window at the If accout being considered is taken imto sequence number of the the first uneeknowledoei Current the within smont lies dota byte of the TCP Sand w4ndow the seogent CoP remainder tNepoef will timer A Petransmission will be tPoanmitted The lenoth of the timer may very# doe staptod Do me PtPansmission sending oan timer tyer but the o If the timo elasses TC e0animp emoine the sago Permitted as Segment will Psend the sDOPODPiatO OV the send o elosed whon mauimum number of Poe window transmission$ hove beo $ont the Connection will It should be notod that elosure as a result of network transmission failure will not Ins elude a IN eohange with or sending on oppop mess sge to the remote TeP rosoelsine will be local Essentiallv the close '#evislon 3L Foruay 8p 1960 26-FEBM79 1 790664e4 UNCLASSIFIED PACE 98131 SPECIFICATION# MARCN 'Joction 24 Connection 1979 F I N AL 0 PAGE taming a ConneCtion Processing Mai 31 Tito timeout value for thq network transmission failu e retry will be initially set to om@ $ Conde The timeout value for waiting fop destination TCP acknowledaomt will be based am the 1ine Good of the destinatiom user CCtjmhost channel for date egements and will be orowiatolv 10 seomds fop coptain control only segments SYN FIN and flush reauset o There art several types Of central Segments which ape mot Considered for petransemission These spot ACK# status# out-ofoband imterruote WACK end TCP srrar esaeSeg mts The information carried by the AqX and Status segfiMets will be sent again as aldi tional s Ametsa ape received fpomp the remote TCPs There is no TCP accountability of these tyos In addition TCP error messages deof 8 semnts nate that there is a catastrophic error in the By$tam% at the TCP opatoeal or network potocol level Relying rsaviping that the connection be Closed om the other TC to acknowledge for these messages is ouestionablef 2 303 Inteppuot PlueN Feature The TCP interruct flush feature Is actually two s#earat functions as defined fop AUTODIN 11 users Both functions or@ Verforomed at the reouest of TH A reauest fop a flush causes TCP to discard all not vet somentiled $ Ad rtaosto Send events SnO Sand a contrOl segment with the flush indicator Set to the remo TCP The remote TCP will discard all segmenmts having seauenee numbers lower than the Seguence nuember of the flush Control segment and cass the flush regaueSt to Tb4P Interruot Return event in the MCCU TH P will then discard all data not yet aueued to In the CCus and TACO all rem NSI Oar deliviery to the user ouests for the TCP Interruot flush feature are generated by THP imterruot funCt4ons @ee Reference 9 7CP also uses the flush feature for am immeodiate close of the Connection see Papagrash 2 4 2 o A reouest ioP an finterruotO Causes TCP to send a ontrol segment with the Outmofeband Control indicator Set to the remote 7CP The remote TC' will notify the remote TMP via the Intorrunt noe'turn event that an outeoomd interrupt has beon reouested This feature is referred to as interm ruot function 16 IRIS in the THP Specification Reference 9 280PERS79 TOAS6644 UNCLASSIFIED PACE 11631 11oJULo 9 86a4a938 TCP $P CZPICATZON# MARCH So 1979 F I N A L Section 20 PAGE S0'S32 UNCLASSIFIED PAGE 32 Connection Processing 0 Meinteiming 4 Connection 10314 Processing Dote fa the Notw@Pk Although SIP proviaes CCUOSCM network protocol support it does not Process the network date stream other them to en from lyse and remove the binary segment leder 851 The received qegmenrts ape passed to TCP via Rom segment Wyle Date events In the KCCU TCP will do all the processIiMg necessary to associate the segments with end dolivof- the This open segments to the appropriate virtual connectione seem cessing can be broadly Categorized sreas # as dfsccussedbelowo I@ domultislexmil three general under the network dote stream T'here 4F9 two types of Segments reeiVed by TCPt fop the werp date segments op these with dae dete control segments end those without data for the user control only segmentts Fop each rPee coived segment there are certain steps in attempts ing to associate the segment with a local user ena his active connection If any and In determining the proessing requirements for the segment stems Involve the addresses associated with subscribers and with the received segment Those local For each legal TAC user there is a Unique network For each CCU user there is a Subscriber address common network subscriber address for the CCU and a subscriber Part ID which Is not necessarily e unioue Cso Poeeh 2 1 7 If a user has taped an open or listen reguest via the THP Open event TCP will be aware of the Weser that Is# will be aware of the subscriber addrese port ID If the uOer's Open Or listen reQUest specfied a destine tiom subscriber the local address will be associ subscriber address foreign the with ated oddriess Port ID of the detination user o These two addroeses make up a fully specified' address socket PaiW which Is associated with the virtual Each fully connection Once It Is establishoe specified address Is unique within any One CCU Or TACO 1f the user's listen request did not specify a destination subscriber the local address will net be associated with a foreign address and imp from TCP's viewpoint a 'partially specifiedO ado dress when a segment is received from the nietwork TCP aittrats the fully specified address from the sea mont and attempts to match this with One of the fully specified addresses associated with that CCU go TACO Revision to July a@ 1979 110JUL079 T9044938 UNC4ASS FIEOO PAGE 632 26-FEB-79 T6636644 eUNCLASSIFIED PAGE 68933 eae eae CP SPECIFICATION MARCH go 1979 F I N AL a action 2 Conection Ppoeessino 0 mfintainino a Connection PAGE 33 If a fully soecified match is not found TCP attemot tq match the artiallv soeecfied address destination sddpess of the received segment ectually the address of the local user with one of the partially soecified addpesses of which TCP 48 swape for that CCU OP TAC 1f a oa'tiallv s0 eified match I$ Still not iound TCP use the partiolly seified local address of address ifom the segments ignoring the foreign to match on any similar the received segment again local address The local address may be associated If a address# in this case with nother foreigA match is found TCP will analyze the associated TC8 for ossible opee9motion see Paregrapc 2 U 3 If to the above 4ny of Was not fOUnd O or if preemption was nt oossible TCP will a TCP-TCP eppop messao segment to the of the segment with scofnection does not indicated a match temots petpn sender exist Jf a match is found TCP will peropm oproCessing as reauired by the received segment type and the cuPSpecific informePent state Peflected in the TCB tiom Cam be found In Apoendix D THP State Tables 2 Peaeembly aueue or are either date segments Secause seaments or data segments with eonsegment TCPTP -cotrol functions TCP tpol information one of the majop path is assembling the dats for the etwork-to-user Oue to the nature of the paCkto oe given to THP et switch netwopk segmots do not necesse4ly arrive at the destinotign Im the order sent from the For this reason TCP must accumulate souree TCP end reorder segme8ts baed on the segment sequence numberps before vassing the dateamo to TWP seaaCknowledgment Destination TCP will not send to soure TCP fop an octet until all octets moent received# been wit lower' seauence Numbers have eesetially until the data hOt bem acknowledged always TCP event fpom THP bV a geceive Retu THP The THP 1lttep to sends a complete the TuSegment of edeof-eetter indicator is Dart headep c ntrol information I DerorminO the rorderie #unctomo TCP ensupes tnot duolicate segmemts are discarded and that this To oerform honored TCPs receive window has bee these cheeks# TCP Considers the becinnna sequence field of number sequence numoep one In segment 280FE9-79 T0336644 eUNCLASSFIED C 0 ee 5 000 0 PAGE 90933 2 ALImMI TCP SPECIFrCATION Section 2 T eCH 5 CL A S1 1r iAGE 0031 F I N A L 1979 PAGE 3 Connection Processing - maintaining a Connection T-smg-ent header an the emcin seaueece number ne innimo sequence munmer pluS text lemgth minus one for incoming the segment and the Current Pe- ceive acceptaoility range The receive acceotability range is determined ov the sequenee number of t e last acknowledged octet clus one left edge of receive range and the seouence numoer of the last octet which will Oe acceoted left emne clue receive window minus one The following rules 1 If the starting seouence mumber lies to right of the receive accectaoility range or enri o sequence number lies to the left of ranmQe the seqment will be Ciscarde- 2 If the starting seouence number lies tme the the to the left of the receive acceotability range and the en'14mg seQuence numoer lies within the range the start of tme segment shell ce adjusted to Coincide with the current left edqe The octets preceoing that have already been acceotel orocessed ana ackmowledgeo the startino sequence numner lies Within the range end the encimg sequence number lies to If So the rloht of the ranger the entire segment will be acceptea iff in aoaitiomo no segments are currently On the reassemoly oueue 14 there are other segments on tne reassembly oueue t is segment will be aiscaroed the starting sequence left of the range and 4 If nmber ent S lies will tO the right number the of the lies to the emaing sequence range# the seq be oiscaroed If the starting and ending Seouence mumbers lie ithim the range the segment will be insrtesd in order in the reassembly oueue 4hen an en- tire letter has Deen accumulated and if there can be another letter sent to TP4P see Paregrach 2 3 1 TCP will send the letter to TMP 3 senoimq acknowlewo3ene The ACK provide tion - segment iS iss accountability to the source TCP ACK W segments ------- Se y the ann roceive inen the the acxnowleogmpnt fie1 duence number of the next octet siot destination 2-AUCG-7 Tt TCP This seQuence o QCLASSIFEO O I6936 0 0 0 0 0 0 -aft destination TCP to mindow informaACK control is contains the seevoocted bV the number 4molles that Qevisfon 2 AuQust PAGE % 534 3 l97q 2-AUG-79 TAau6936 UNCLASSIFIED TCP SPECIFICATIONp mawCk 5 1979 a'a F I N A L Section 2 Comnectiom Processinq u PAGI PA35 PAGE a 35 a Connection ataan ng all octets with seouence nuwoers lower then the acwmowleogment value have been aelivered to amo actmowleaged oy nestinatiom TmP The ACK serivent its or without user text will me sent to the source TCP under five conditions I A Receive Return event has been receaveo from the oestination 1HP which Causes the value of the next octet evoected to increase by the letter size This ACK sepment will acknowleoge for received oelivereod octets 2 Pew beem has segment Immeoiatelyt if a Iata ceived from source TCP the sequence numbers for all octets of which o not lie within the accectable seQuence numoer range This ACK seqent is Sent to iterate the destimation TCP's receive wi now ero t'e value of tne oreviously ackknowlelgeo seouence number 3 Imlmeoiately if a va44l SYN segment is received end processed 1mig ACK se g ent will comnlete the three-way handshake see Pararaoh 2 2 2 4 1 ieolatelw is if a valio flush receivea and orocesseo reouest see segmnt Paraqraoh 2 3 3 S AS SOOM as all octets with seguence numbers lower than a receiveo FIN se0went have Deen aceounteo for Tsis ACK segmrent comoletes the FIN evehanqe secuence of connection termination see Paragraoh 2 94 control handling the T-seqemtt caerrie 4n forhatlom Control header is roCesseo accoroinq to the current state reflected in the TC5 Speclf4cs of tmese relation smlos can be founn in Aocenoix 0 It should oe iterateop however that some TCP-TCP control imfopa mation is not acknowledgqed Only SYN FIN flush amc OPEN Control SeQnents are subject to accountability As Ofscussed in Papa raoh 2 3 2# te noature of the unaccountable Information eli inates tie eel for retransmissiOn or accountino of some TCP-TCO comtrol only seamemts If the uaccount Wole Control lnformation is carried in a Iata seoto the memt however the seqgent will ve sucJect ccoUe taoilftv of the data segment evision 2-AUG-79 T- 146 936 UNCLASSIFIE r 2 Auqljst 3 197R 04GE 000 35 28 PEB-79 Tgi34644 CP SPECIFICATION# mAemN 3# 4ection 2 tUNCLA8 EooD 1979 PAGE 89e93 o F I N A L Ct PAGE 36 Connection PPoCet64ng a TePminating a Connection 2 4 TERMINATING A CONNECTION to FPom TCP'S view09it Cownection can be Closed either event op eallv by TCP itself or at TNPos request Close if the close Is Pemote pemotely by the emote TP op TCP TCP will not be aware of the peson for the close unless 4 was due to a poorted ePro In that cast a TCP-TCP error Exaet oPocessing far all message segment would be Peceived Aooenodix D classs can be tpaeed using the state tables in The PelOtionseia between each elgoe twoe and each oeuible rOPcduPt There Is a genePl connection tate ap9 meayt howevepe which cam be summapized hopes 1 Initial stimulus The initisl stimulus for teeminatipo a connection may be a THP close Peauesto a TCP detected ee'or or timeoyt or TCP preOmotio of te aom eetiome Each case is