lest - Available Copy E8 5 1 I'll Modification to Internal Protocol Model by William R Bush DEZ 2 1 December 1978 Sponsored by Defense Advanced Research Projects Agency DoD ARPA Order No 3079 3 Mon itor ed by Naval Electronic Systems Command Under Contract #N00039—78—G—0020 A’ toc re1ea s pu i pst 1 U 1 u L ’ ’d - The views and conclusions contained in this document are those of the authors and should no t be interpre ted as necessar ily representing the official policies either expressed or implied of the Defe nse Advanced Research Projects Agency or the U S Government ‘8 12 2O - - u 18 unclassified S E C U R I TY C L A S S I F I C A T I O N O F TNIS P A G E f$7 • D u o Ent d DEor ‘I ° A I IEIJ’FATIAkI D A E I# J% Um ‘ I I R E P O R T N U M B E R - R E A D IN S T RU C T l O S S EF O RE C O M P L E T I N G F ORM 3 2 GOVT ACCESSION NO 4 T I T L C wd SubSSIl —1 1 TYPE OF RE POR T I PIRIOO C OV R E O o di f fc a tion to nt ernal chnical re 4 d rotocol Modelø PE R F O R M I N G ORG R E P O R T N U M B E R S CONTRACT OR G R A N T NUMSZ R i 7 AUT HO R iam R Bush 1 PERF RE C I P I E N T S C A T A L O G NUMB E R NO O R G A N I Z A T I O N NAM E AND A D D R E S S _ _ _ _ s_ _ -e fe er r_ L 4O — PR 3 A AR EA S W O R K UNIT N U M B E R S I Center for Research in Computing Technology Harvard University Cambridge Massachusetts 02138 II C O N T R O LL IN G O F F I C E N A M E A N D A D D R E S S -M --— _ _ __ _ __ _ I ecember 1 78 1 Department of the Navy Naval Electronic Systems Command Washington D C 20360 II NUUBEROF PAGES 14 M O N I T O R I N G A G E N C Y N A M E 5 AOD RESS SI dIll rai Iron’ ConIrolIing 0u Sd five IS S E C U R I T Y CLASS ol lbS r•p ofl unclassified 11 D E c L A S S I F I C A T I O N O O W P I G R A D S N G SCHEDULE IS D I S T R I B U T I O N S T A T E M E N T OS lbS R port unlimited 17 D I S T R I BU T I O N S T A T E M E N T of A ab t ct aiu• d in Block 20 51 dlft nt from R p t - t i’l I IS SUPPLEMENTARY NOTES IS K E Y W O R D S Con tlnu on v aid St i co ay aid Sd n5SIy by block nim b r Transmission Control Program TCP MSC interprocess communication protocol flow control Ø A B ST RAC T CaiSMMO v n’i r id St n e oa vy aid Sd nlSIy by bS #ck monk An abs t rac t mod elof written as a test of report evaluates the use the Transmission DD _ _ _ _ i _ 1473 _ _ the interproces s communica tion sys tem MSG has been software development and maintenance tools This maintenance effort involved in changing the model to Control Program TCP network protocol LO ITION OF I N O V 11 5 OS$OL T $ ‘N Ol0 3 O l 4 • 510 1 _ _ _ _ _ _ _ unclassified IICURITY CI A$$IFICA ION OF THIS PA GE Shin D•io tAII 4 u - - _ _ __ __ __ _ _ _ _ _ - _ Modification to Internal Protocol Model by W illiam R Bush ± An a b stra c t mo d el mo de l of the - i nterprocess communic a t i on s y stem MSG MSG has b een wr i tten as a test of software development and evalu ate s the maintenance ma i nten ance tools This report effort involve d in ch an gi n g the model to use the TCP network protocol TCPJ There are two aspects to converting to TCP The first is disruption that is the m i n imum amount of wor k nee d e d to get the old system to work in the new environment The secon d i s o p t im i zation ma d e possi b le b y the new env i ronment involving abstract enhancements to the functioning system The model would be disrupted not at all by changin g to TCP an d facilitates possible cptimizatio ns The mo d el’ s i nterfac e to the network is its general para digm for Input — output the channel A channel is a data path between two processes The pr imitives for manipulating channels are CHO PEN with whtch channels are opened SEND for sen d ing d ata RECEIVE for r e c e i v i n g d ata an d with CHCLOSE wh ich channels are closed The notion of’ a channel is t h a t of a TCP c o n n e c t i o n and directly to the TCP the primitives channel OPEN pr i m i t i v e s map SEND RECEIVE an d Page 2 A channel identifier the name g iven a CLOSE res pectively channel ma ps to the TCP socket in TCP is that of specifiable conne ctions only d oes not pass affect connect ions