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Annotation of 43BSDReno/contrib/isode-beta/doc/practical-osi1/end-to-end.tex, revision 1.1

1.1     ! root        1: % run this through LaTeX with the appropriate wrapper
        !             2: 
        !             3: \dotopic{0}
        !             4: \begin{bwslide}
        !             5: \part  {END-TO-END SERVICES}
        !             6: \end{bwslide}
        !             7: \doparts
        !             8: 
        !             9: 
        !            10: \begin{bwslide}
        !            11: \part* {OUTLINE}\bf
        !            12: 
        !            13: \begin{description}
        !            14: \item[PART I:]         CONCEPTS
        !            15: 
        !            16: \item[PART II:]                BUILDING BLOCKS
        !            17: 
        !            18: \item[PART III:]       ACHIEVING CONNECTIVITY
        !            19: 
        !            20: \item[PART IV:]                COMPARISON TO TCP/IP
        !            21: \end{description}
        !            22: \end{bwslide}
        !            23: 
        !            24: 
        !            25: \begin{bwslide}
        !            26: \ctitle        {A BIG ACKNOWLEDGEMENT}
        !            27: 
        !            28: \begin{nrtc}
        !            29: \item  MY INTEREST IN END-TO-END SERVICES IS ONLY AS A USER,
        !            30:        NOT A PROVIDER
        !            31: 
        !            32: \item  AS SUCH, I'D PREFER TO USE THEM AS A BLACK BOX
        !            33: 
        !            34: \item  UNFORTUNATELY, THIS MODEL DOESN'T WORK IN PRACTICE
        !            35:     \begin{nrtc}
        !            36:     \item      THE LOWER-LAYERS AREN'T HOMOGENEOUS
        !            37:     \end{nrtc}
        !            38: 
        !            39: \item  THE PRACTICAL PERSPECTIVE PRESENTED HERE IS HEAVILY INFLUENCED BY
        !            40:     \begin{nrtc}
        !            41:     \item      STEPHEN E.~KILLE OF UNIVERSITY COLLEGE LONDON
        !            42:     \end{nrtc}
        !            43: 
        !            44: \item  AND HIS PAPER
        !            45:     \begin{nrtc}
        !            46:     \item      ``AN INTERIM APPROACH TO USE OF NETWORK ADDRESSES''
        !            47:     \end{nrtc}
        !            48: \end{nrtc}
        !            49: \end{bwslide}
        !            50: 
        !            51: 
        !            52: \begin{bwslide}
        !            53: \part  {CONCEPTS}\bf
        !            54: 
        !            55: \begin{nrtc}
        !            56: \item  BASIC TERMINOLOGY
        !            57: 
        !            58: \item  NETWORK SERVICE
        !            59: 
        !            60: \item  TRANSPORT SERVICE
        !            61: \end{nrtc}
        !            62: \end{bwslide}
        !            63: 
        !            64: 
        !            65: \begin{bwslide}
        !            66: \part* {BASIC TERMINOLOGY}\bf
        !            67: 
        !            68: \begin{nrtc}
        !            69: \item  END-TO-END SERVICES RESPONSIBLE FOR
        !            70:     \begin{nrtc}
        !            71:     \item      DATA TRANSFER
        !            72:     \end{nrtc}
        !            73: 
        !            74: \item  APPLICATION SERVICES RESPONSIBLE FOR
        !            75:     \begin{nrtc}
        !            76:     \item      INFORMATION TRANSFER
        !            77:     \end{nrtc}
        !            78: \end{nrtc}
        !            79: \end{bwslide}
        !            80: 
        !            81: 
        !            82: \begin{bwslide}
        !            83: \ctitle        {BASIC TERMINOLOGY (cont.)}
        !            84: 
        !            85: \begin{nrtc}
        !            86: \item  TERMINOLOGY DIFFERS BETWEEN NETWORKING COMMUNITIES
        !            87:     \begin{nrtc}
        !            88:     \item      WE'LL USE ``OSIFIED'' TERMINOLOGY