different In tnot the close opocessing may be deferpeo waiting until dee liverv of user's data OPI mmedIates Ii the close ococessino is to be greadual tdfeped so pemote 'R Is actively sending date and the close mnts TCP will motifv the pemote TCP that The 9tatu$ segment i used eoogespino has b qun the Onforms fop teis BupPoee %is nOtification remote TCP that no maps data should me sent on the sending connectieon The locsi TCP will continue his usepes Gate Cthat peeeded the close reauest destineuntil all date has been doliveod to the tion TMP TOe closin TCP will nat send the status segment URIess a Iota segment pemOte TCP after elote opocessin Peceived fpom the has begum I the Close orocessing Is to be immediate or once is comolete as discussed the deferred delivepy above TCP will begin the net @too the connection The hanosneke is nat aee temotton handehake PPOP comolished if the termination 4 due to TCP or opeemotion ee Papeopooh 2 4 g 2 to the FIN sequence a The FIN seauemee Is similar 3YN 8egment exchange of the threeewVy handshake for It consists of each TCP establishing a connection tendina a FIN segment Peceiving a FIN segment from that segment the other TCP acknowledging the FIN Peieiving the CACX egment and wes peceeived seenowledoment for the FIN eement that wOO sento tOincidently aCknowl thee acknowledgments will# see Segment edge all octets Poceivod 0e the FIN tan Sequence numbee will be OhighePa auence numbers foe orevious date segments sente These General opeocedupes 286FE9079 T066 b44 eoly to most close UNCLASSIFIED Soeifie PAGE 98836 In 1I JULs79 UNCLASSIFIED TO84b938 TCP SPECIFICATION# MARCM S 1979 a's F I N A L Section 2 Connection Processing formetion PAGE 1933 PAGE 17 000 Terminating a Connection the d4ffopent trsn of connection Closures Is on Given in aubleouent 204 1 Lcal PoPeOPsoDes Graceful Close os sese 000 0000000 The locgl graceful Cls9e type is also roferred to 6s a dee The stimulus tI a reauest by tho fipped op graduel Close to In the CCU this request user to close the connection entered vie the THP close command no eonveed to TCP via It is see the Close event with the deferred Indicator Sot sumed that whom the usep enters the close commend he went all data previously entered whiOh may still be In the nets Me does not# wopke to be delivered to the destination usep the Conneetions howeverp went to Peeivo any moPe date on this and If date Is actively being sent to the Consioaring remote TCP# the by the Closing uep see Paragraph 2 4 log closing TCP will notify the remote TCP# via the statue The remote TCP ment toot close processing is beginning Once all will then oe In the remote close received states acknowledged the Oprevioulv Sent data octets have boen closing TCP will begin the FIN seuence described in Pes Graph 2 4 204 2 Local Immediate Close referred to as en The local Immediate Close tvpt is also abort One stimulue fop this type of a ClOne is a pequest In the MCCU by the user that the connection be aborted this reoauet Is entered via the TmP abort commend end come flush indicator veyed to TCP via the Close event with the It Is assumed that the user loe not went any more $ t data to be delivered In either direction om the eonnoetione Another stimulus is a second Close event for the coanoetien It is assumed regardless of the deferred flush Indicator that a subsequent close Peauest Close event was Generated under conditione which Pequ4re immediate action for Closures A third stimulus fop the immediate close is a local MP des is Conveyed tacted protocol error see Reference 9 0 whigh still way s a user abort request to TCP in the Same another Stimulus for the Immediate Cloe is a TCP detected epop or timeout condition In the first three Cases the closing TCP will begin the FIN in Paragraph 2 4p so sOOn as the items described sequence ulus is revlved All dOta Currently 04 TCP 4oe In the ogmentfigdp w411 be reassembly ousuO Or waiting to be flushed TCP detected ePPOPs do not result In the FIN Revision ip 0 IleJUL- 9 Ta4936 UNCLASSIFIED 0 eOC 0 PAGE 1 0837 @e July 40 1979 CP SPECIICATION# MARCH So ectfon 2 PAGE 88138 UNCLASS F EOo T9036644 26-7E8079 00e00ree0i00re 1979 F0 I IN AL 0 PAGE 38 Toemiiatimo a Cme'ectieo Connection Processing The Clos hpfoe Only the Opop me$sese smemt Is $ento A TCP Ina TCP then coeidePs the connection to be cloeed peceiving cation-of an orpop messaoe seqmet @epforms co tail vmopiff the oppoP -Osseo@ soemet e Porogpooh 2 1 ande If the seqment is Peliable Comsidees the Connection to be terminated and motifies the loeal THPo 2 4o3 Comnection Ppeomotion a ahighapr ithpee by A eomnectiom is subject to artemetiom fop cooctle or because 0f eritical opgeedece Feaucet The subject of this d4SC4usi@A will Primarily buffer sace retmotfom is subResouce Connection reemotiono be fo connec McCue Zn the ject to imolem mAttiom PeQuipements only if there tioa will be opeemoted for PeSource deoletoe TCP will always peemot lower are mo alternative solutfons catecopy 14 _ eomnectiOns flist oeoemotivq eateopies 11 amd III only if the situation dictateo Category I tios w411 mot be oeeemPted fop amv reasoet commees As diSCUssed im ParPvieoh 2 3 4 am otteMot IS made to mate% reeCived gegeet with a local Subscpiber and a cOPPosco@dis received If a 3YN segient iag Connection ifa oulble or am that is mat ssolciated withan established commeetio already try to fimd am lists TCP will outit4tdira established sonection fop the addreosee of the SYN SOGmett fop Is a Caed4date that Co mietiom If a match is iou d following critereia must be satisfied comoreemwtaor The foe the oceemptiom to occurs c1etalye hOwevepr 1 2 the SYN segmemt for the seqmenpt must be a valid isf the Oqcupitv oePCOdemce and TCC that useP local by the use fop be authorized must SUb$IPibee DOPt 10 the subfCpibe oopt comectiome state other 3 ite@ the 10 must be In established e the Connection cam mot be In any established SYN segment the foreion subScIbeer oort 10 im the 'upt be diffeect them the Csemdee of the segmect the of address soecifed the fully one im established Connection 4 the commeetfom must be is Indicator ovemt in mCCU ev checks So 26 FES-9 the SYN segmemt T0036644 marked oroemotoblov thie In the oec reguest Ooem Carried end maved by TCP for such conticnme pecedeee must be UNCLASS3IED In a higher PAGE 1036 eo 86S1YES 79 T633 644 plot 681139 UNCLASIFIPED CP SPECIFICATION# MARCH So 1479 F 1 4 AL a'PAGE Section 2 Connection Ppecesu$Pmo 0 Tepointirmg Coeectton 39 tegopy to Its III# IV then both the uend an d Poo ceive the pe cedtes of the established coAmeeti@m see Par easoh 2 2 2 be neither 0peede mge level of the established Commece tiom Mov be In ceteqcy I 10 0 d Cisiam is mad to oeefiamat the established coi'm oimi TCO will se' d on epor vesseae seginemt C'comnectio' opeompte ed to the Pemote TCP and comoletses tablishmt of the mew connection The following steps are taken in am MCCU Poon cardingq areemotion pocessimat 1 evaluate or PePtabityq as de scpibed above# daterimn that oceeffition is possible 2 ge d 'comr'ection DPeempeedo M099800 0091POt to motO TCP am the PreeMoted old eomectfom Poo 3 eefopm Close DrocesSime on the old Cofnect'iomp irm cludi @ ermd4ig e Close Rotupm event with Commectiom 0'remtlO reason gode to THP a peaeet now Tea top now connection 5 apace SYN segoomt fop mew commectio en d coninrue thpoeawav hamdahake for m ew commv ctiom' be oes throae-way hamepdhav Is comoletoo ue'9d Proofflt fmdicatimo that 0000m comolete evomt to THP DP66055ima to P0e0Oued foip mew comectfo' 7 calculate and P0leV via Seed Windaw event T PQTCP send windOw fop the mew connection aserrEP07q T0336644 UNwCLA$31FIED PAGE 00039 the 78e 11644 P SPECIFCATIONo MAPCM So UNCLASSIFIEo 17F I N A L e i9 PACE 00040 PAGE a@ INDEX AUTODIN 1 ummapv 2 abort • • • • • 37 aCCOUntability 7 9 ACK segsmgrt • a Clog event • 9 a 0 37 o 36 37 38 conoection Deemotgrp 16 connection DoeOmot4on 38 connection opocessira S control control kIedliRa segment$ • 23 11 32# 3S close pPocessinA date seguents data struCtuPe s defeppe cloge a deultiolow1 ng domultipolel'ng OPPOP 069Q4u a • 9 5 • 37 32 32 9 establishing a connection 16 evenlts 0 FIN Segments ilo' con trol ilush 9 0 26 o 0 fiush Poauest goaceful 19 22 6 clog most S00e94e4 31 9 37 intepface h48 3 immedate I _ 37 qftorrunt flugh feature 31 local close o a 37 move connection 24 Open @cessiO ta 16 22 Goo M peOust a a a a 60 16 uteofeband Itterruot 31 Outeofeua interrupt 9 Docket wetgi 26419 9 22 Metwork 2 74 3eao oUNCLA$SS IED PAGE 16940 Indew aj uo 32# 33 Receive Data events 32 Receive events Reotremef$ a 32 4 I@4 ce Protocol lmtep 3 eomemt PAGE A1 1 q N A L TCP SPECIFICAT ONe MARCw S 1979 peussembly PAGE 6141 UNCLASStFIEO tI836644 280FEB079 CSIP 2 28 28 Send Oate Retupn events 28 2e Send eyents 7 secuonce nueeps effi@' t Send Oats eyvents 2 SIP status secot t 9 It SYN segment SYN segm Mts Teseomemt a a e tcO a TCP 0 0 6 6 9 6 65 21 window r@cel 21 TCP send window TCP states 6 TCP-TCP eppom massages 9 terminal amlNler T 3 Termimaletawo4st Protocol TNP 3 a connection 36 37 38 te mimotiat TIP a a 0 0 0 a 3 22 6 8 11 Op a0sk tspite-way Tensmission Control Slock 5 UG P profile WACK Segmet wOPEN seament 26FES79 3 9 16 19 22 PI36e4 UNCLASSIFIED 44 6 6 l PAGE 00al 2- UG-79 UNCLASSYFIEI t APPENflIx E A-1 A T-SEG ENT HEADEP ThIs aocenaix describes the TCP TCP T-segment header forat to be usee ny a TCP aesrelg to interface witt CCU T C TCPs om the AUTCGI - II network There is no vaeiation to the for'rt as cescriDed herein The memory jaqp sown% iin this aooenolw shows 3v bytes e pThe last byte 2q 29 for the T-segmeo t heaoer t'ru oresentel cy oashes m p is mot oat of the T-segment T header he T-seumemt heaoer buflt oy TCP for each segment sent to the Met Ork is 29 bytes long Each field In the 2q-bvte T-segment header is oefined ie the oocumentation fOllOwinq the memory imgqe The fielos that are aescribed as 'unusea are always zero The format is smown in stariard DEC PDP-11 memory image fopmat# with the least siqnficat Myte 0m the right even numter ana the vast significant byte an the left ode The bitS are labeled Z to 15 Wore a tIhbit of number least sigmificant to most sionificant right to left in the worede To irection of transmission is from the least sighi#lcant byte least significant bit C to the most signifle cant byte ost siQmificant tit 15 for each word i Qevislon 20 -AtIG- q t 'u 937 L 0 00 CCeeeetE0 IUNCLA$STF1EO ugugt S 1q79 943b69 ibePE e79 UINCLASSIFIED PAE - TOSEGMENT MEADER 26oFEB 79 BYTE IS 14 II 13 MSBLEN 12 11 1S 9 I 3 umused 55 i I a 1 6 3 4 M'ORLEN I I EXLEN 2 VER BYTE I I 1 14GSEV1 2 4 1 OSILDSNT1 171 LOuET tI 30TC 21 1CaNTALK 26IaP260 g 7 S Ussu33 FESR 03CP 1 16 1 28 005 1 ssbgq UNCLAS51I ED o PAGE A-3 ToSEGMENT H4EADER 26 FEP679 BYTE IS 14 27 1 1 A2 It 1 utmused 9 a 7 S 56 3 wmume 26oE 9 TM3509 UNCLASS1I ED 1 9 BYTE 26 ICONEXT 21 2 11-JUL 79 T0uI44940 UNCLASSIFIED PAGE A-4 TeSEGmENT HEADER MNtEMONIZC VER 0 OF SITS La DESCRIPTION TCP Vsersion Nu 66r Value reOOeSOnting the version of TCP being used by the senaer of the segment IIORLEPI H eader Length Value specifving the length of the Twaegment header for this seaoet The value is currently 29 byte$ Text Length CM39 most significant 4 bits of the value reopeseniting the length in byte$ of the text carried in toie segment %SBLEN 4 TEXLEN BText unusfid 6 PIGSEQ 16 Segment Sequence Number 4389 most significant 1S bits bit IS Is mot used of sequence nuffior fop this segment If status segfpmt Most significant S5 bits 64 sequence Twumber of last consecutive octet resolved by the sender of this segpmt L0103EQ lb Segment Sequence Number L3S o Least signilieant 16 bits Of Sequence Mum6er of this segment If status segment least si'anificant 16 bits of stauenc number of last consecutive octet received by the $ moor of this segment CONTRL 16Control Imformastion TCPwTCP control indicatepsa bits 3 2 8 specific TCP functiong bits 3 5 are unusedl bit 6 8 wACKI bit 7 w wOPENg bits 6-9 are unusedl bit to a flushl bit It a endeofelettert bit 12 Is umusedl tit 13 a FIN$ bit 19 2 CKj bit IS a SYN See also Te egmenot Mec0#r Control Field Expansion 050 DESUSR 1l JUL-79 Length CLSS Least significant 8 bit$ of the Value rP resenting the length in bytes of the text Carried In this stgmt This $-bit field Is mot used Statictownamic Indicator Sit specifying static or dynamic destination opt 10 for destination users 11Destination User ID Volvo representing T0i4u4940 UNCLASSIFIED Revision I# July 4i 1979 l1 JUL 79 PAGE A-5 UNCLASSIFIED T944494 TeSEGMENT FADER 396JUNO 9 MNEMONIC 0 OF BTS DESCRIPTION useP ID Dortion of aestination Dort I Destination Function Suffix Value rePOresnting Suffix Portion of destination port IDS DSSUF SD 1 Satic Dynamic Indicators Sit spicifvig static or dynamic source port ID for source users 8OUUSR Source User It 10 ID portion of value oeeonting usop coures poet ID Source Function Suffix Value SOUSUF reresoenttng function suffix Portion of source port 10 DESNET a Destination Networks Value representing the destinetion network of destination usef currently set to sere DITCPL a Destinetion