data eight— bit the need The only channel idea not m od el only byte All TCP bytes This restriction since pass size inter— MSG In sum chang i ng to TCP woul d not chan g e the a b stra c t mo d el at all an d the eight— bit network bytes refinement of the four channel p rimit i ves to their TCP counter parts would be straightforward C ha ngi ng optimi zation to of TCP woul d ma ke p oss ib le the inter—MSG pr o t o c o l an d a c o r r e s pon di n g simplification of the abstract model is The fundamental idea to model inter— MSG transactions in the same way as local transa c t i ons wit h a separate This woul d channel per pending TCP’ s event el im i nate the ne g ot i ation currently re q u i re d by the inter—MSG protocol The optimization is by su b stanti a l made possible rel i a b le transmission fe a ture whi c h obv i ates the nee d for inter—MSG confirmation messages In t h e abs t ract mo d el each cannot be sat i sf i e d i mme di ately MSG user a p en d ing associated with It a channel between the MSG used the u s e r assoc iated p rim i t i v e user c a se event has process and for passing the final result of the primitive to In a s i m i l a r m a n n e r with it a each p e n d i n g networ k event can have channel to the appropria te remote MSG over wh ich inter-M SG communication the that passes In of messages and alar ms after the user executes a _ _ _ _ - - - - —b V Page 3 sen d primitive MSG executes wh ich automatically a non—blocking opens the channel channel SEND When the receiving MSG i s p re p are d to rece i ve a messa g e or alarm i t executes a corres pondin g RECEIVE The t h e sen d er an d r e c e i v er channel identifiers ar e enco d ed in socket numbers o p ens com p lete the da t a closed process class and instanc e of ar e the i r r e s pe c t i v e When both automatic transm i t t e d an d the c h a nnel No confirmation from the receiving MSG is necessary since TCP will see to that The case of direct connections is similar th e d ifferen c e b e i n g that connect i on id ent i fiers are exc h an g e d an d t h e c h annels are t h en p asse d to processes Th e timing associated channel the t i min g of the user p en di n g e v e n t s i s d one t h r o u g h network channel primitive The p r i m i t i v e is g i v e n t h e same t i m e o u t i n t e r v a l as t h e pending event If the p r i m i t i v e f a l l s t h e p e n d i n g e v e n t is aborted The above considerably discipline particularly simplifies the and four En Q O u t p u t output the alarm initiate to routines inpu t eleven that connection direct connection rout i nes EnQOutput cpenCon n En Q lnputOpenCo n n and —— that a a These routines remain unchange d level decision routines lower four output complete initiate EnQOutputC loseConn The the En Qlnput complete close model routines initiate En QRece ive R e c o r d O k and c o m p l e t e i n p u t three abstract queue management Twenty t h r e e r o u t i n e s are reduced message the and a connection connection relatively exempl i Page l gratia HoldOrRejectMe ss become unnecessary The interface rout i ne reflect the routines are Del i ver To RemoteHost channel stra tegy The is change d network to server simplified s i nce format t e d MSG p rotocol items are no l on ge r necess ary The cancelling of failed p end i ng events proceeds as before b ut th e t i mer p ro c ess i s no lon g er nee d e d s i nce it is subsumed by the timed channel primitives Page 5 References m o d e l H o l l o w a y G Bush W Abstract and Mealy C Mo d el of M S G Technical report TR 25—7 8 Center for Harv ar d Research in Computing Technology Un iv e r s it y October 1978 MSG semi— annual M SG design specificatio r i-n “Third for the National Soft ware Works ” technical report M a s s a c h u s e t t s C o mp u t e r A s s o c i a t e s Wak e f i e ld M a s s F e b r u a r y 1977 TC P Specification of I n t e rr i e t w o r k Postel J T r a n s m i s s i o n Co ntrol Pro g r am Ver si on 4 Informat i on Sc i en c es Inst it ute Un iversity of Southern Cal i f o r n ia September 1978 i I 1