        !            89:     \end{nrtc}
        !            90: 
        !            91: \item  A NETWORK CONSISTS OF A COLLECTION OF SUBNETWORKS CONNECTED
        !            92:        BY INTERMEDIATE SYSTEMS AND POPULATED BY END-SYSTEMS
        !            93: 
        !            94: \item  DATA TRANSFER OCCURS BETWEEN TWO END-SYSTEMS,
        !            95:        POTENTIALLY GOING THROUGH ONE OR MORE INTERMEDIATE-SYSTEMS
        !            96:        IF THE END-SYSTEMS RESIDE ON DIFFERENT SUBNETWORKS
        !            97: \end{nrtc}
        !            98: \end{bwslide}
        !            99: 
        !           100: 
        !           101: \begin{bwslide}
        !           102: \ctitle        {THE NETWORK}
        !           103: 
        !           104: \vskip.5in
        !           105: \diagram[p]{figureE-2}
        !           106: \end{bwslide}
        !           107: 
        !           108: 
        !           109: \begin{bwslide}
        !           110: \ctitle        {END-SYSTEMs (ES)}
        !           111: 
        !           112: \begin{nrtc}
        !           113: \item  CONTAIN BOTH: 
        !           114:     \begin{nrtc}
        !           115:     \item      THE LOWER-LAYER PROTOCOLS NECESSARY FOR DATA TRANSFER, AND
        !           116: 
        !           117:     \item      THE UPPER-LAYER PROTOCOLS NECESSARY FOR INFORMATION TRANSFER
        !           118:     \end{nrtc}
        !           119: 
        !           120: \item  WHERE THE APPLICATIONS LIVE
        !           121: 
        !           122: \item  WHAT THE USERS ARE INTERESTED IN
        !           123: \end{nrtc}
        !           124: \end{bwslide}
        !           125: 
        !           126: 
        !           127: \begin{bwslide}
        !           128: \ctitle        {INTERMEDIATE-SYSTEMs (IS)}
        !           129: 
        !           130: \begin{nrtc}
        !           131: \item  CONTAIN ONLY:
        !           132:     \begin{nrtc}
        !           133:     \item      THE LOWER-LAYER PROTOCOLS NECESSARY FOR DATA TRANSFER
        !           134:     \end{nrtc}
        !           135: 
        !           136: \item  ULTIMATELY CONTAINS HIGHER-LAYER PROTOCOLS TO SUPPORT MANAGEMENT
        !           137: 
        !           138: \item  IN ADDITION TO PASSING ALONG APPLICATION DATA,
        !           139:        INTERMEDIATE-SYSTEMS COOPERATE AMONGST THEMSELVES
        !           140:     \begin{nrtc}
        !           141:     \item      e.g., EXCHANGE ROUTING DATA
        !           142:     \end{nrtc}
        !           143: \end{nrtc}
        !           144: \end{bwslide}
        !           145: 
        !           146: 
        !           147: \begin{bwslide}
        !           148: \part* {NETWORK SERVICE}\bf
        !           149: 
        !           150: \begin{nrtc}
        !           151: \item  NETWORK SERVICE IS RESPONSIBLE FOR MOVING DATA FROM ONE END-SYSTEM
        !           152:        TO ANOTHER
        !           153: 
        !           154: \item  UNFORTUNATELY, THERE ARE TWO DIFFERENT VIEWS AS TO WHAT THIS MEANS:
        !           155:     \begin{nrtc}
        !           156:     \item      CONNECTION-ORIENTED
        !           157: 
        !           158:     \item      CONNECTIONLESS-MODE
        !           159:     \end{nrtc}
        !           160: 
        !           161: \item  PERHAPS THE GREATEST ``RELIGIOUS'' ISSUE OF THE DECADE
        !           162: \end{nrtc}
        !           163: \end{bwslide}
        !           164: 
        !           165: 
        !           166: \begin{bwslide}
        !           167: \ctitle        {CONNECTION-ORIENTED NETWORK SERVICE\\ (CONS)}
        !           168: 
        !           169: \begin{nrtc}
        !           170: \item  BASED ON THE NOTION OF ``RESERVATIONS'':
        !           171:     \begin{nrtc}
        !           172:     \item      ON CONNECTION REQUEST, MINIMUM REQUIREMENTS ARE STATED
        !           173:        \begin{nrtc}