Subscriber Address LSO Least significant 8 bit of the deStinstion subscriber aOdress DITCPH a Destination Subscribep Address mSB Most significant a bitS of the destination subscriPer address SOUNET a SOUTCP 16 Source Networks Value reoresenting the source network of source userl currently get to zero Source Subscriber Address Value repreoemting network address for source subscriber HIGACK Acknowledgment Field M$8 4ost Significant 15 bit$ bit 15 IS mot uod of seauence number of next octet exoected by seneP Of this segment If status segoment most significant 15 bit$ of lost octet delivered to THP vy 16 sender of this segments Acknowledgement Field CLSS Least Significant 16 bits of SeQuee number of next octet expected by seonder of this segment If status segment least igniffceat lb bits of lost octet lb LOWACK deliveeoa to TMP by sender of this segments lloJULo 9 TON44940 Revision UNCLASSIFIED O so s s so so i l l I July Me 79 lj-JUL979 0444U94V UNCLASS 7 ED PAGE A-6 TeSEGMENT 14EADER 39eJUN-79 MNEMONIC SEGWIN a of @ITS DESCRIPTION 16Receive nmdews V4lU9 Of d ltimatiO#' TCPO s eedeP of this seafflemt receive wimdowp oxoeess d Im fMUffbep Of Octets which d st4Fmatiom TCP is Williimg to acceot from source TCPv CONEXY a Comtrol Data Extem$4io'9 Filid conaimirg various 1rmfopmatiom to be used by TCP So Comtrol Data Extensiom unused A This field is reserved foe the most sianIficant 8 bits of the TCP ePhecksump however# CCU TAC NCC TCPs do mot use the field unused a Th is field is reseved for the lease significant 6 bits of the TCP Checkaum however# CCLJ TAC NCC TCPs do not use t e field 11-JUL079 Ti4Q940 UNCLASSIFIED Revision If July 4 1979 26-FESoT9 6936569 UNCLASSIFIED PAGE A-7 TesEGMENT HEADER CONTROL FIELD CONTRL 2beFES-79 BYTE 15 14 13 12 11 10 9 a 7 I ISYNIACKIF NI AAIEOLI PFLI UM U9 dlWOWAh 1 ZbSEW 9 T336S@9 UNCLASS F ED 5 4 jUPaed 3 2 I 1 0 COND13S BYTE 260FEB079 t0036S09 UNCLASS F ED PAGE A-a Y seGmENiT HEADER CONTROL FIELD CONYRL 2b FES-79 MNEONI 0or %TS DESCPXPT 0W CONDIS 3 TCP Function Indicator YhP @ bit Code ior iumetlon carried by this $eGmmti a mo TCP fymetioni I a Control extension field CONEX eontains 91pe code for sogment PeCeiv do 3 a outoofubamd intorruot 091 Peouitstal 4 2 Status Cantrell 2o So 6 and 7 are met defined unused 3 This 3obit field is not used MAX I WACKI dieatoP whom smto lndlcates the 5@0a@fmt is am actknewledgeot iop a r OVEN asefomt 00 IWOPEN rndieatep Whomn set indicate$ the seomont contains WOPEN conteol 4iopmo'tiom new TCP Pecelv windows unused 2 Th is 2ob4t field FL I EOL I Flushi Indicetps ho sIenat indicates th' e@'a ootIs ceQuostino tha t the cfeeivlng TC Veeform 6 CP ilueh funct lam EndsoisLettem Imdieato 0e gt# seo indicatos the seomomt Contains the last byte im a THP letters A aunused iThis asmet uood 1-ebit iield is mot used FIN F INJ Indicateps Whom sets indicates tee segmgiet contain final acknowloccement information amd that the somdep of the segment will send No aoditiomal data or Control an the comnection amd will deliver no additional oats to the local AC' ACI Indicators whom voe indicates the acknowledgemont field NIGACK no LOwACK eontains an acknowledgement 4op octet received by destination rc sendS of this segment 3YN 2boFERS7q I 4836SM9 SYN Indicators When set indicate the seaomt contains SYN control UJNCLASSIFIED that bm6FES 79 TJl3bSNq UNCLASSIpIED PAGE A-9 TuSEGMENT MEADER CONTROL DATA 26uFE 79 BYTE 1$ bePEBc79 14 13 12 1I1 IS 9 a acm TS 36gBq oUNC 9 7 6 I $sSrVzEo 5 4 SoO 3 S 2 1 BYTE SIZE S I1 JULw 9 T9449a0 PAGE A-10 UNCLASSIFIED0 1 GIMENT MIADER CONTROL DATA EXTEN3 ON 36 JUNu79 mNEmONIC 0 Of 4IS DESCRZPTZON ft error m Sao CO'OISt 0 contains code for ePor detegtodl octal values 1scomeetiom does Mot e5 stg 2sbed $YN Controll Sire Errop iZE 35hilf O0011 1669 IuPitY OP•PrO ltuSSL subscriber address error 12UTCC epror I3sTsegmomt header SubsOcEber adress errore If 3YN contpol lmd cetod contels soproxumete number of gro4fS Cre im a 64 bytes to be semt in a TNP letter SPO 11 JULw 9 3 TS494406 Snout Lime Soeed 3-olt coca for the saed of te line m bon betwem source user and source CCU TACO 0 a IS 4 or eel I a 3Se 2 • 6691 3 a 1 e0 a 2801 S a 480et 6 8 960@1 7 5 19200 or mope Field 40 used oMlV if SYN control 40 imd4iated UNCLASSIFIED RevIgo 1t Jury I IQ 9 PAGE B-1 TCP MCCU DATA STRJCTUQE T74I ao0ondit describ s the MoJoP TCP date structupe of the CCUI the Tpeaomise o Control sloek TCe This structure ll the Information FeouiPed to oerfopm TCP comnmeContains toe eo e4ssimo fao am MCCJ The exaet ioemet for the TCS is unique to the MCCJ however siilar infoemation eoncerning te vep $ Coenection must be ma4htuimod bY any TCP9 The 4oremt is in steadard DEC DOnr1 eamoev Imeo fosemt the least 6o49lficat byte op the right eveh number and the goot 84 AlfIeSt byte on the left odd humoop of a 16ooit words The bit retosoeled 6 to IS least Si ifie Cent to-mot 04amifieort rioht to left In the word with The emory iaGeo fop ieh structure hown in this ooend1u is deacpibed fay-on4ecompoovyi mpetive The site bvte wordt Of each unit Ote wfthiv te structupe 0ev cese Neutrl bytes within or at the e of the structupe The@e OutPe bytes aoe nOt used end may be MoPkod as such or not defined In the narative They wi11l a Peoreseed by a feree of dashes w a a in the memory Isaae ad oee always zeo If the outpe byt s is within the structure# it is If the of coupe coumted in the lemath of the structureo Sites byte I is at the end of the stPuCture it will Mot be Counted i the Moth of the stputwupre Revision 3 roebpuapv of too@ 7F 09 TB033699 UNCLAS31I EO PAGE B-2 TCP CCU DATA STRUCTUJRE TRANMISIONCONTROL Rt OCK TCS TI' TC9 ea-timl most of thIm4fopmaioe' ecuied by TCP to DeP#OI'k COFMOCtjOm co@cessir@ heea is ormo TCB oef' comme tiom ev Pmt Thq TcA is treaed im the CCU wm' A a valld Do is reetived4 from THP# tmd d loted One@@ COPm9OetiOm cloo $UP is Coweleted ThereO ore othaeP ''or date Stpuctures used by TCP howeoe' p tese ape imclemePtatiOn-Gp1 nted sma are maOt di$CWugod im th'is o00Oe' 270FER079 T09369qq UNCLAs31F 1O 2beFEB-79 T0236509 UNCLA3S P ED PAGE B-3 TRANS'41SS ON CONTROL qLOCX 26eFE 8 79 BYTE IS 14 I I 13 12 11 1 7 ISTATE a SEN PRC 3 1 I 5 Ilf 9 7 b 5 3 S 2 1 BYTE 0 ITCISEC TCSTCC O 'FLG I 2 I RECPRc '4 I TCBACK b 1 t3 1 2 1 6 is 171 tI wj QI i 2111 I 231 1 2 231 1 24 LAAC 6FR7 T360 SENNLA 1IED 9 TSJ3b609 260PES 79 PAGE B-4 UNCLASS F EotO TRANSMISSION CONTROL SLOCX 26-FEB 79 BYTE 15 14 13 12 11 1@ 9 a 7 LASACX 6 5 £4 3 2 1 BYTE 0 32 1 1 3s 36LSI CLES 29 1 3 1 1 I cN 3 1 TCEALID 1 453 SET2 PFG1 4 1eCTSEWD4 71 UwE9 06@ SEHD4 I NEASFE Z6oUESm7q T9336509 PAGE B-5 UNCLASSIFIED TRANS'4155 ON CONTROL BLOCK ZbwFE58 9 BYTE 15 14 53 I 1 t2 1£ PRt4P'LG Is I 10 9 B 7 6 5 a 3 2 1 0 BYTE IUNACKO S COLN1 5 F I SE 53 1 CLC 562 651 57 SEGJT I 671 59 fa 1 I 5 b61 AC CN UNCKI3311ED8 26-FES-79 0 9 UCASpE PACE B-6 TRAN3 133I0N CONTRO0L 9L0CI 26%UEB q MiNEMONIC 9 OF PITS TCBSEC BStcupitva secuity level gociffod 4 m ODem Vfmt1 If Meoe soeCIfled In Ooeem 9ve tooteiAg maximum fecuity level Suthoriled fop us by this user SENPQC TCOTCC DESCS PTION Send Pr'ecodee Procedeme level scocifiod im Ooe 0 vomtf If meo specified im 009A ovomto Contairms maximum oreeedence level autherled for use by this user It TCCo S4iAep value for TCC soocifieo In Open even if meoe soecffied In Oven ovemto Coemtaies taro RECPRC aReceive Preced ence Precedence level of the Rmetworketo-u5 f via o4 the commectiae to be used by the remote iCP i 'so5ridirma data to local userj value is used in Connection peemoetiom OPNFLG a oeem Plea' Floo from Ooeem oveqto Indicatin g which aome P Quest Varaffettrs War maot specified by usopt set if Daremiter Is u'sooclild bit 0 a socurityl bi I a sema PPeeCdeeceg bit 2 a TCCg bit 3 a destimotio address TCBACM a STATE aCovtection Stat Field desigmatin' Curremt state of the commoetiomf 8 a listePm I a ooomt 2 a 3YN s@mto a 8 SYN sent receivedl 6 8 establishedi lb X local CIOse receivel Is a FIN somtg to n FIN $eAt reIvaGj 22 a FIN receiveal 24 a reffiet close PCocivedf 32 a cl osed TCB Aekemowsdaemeeet Flaas Field used to Govern trossisoe of ACK# Status 051 W0PFN# and WACK Central geqmemtsg status X-11I ACK X 11 WOPEN a 2l wACK a 31 081 a 0 SENNEW 32 Next Seautmee Numbse Value to be assigned to melt seaport So ts SENLWE 32 Semd Left Window Edge Value of seautmee number for Oloest uMaC mw'odged Octte 2b 'S7701936S09 UNCLAS31F E0 TUI365M9 26 FEI UNCLASS F ED PAGE B-7 TRAN3MIS310N CONTROL BLOCK 26sFEW9 MNE 'ON C weem-oe e 00 nF 9IT$ 0 4 ae DESCRIPTION emeeww which may SENWIN lb Sed wmldow wumbeP o octet$ be sept to remote TCP WINPTR lb Wimdow Poimter Polmtop to wimdow array entpv iO co ecti0ml eorltaims in ormatiom #or' each comemectiom such as receive w4rmdows max4mum peceive windOw ever issueds imout amd cutout ard imout lime sooed fo Comect4or amd outPut aooroxmate ltter sizes current RECLwE 32 Receive Left Wl4dow Ede Value o mext seauenCe number exceeted fPom remote LASACK 32 Last Acknowledge0 Value of seduence mumber of last octet suceessiully delivered to THPi used 4 TCP close aCCOUtobility vroCelS mg CLOSID A Close Event 10 Tramsectiom 10 o# TIP Clo$e event or zero if more received CLRESN Retransmission Tail Ponter to next available entry In retrasnmlssioa ueue SEGTAL ACKTAL Close Reason Code for close reasomsl a local user Issued a close and no error erropsccuppedl nomeerOePa Is Ceusino close om'd4tiO AAckowledoememt Tail Poltep to newt available emtev In ckowledgemet Queues RECBAS 32 Receive Base Value of seoauece number of flest data byte Peceived on connection fpcm remote TCP RECSEO 32 Receive Left Egoe Value# relative to of Seauence n umber of Receive Baas# receive left edge Receive Queue Pointer to head of AECHED receive Gucue RECC14T SReceive Count Number oi elements om receive euewe T RIO 26-tE s 9 t6 Te3509 Timer 10t Timer Identiflcation of Retpv 0 000000 IUNCLASSIIE0 260PE5079 TOA3S699 PAGE B-8 UNCLASS FIED TRANSMISSION CONTROL SLOCX 2b FE S79 MNEMONIC 0 OF SITS PESCRIPTION event auguod becauee of elements om Petpemo issiom aueue op WOPEN control outsloniOa wOPFLG A Flea Flea imdIeaitmQ mumbep of heve beem made of WOPEN contpol which %eve mot boom ackmawledged by WACK COmrtoI segNeMt wOPF tPmsfissi om Reaesse-mblv R$FNX pi4 ter Pointer to met available free Deco iM peassembly queue Semd Queue Head Pointep to head of semd queue SENHED 8NCNT Send Queue Count Number of element Cm send queue umueq 16 1b-bit field is mot used Reassemblv Heed PoiteP to Need of peesembly queue RESNE0 RESCNT This 6 Roassembiv tourmt Numbe - of ei emato am Peesesebly queue Retransmission AekmowledQememt Pointer Poimter to fieet element In petpeasmiss4Or oueue which hes mot been UNACPK ackm@ledgec PRMFLG A Ppeemotiom fleg irom Ppeeotiom Fla 00cm event$ imd cat4 'g 0'ethier the commectiom Is availeble fp opeemotion value is ome or mot value is tepo CONLCN Ppeemteea LCN Conte4n Local ComectioM Neme top oreefated SEGNEDa Reaesemssion Need Poimtep to head of retrmsmissaom queue $EGCNYT 8 Retpemigsg'iom Coumt Number of elements Cm potpe gmis8iom Queue ACXWEO a ACK Queue Need ACKCNT 8 ACX Cou i queue 2bE79 01365@q o ACK Number of elememts am ACK UNCLASSIFIE Po4ter to %eead 26FS-9 Y2e3p9 CUNCL S PI E e PAGE B-9 TRANSmjSSION CONTROL BLOCK WJEmONIC FINSEQ s oP qIT3 32 OESCR STION Received FIN Seduerld Number Value 04 secuemcs F'umber oggiord to FIN 809momt received from remote TCPI value is negative If FIN sgmen@t has mIot been received as WOPSEG 26-FEW97 32 Y0036509 Vat WOPEN SQQQemee Ijumbop Value of s ouomce mumbep of outstamaima 'OPE'N segment sent to reote TCP UJNCLASSIFIED PAGE C-I APPENDIX TCP EVENTS FO C 4CCJ Th'is soemfdivlW1ecebes the @V Mti neeiVed3 and somto by in the CCU Fop the metwoek-toeuse ooecessemq Dath TC receives events from SIR amd se•d• events to TIP Fop th e u•eptOoAotwOpk opocess4g Path TCP receives events fpo% T4P ena ououe events to SIP TCP TNeG• events ae• 4 olemetstiOmOrieted mOO in feeta eon Deesont one 4CCU imlemomt•tiom This eooend4v Is Not inn temded to oeovile documentotiOw foe the MCCU evenlt that 41 oovided ui•e 1100eo•te covers It 480 eathee int•nosa to suggest the tVe of 4RfoePtion that must be Dassd betwee a TCP and TMP or 310 IN am imolementetiom similar to the MCCJ In t e MCCJ the letook Protocol oPocessimo fune tiom of the SIP Is hndleo oy the Network Imnteefae• Protocol Events hetween the TC function •nd this function In NIP te 4CCJ ape s mO with the SENOER or 4ECEIVER of the event being NIP as OOPODpiet• The fop'it I1 shOwn INstandaP DEC PO'e1 merMv Image fOe met# with the least 140sO4filt byte on the Platt eve numBe end the most sinificant byte on the 1lft COdd numoep Oi a tbeb4t worI Th• bits are labeled 0 to 15 least signifieent to most o4nifleent PiGht to left In the wO Pd The memory imae for aich Steueture show In this ooemedu is deseelibl by en actomPlnVim Narrative The site byte wed te of tech unit within the structupe may cause olutPe yte$ within Op at tme eRd Of the Structueg These extra byte$ Iee mot used •md my Doe marked as such or mot defined in the Narratives They will be PeOlesentld by a always of dashes a