        !           174:        \item   (e.g., THROUGHPUT)
        !           175:        \end{nrtc}
        !           176: 
        !           177:     \item      IF REQUEST IS GRANTED, THESE RESOURCES ARE RESERVED FOR THE
        !           178:                CONNECTION'S DURATION
        !           179:     \end{nrtc}
        !           180: 
        !           181: \item  CO-MODE SERVICE PRIMITIVES
        !           182:     \begin{nrtc}
        !           183:     \item      N-CONNECT: CONNECTION ESTABLISHMENT
        !           184: 
        !           185:     \item      N-DATA (N-DATA-ACKNOWLEDGE): DATA TRANSFER 
        !           186: 
        !           187:     \item      N-EXPEDITED-DATA: EXPEDITED DATA TRANSFER
        !           188: 
        !           189:     \item      N-DISCONNECT: CONNECTION RELEASE
        !           190: 
        !           191:     \item      N-RESET: CONNECTION RESYNCHRONIZATION
        !           192:     \end{nrtc}
        !           193: \end{nrtc}
        !           194: \end{bwslide}
        !           195: 
        !           196: 
        !           197: \begin{bwslide}
        !           198: \ctitle        {CONS (cont.)}
        !           199: 
        !           200: \begin{nrtc}
        !           201: \item  GOOD POINTS:
        !           202:     \begin{nrtc}
        !           203:     \item      LOW OVERHEAD FOR DATA TRANSIT
        !           204: 
        !           205:     \item      IMMUNITY FROM OTHER NETWORK TRAFFIC
        !           206: 
        !           207:     \item      ACCOUNTABILITY
        !           208:     \end{nrtc}
        !           209: 
        !           210: \item  BAD POINTS:
        !           211:     \begin{nrtc}
        !           212:     \item      HIGH OVERHEAD FOR CONNECTION ESTABLISHMENT
        !           213: 
        !           214:     \item      QUESTIONABLE RECOVERY CHARACTERISTICS
        !           215: 
        !           216:     \item      IF RESOURCES ARE RESERVED, BUT NOT IN USE,
        !           217:                NEW CONNECTION REQUESTS ARE DENIED
        !           218:     \end{nrtc}
        !           219: \end{nrtc}
        !           220: \end{bwslide}
        !           221: 
        !           222: 
        !           223: \begin{bwslide}
        !           224: \ctitle        {CONNECTIONLESS-MODE NETWORK SERVICE\\ (CLNS)}
        !           225: 
        !           226: \begin{nrtc}
        !           227: \item  BASED ON THE NOTION OF ``COME AS YOU ARE'':
        !           228:     \begin{nrtc}
        !           229:     \item      NO CONNECTION REQUEST, JUST SEND DATA
        !           230: 
        !           231:     \item      TRANSPORT MUST DYNAMICALLY DETERMINE IF REQUIREMENTS ARE
        !           232:                BEING MET
        !           233:     \end{nrtc}
        !           234: 
        !           235: \item  CL-MODE SERVICE PRIMITIVES
        !           236:     \begin{nrtc}
        !           237:     \item      N-UNITDATA: DATA TRANSFER
        !           238:     \end{nrtc}
        !           239: \end{nrtc}
        !           240: \end{bwslide}
        !           241: 
        !           242: 
        !           243: \begin{bwslide}
        !           244: \ctitle        {CLNS (cont.)}
        !           245: 
        !           246: \begin{nrtc}
        !           247: \item  GOOD POINTS:
        !           248:     \begin{nrtc}
        !           249:     \item      LESS DELAY FOR INITIAL DATA TRANSIT
        !           250: 
        !           251:     \item      POTENTIALLY MORE ROBUST WITH CHANGES IN THE NETWORK
        !           252: 
        !           253:     \item      SQUEEZES ``LAST DROP'' FROM AVAILABLE RESOURCES
        !           254:     \end{nrtc}
        !           255: 
        !           256: \item  BAD POINTS:
        !           257:     \begin{nrtc}
        !           258:     \item      HIGHER OVERHEAD FOR DATA TRANSIT IF MULTIPLE SUBNETWORKS