s 0 in the memory ima01 and ape series it isi if witNin the steuctup byte $ •ntpe zero$ If the the 1 the length of the eUetaee counted in of courle extra bytets is at the end of the steuetueet It will counted in the lenoth f the mot be stpuctupse qevision 3 February Bp 198F 2b ba9T943bM91 e'UNCLASSP ED PAGE C-2 EVENT SPEC F CIT ON EVENT NAMES NEh4ONICI CPCI CLOSE EVENT1 OCL03E MCCU SENDER RECEIVERS THP TCP PURPO SES This ovemt allows TI4P to P00u st that TCP close a viretual copmpect iom REASONS TN'P issues Close evemt Im p gvom2# to a close comad fethe User op as a result oi a opotocol error gFmeoumtopeo im oeocessrm@ iop the pef@P@Peed cori9etle COMMENTS I If TC12 P CSlVeg coriectio seComd ComsecUtivs Close oVert fop 4 0 0 Close everto hut before Cleo will serd a Close omd treat VERSION a Clos gvemt P Coivod followima smother Retupm evemt the gecoramaas4 cocessima Is comalet TCP fop the ipst lushima Close r9ouest 29-SE e7S 260FEW 9 70036491 Close eVert eaLNCLA3rFIEote Tea3b1191 260FEWe9 UNCLASS F ED PAGE C-3 CL0SE EVENT BYTE 15 I t4 S 13 12 11 10 9 TRANTO 7 6 IOPCODE LC2 31 CLSTY P 5 26ePEW9 a TOA36491 UNCLASS PJED s5 4 3 2 1 0 BYTE 6-'ES T9 TU036a9q e UNCLA$SSTFEOO R eeete e e PAGE C-4 CLOSE EVENT MNE4MONIC a OF 0173 OPCOOC a DESCRIPTION Event dtertifiep Value fop Close event a 67 TRAND TPanosaction ID Seaueoce mumob fop this event fop coorldiation of PetuPm evevt with ramat 102SS LCN l Local Comeectiom Name Intereal TWPvTCP connection Identificeatio value with ranoe 1-32 CLSTYP lb Type of Cloe rdIc ees what type of close should be verformed by TCP 0 a defeoepedo all Send eventu Issued OploP to Closeeevet will be deliveped to dee 49tiom if ogssiblet 1 ifmmeite all Soe events mot yet segmetized will be Peupmed and TCP close oeoSesIagdmgoe Immediatelyj 1 tither case# mo fupthe Receive events will be auoued to THP 6o B 9 Tuq36oe 1 26PEe0e641S3 C UNCLASS$PI O 2 oFW9 T@36491 UNCLASSTP EO PAGE C-5 EVENT SPECIFICATION NEm ONICt 3ENOER-1 RECEIVERs OCLSOT TCP TH P PURP05E I Th s event motiiie TMP that TCP class oacess' ma has boom eoffleted oft a corPmectfoP'P RE ASON1 Th'e event will be isaued fm posoome to a oroy'feus Clos 9VO t or iop several exucootfom comditlomesme oumtortol by TCP# such' aso Poqet user eloslimat S P T errors eegtimatiom subscri4ber dowf'p etc COMMFNTS1 14 TCP soe$ am unsbolicited Close Petupm ev pt f e not caused bY o ovious Close ovt-t toe Tran saction t o Petup VERSIONS eet wHi be Zero 2qoEPo78 26SPE5079 T9136401 C UNCLAS1IE D one 10 oi T1616491 2e PE8079 PAGE C-6 OUNCLASS 7 EO CLOSE RETURN EVENT 290SEP078 BYTE is 14 13 12 11 0 m a mmaaaaaa I 31 51 1 TANf 10 9 S8 7 6b I a mm am m ame aM a e 4 5 M am 'aa 4 a 3 eM 2 ma 1 0 mw t BYTE IOPCOOE 1 9 LCN 1 2 CLRSTA1 1 i qT r 16-FEB 19 0236491 PAGE C-7 UNCLASS PIED CLOSE RETURN EVENT MNEMQ4IC OPCODE 9 OF SITS PE3CRTPT ON SEven t Identifier Value ee Close Retpm event TRANID N 43 STernuaction 10 S auemc number for op'evious Close events 4f Yo with pang 10251 this byte will be t@o it ovemt 4s unbolic'ited tP@ petwP LCN 16 Name Imtermol TH PwTCP Local CoF'i octio connecto idn 3ctinvau wt CO STA 16 Close Status auiccousijl local lao closer 1685CM security eppopt 178SCM4 opeceoemce pearl 18uS km TCC Pearl t9escm address orpor 20adostirmatioa subscriber dowmi 212dostimsOtIio access circuit dowmi 22odestiematiom busyl 309pos oto TCP seewrity euuoei 312juote CV TCC pearl 32spsmote opueeatg 33Ssoece Dreemotl 348ha lf Go an 358mo 1U#moAexi'stort eommectim $er8 I ock 26 FEB 79 0136491 rcyal 36 liu O UNCLASSIFEo oippoe Ue ES 9 ya3I6491 UNCLA$$IF EO PAGE C-8 EVENT SPECIFICATION EVENT NAMES INITIALIZE TCP EVENT MNEmONICi OINITT CPCIi CCU 3ENDER I RECEIVERS SEC TCP PURPOSES This event imiorms TCP that the MCCU has been iitialized aMd Pelaev the subscibeP address iop this MCCU REASON T CP m ust i piti al i s tse ve al o fi t s 4im te me l t a b les P p lo rto exeCution and also must be imfoprmd of the local subseribep OddP 90 ioP this MCCU in OPCIe to send and Peceive COMMENTSt VERSION 13-SEW-78 iT@36491 UNCLAS IE PAGE C-9 UNCLASSIFIED T9436491 260FERST9 INITIALIZE TCP EVENT 13 5EPe 8 BYTE 15 14 13 1 0I I 8 7 6 S a 3 2 I 1 31 9 cm- - - m mace OPCODE I mmcm mm mmc me SUBRID I ACSSPO SI T630 1 OUNCLASSIFIED a m mao c 1 0 BYTE I I I a a 1 2 26-FESS79 7663b491 UNCL ASS PIED PAGE C-10 IN171ALIZE TCP EVENTr MNEMONIC O'CODFl 0 OF JJT3 8 DESCRIPTION Event z0 ntiliep value for Initialize TCP eet a 73 3SRID 16 Local 3ubsco-lbee ID AC33PD 16 Access Lime Soseed value peOresemt nq soood Of acceS lime between MCCU and 260FIS79 TO3640tUNCLASSIFIED 79NL8SP 7613 491 PAGE C-11 EVEN T SPECIFICATION EVENT NAMEg NEAMQNtC CPczt I INTERRUPT EVENT OINTPT MCCU 3ENDERS TwP RECEIVER TCP PRJROSE1 71' vg t ilushi' PscOue@t me tfam ic t Set TCOpa POfp data bem s@ t Oplalatom ai Imteerut Ove't OthepF mi Ope tph mt fpW urtP soupe to the Oeastimat4io on' the REASONI 1T usop is Olvom 19 fmt4 PPwOt fumetam Okeysm Whc cause 10 imftpuct fUtmetions 0# these Oms causes an OUt ofeb 4 TCP fOe p URCtfam id Several cause ff em TCP ilugA VdERSIGNt iufetiom These CP $mterrUct ilus 290SEPS78 2b FE 79 3 q OOINCLASS PIEDO lumetiomg apt 2buFEB079 TP036491 PAGE C-12 UNCLASS F ED INTERRUPT EVENT 29 5tPam BYTE 15 14 I I 13 12 -u 2beFERO79 9 a 7 6 TRANTO 3 1 sI 10 5 4 3 2 1 BYTE 8 OPCOOE LC m T0036491 I OLNCLA3SS 7ED 2 INTYPE I Z2'VEWm9 T6036491 UNCLASSIFIE PAGE C-13 INTE3RUPT EVENT 29v3EPv7e M AeN c OPCODE OF %ITS 8 OESCRIPT ON Evont Idomtifisp Value for Znterr#uot e ept BRNI a 69 Tpenrsetiom IQ seouevmet AuWb p for thiS V Ft# LCN 16 Of retupm Loeal CoAmetio Name pmtepual TI4PoTCP value wit ' eMO CtIOM fdontf4ation ro q 1-32 FutMetOOM Ivoe' Value imdiestimo tyoe of Peauol 0 u fbPdivterpuctl I INTYPE 260ER79 foP £Coedinetio TI 3641 OU CLASSIP EO ' T0136491 26-uPS-79 PAGE C-14 UNCLASS FIEDo EVENT SPECIFICATION INTERRUPT RETURN EVENT EVENT NAME OZNTRT MNEMONICS OCCU CPCII SENOER RECEIVERS TCP THP PURPOSES This event jm4opms THP that roautted im a oPevious the teeruiat ilus I terPupt vot has boom' completed Ii there was met a ppevious Interrupt even is lero UMctio@ this evemt mctfom Transaction I0 jimorms THP that am imtoruot flum' was P euested by the Pemote TWP REASONS SouPce THP has requested am imteppupt flUl end destim4tion THPa has beo must be made aware thet the fwmctiom performed so that any TwP fol1lo -up opocessim be completed COmmENTSs VERSIONS 12aOCT-78 2b-PESP79 end both source T0436491 UNCLASSIFIE av Tea34qI 260FEWe9 INTERRUPT RETURN PAGE C-15 UNCLAS3SIED EVENT t2 acTo78 BYTE 15 I 14 A 13 1 It 17 9 S TRAM O 3 2 26FE07 d 36aq1 YT 1 AINTYPEA 5 114 TSTA 0 OPCODE1 LCN 3 1 1 aeNCLASSIFtEO PAGE 644 2 26 FEW 9 TM6491q PAGE C-16 UNCLASSIFIED INTERRUPT RETUJRN EVENT 12eOCYe 78 MNEMONIC 0 OF SITS OPCODE 8Evont TRANID 8 DESCRIPTION Id@mtifief' Value for Imtoprupt Retupm o ot 8 39 Tremsectie'm ID Sequemca quffbep for COPP@20c0 Imtrruot ovemt witm amoe l 2551 Zero if t 1 Is urmolleited Imtepuct Return ovgmt LCN 16 Local COrMAOCtiom Na mtopmal THPoTt A ramae 1 32 INTYPE S INTSTA FuFmetiof Tvoe d Value im4catirmq tyco a# I oUtG-fbamd 4rmterruct iuMCetOmt Rtturm Status 0 a suecessfull I a eonnIoCtoV% 0oes mot mlmti 2 a fu'mctiom mot loal lop' current TCP statel 7 a iufnct40 9 not eamaioeted umdelivow'od T0336441 UJNCLASSIFIED 2 FEW9T T003b6491 EVENT EVENT NA'4Es MNfMCNICI CpCIt PAGE C-17 UJNCLASSIFIED SPECIFICA1ON mOVE CONNECTION EVENT OMOVE MCCU SENDER RECE vER TWP TCP PURPOSEI This evemt ptuests that TCP verily a user as authapiezed to receive am already establishe d comm efiorm REASON TWO has received a reouest o'm em active co'%Fectiom via the movO COffifflamd that the CO'mreetiom be moved to smother user am this 4CCU Luthari @d THP Must ensure that the security OPecedene establishec co ntetiom CO mENTSI 29wSEPu78 26-FERW79 To 36uq 1 ard TCC oi tee To ac ulre this authoprstiom en7 fsts TCO VERSION the user is UNCLASS FIEO T 4P 26 7EB079 T0436LI91 PACE C-18 UNCLASS F ED OOVE CONNECTON EVENT BYTE 15 14 I I 13 12 11 1@ 9 7 b sI T0836491 5 aJ 3 2 1 0 BYTlE 0 O PCOOE TQANro 31 26-F'EB-79 a LCN 1 2 PORTI 1 4 UNCLASSIFIED o 2beFEWS9 Te391 PAGE C-19 UNCLASSIFIEO MOVE CONNECTION EVENT zq SEP-Ts MNEMONIC OPCODE 0 OF @ITS a DESCRIPTION Event Idemtifiep Value foe Move Commectiom evomt a 74 Teersactiom TRANIO evets evento 10 Solueece number of this atio wit Petur fp eoopd4 with remge 1-2550 LCN 16 Naee Tmtepmet THPwTCP Local CoMMOCieo value with eOmctiom idemt4ficet4oa peeoe 1-32 PORTID 1b Local Poet IDO Value for local Doe 1 foe maw useeg bits 1-11 8 user 101 bits 12-15 a fumctiom suffixi bit 0 a static dVyamlc DOt imdicatoe 26oFPEWo7 T036491 UNCLASSyFIED 2 E8qTe9336491 U4CLASS FIED PAGE C-20 EVENT SPECIFICATION EVENT NAME1 MOVE CON NECTION RETURN EVENT MNEmONICj OmOVRT CPCI MCCU SENDER RECEIVERI TCP TMP PURPOSES This evert F690oog to THPgs move commectiom evomto 4 mdfe tl'g whethe r the mow usep' is auth'orized to reee'qv the estabishled com9ectio9 REASON 1 TCP Peieved a move evemt verpicatiom be mad i 'm TH P ' questlim as to the authoft'zatioA to use am established eOavmctiom COMMENTS vEQSIONI 29SP7 26OPES679 Te036aq1 UNCLASSIFIED that a oi a now user 26oFE o 9 T0336491 PAGE C-21 UNCLA3srFrED MOVE CONNECTION' RETURN EVENT 29 6 1Pm 7 YTE 15 14 I I 13 12 1 ii i 76 TRANrD 31 4 3 1C 1 BYTE 1 MOVST T0436491 2 OPCODE sI 2beFE o79 5 OINCLA3S P ED 9 36491 UNCLAS31FIED PAGE C-22 MOVE CONNECTION RETURN EVENT 29-SEP-T7 MNEMONIC OPCOOE 0 OF BITS a DESCRIPTION Event o'tfie Value ior Move Connection Return evemt a a$ Tpeameact4o TRANID ID 8eoueme numbeP e the move Comemet to event eoresooedima with range 10255 LCN OVSTA 26 XKB 9 -- ' 1 1 16 Local Connection Name Iteeora THPwTC9 value with Idemt4#ieatleo CQoAeCtioe range 1-32 a Status of Move veMt oCeses mj 0 a i Maw User is outIhoezed to receive r0eep9eced coectqoM1J I a new User 4 not SuthoIited to PeceIve Peiepomed T68#9 tNLAtttI1t Tee3eaq UNCLA$$ FIEO T00649t 2o-EU 9 eUNCLASS P FlEO PAGE C-23 EVENT SPECIFICATION EVENT NA 4Eg OPEN COMPLETE EVENT MNEMONIC OOPCMP CPCZI M4CCU SENOERi RECEIVER# TCP TmP PURPOSE This vemt matifies THP of the eCurity BPSC dO mc@ TCC smd 46reigm addrpess of the commectiom have beam boeciied iM the Cemalmal coage These fields may not Goem evemt or im the orecedemce may have beam changed by TCP SE A SOk S This evemt is issued miter the fOpgt ISYN segment is received ipom the remote TCP for the gommectiam At that time all umsejifled cars- tars of the ooem Peautat become bouftd by th values of the imcom'imo seamemt COMMENTS The local user must be authorized the 14404er opecedemce ama all values associated with the mew comnectiom that had been oreviouulv umseoeclfled im his ooem requests VERSION 26 FE8079 26oFEB-79 T@036491 UNCLA331FIED UNCLASS PIED T1236491 260FEWm9 PAG E C-24 OPEN COMPLETE EVENT BYTE 15 14 13 I I 12 11 1 9 -8 7- TRAN O 31 6 S 4 1 8 BYTE PEC 1 3EC 71TCC FOPI W o169 NLA3FE PORSLJB 2 4 a itI 269 2 OPCOOE LCN 51 3 I 6 26 V- Eeq TSO06a1 UNCLAS$ FTE0 'PAGE C-25 OPEN COMPLETE EVENT 26sFEI 79 MNEMONIC 0 OF AITS OPCODE TRANIO Event Ide tifiegp Value for ODen Comolet event a 4 S LCN 16 SEC S P EC TCC OESCRIPTION Transaction 10 Seouenee number of the CoPrOeSomdime Opoi eve't with eaee 1-255 Local Connee ion Na Iternal TMPaTCP COMctiOa identification value with epeog 1032 Connectio Secup4ty Level 15 is higqh 0 is low ComrectIom Precedence Level$ Is Is hchl 0 a low 16 Connection 012 TCC BiSiav value wits Pie psup 16 Fo'eigv FORPRT 16 Foreign Port 1O 266FE 7 T J3 6 4 91 Subsep4ber 10 NCLASSIFIED e e e eeeae 26SPES079 T003691 PAGE C-26 UNCLA3S FIED EVENT SPECIFICATON EVENT NAMEi OPEN EVENT OVEN N mONCt Cpc i CCU 3ENWERt THP RECEIVERI TCP PURPOSE this ovent allow THP to $0gOcfY the pei'a eteps of mow comme t io REASON YHP builds am Ocem avant whom it peesives am ooen or listen commomd tp@'m the user whomn a connectiom 0Co $2 forms Xisto or whom it an auteouliste mot already or autosooen iumctiom In t oecase of a listen r ouOstV tlhe dostimation address socup4tv pocec edoe or TCC may be ungcoee9f$ed COMMENTS I The ifimnd4ato Peturm event OP9n Return event Pely sf m f4 $ that the carameters s ot i6d In th e OOM evant w P valid 400 the useps Tihe connection stobllihea Unmtil TCP e mo1etes This will be CAused by 79364 91 mot Sand event by oi 00w the 10Oal OP 266PEB 9 260 9847e is the t pe'eway handsliake eeote TMP VERSION1 liowovep UNCLASSIFIED 2b Es q 133b391 NCLASSIFIED PAGE C-27 OPEN EVENT BYTE 15 14 13 2 I 10 9 7 6 4 2 1 0 BYTE I 3 1OPNFrLG 51 I PWEC PREFLG 3EC 2 I ' 7TCC6 91 FORMU iI FOPT I 13 1 LOCPRT 1 12 I3 I LOCPR 1 14 26oFES 79 T8136491 UNCLASSTP CD LE3 Z6-FES-79 TO364q1 UNCLASSIFIED PAGE C-28 OPEN EVENT 2b Ff8 7q MNEMONIC x OF $ITS DESCRIPTION Event OPCODE event Ident4fier Value fop em Oven a 64 Transaction ID Scuorce numbOep for eoopdimFtiom of Petupthis event fo ovmtsae wits pence 1-255 TRANID PREFLG a Ppeemotio F1 90 Flog indicat4ng if a 5 th4l conection con be cree'oteod Dpop@otiom not allowedt I a Connecton cam be peemotec OPNFLG 8 Oven Flog Ryte Fleas ldicatia the jyeoecif4ed caraoeIpI of the ooen pecuest I0 set bit a a me s@cupit'vi bit 1 2 mo cocedemcei bit 2 a mo TCCI bit 3 a no fopsiam subscriber address SEC a Secuity Value foe secupity level fop 0 in the mew connections 15 is h4gh low PREC a Sed Precedence Valve iop sd oPecedemce level foe tse mew coPeCti o-l 15 is 14101 0 is lOw TCC lb TCC Value fop 7CC of the mew cOnMeCtion with raMge 0-512 FORSUP lb Forecam Subuc FORPRT 16 ope4gn Dart Foreeam port 10's Value iop 111 a user 0its 10 for new eompectiomI I4ee 10 101 bits 12oS13 fumetiom su fixi bit a a stat4c dvrmic oept 4nldatoe LOCPPT ib LETSIZ a Local Port ID Value fop loca1 ot ID tI loll a user fop now comrectioml I01 bits 12-15 s funCton suff x bit 0 indieator a statiC dPm'4c cot Letter Size Aoooui$ate umbep o4 to bt Come Gain1 a b bytes thl sent Im a TNP lettee o Greain connection po imot lime sote Line oeed Code 4 boa foe hostoCCu chneael fop t a userl 0 0 ISO op lessy I a 3001 2 a 6001 3 l2S a a 24ael S o £ 8aef 6 a q6001 7 a 1921S amd oeOo SPD 26-FEB-79 Tu3bB91 e UNCLASSIFIEDo 00000000000 T6u9 26 FE8 79 C-29 NASIO PAGE EVENT SPECIFICATION EVENT NAME OPEN RETURN EVENT MNEXONIC OOPNRT CPCI MCCU SENOER RECEIVER TCP THP PURPOSE lThis o et imyaoens THP oi the local CommOCtio ioe th'e 'ossibl eommectio'np or petuPmv am prop 0 the ODOM Mom CLCN verit was valid statust if t4e Ooem evomt was pelected REASON TI4P must be i iow' d 0f thei ODOM P QuoSt was imvarid Be that the veep Cam be ir'0Opmod of or# 4m t e Case an Pr op# of a suceessiul ODOM rsaueuto the epoacteristieg 00tiom cam becim This actbam Is Derformad Or'ly Comandor feature awazo the usor 0f caseId tie ODOM reouest OOM to COMMENTS This yomt does mat am that the commectio9 has boom 8tablliehd IA iact# the thp'OeWeOV h Mdsiake oe yntjl the ileit Send ovemt #pom 7 0 Will AOt take The Somd evemt oued as a r'@gult oi the OoeP Returm ovomt CCeipectopisties CYvot VERSION Gotiom Pecord w4ll be the tilest Semd smd tolus will cause the thr'etewe 26- PE oQ 26-FEU 79 76636491 UNCLASYF ED headshake AC-AGGI756 UNCLASSIFIED WESTERN UNION TELEGRAPH CO MCLEANVA GOVERNMENT SYST-ETC F G 17 2 COWUTERPROGRAM DEVELOPM4ENT SPECIFICATION TRANSMISSION CONTROL--ETC CUl FEB 80 OCA200-C-637 SBIE-AD-EIOO 342 NL II1 1 'nll'- LLL S 1112 0 1111L125 III 6___ MICROCOPY RESOLUTION TEST CIt4AT NATIONAL BUREAU OF STANDARDS-963-1 26e geS79 UNCLA$S IZO 78836491 PAGE C-30 OPEN RETURN EVENT 26efE o 9 BYTE 15 t4 11 tj 11 ttg 9 8 11TRANTO I 31LC N 51 26FB 7 OP NS TA T0369 UCASFE 6 S 3 1 t 9 YTE OPCOOE 0 1 2 4 260FE6-79 T63b491 UNCLASSIFIED PAGE C-31 OPEN RETURN EVENT 260FEB079 MNEMONIC # Or 6TS Se@ mnmm oem mmgq Omwo OPCODE a DESCRIPTION Event Identifrf ee Value #op Ovefn RetuPn event a 4e I TQANID a TrPasection 1D Sequence number of the c@Peseoendia Oven event with PeAce 1 255 LCN lb Local Conmectio n We ftepmal THP-TCP eemoetion ident4feotion value with pange 1-32 OPNSTA 16 Seatue of Ooe evsmt oPofset g3 aneao eePorl astommeetion f feee ined onee evemt eriete 3sunknow users bsinguff iei t Peoeueee foe mow @onrectiOgi SseePupity eorerl srpeceden'ee oepeer INIWNO lb 1OTCC error Initia1 Send Window Value which provides the initial ThP letter eeiling Im numbep of lettere which- my be outstendia to CP CSemd Return events not Pece4ved Possible valueo esorei 6 Oven event woo partially seoefied listen reoauet THP Send events are blockedr I a Oven event was fully DOCifiad Cooeo eouoes TMP may send one lettrt inItial value will not be more than 1 4 9 i 2bo S q S hbA9I CUNCLAS PlEe 1 aborpe3 78836491 PACE C-32 UNCLASSIFIED EVENT IPEC PCATIO4 EVENT NAP4Ei PREEMPT EVENT Mt4ERONCe OPR'4PT CPCIi r 4CCU SENDER1 RECE VERe TCP TSP PURPOSEs This event n'otI es THP that a mow conneetiom is bofng stablisOea IM miace Of 4 DPsemoted SO# Whig% has been closedo TwP will have received an unsolicited Clo e Return avant with DP@@motion as the Cleo status To Ppe 00t vent Get as 4 Coen Complete event lop T4P0 ise u0On re 01st Gi the Ppe mpt event THP will Send the Chtepecteristigs ootiefn record THP reacts the some way to am Dooen Comolete avant when the comnetion 4s listening COM96E NJ 3 THP pteuies the Lem of the eoetw'ted connection fop coaedination puroses in fnishing the close opeess ng fop that Connection VERS1IOs P8 PEB 79 260E t T9836491 UNCLASSIFIED T5S3491 UCLAS FD PAGE C-33 PREEMPT EVENT BYTE 1$ 14 1 I 12 1 10 9 TWND I 31 51 4 o 3 BYTE IOPCOVE LC REC 71 ISEC 1 4 FCC 6 91 FORSUS a 3 OLDLCN l eP cT9@36S49t I 6 UNCLIS171Eo 0 0 1 12 260 9ES TIgS6491 UNCLASSIFIED eeeetee ete PAGE C-34 PREEMPT EVENT IS V S 79 MNEMONIC O O $ITS OECRZPTON OPCODE S Event Identifiepo Value feP PPeemot event 8 4 TRANID S Tpnsacteon IDThis byte Is always Rope foP the Presmat @vento LCN lb SEC a Conneetion Seeupfty Level is low PREC a Connection Peecedeee Level hicho 0 i8 low TCC b Connection TCC S$msev value with Fao 0 S12 mtepael THPmTCP Local Connection Names eonnoct4 9 n ido-tifiestion wnth pange 1w32 This field eontains LCN for new connection IS is high 15 is FORSUS 16 FPOeaou Subscepibe FORPRT l6 Foeegi PoPt T0 OLDLCN lb Old Local Connection Meme LCN of the opeemoted eoemectfeeo 9e9eeeSFeeee 10 T#036491 26 9S 79 UMCLASSIIPEOO PAGE C-35 EVENT SPEIFVICATIJON NEMVdCS c PURPOSE# This event moio I Anetwork CP that a segment has oprved #P@ the to be opocess de REA30ke COMM'ENT31 VER'SIONI 0t SEP 7I W381 UCASIID @4136491 2ieFEs- 9 PAGE C-36 UNCLASSPFED RECEIVE DATA EVENdT BYTE IS 14 I I 13 22 Iu 9 REASONJ I PREC 1 3 4 1 I i 5 OPCODE DESS 31 £ 5 7 6 SEC 2 1 BYTE I I I 9 2 1 Ii 71I CC I 91 SEGSUF I 1 6 I 8609809 PI36491 S a UNCLASSIFIED 6 A T@3ie49t UNCLAISIF7 o e eeee PAGE C-37 RECEIVE OATA EVENT IuEPeTS MNEMONIC 0 OF $ITS PESCNIPTION OPCOOE 6 Event Identifiep Value fop R@Ce4ve Oata event a it REASON I SIP eaeef 4e DE33UB 16 SEC field unused by TCP Destination Subascpbep 10 SecuPity Value fop ofCupity level of the incoming seomeni PREC 15 is higho 0 to low$ a Ppocedenceo Value f0p oPecedomee level of toe iomina leoent 15 is hi4h 0 TCC 16 TCCo Binaey value for the TCC of the incoming segment with Ponts 96S12 SEGIBUF 16 Ouqf#0 2eUVE8o7 7gg364q 10 oi the incoming esqmet UNCLASSI IED 6 VEB79 t946491 UNCLASSIFIEO PAGE C-38 EVEN SPECZFICATION RECEIVE EVENT EVENT NA SE ORCEIV MNEMONIC# CPCli MCCU SENDERI TCP RECEIVER THP PURPOSEI This event passes a letter ot data to TNP ioP output to the user am the soecified Gommectio REASON TCP has reeeived dot te frOfi the network thet must be sent to user COMMENTS i The tPiplet buiier Osgod via this event contais buffer 1Ds fop eah imeafflima segment that makes up the T P letterP Each group of 3 words reoeesents one segment witN the f4plt word in the triolot bufer bemo the mumboer of segmemts in the letter emd the secod word im the triplet buffer being reserved fop future use ' iO ee ti6 49 0a 0 0 0 ' 4LASSeeIPI Do e ee 260F BES9 T@936491 UNCLASS IED PACE C-39 RECEIVE EVENT 29 SEP 7S BYTE o -mo o o o o o 15 14 13 12 tg 9 7 me o mm S 4 3 2 1 a I 1 Il YA4OI BYTE OPOO I i 1 I 31 I LCN1 I £ 5 1I ooE8 m T@63m o e mmm mm mm e m eeeoetteoeaaa 2 ES 79 I 1 BUFID 1136491 UNCLASIFEO m m 4 26-PES079 T0436491 UNCLASSIFIED PAGE C-40 RECEIVE EVENT 19 S P 6 MNEMONIC 0 OF SITS OPCOOE DESCRIPTZON Event Identifiep Value for Reee4ve event 9 42 TEANID a Tpensaction 1D Sequence number for this evemt fop oopdination of Peturn evemto wi t range 1 2SS LCN lb Local Connectiom Naee Internal THP-TCP COneectien Identlfication value with pence 1-32 SUFID 16 quf ep I0 Tea used to eo to the tPoloet buffer Conte4nlnq fmoimetlon about segments to be Peocessed word 3 a number of eacmentql wOPd I a PesePved for future use words 2-me in geoups of 30WodP entsPesl fi4st Word 8 segment Ouff p ID# second word a offset to first date bytes third word a nUmber of bytes of date to be DPocessed in se9mentF Ih F I 9 TOg6t e C UNCLASSIPI OC e4eeeeee T9036491 2WiES- 9 PACE C-41 UNCLASSIFIED EVEN SPEIFICATION RECEIVE RETURN EVENT EVENT NAME ORCVT MNEMONICi MCCU CPC I SENOERS RECEIVERS TWP TCP PURPOSES This event notifies TCP theat letter has boeen ioP delivopv to the user on the co ection pOceseed in WePfaeend the eoPPesoomdi$a Receive event REASONi THP hel deaueue# a Reetive ovemt amd has opoceeeed and moved the date toeuse bufier may oe mv mot User eventn all In the TMP letter to a Otowuse iso %eve boom sent to HS actual cutout to the User The Seamet bu ieop have bem reoeessed amd buffer The CTo trig1et and Petaased how veI COmmENTSt The ReCeive Retupm event a seknowledQement releived VERSIONS mPy be Is used bv TCP to detetimle $et to Pemote amd delivered to iMP 2bwPEB q lb'ER079 TOS6491 O UNCLA331 E TCP iso date when ZbeFEI 9 3649I UNCLASSIFIEO PAGE C-42 RECEIVE RETURN EVENT Zb-FEB T9 BYTE 15 14 1 9 7 8 b S 3 1 6 BYTF eemem meeem memmWmmomeUgmmee e m euomm m ee mlum@ m TeAI1D I I I I 31 eIRI OPCODE T 69 Te $bqI UNCLA 1 I 1 LCN 7 I I D o UNC LASS IEO ZiIlB-EI9 916491 UNCLASSFPOE PAGE C-43 RECEIVE RETURN EVENT 04kEONIC 0 OF OPCODE ITS a DESCRIPTION Event dein i4ep Volu fop Recilve Retup even t a 664 TRANIO LCN a 16 Tpameaction 10 Soay co number of the coPreeo oedio Receive event with Pong Local Connection Nopo Intepmal TNPvTCP OMMOCtiOm Idemtifliation value with p6awe 1 S2 6ro1 UCASPE PACE C-44 EVENT SPECIFICAYION EVENT 'dAME MNEMONICS eCPli RETRANdSMIT EVENT ORETRY MCCIJ SENDERS RECEIVERS TCP TeC PURPOSES Th4 event euses TCP to seen its retensmiseioen a eonneetion to find seoeomt e Queue fop that should be pot ee mi tted REASONS Effeetively# DEC Teo oueues this event timer iumetiom SIMe to itself thpougk the j4eih Plees the event TCo diSepeteh Queue after the eoeeified ti e in the eri COMMEN ST TCe ma4nta i one timer ae eoections if the connection has ev elements o its petpenee1sion timeP eoiree9 TCP will ueue when the deepomet the timer eount far eec seeaent eligible fop retrenmisin end if any Count reaches ergeo will Petranwit that 8e00t Teo will reissue the tieop avent unless the PetPersmig4or VERStO Queue become eonneetion eloe estve A1eFres6e Revision 3 A op the FObPuOPv a# IS Ie6oPES 9 T066491 1UNCLI PAGE C-45 EO RETRANSMIT EVENT BYTE 1$ 14 13 12 1 -m 10 9 8 6 I ° I 3 1 Eb FES79 T 3 491 U CL SS U L S 4 OPCO0E LCN • 9 8 a 1 a BYTE £ 1 0 I 2 26o0ESo79 T08$6a9l UNCLASSIFIED PACE C-46 RETRANSMIT EVENT MNEMONIC ewmm m oeee ew OPCOE OF $ITS a LCN lb I W ES 9 SO3baqj OESCRIPTION SSgeQswmm Event Identifie event a 7 Value for potponspt Local Co@neeton Name Internal TCp connection Identification value with e6oe 1o30 UNCL S$ PIEO 4 666 v s°qi pAGEc-47 'UNCLA$8IPIEO EVENT SPECIFICATION SEND DATA RETURN EVENT EVENT NAMEi OSOTRi MNEMONICS CCU CPCIS SENOERE RECEIVERS NIP TCP PURPOSES This event Motesfe network errop status TCP of SIP opocessm4a status end psioren¢e to ceoProo0on4fM Send Date event REASONS Thie event is o mally @ At when SIP eompotat of the toot E9 suceessful to the soupee switche Either transmission op unsuccessful event is ls sent I0 SIP is Petuened On this ease switch that indicates a fetal condition to TC Thee status conoiti@e' below CO'MENTSt 29-SEP-T 260F11179 T0636491 The eceives a n etwork delIvPV status indicator #pom its SoupOc VERSIONI tpanmissiOn UNCLASSIFIE are shown 71436491 260FE9079 UNCLASSIFIED PAG C-48 S 1 SEND DATA RETURN EV9NT a'SEP 7a 1 BYTE 14 1 2 t 10 9 T9ANID oo se e oem e e e 8 7 b 5 I oeec -C e e o- o o U oCooo e II S LCN e e 26-eOF979 ee BYTE 1 S 0PCOVE O I I I 4 ee e ' e urnee e T 36491 UNCLASSIFIED 26-FIS-79 P336491 UNCLASSIFIED PAGE C-49 $ No DATA RETUmN EVENT 29 SEP- e MNEMONIC OPCOE 0 OF 9TS a TRAN O DESCRIPTION Event 1de'ftfiep Value for Send Date Retupn event a 72 Tensaction ID Location o leQment Pefpeced bv the Send Ota Retu n tvqnt Thui eddPes is word# not bvte oriented LCN tb Local Connection Name lt@ePnS SIPYCP connection identification value with panae 1032 SORST 1b $t tu3l aeucceeul to source SCot a3Ce ilow refeeti 16seecurity oppopg 17opeagodaece qpropl 188TCC eprorl 19nmvellid addpeosg 20aaeat4motfio subscriber dowl 213d etfintion access circuit downs 2 2destimlatio busyl 3baline eProp 2609e079 TP 3b6491 UNCLASSFIEo 4 4 0 o h subscriber T9I634q ileP 3u 9 UNCLASSIFIED e PAGE C-50 VENT SPECIFICATION SENO EVENT EVENT NAMEi MNEMONICj CPCfi OSENO MCCU SENOERS RECEIVERS TmP TCP PURPOSES This event allows TMP to Sod a letter to the network iOr the PoiePOAeed ecmoetiOA REASONS TWP builds a Send event whom It has received emouch date rom MSI to satgotv the Docket eleaseo mochaniem fop this user COMMENTS TCP will peloas DpoCesOsiO VERSIONS is the letter buifer whom Send event ¢omolete 29-E$P- 7 2 7s 7 NCLAS PV e P a9 26wFEO 9 uU36491 UNCLASSIPED PAGE C-51 SENO EVENT 1 9 SEP 76 WY9E IS 14 C Ccuee 13 12 10 m e 9 8 7 eooo oomomeueCe Umu m 1 1 T ANO 5 S 4 3 2 m 1 m eec eommeoeee I SYTE B ee OPCOOE I I 6 I 31 LCN m e e me ee me £ S I e em I m m e e e c e e 2 c I SUFIO I 4 £ 7I SUFLEN _ _e C _ 1 me_ eme cceC C mmcC C r m 260FEBO79 336491 A UNCLASSIFIED maul 26eFESe 9 T9636491 UNCLASSIFIED PACE C-52 $ENO0 EVENT 290SEP678 MNEMONIC 0 OF PITS seameOwe ESCRIPTION Jlmo00000 004w0o OPCODE Event TRANIO Tpae actiom Identifiep Value fop Send event to Seaueme umbep of thu event# fOp eoopaimati4o with Peturn event with pence 1-255 LCN 16 Local Connection Name rtePel THP-TCP CoMMCtiom identification value with Pence 1-32 BUF D 16 Buffe D e agyed to mo to the