        !           259:                ARE INVOLVED
        !           260: 
        !           261:     \item      REQUIRES WELL-BEHAVED USERS TO PREVENT OVER-SUBSCRIPTION
        !           262:     \end{nrtc}
        !           263: \end{nrtc}
        !           264: \end{bwslide}
        !           265: 
        !           266: 
        !           267: \begin{bwslide}
        !           268: \part* {TRANSPORT SERVICE}
        !           269: 
        !           270: \begin{nrtc}
        !           271: \item  TRANSPORT SERVICE IS RESPONSIBLE FOR MOVING DATA FROM ONE END-SYSTEM
        !           272:        TO ANOTHER~---~RELIABLY
        !           273:     \begin{nrtc}
        !           274:     \item      (WE'RE CONSIDERING ONLY CO-MODE TRANSPORT SERVICE)
        !           275:     \end{nrtc}
        !           276: 
        !           277: \item  IF CO-MODE NETWORK SERVICE IS USED, THIS IS TRIVIAL
        !           278: 
        !           279: \item  OTHERWISE, SOPHISTICATED ALGORITHMS ARE REQUIRED IN PROTOCOLS
        !           280:        WHICH IMPLEMENT TRANSPORT SERVICE
        !           281: \end{nrtc}
        !           282: \end{bwslide}
        !           283: 
        !           284: 
        !           285: \begin{bwslide}
        !           286: \ctitle        {TRANSPORT SERVICE (cont.)}
        !           287: 
        !           288: \begin{nrtc}
        !           289: \item  IMPORTANT IMPLICATION:\\
        !           290:     \begin{nrtc}
        !           291:     \item      AVAILABLE NETWORK SERVICE DETERMINES WHICH
        !           292:                TRANSPORT PROTOCOL CAN BE USED
        !           293: 
        !           294:     \item      HOWEVER, WHEN INITIATING A CONNECTION,
        !           295:                TRANSPORT SERVICE IS ACTIVE PRIOR TO NETWORK SERVICE!
        !           296:     \end{nrtc}
        !           297: \end{nrtc}
        !           298: \end{bwslide}
        !           299: 
        !           300: 
        !           301: \begin{bwslide}
        !           302: \ctitle        {CHOICE OF NETWORK SERVICE}
        !           303: 
        !           304: \begin{nrtc}
        !           305: \item  CHOICE OF NETWORK SERVICE IS ECO-POLITICAL NOT TECHNICAL
        !           306:     \begin{nrtc}
        !           307:     \item      EITHER APPROACH CAN BE MADE TO WORK WELL
        !           308:     \end{nrtc}
        !           309: 
        !           310: \item  CO-MODE NETWORK SERVICE IS MORE SUITED TOWARDS A COMMON-CARRIER MODEL
        !           311:     \begin{nrtc}
        !           312:     \item      ACCOUNTABILITY AND ISOLATION
        !           313:     \end{nrtc}
        !           314:     THIS IS TYPIFIED BY PUBLIC DATA NETWORKS
        !           315: 
        !           316: \item  CL-MODE NETWORK SERVICE IS MORE GENERAL
        !           317:     \begin{nrtc}
        !           318:     \item      ADAPTABILITY AND COOPERATION
        !           319:     \end{nrtc}
        !           320:     THIS IS TYPIFIED BY CLOSED COMMUNITY NETWORKS
        !           321: 
        !           322: \item  HOWEVER, THE TWO APPROACHES DON'T MIX WELL
        !           323: \end{nrtc}
        !           324: \end{bwslide}
        !           325: 
        !           326: 
        !           327: \begin{bwslide}
        !           328: \part  {BUILDING BLOCKS}\bf
        !           329: 
        !           330: \begin{nrtc}
        !           331: \item  ADDRESS FORMATS
        !           332: 
        !           333: \item  NETWORK BINDING
        !           334: 
        !           335: \item  TRANSPORT PROTOCOLS
        !           336: 
        !           337: \item  APPLICATION USE OF END-TO-END SERVICES
        !           338: 
        !           339: \item  EMULATION OF OSI END-TO-END SERVICES
        !           340: \end{nrtc}
        !           341: \end{bwslide}
        !           342: 
        !           343: 
        !           344: \begin{bwslide}
        !           345: \part* {ADDRESS FORMATS}\bf
        !           346: 
        !           347: \begin{nrtc}
        !           348: \item  HIERARHICALLY STRUCTURED
        !           349:     \begin{nrtc}
        !           350:     \item      ADDRESSING DOMAINS, SUB-DOMAINS
        !           351: 
        !           352:     \item      UNAMBIGUOUS PREFIXES
        !           353:     \end{nrtc}
        !           354: 
        !           355: \item  MAIN GOAL: FACILITATE ALLOCATION
        !           356: 
        !           357: \item  NO IMPLICATIONS ON ``WHERE IT IS'' OR ``HOW TO GET THERE''
        !           358:     \begin{nrtc}
        !           359:     \item      BUT STRUCTURE MAY FACILITATE ROUTING DECISIONS
        !           360:     \end{nrtc}
        !           361: \end{nrtc}
        !           362: \end{bwslide}
        !           363: 
        !           364: 
        !           365: \begin{bwslide}
        !           366: \ctitle        {ADDRESS FORMATS (cont.)}
        !           367: 
        !           368: \begin{nrtc}
        !           369: \item  AN ADDRESSING AUTHORITY DEFINES STRUCTURE OF DOMAIN
        !           370:     \begin{nrtc}
        !           371:     \item      TERMED AN ABSTRACT SYNTAX
        !           372:     \end{nrtc}
        !           373:     AND ALSO ALLOCATES VALUES
        !           374: 
        !           375: \item  A TRANSFER SYNTAX DEFINES HOW ADDRESSES ARE ENCODED
        !           376: \end{nrtc}
        !           377: \end{bwslide}
        !           378: 
        !           379: 
        !           380: \begin{bwslide}
        !           381: \ctitle        {TOP-LEVEL}
        !           382: 
        !           383: \begin{nrtc}
        !           384: \item  ADDRESS IS DIVIDED INTO TWO PARTS:
        !           385:     \begin{nrtc}
        !           386:     \item      INITIAL DOMAIN PART (IDP), AND
        !           387: 
        !           388:     \item      DOMAIN SPECIFIC PART (DSP)
        !           389:     \end{nrtc}
        !           390: \end{nrtc}
        !           391: 
        !           392: \diagram[p]{figureE-3}
        !           393: \end{bwslide}
        !           394: 
        !           395: 
        !           396: \begin{bwslide}
        !           397: \ctitle        {TOP-LEVEL (cont.)}
        !           398: 
        !           399: \begin{nrtc}
        !           400: \item  AUTHORITY AND FORMAT IDENTIFIER (AFI) DEFINES HOW
        !           401:     \begin{nrtc}
        !           402:     \item      IDI IS INTERPRETED, AND
        !           403: 
        !           404:     \item      HOW DSP IS FORMATTED (DECIMAL/BINARY ABSTRACT SYNTAX)
        !           405:     \end{nrtc}
        !           406: 
        !           407: \item  INITIAL DOMAIN IDENTIFIER (IDI) SAYS WHO OWNS THE DSP
        !           408:     \begin{nrtc}
        !           409:     \item      MIGHT BE VARIABLE LENGTH
        !           410: 
        !           411:     \item      MIGHT HAVE (SIGNIFICANT) LEADING ZEROS
        !           412:     \end{nrtc}
        !           413: 
        !           414: \item  DOMAIN SPECIFIC PART (DSP) IS JUST THAT
        !           415: \end{nrtc}
        !           416: \end{bwslide}
        !           417: 
        !           418: 
        !           419: \begin{bwslide}
        !           420: \ctitle        {EXAMPLE 1:\\ X.121 ADDRESS}
        !           421: 
        !           422: \begin{nrtc}
        !           423: \item  AN X.121 ADDRESS MAY BE ENCODED USING
        !           424:     \begin{nrtc}
        !           425:     \item      AFI = 36
        !           426: 
        !           427:     \item      IDI = X.121 ADDRESS (UP TO 14~DIGITS)
        !           428:     \end{nrtc}
        !           429: \end{nrtc}
        !           430: 
        !           431: \diagram[p]{figureE-4}
        !           432: \end{bwslide}
        !           433: 
        !           434: 
        !           435: \begin{bwslide}