buffer contaiien the lettep to be sent to the MetOwOmko SUFLEN 16 25Fe Eo 9 TPi36401 Wsffep Lenoth Size in bytes of the letter to be sent to the networe UNCLASSIFIED 460FES079 T6636I91 UNCLASSIFIED PACE C-53 EVENT SPECIFICATION EVENT NAMES SEND DATA EVENT MNEMONtC OS'IDhT C9 C MCCU SENDERS RECEIVERS TCO NIP PURPOSES This e 't allows 7CR to reau at that SIP emmt a 8 0ment to the SCM REA30NI SIP must build amd attach the 5$RaeY Seqmeat Leader to the seqm mt boina Se't to the Metwo k by TCP COMMENTS TCP semds bat% geaoemts that Contaim' data a19d seam o'eg that VERSIONS 29-SEPe 78 26OFE8079 T9836a91 UNCLASSIPIeDO 2b-FE9079 T00364a91 PAGE C-54 33NLAS1FIED SEND DATA EVENT Z90SEPu 76 BYTE 15 14 13 12 6 7 5 L 31 qJr I 1 9 3 2 1 a BYTF 2 OPEC3COE 3 1 Tee '4 971 DECCO HOLN1 sI TXTREG 91 ELN1 11 11FE7 44 T0369 UCASIFIED tiS 2 2beFES07q SEND T993b491 UNC1 A3S 7 EO PAGE C-55 DATA EVENT MNEMONIC 0 or' SITS DESCRIPTION OPCOOE a Event Identi fier Value for Send Date evenit a 9b TRAIO a TePmhectiom 10 Location @f segmenet referenced by toe Send Date event This address is word# met bvte oriented LCN 16 Local Cmoectiom Name Iternal SIPvTCP c@Amectiop idefqificstie - value with ra'mas 1032 3EC Psecurity to essiam to the seamentu is hiQhJ 8 is low PREC a PeedemC 15 to assign to the 99e tg is hight 8 Is low 15 TCC 16 TCC to assiam to the seamerit with DESTID 16 002timatiam subscriber 10 to as8849m to the ueaomnt SDTFLG 16 Send Date Flea word Values curren tly umde4iimd fop the OCCU MODRTAG 16 Butter 10 oi the Tesegmemt header NODRLEN' 16 Lematse ' bytes# oi the T-sagment header ' TXTTAG lb Buffer ID oi the data ooerti@'m of the sea ev to ePo if meo data beimg se 4t TXTe1EG 1b Offset range into the date buifer to t 0 fiist byte oi date to be tr nsmittedy value is peativ to am # mat tepee TEXLEN 2b FE6079 16 YFO36491 Number of bytes to be t Rsmitted UJNCLASSIFIED lbeFES-79 T@636491 UNCLASSIFIED PAnQ C-56 EVENT SPECIFICATION EVENT NAMEt MNEMONICS CPCIi SENO RETURN EVENT OSNORT MCCU SENDERS RECEIVERS TCP TWP PURPOSES Ti4s event opovides THP the status oi the copptienoding S md event opoce•s•fo REASOkj This event Is returned if TCP finds an error 4 ppelimjnapv v teicatiom of the Send ev ts the If the data peferenced in the event is deliverede or if the date Is not de14vePed TwP must be aware 0 S the number of eomOletfo limited as oert of Send event DpOCe8s4ig outgtmndira Send events 48 the flow coptol mechanism ior the mCCU@ COmmEPNTS Ii an umdel1voeed he closfrq status Is The oaticeula peturmedo reeason ior the close will be Petupned ia a Close RetuPn event VERSIONS 29qSEP-78 26OFFRO79 VY''36491 the gOmIeetiOn will UNCLASSIFIE TOPS6491 26wFEBm79 PAGE C-57 UNCLASSZFZED SEND RETURN EVENT 29sSE P 7 BYTE 15 1 11 12 1 ISTRAYJ D IP 9 7 8 6 I 31 S 4 3 2 1 0 BYTE OPCOOE 0 LCN 51 P40FIA079 SNOSTA IPOS6491 UNCL SS F1EOo 2 1 ' 26 PEWe9 T936491 UNCLASI P EO PAGE C-58 ENO RETURN EVENT 290SEP-To MNEMONIC S07 OfSTS OPCODE DESCRIPTION Event Iden't'ifierg Yalu ior land Retupm even t a 41 TRANIO aTpams ction 10 30auenge murnber 04 th'e CoPpgi@@ di Send event with pangge LC N 16 Local Conn eection Nsmo'q Imtoeml TH'PmTCP CO1'MeCtion identlication value with pang 1-32 SNOSTA lb Status of Send event orocessimqi Sedate II8comme ctiom clesime when Send even t peceivedr 589efd 411eg01 IM listen statti 7adate umdoliv ed Conne ction will be closed 2W EWe9 T@036o9t UNCLASIFIPED 0 A4 b t 26s-E0e 9 eUNCLASSIFIED T9036q1 PAGE C-59 EVENT SPECIFICATION SEND WINDOW EVENT EVENT NAME 4NEMONIC CPCIi 03NWNO MCCU SENDERi RECEIVERo TCP TwP PURPOSEt This event notifies TMP of the mow value to be used as Send window oan the uoertoometwork have outotandina to TCP at TCP with oth The valUe the mbximum numbee of Send event8 that THP mov reoeets number of data the eny one time That is# the Send events that have not been aenowledoed by corresoond4ng Send Return events REASON1 The send window ensure that of data in any area is part Of the the virtual flow control connection sustains a steady flow either diceetlon with no aooPecible If the send windOw close TMP will stop seno4na FPom User Return events to MS1 eventually beoin holding o f the host COMENTSI VERSION 29aSEP 78 26UPE9079 used by TCP to T69'36491 UNCLAIFI backups in oventuolly and MSI will proES 79 I63649I PUNCLA$SPEO PAGE C-60 stNG WINDOW EVENT Z9 SEP 7S is BYTE 14 a 13 12 11 o lf 9 7 4 S 5 3 2 1 e 4 OPCODE W@ omo 1 31LCN BYTE T6636491 0 4 Co meoC eo oweCCoooooee o o 2 1 inoo ewe m ooo o-o0 S I I oooooo @o oC ooeooo@ oooo ooe@ o ooWoC o oUoooo o a It TB13491 24 PS 79 UNCASSEO 000 0 000 ab-plsu TP63lliq UNCL SS V O PAGE C-61 elaeoit Oie e SENO INDOW EVENT 290SEP076 N OPCODE LCN lipC IT 0 lb DESCRIPTION Event IdertUIfre avant a 46 Local Connection conne0tion NElbND 16 Value for' Send Window Namo Iternal aentificgtIO THP TCP value witt New 5ind window' NOW value ior send window indicting tke number of letters wich may be Outgtamd' to TCP $e d Return ve to mot Peceived Value must be CreatoP then or egual to th current $ Rd wldow value i 26FEFpOI 7PP349i1 UNCLASSV EO iheFE8 79 YGM3649t UNCLASSIFIO PAGE C-62 OWeeeoeeeeWW EVENT SPECIFICATION EVENT NAMEt STATUS EVEN T W4EONICI OSTATS CPC CCU SINOERt RECE VER Two TCP PURPOSEs This event PeQuesta that TcP Pturn the current status Of the saeC fle eo mrctioM as Pelate$ to the local TCP REASONJI The user thePe has @Rteoe a THP tatus eamelam is an active COmmCWtOR TwP Itself TMP Iest Peouestl that is mot and THP believes WM4Qg hold Of in the TCP status of the CoMiNction It that status Is %normal# TbP will cOmmUniCate with the remOte TwP via a Two status Peaueat peCOrd COMMENTS VERSIONt e5-NOV-78 260E-0 attemot 7 oI6491 UNCLASSIFIEo to 26-FE967q TOA36491 UNCLASSIFIED PAGE C-63 STATUS EVENT BYTE - o - eeoo o ece o oo eao o o 15 14 13 12 11 I 9 8 I I I TRA Ia 7 6 5 II I 3 OPCODE 2 1 BYTE iI I 31 LCN I mama m a a 9 macmmmaemm- - amm 2boPI e 9 4 T 6Q Sb9 UNCLASS P ED ' 2 c oame 2e E794 636491 UNCLAS31P EDet PACE C-64 STATUS EVENdT USONO V 7 MNEMO NIC aOF @ITS DESCRIPToN Event Identifier Value Oop Status OPCOOE TpoAe'aetiori D 3 quoee pumbgp oop this eve'mtf for cooep4Aation of the TRNDa eeturm event LCbJ 26-ER79 16 P393q1 With pOaoo 1025s Local Commtetion Naee ternal TmPoCP COMROeelom identifiestiom value with pence 1032 UNCLA3SIFIEoo Ie F979 1'3 41 OUNCASS EO IPAGE C-6 5 EVENT SPECIFICATION EVEN T Nx E'l MNEmONICI SENDE i STUS RETURN4 EVENT OSTSRT TCP RECEIVERI TNP PURpOSE This overt MOti ooe t 3 ealmeetigP TNP of the cuPrort status of the so Palates to TCP REASON This ve9t is sent Im pitD@ISO to a status envent COMMENTS VERSION QSP7 I PS 7qT9036491 o LNCLASS PIEDoo 2 T146a91 PEI-79 PAGE C-66 UNCLASSIFIED STATUS RETUON EVENT BYTE 13 12 14 IS 11 1i 9 go mccceccwmowomcccwwsw 7 b S TRANID I I 2 BYTE S OPCOOE S 3 I LCN SEFLG I 1 mmeem 7 4 ecQmoccccmmm Ocgm Oc@ I I 3 1 S a ccccmw wcmcmcm e em cc• We ac- mmcc e e Q8 9 2 REITSTA 4 RCFLG 6 e1rmcmWcmmccmmc S CLA SIF co o cc • • i -IE 7 21u-EB T9 T0336491 UNCLASSIFIED PAGE C-67 eileeeeiigo STATUS RETURN EVENT 290S EP 76 MNEMONIC 0 OF BlTS afeaftmea 000ee8me OPCODE DESCRIPTION iee Event Identifiep Value fop Status a 44 Retupm event TRANID Tpa' sactieOm Sequence number O4 the COPesa'dita Status event with rane 1o255 LCN RETSTA 16 8 Local Connection Names mote al TIP-TCP connectio Identifieation value wlth pane Io32 Rttup% Status a a comU c Om establi4skedl I a confte tiom does esisto 4 9 connection Is Closing ot SENFLG a Send Flag Value indicating curpe t TCP status of tse send oathl a a 0e I I blocked RECFLG 8 Receive Flea Vlue indclating CupPedt TCP status of te Po elyv oaths 0 a oOevm 1 8 blocked# wldow elasoot 2 a blockedo Pessemiblv euue 26-PES-79 T 3e'a W O36'ee1 IED UNCLA$S PIEO I16JUL e79 T00la4939 N L 3I ED P G D- APPENDIX D TCP STATE TABLES This appendix contains tables which describe the Seti@'m taken by am mCCU TCP depending on the current state of the connection reflected In the TCS@ and the stimuli received There are many different Stimuli received by TCP eeg Send The events from TMPI Receive Date events from SIP# Otce Processing reguiped by each stimulus is a function of the state of the connection at the time of receipts It should be mated that them state tables are relevant only if a TCS est Igoe# TCP is aware of the local user via an open or listen request If a TCB does mot exist# TCP will perform one of the following actionsi Is If stimulus is an event connection does not exists status will be returned In appropriate return events 2 If stimulus Is an Incoming nonerror sogmont am error Segment with control dat extension set to Oconnection doe$ mot euist will be sent to the source TCPs 3 1# stimulus Is am incoming error segmmnt TCP will discard the segment Returning another error soement would result In an endless loop of error messages between the two TCPse These tables do not address aoemtion They revresomt the processing accomplished by en mCCu TCP once an appropriate CB is found The reeder a attention is directed to the TCP Specification Paragraph 2 304 demultipleuing function amd Paragraph 2 4 3 prpion110 Definitions for TCP states are summarieod here with defii tions of other terms to aid the reader in interpretation of these tables eeeeee e Revision 1 July 4v 1979 I1e JULe 9 T0044939 UNCLAS31PIEo 11-JULo 79 0444939 UNCLASSIFIED TCP STATE TABLES Definition of Terms PAGE 0 2 TCP states 1 ace n a T P Kos issued a fully saacified O06 event bwt the thpeoway handshake he@ mot beaun 2 listem w THP has issued a partially gspefied Open TCC# or destination event security# precedence address were mot Specified 3 SYN sent a SYN segment request to synchronize GOnd seQUence uMWbers has boom sent beginln the thpoe-woy handefhake 4s SYN sent received a TCP as sent and received a SYN segment but the aCknowledgoemnt keg mot been Pe esivea for the 3YN Segment that was sent So established - the theee-way heashake is TCP completel has merit end received a SYN segmenit and has received an aCknouledgement for the SYN segmet that was sent 6@ eeved a ClOse local close received w TCP has T'qP# requesting a deferred event from the local qreeeful close of the connection but has not sent the FIN seamonty network data will mot be for delivered to the local TMP Receive events this connection once this state he$ been entered 7 remote clase received a TCP has recived a status control segment fpom the remote TCP# indicating that the remote TCP has begun close processing for TCP will continue to accept net the connectioni but work data and pass it to TM4P Receive events will accept no mope IM4P letters destined for the network Send events So F1IN gent e TCP has sent a FIN segment beginning no further got will be ace connection closurci Ceoted from Send events Or given to Receive events the local THP ont this conneotion 9 FIN received e TCP has received a FIN Segment but is unable to send a FIN segment because all octets sent have not boom accounted for as yet 10g FIN sent reeived e TCP has sent and received a F segment but has not received en acknowledgment for the F'IN SegMmt that Was Sent Revision to July 46 1979 11-JUJLe79 Tgd44939 CaLNCLASS1IED I1-JUL 9 T0044939 UNCLA8SZFIED TCP STATE TABLES Definition of Terms PAGE 0-3 Its Closed •TCP has sent and receiveda PI sX egmert end hem received en eckmowledgement fop the FIN edgmest that was someo but TCP Is waitimg fop ell its ausueS to clear before deleting the TCB other terms 1 retranemission Queue - am intermal TCP oueue whtcV holds all unacknowledged segomeue egments may be retronemitted If mot acktowledged by the remote TCP within a cartain amount of time or If a lime error in4destion wes received from SIP 2o segment SeOuneeo number a 31obit value reoresentina the nUmbeP Of the first octet COot character of the segment ge alseo Peragraph 2 184 of the TCP sei fletion 3 akMowledgement Seauence number w 31-bit velue Pepresent4ng the number Of the newt SesecteOd b the sender of this segment octet# the aCknowledgemoet ndicateos that all octets with a lower seauence number have been delivered to THP 4 send loft wimndow dge - 31-bit value reoresetlng the number of the first uaecknowledged octet sent to the remote TCR on the virtual Connection S receive left winaow edge a 31tbit value reoprest fig the number of the Mext octet expected to be reeeived from the remote TCP on the connectio 6e receive w4now a lb-bit value numOer of octets which will remote TCP on the connectionp reoreueetinq the be acceoted from the value Ie sent witm every geomeni 7 e$md windOw lb6bit value reoreueetimn the numboe of octet which may be cent to the remote TCPj corpesonde to remote TCP s receive window Revis4on 11-JUL079 384939 UNCLASSIFIDe 1 July 40 1979 TCP State Tables STIMULUSI SYM segment received from notwoek CURRENT STATE ooo s • OIEI PAGE D04 PROCESSING qgguIREo ot value of passive left windOw edge to that of SYN segment soaueneC numbep glue oneo acknowledge the SYN seas $ Ad a SYN seamentl ment peolvedi move to SYN sentcteolved number of boquene Pecord value of stator SYN sealant Pecolved SYN ent Ooplop som opoeessienoas fop oDO SYN seont peceved using velue of the seauence number o OP44 nel SY segment eeeovede verify that SYN OP segment Peeolved Is a retransmissionofo I# not# meno an umeeo SYN Peesivedl anal return TCP elotable 9YNO mossage to remote events to TWPP send a Close Retu n Seo all 4f event to T4P end move to Closed stotel Potpnemlission discard the sogment established usino value fop sequenes number of oapelnal SYN segment Peceivede veify that this Is a Pstpsnsssion #of Original SYNI If not send uRneecootable SYN8 message to remote TCPP anA Peturn all not yet segmentitod Send events to Two with undeliveped status# soed a FIN seqs ent# aid move to FIN sent $total if Poe tmenml1ssign discord the sement all Other states disCaPd the seoent state This table does not addPess oPeemotion It PeIopIIe ts the rOCessein aecomolished by an %CCJ TCM once an sooPeoplate attention Is directed to The Peoe $ TCB has boon found the TCP Soeocficatfont MorsOaPDh 2 3o' demult4oleu4ng function an De r opooh 2 0U opeemotion fop additional detalis Qovision 3 o Pueyr 5P Z7 FEP 79 TCP State 3 5 q UNCLASS FIEnte PAGE 0 5 Tables STIMULUSI ACK segment received feo' CURRENT STATE metwoPk PROCESSNG REQUIRE ooemecloee discaad the seemert SYN the SYN Check if this stapont acknowledges $egment tht was Sent and also Caprie a SVNI acknowledoe fo SYN pea if both are trueu ao ceived seed Open Comolete event to TNP# seam if this ACK move to established etatel met is mat am aekrowlaedemet fop SY% $ego ment that was sent discaed te segment sent SYN sent oc oved check Uf this seamemt segment teat was uent kmowl If So the SY% send ODeM Com- ges olet evqnt to TN4 and move to stablishe statel if MOt disceed the Segment establishee chock if this eefemt acknowledge$ saothing gsioauguel if not# diseapM the petrPans sme uodate velue of of so the seomentl left window edge with the Sequence number im delete all Segthe acknowledgement fields menet fpom the petepnsmission oueue with a Segment# ACK SaueAce number lower than the ene send a Send Return event with sUCce5eul delivepy status fop each Send event carPina acknowledged dots O local close peceived am foP esteb imhec Derform sme opocessio state as fop eeta is el Depfoem some opocesging as for estaplis'ej Verform Same opoceesing st ate remote close Pece4vev FIN gen state FIN received Oerform Same orocessim e fop estebliseo ol data Sent has beem aCcouteo 91% and move to segment FIN Set peeeveq4 state State if foe send a FIN seMt reeQcvog as fop esTeaoliehe $ame opoceeeing Send left widoow eQe now the if statel est someo seQue ce eus$ the value of the nmumoaB move to closed state oeplope e e ee1eeot oe I7-FE TCP $tate ATIMULUSI Yu036599 - 9 Tables Date received UNCLAISZPEO PAGEDk PAGE Dub rom CURRENT STATE @geeclosec PROCESSING REQUIREM the soament discepc 5YN sent discead SYN dlicaPd trho seame t Set Peceived established local toe segment Check foP valid seouomce mumbepIi ve1 4d order the date segment On the p 8geeMtjly queue# of h9ee JR the reasembly Queue ate segents arrive i oapoe aeif filled or liver data to TWO Receive event close Check ior velid seaoece fumbe1 if valid order the data seamemt an the peassemlv queue es holes in the peassembly Queue are filled or if segmets arrive ic oPe0or uodete the value of the receive left window dje send a status eontrol segment to the pemote TCP Aend delete those Se eCmtS am the reaes sembly cueue that are beima aeknowledoed Peceiveo remote close received Derform some orocessllo state of as for stablistte F14 sent oepform see DPOecesIIa reeitve state FIN Peceived Depfor m lame opocesslq as foP establil ed Itatel if the data Peceived cause te me receive left wim ow eoe to euaI the Value Dll one Of the FIN 0eegmet thet was Pam eeived seed a FIN segment wit ACX for t c FIN leg-emt that was eeceeivt and move to FIN laet Pece4ved state FIN soet eceived Depfopm same ococeslima as fop local ClOe received statet if same left window eqe eauals the value of the next send Seauocce flubePeand 9auals the the value fop lft receilve olus one of the local Clase window 0199 FIN ie9weRt that was PeCelve d land a status COntrOl IIQ meet to 6CknawIl ed the FIN segment that was Peceived ACd move to Closed state PIS436599 NCLASSFIFE0 T 2-AJG-7q 37 - TCP State Tanles STImULUSI FIN no flush UNCLASSIFIfO PAGE 0-7 segment CURPENT SlATE ovenocloseo received from net-ork PhOCESSIG REQ1UIRED disCard the segment SYN sent discara the segment S3V semt recelvea aiscare establishec local close received remote close received other return all not Yet seimentized Semd evemts to T04P ith umdelivere status record the seQuence number of the FIN segment that was receiveo and move to FIN received statef f that segmept the sequence number of the FIN was receivet eouals the value of the current receive left window eige increment the receivel left wmdow eoe and send an ACK segment for the FIN segment that was receiveto to FIN and move seqment a FIN sendo sent received state perform same orocessimq as fop establiseo states it shoula te noted that this situ to am tion chanqes the graeceful local close immediate close abort record the speuence number of the FIN segment that was received ana move to FIN received state if the sequence number of the FIN Segment that was received eavals tme current receive left window edge increment the value of the receive left window edget sen a FI% segment with ACK control amd move to FItN sent receiveJ state record the seouence number o f the FIN segment to rIN move and receiveo -as that if the sequence number sent received states of the FI seqment t at %as received equals the Current receive left window eoge imcrement the receive left window eageo send a status control segment for the F1% segment that was received ano stay in the FIN if the send left ximdOw semt recelved states edoe eouals the next seno seouemce number ama the receive left miaow edge eouals the value olus one of the seQuenCe number of the FI% segment that was received$ move to closed state FIN sent all the segment states aiscard the segment Rev4%ioA -aJG-Tq t 4LbqS7 iJNCLASSIFlE ee 00 0 0Oft 2p AuQust Sp 1979 2-FEP- -9 P135999 UNCLASSIIEDO CP State Tables JTI1ULUS1 FIN flush sooment received ipom network CURRENT STATE PROCESSING REQUIUEO oerm glogoc disCard the 3YN seot discard the Seament SVN ge't roceeved discard the se4ment established PAGE 0o retun all TMP with 4m@om@t not vet ee 3Pmomtid umoeltveped Pesstmbiy Queue# get ede FIN to eeomem the eeoumeC toat was the Send status# events nyreo receive left to toe windOw numbeP olus one of the Pectivede meeo a FIN with am ACK fop the FIN segment toot received and move to FIN set rece4veo seomert was state local close received oepfopr dame prooeessfG as #or establihec 4 Stott it should be meotto that this twaato close tiom chanqes the graceful leea immediate close abort remtoe close received Durge the poagiambly ouee got the receive left window edge to the seauence number olus one of the FIN segment that wee weCe4veae p@ ber oi the FIN segment sequence the Cord oeegmesmto PIN that was re$eived seede am ACK segeemt for the FIN Segment that was pecetived cad move to FIN seMt rpceived State WIN perform some opocessima as for remote close tho value of the statep howeverp if pCeivOd melt $ed seouetmce number eiual the se-e left windOw deae move to cloeO state as o o posed to FIN st received state set all other states 270FE9 79 70836999 diSCord the seafmot UNCLASSIFIED 27OPEDS79 T8436S99 UNCLASSIFIED eeeeweeeee TCP State Tobias JTIMULUSI PAGE De9 Status sgmomt received CURRENT STATE fpoe network PROCESSING REQUIRED opemCloseo discard SYN sent dsecard the s Qm Mt SYN $ At peCeived disCSd the meoweMt eetabfishea loco ClO$e receivea remote close Pe eeved the seomeAt all niot yet geomemtiled Sena SvOntf tO PetuP with ufdflivep@o status amd MOv0 tO Pa MP i seouence received Statel mete Close o f the lost octet deliveped to pemate nUmber pltr mqtjs4O TMP aCknroleeoss Items on the auouue uodate value of send 10t widOw emqeo delete all seQmemtq acknowledged fPOm the pebuild Send Return ououe eri tPOras153@om tech Seed evemts with isuC slfYl status for f the so aekmowleded dotal event earrlvi' au@eC number of the list octet umdelIve9ped eeces a segmemt on the but aecounted foe pete PttPerolilsOn oucueo uodate the value of the wlmdow elgeo delete all segments memd lift from the peo soauemee mumeers with l9woe Ad build a Sed RetuPm aufuu tralsmissao event with umdeliveeod status for each Sena event Ps Cffc d also 4A this implfes that the remote TCP is Petupm all mot vet oPoceas of elosivo i the e d a FIN seamemtized Sema events to TwP# It seQmet# and move to the FIN 90mt ststel sltuatiom Cmes should be noted that th4s Close to ami4mmediate opeceful loCal the as processhig some DePop lose sbopt I fop establmhed9 state witk Pesoect to se- as for eatablishea ceefom same opoceslm state with Prsoect to seauemCe number$ FIN sent OP totalf liseo as Defopm Iame opacessimo state with PeSOeCt to seoufmce mum-bps FIN as #OP established Deforl same OPO¢OgSima mumteps state with Pesoeet to se ouse pectivee FIN lemt Poceived 27M-ES791 T0 3q99 establlshed im as fop SMe VPOcelm If MUVMbePs seaucACe tO PeoeeCt state with edge left window the value of Curent Sam send Sequence value of iext matches tke uibep move to closed state eePfOP UNCLASSF EOe T003999 UNCLASSIFIED TCP State Tables SYIMULUS PAGE 0 10 YCP timecut CRetpv event occupped CURCENT STATE all othoP states PROCESSING REOUIRED discapd the oeamgmt ior all seamtmeg an the Permm eo aUOUt that sa withif the eueeoMt sand win dow ama have p Ceived a Send Data 4etupm event fro@ SIPS deceemt Oumt of Until POtra Ofilsgoo Muffb p of $ comas of the seawomti 4#th soConds count lop a Segment peces Ieec ofta tiece have boom less than three tPomsmiss om atto Dts top t o 9491 00to petramso-it too $ego mont and Popk 4t NSeed Oata Qotwpn ovomt outo star'dingi' if the tra'9srnssiom caumt emeac es thref close the conn ection TO836999 UNCLA33TF Ele 27oPEDoiq 9036999 UNCLASS EO CP state Tables T MULUS TCP Megisoai ptive 8COlaeCtiOn does mot D-11 exist CURDfNT STATE OoemeCl@Oo PROCESSING REQUIRED discard the eamomet states all other PAGE froPm remote TCP if the eoau Ce number in the aCknowledgement field efeprenees a value betweo the CuPPe@A send left window edge and met send ieauamce uffibpv 0eefeprm immediate for the Connection# 0 rot close orec@sl2 diseced the sea- ment seocurity violatiam CURRENT STATF evolas0e 11 OTCC othr states PROCESSING REGLJI'MI disCarm tole semmvmt if the stUu m¢o mumb0P in the ackowledooCe field references a value btweei the curpent send left window #dg aid next send seouence lumbop oepfom immediate CIO Opocessiri #Go the COnfectioI m f mot discard the teg- violation CURRENT STATE PROCESSING 60 m loseddiscard the 990om t a11 other states if the seouemce number Im the ea o ledge-e field peferences a value be teen te cupemt send left window age end mext veod seruecee numbep VafO Immeiste close opocessi q iO t t commoctioi I f mot discapd the seqment acomrection OP emOtOd CURRENT STATE PROCESING open cl osoe SYN sent # Sl SY4 9 entipcelved 11 27o l 9 Other states t I 3jqq discardj the segment if the tauerIcq mumbOp Im the ackmowledoement field pefepences a value between the current send left windOw dge aid next send seauem¢e umbe perform imeato Close opoeesei #OF toe eonnectiot If mOt# discard toe seg- 0 ttal 0 IoEOPE UNCLa$SyPfo PAGE PeIS 27-FEB079 7PA36599 UNCLASS1IED TcP State Tables STIMULUS TCP tm0se00s Poeioved fro Pomoto TCP PAGE Dm12 Gu aCevtable SYNO CUROFN T STATE PCESSING field pefero'ces a valwo betweeen too Cuppe t gond loft wimelow edge amd M xt send secuence 9TUmbOPO OPavmpm immediate CIO@ opocess41ng top the Conpoctioml meft all otht p states 290OF01 T073644 d4sCa 'd the seam nt UNLS1F@ If mate disC cr t e logo 27-Fe9 pp36sq TCP Stte Tlebes STIMULUSI Send even UNCLASSTP D PAGE 0-13 eeeved from locel TMP CURRENT STAT OBef PROCESSING REOUIPEO queue the Send even for the eQmentigzp FOO iP4tiate the thpeoway h rmdhake Ov semOimc 8VN samemt to reote TCP and movi m to Sy sen t state 8Y' sent VN e t reeo 4vel event for the segm mtifze oucue the 3eum event for the eegtme'tige auOuO the Senda eet for the 98 M e establ1ished local clote recetved remote close received FI oueue the Sei sort petur n Se n Return event to THP mection colina status wito CoM- petutP a Send Retur event to TmP nectio c 1 osima status with COMM return a S ml Return event to TH4P with COM- Closi% mecti4o status Peceiveo return a Semo Return event to THO Aectiom cloeia status with com- FIN Bet received return a Se Retur event to THP miection closie status with CoM- retun a Send Return co ectio F Closed doe event mot elist status 7013 9 U i E l MiI L its 11-JUL-Tq T8444939 UNCLASSIFIED TCP State Tables STIMULUS Receive Returpn event received from local TmP CURRENT STATi PAGE DeIM PROCESSING REQUIRED ovenecloved ignore the event SYN sent ignore the event SYN eent Peceived ignore the event established uodete the Peceie left window cage by the nVmbep of octets acknowledged in TP's Res coive Return event end sent e ACK segment to remote TCPI check reemsemely