        !           436: \ctitle        {EXAMPLE 2:\\ ICD ADDRESS}
        !           437: 
        !           438: \begin{nrtc}
        !           439: \item  AN INTERNATIONALLY RECOGNIZED ENTITY MAY ALLOCATE ADDRESSES USING
        !           440:     \begin{nrtc}
        !           441:     \item      AFI = 47
        !           442: 
        !           443:     \item      IDI = INTERNATIONAL CODE DESIGNATOR (4~DIGITS)
        !           444:     \end{nrtc}
        !           445: \end{nrtc}
        !           446: 
        !           447: \diagram[p]{figureE-5}
        !           448: \end{bwslide}
        !           449: 
        !           450: 
        !           451: \begin{bwslide}
        !           452: \ctitle        {EXAMPLE 3:\\ LOCAL ADDRESS}
        !           453: 
        !           454: \begin{nrtc}
        !           455: \item  ANYONE MIGHT USE A ``LOCAL'' ADDRESSING FORMAT
        !           456:     \begin{nrtc}
        !           457:     \item      AFI = 49
        !           458: 
        !           459:     \item      IDI = NULL (0~DIGITS)
        !           460:     \end{nrtc}
        !           461: \end{nrtc}
        !           462: 
        !           463: \diagram[p]{figureE-6}
        !           464: \end{bwslide}
        !           465: 
        !           466: 
        !           467: \begin{bwslide}
        !           468: \part* {NETWORK BINDING}\bf
        !           469: 
        !           470: \begin{nrtc}
        !           471: \item  HOW DOES DATA GO FROM ORIGINATING TO DESTINATION END-SYSTEM?
        !           472:     \begin{nrtc}
        !           473:     \item      i.e., HOW IS ROUTING ACCOMPLISHED?
        !           474:     \end{nrtc}
        !           475: 
        !           476: \item  NETWORK SERVICE AT ORIGINATING END-SYSTEM DECIDES ``NEXT HOP''
        !           477: 
        !           478: \item  IF DESTINATION END-SYSTEM IS ON SAME SUBNETWORK,
        !           479:        THEN NEXT HOP IS DESTINATION END-SYSTEM
        !           480: 
        !           481: \item  OTHERWISE, NEXT HOP IS AN INTERMEDIATE SYSTEM (ON THE SAME SUBNETWORK)
        !           482:        WHICH IS ``CLOSER'' TO THE DESTINATION END-SYSTEM
        !           483: \end{nrtc}
        !           484: \end{bwslide}
        !           485: 
        !           486: 
        !           487: \begin{bwslide}
        !           488: \ctitle        {DETERMINING THE NEXT HOP}
        !           489: 
        !           490: \begin{nrtc}
        !           491: \item  NETWORK ADDRESSES DO NOT CONTAIN ROUTING INFORMATION
        !           492:     \begin{nrtc}
        !           493:     \item      IN THEORY, AT LEAST
        !           494:     \end{nrtc}
        !           495: 
        !           496: \item  INTERMEDIATE-SYSTEMS MAINTAIN ROUTING TABLES WHICH TELL
        !           497:        ``HOW TO GET THERE''
        !           498: 
        !           499: \item  SO, ONCE THE DESTINATION END-SYSTEM'S SUBNETWORK HAS BEEN REACHED,
        !           500:        NEED A WAY OF DETERMINING ``WHERE IT IS'' ON A PARTICULAR
        !           501:        SUBNETWORK
        !           502: \end{nrtc}
        !           503: \end{bwslide}
        !           504: 
        !           505: 
        !           506: \begin{bwslide}
        !           507: \ctitle        {SUBNETWORK POINT OF ATTACHMENT (SNPA)}
        !           508: 
        !           509: \begin{nrtc}
        !           510: \item  A NODE (ES or IS) IS ATTACHED TO A SUBNETWORK AT A
        !           511:     \begin{nrtc}
        !           512:     \item      SUBNETWORK POINT OF ATTACHMENT (SNPA)
        !           513:     \end{nrtc}
        !           514: 
        !           515: \item  A LOCAL DIRECTORY IS USED TO MAP BETWEEN A NETWORK ADDRESS
        !           516:        AND ITS CORRESPONDING SNPA
        !           517:     \begin{nrtc}
        !           518:     \item      NOT THE OSI DIRECTORY (LUCKY FOR US!)    