Queue for a complete letter# the beginning sequence number of which equals the new receive left window edgel If one Is found Send letter to THP via Recefve event local cloe pecetivea remote close received ignore the event perform came oroceesing state FIN sent ignope the event FIN received ignop FIN ment received Ignore the event as for esteblisheo the event i Revision if July 'e 1979 11eJULu79 T044939 _ eUNCL AS3PIED ttm uem Jiit UNCLASSZFIED Tga3bS99 27afE -79 TCP State Tables STIMULUSt NOTE PAGE D-IS Send Data 0otu-m evet lop etrensmIssio Date SYN rIN flush and WOPEN e00Mamts retPanmissio n queue elemeents other pe PROCESSNG REQUIRED discard the eeamet CURRENT STATE oe eIl queue olem t stetes exceot closed by tme 3ema Pefepence locate the segment Oate Return vent o the petpnsmission queue ad eark the seqPe't Sed Date RetupA event If the peturn Status is successreCOJvgd1M ful icPement the count of successful o# the eaent end set a petramsmissias if Tvoe Iaptor transmission timer intervalf status nondelivepy notice - flow control amo the AfCCP lime error was received Im¢psmem tranlmillion• of t e of unouccessf4ul count has count segment end if the tpeosmissiom mot reaeced three set a ome secono timep fop if the count retransmission of the soegfet has reached three move to the closed state delete all seGments froM retransmission Queue received Data Return event with OSend status$ soairi Send Return evente to ToPo as all Other Queues 4p tNe ecorooriate oupge cOMMe4tion and send a Close Return event to aooroopiste status as soon as a1 1 THP with if Tree 2 Or 3 segments have heen dolete d eprOr status momdelivery notice a wmdelive@Jectf reboect4velv was able Op vlidatiom move to closed state and imitiate receiveo commectiOg Closue as descpibea for Tyce to eliminating the retrsms-isslon atte'ots closed petpertsw•iom on the the segmet locate queue and work the oetent 'Senod Data Roeup the petrans 49lelo scam event received ' queue and delete all segfmentS with Send Date Return event rocoved status and Issue sorroopiate Send Returm events to THPI once 411 have the petran fmision aueue On • omsi been deleted issue a Close Return event to TMP i l se et e UN CL I 27wFESwvq TZJ36S99 OOUNCLASS F EO TCP State Tables ST 14ULUSi NOTE1 Sen d Oats etupm ACK event ice ACI @'iue 0leinet STA wACK amd Og segmsmts are ACK aou CURRENT STATE 60eM SYN sent PAGE 0-16 elements PROCESSING RE uIREO discard tmo seaomt stablis Ae local close rece veo P@H'Ot@ I close FI ectivoi locate the sg m' pef Ipemce 1 i the Ser Q Data Returm event and delete it fr om tne AC' outuol If Tvot 2 or 3 prep status momtmelvery - undelivepable op validatlon Pelecto resoectlvoly was e'etw med move to closea state# delete 41l sgentes from the Petpees-issiom Ocueu wit Send Data Retwpm event received statue outce all other come moctiom cueues armd# If all aueues are emot ys send a Close Return vent to TI4O FIN @Met qe eIVed per form go-e opoos4' as described sboves f Tvae 3 trop is not e'eteived g eck to see if the Semd Data Petwem evomt Is fo the ac towledaeemt getf for tm e FIN segment t at was beceqvcol Ccupot semd left wineow ellok is Couai to next send souatco rumbop f 40 the ACK seoameft warn for the FIN segment tl st was rectived Move to closed state atrI 14 all couetectio cueues are ematy send a Close Retupm event to TOP cloer ocate the cogmefnt Poe e-ceo in t' e Se'mo Data Return event aml delete It from t e AC'K cusuer if all eom-ectiom atuewes are emr ty smd a Close Return event to THO p wooe T0'A303194 OU'CL ASS TPTIrn 27 PB q TP436599 U4CLA331vIEo TCP Stote Tables STIMUI USI IF'tefpuot event pec jveq ipa CURRENT STATE op@'ecloue@ SYN sent PACE Dot local THP PROCESSING REQ UIRED reject Peoutst by somd mg Z'mtepruot RetuPP% @ ot With connpection does moat exist posago code Ptect Pgauest by Sfmdimg '9tepruct Returevont with cOm eet4Om CSS mot exist reason Code SY'4 Semt Pteeved Weaet Oveme code stablishea P9ouest wit by semaimg Imtepruot Rqttfam connection does mot exist pesan if flush indicator Is Set all oth er states evemt with commectio er q7q Ttv36S9q in poe st petu mot yet seqmeemtf ee Some vemts to I4P with umoelivew'ed status and seno flush camtrOl s GF m to pt'oto TCP CNOYEI flush cotpol segment is sublect to aCeaumtsvility 1mcp theE@fo g will be Cut am the pe tiemmgsior l if 1imtruot imdietop Is stmt f % P Cuesto emd am out-oi-band imtep Puct CD81 control 8e9mermt to remote TCp NOTEI 09I Comtpa1 s mAt r mot Subject to accountab'ility mot thopeforp will be But 04% tis AC'K Queue PeJVCt fequest by somdimo Imtoppuct Rotup#4 all eUNCLASS1IE De celing reason too 27-FEB-79 T236599 TCP Steae Tetsl STImULU$1 Close event CURRENT PAGE D I received ipom STATE 0DeM SV CUNCLASS FIED Sent local TWP PROCES3ING REOGUIRE ouPge all Connection aueueS and semd TMp Close Retup event with successful local CIose status retu m all Send events to YP witf undelivtransaction ID of the status# record te Close eveto ana Move to Closed statel Once espte aPe accoruto alPesdv tpai all leffeot event witp ed fop Send TWP a Close Return successful local close status seod same Processing as iet state sYN se t regCived perform estableisie record the current value oi the receive left window eoe fop cossible use latsp im status Control segmentl if defepeo graeefvl close is soeeiiiedf aueue the Close event fop the seae'tzem If mo ntries are o the seed aueue send a FIN segment i ediately and move to FIN sent state if am immeoete return all mot yet eeqIs loeclleds clost mentized Send eve ts to T4P with umdeliverei status send a FIN fruit sememtP and ove to FIN sent state local close peceived remote close received for 3YN assume this Is am fbopt eaueet secorl Close return Close Refrom TH P vecelvem event witi close tupm evemt fop fiest Close evert flushed status return all mat vet seteme tihea sem events to TNP with umelivepee e move to Flk se-t FaIN se sendad status# state and record teameaction 10 of mew Close evemt record the cuepert wlmoow @oe send FIN Sent state value of the peceive left a FIN seamento andmove to FIN sent $ed TNP a Close Return evemt with flushed status for f4pot Close event event FIN Deeform same opecessima as foe establlse of the pecelve left value the set state wltdow edge to that of the value of the see one 4 the FIN segment number olue Guemeo that was peceived semi a FIN segmeto semi a status Control segmemt foe the FIN seg-emt to uik move and reeived that was semt peceved state received 2 UNCLASSIFIED close Close 7'WESu 9 T@136sq9 IJNCLASSIFIED TCP State Tables STIMULUS Close evemt prcelved ipom loel FIN 4eet pCeIved PAGE O- q THP O@rfom some ProceIsi o as for establiede Otatel it sould beomted that this o4twoe tiom Chlmqa I the qp@Ce4UI local Close to am immediate close abort seed Close Retupn oevit with Comeettom losed not exist status -FEP- 7q 10036399 UNCLASSIFIED 4 bhId644I4 does I-JUL-T9 TCP State Index T8844939 UNCLAS$1FIED Tables PAGE D-24 INDEX ACK Segment Peeeiveo fpom network 0-S Cleose event peeved from local TmP D-lb Data resolved fPOfW MetW@Pk 006 defimitiom of tepee@ 00°2# 0-3 FIN flush oogpmt P eefvod from netwopk D-6 FIN nlo flush setiment POCtived from fletwOPk D 7 Intopruat event received from local THP 0017 R9e4VO RotuPn event P eeived from local THP DeJ4 $and Date qetwpm event De15 Delb Send event Peco4voO from local TMP DwI3 Status sogqMet received from Metwo k D 9 8YN eegoM PotvoO from Motwork 004 TCP moessages P oioved from remote TCP Dell TCP timoout Rotpv event occurred DeLO eeedeteu povisopo% 116JULoT9 10944939 UNCLASI$FIED to July 40 1979 ll-JULe q TOA44939 UNCLASSIFIED PAGE E-1 APPENOIX E AUTODIN 11 TRANSM1S1ON UNITS There co standaed Units of tPnsm ieon fop each component It 4i Ime HSI op TM# TWP TCPP and SIP of a CCUVTAC Ise POPtrmt to rdePeteid the terinology used to describe each Content$ of echo and the Petltiomeio of all the ulits the of tremisesion The units ore discussed below beginning with the smllesto unit user text to the largestO SIP poles of the A visual conception op AUTODIN 11 segment tiorehis i snOw n Fgupe Eel Figure E-2 shows dirpee tion of transmession schemotie t is the smallest fop a CCU TAC User text Is rece4ved by HSI or TO on the hostatooCCU op tepmoineleto-TC lin# Peeosectivelv The text may Come in a cherectep at a time or In blocks 45K TH aecumulates of severel chopctepse text and Posses it to THP vie the From User event in the MCCUo and by an euivelent veh4e de in the $CCU and TAC EGO event may bpin ome Op many characters d eeding on the Dore link protocol the ari ticulap type of user being used Fop the ouroose of this diseussiont ard from TMoPs viewnoil t the unit of weep text' Should be come tpanmission collect siderd as one or mope user text Charetees wtich as a unit# have meaning to THP That meanng to sOecial Ie some cNarecteps have as inteprut function chaecteper TmPo such 146 return# crepigee eose line cherecteps nefeed etee Other ePeeters hove o O sel meaning to TNPo end are accumuleted as date to be tpansmitted to the network In a unit called the THP data rocoro user text a This unit of traens issio Revision 1 IIoJULe 9 T004493q UNCLASSIFILC 05 ccc c 00 5 July 4 1 0104939 11-JUL4 7 AUTODIN 11 TRANSM1SSION e UNCLASSIPIIeDa PAGE Ee2 UNITS as TMP record 0 This unit of tranSpiisiom 40 teo That Is# moons by which TOPS eommumicate OeC TOP record conteims Information instructs The ieo YMP as to toe Poueod Processing lt common TOP POCOpo the data Pecopdp Come usep text characters opecedod by am gifts of S-bit pOcord mopk# an sebit record typee MGO a Other TMP records comlength fields I6abit am 8bit record Silt Of Oe Sebit record mareP type# end optional ePmOtOP bytes All TOP record tyDO$ end formats ape defined in Apoe dices A end 9 of the TOP Transportable Specif 4eetions 3 TOP letter - This unit of trensmission is as SeoIeted with THP and consists of one or more TO4 peeords If only user text Chopecteps are In being transmitted on the coneetion aogo # binary mode# roauiping no other TO control pecorde# there would be o@e TMP data record In If other information IS b img the TOP letters fol user text charoCtOPe tponsmitted eogo# letter would lowed by On option reoueoto tho consist of a TPGeta record followed by a TNP gotion record The site of the letter is dee toermOed by the various packet poloese meeen Isms of THIP see Reerene 9 g LottePe ape passed to TCP via the Send event In the MCCUe In an SCCU or and by am oevalent vehicle 4 Tesegment 0 This unit of tpomemission also known as TCP segment is associated with TCP never and eonoistS Of Rnoe oem op mope# but lttopep opeeeOded by a Tosgment partial TP The Tesegmemt header is the mens by hoede which TCPs communicoot and convoys TCP send peceive flow control informatio control InfoPmetion end addressing Imfoema A of the TCP Transportable tio see Appeodi 8eeeification The T-segment is passed to SIP fop traemission to the SCM via e Sona Date event In the MCCUe and the eauivalemt In em $CCU or TACO So 11eJULe 9 $esement 0 Tole unit also of transmission known as SIP segment op AUTODIN II segment is associated with SIPS It is the unit tpoes The fopped between the CCU or TAC and SCMI $esegment consists of toe Tmsegment prOeeded by a binaPV Segment leader CSS5 0 The SSL CC addres contaims secupity precedencee Ing anid SIPSCM control imfopmetion concerns Ing te Se oegment being sent Revision 1 T0844939 UNCLASSIPIED attaetetat July 4V 1979 UNCLASSIFIEO e t04e4939 11eJUjLe 9 PAGE E13 AUTODIN 1I TRANS ZS5 O' UNITS flguro Ent AUTODIN 11 Segmont FOPmt MEIORY IMAGE AUTODIN 11 SEGMENT FOJ'NAT PDP-I L lE UORI 15 1 13 12 11 10 9 8 7 6 5 4 3 2 1 6 i I Errm 3 3 S YE spare I 1 START TIME 4 6 2 3 SOURCE SUBSCRIBER ADDRESS 3 4 DESTINATION SUBSCRIBER ADDRESS 10 5 12 14 6 16 a is 9 SEOUENCE N'4ER - MnST SI NIFICANT $ITS MSS 20 tO $ITS LSB 22 11 REASON FOR OUTAGE WNDOW OR DURATION C01AND COWTMOL FIELD 1PRECEDENCE ITCP VERSION 11 13 pr ITCC-1 15 SECURITY-2 17 LENGTH- 19 23 ISECLMIY-l spare I TCC-2 HEDE _LENGTH - OF TEXT SEQUENCE NUMBER - LEAST SICKIFICANT CONTROL rNFORMATIO% 27 1S D SUSI 29SEX U 33 161 vXRsIo I unused 25 31 0 2 9 21 SEGMET D DESTINATION TCP LSD SOU'RCE NETWORK 35 ______________________ D D 24 12 26 13 S 28 14 DESTINATION NETWORK 30 is DESTrATIO ' TCP 055B 32 16 34 17 OUC 37 ACKNOWLEDGEMENT SEQUENCE N 13ER NSA 36 18 39 SOUE ICE NUMBER LSD ACKNOOWLEDGEMEN4T 38 19 RECEIVE WINDOW IN BYTES 40 42 20 44 22 41 43 CONTROL DATA EXTENSION TCP CHECKSU71 MsB TCPCHEKSU LS 45 4J7 NOTEI 7 12 21 j THP RECORD MRK byte 0 USER Tr X 51 USER TEXT byte 2 TCP eocksum field the CCU TAC NCC TCP Ffqup Eel@ 46 23 TIHP RECORD LENCTH MSR 48 24 USER TEXT byte 1 50 25 TP RECORD TYPE TP RECORD LENGTH S 49 vt v 43 end 4 46 not used 4n molemetatioF AUTODIN 11 Segment Fomet Noevision I# July 4p 19 9 116JUL'79 tVd44939 UNCLASSIFIEDO OCCOCCOCOCCOCO lieJUL-79 AUYOOIN figupe 70044939 11 IRANSMtM0 4 AUTOD'IN It Eo2 UN4CLASSIFIED UNITS PAGE E s4 3090mt Teamemissfam Seftemetie A q4 - 0 fA 0 aj - OW 4oa -P4 0 o 0r c0 'I I 0 a U - ri a 4 0J 0 0 - wl Id a U 00 ca u 0 0 4 V 0j A qj U W P o 6 o to a N I t II C 0 V -4 T884939 UNCASSIIED a -- v- 44 -1