        !           519:     \end{nrtc}
        !           520: 
        !           521: \item  THE PROBLEM:
        !           522:     \begin{nrtc}
        !           523:     \item      ROUTING IS A NETWORK-WIDE FUNCTION,
        !           524: 
        !           525:     \item      SO INFORMATION MUST BE COHERENT NETWORK-WIDE
        !           526:     \end{nrtc}
        !           527: \end{nrtc}
        !           528: \end{bwslide}
        !           529: 
        !           530: 
        !           531: \begin{bwslide}
        !           532: \ctitle        {MAPPING TO SNPA}
        !           533: 
        !           534: \begin{nrtc}
        !           535: \item  TWO WAYS TO ACHIEVE DYNAMIC MAPPINGS
        !           536: 
        !           537: \item  RUN A PROTOCOL ON THE SUBNETWORK
        !           538:     \begin{nrtc}
        !           539:     \item      e.g., AN ADDRESS RESOLUTION PROTOCOL
        !           540:     \end{nrtc}
        !           541: 
        !           542: \item  USE A LOCAL TABLE
        !           543: 
        !           544: \item  OTHERWISE MUST EMBED THE SNPA IN THE NETWORK ADDRESS
        !           545:     \begin{nrtc}
        !           546:     \item      LOSES A LOT OF FLEXIBILITY
        !           547:     \end{nrtc}
        !           548: \end{nrtc}
        !           549: \end{bwslide}
        !           550: 
        !           551: 
        !           552: \begin{bwslide}
        !           553: \part* {TRANSPORT PROTOCOLS}\bf
        !           554: 
        !           555: \begin{nrtc}
        !           556: \item  AVAILABLE NETWORK SERVICE DETERMINES CHOICE OF TRANSPORT PROTOCOL
        !           557: 
        !           558: \item  OSI PROVIDES 5 TRANSPORT PROTOCOLS, TP0--TP4
        !           559:     \begin{nrtc}
        !           560:     \item      CLASSES 0--3 WORKS WITH A CO-MODE NETWORK SERVICE
        !           561: 
        !           562:     \item      CLASS 4 WORKS WITH BOTH CO/CL-MODE NETWORK SERVICES
        !           563:     \end{nrtc}
        !           564: \end{nrtc}
        !           565: \end{bwslide}
        !           566: 
        !           567: 
        !           568: \begin{bwslide}
        !           569: \ctitle        {NETWORK CLASSES}
        !           570: 
        !           571: \begin{nrtc}
        !           572: \item  ``A'' --- LOW LOSS, ERRORS SIGNALLED
        !           573: 
        !           574: \item  ``B'' --- ERRORS SIGNALLED
        !           575: 
        !           576: \item  ``C'' --- ERRORS NOT SIGNALLED
        !           577:     \begin{nrtc}
        !           578:     \item      LOSS
        !           579: 
        !           580:     \item      DUPLICATION
        !           581: 
        !           582:     \item      RE-ORDERING
        !           583: 
        !           584:     \item      CORRUPTION
        !           585:     \end{nrtc}
        !           586:     OF DATA
        !           587: \end{nrtc}
        !           588: \end{bwslide}
        !           589: 
        !           590: 
        !           591: \begin{bwslide}
        !           592: \ctitle        {PROTOCOLS USING\\ CO-MODE NETWORK SERVICE}
        !           593: 
        !           594: \begin{nrtc}
        !           595: \item  TP0: SIMPLE CLASS
        !           596:     \begin{nrtc}
        !           597:     \item      NOTHING MORE THAN TRANSPORT ADDRESSING AND SEGMENTATION
        !           598: 
        !           599:     \item      ``A'' NETWORKS
        !           600:     \end{nrtc}
        !           601: 
        !           602: \item  TP1: BASIC ERROR RECOVERY CLASS
        !           603:     \begin{nrtc}
        !           604:     \item      RECOVER FROM NETWORK RESETS (MAY INVOLVE RE-ROUTING)
        !           605: 
        !           606:     \item      ``B'' NETWORKS
        !           607:     \end{nrtc}
        !           608: \end{nrtc}
        !           609: \end{bwslide}
        !           610: 
        !           611: 
        !           612: \begin{bwslide}
        !           613: \ctitle        {PROTOCOLS USING\\ CO-MODE NETWORK SERVICE (cont.)}
        !           614: 
        !           615: \begin{nrtc}
        !           616: \item  TP2: MULTIPLEXING CLASS
        !           617:     \begin{nrtc}
        !           618:     \item      MULTIPLEX OVER A SINGLE NETWORK CONNECTION
        !           619: 
        !           620:     \item      OPTIONAL FLOW CONTROL   
        !           621: 
        !           622:     \item      ``A'' NETWORKS
        !           623:     \end{nrtc}
        !           624: 
        !           625: \item  TP3: ERROR RECOVERY AND MULTIPLEXING CLASS
        !           626:     \begin{nrtc}
        !           627:     \item      ALL OF THE ABOVE
        !           628: 
        !           629:     \item      ``B'' NETWORKS
        !           630:     \end{nrtc}
        !           631: \end{nrtc}
        !           632: \end{bwslide}
        !           633: 
        !           634: 
        !           635: \begin{bwslide}
        !           636: \ctitle        {PROTOCOLS WHICH CAN USE\\ CL-MODE NETWORK SERVICE}
        !           637: 
        !           638: \begin{nrtc}
        !           639: \item  TP4: ERROR DETECTION AND RECOVERY CLASS
        !           640:     \begin{nrtc}
        !           641:     \item      RELIABILITY THROUGH RETRANSMISSION
        !           642: 
        !           643:     \item      ``C'' NETWORKS
        !           644:     \end{nrtc}
        !           645: \end{nrtc}
        !           646: \end{bwslide}
        !           647: 
        !           648: 
        !           649: \begin{bwslide}
        !           650: \part* {APPLICATION USE OF END-TO-END SERVICES}\bf
        !           651: 
        !           652: \begin{nrtc}
        !           653: \item  APPLICATION IDENTIFIES APPLICATION ENTITY WHICH PROVIDES
        !           654:        DESIRED SERVICE
        !           655:     \begin{nrtc}
        !           656:     \item      e.g., AN FTAM APPLICATION IDENTIFIES A FILESTORE SERVICE
        !           657:                PROVIDED BY A PARTICULAR APPLICATION ENTITY    
        !           658:     \end{nrtc}
        !           659: 
        !           660: \item  THE APPLICATION ENTITY IS IDENTIFIED BY ITS DISTINGUISHED NAME IN
        !           661:        THE OSI DIRECTORY
        !           662: \end{nrtc}
        !           663: \end{bwslide}
        !           664: 
        !           665: 
        !           666: \begin{bwslide}
        !           667: \ctitle        {STEP 1:\\ MAP DISTINGUISHED NAME\\ TO PRESENTATION ADDRESS}
        !           668: 
        !           669: \begin{nrtc}
        !           670: \item  ESTABLISH ASSOCIATION TO DIRECTORY SERVICE AGENT (DSA)
        !           671:        USING DIRECTORY ACCESS PROTOCOL (DAP)
        !           672: 
        !           673: \item  RETRIEVE THE \verb"presentationAddress" ATTRIBUTE FROM
        !           674:        THE OBJECT WITH THE GIVEN DISTINGUISHED NAME
        !           675: \end{nrtc}
        !           676: 
        !           677: \begin{quote}\small\begin{verbatim}
        !           678: PSAPaddr ::=
        !           679:     SEQUENCE {
        !           680:         pSelector[0]
        !           681:             OCTET STRING
        !           682:             OPTIONAL,
        !           683: 
        !           684:         sSelector[1]
        !           685:             OCTET STRING
        !           686:             OPTIONAL,
        !           687: 
        !           688:         tSelector[2]
        !           689:             OCTET STRING
        !           690:             OPTIONAL,
        !           691: 
        !           692:         nAddresses[3]
        !           693:             SET OF OCTET STRING
        !           694:     }
        !           695: \end{verbatim}\end{quote}
        !           696: \end{bwslide}
        !           697: 
        !           698: 
        !           699: \begin{bwslide}
        !           700: \ctitle        {STEP 2:\\ DETERMINE USE OF NETWORK ADDRESSES}
        !           701: 
        !           702: \begin{nrtc}
        !           703: \item  PRESENTATION ADDRESS IS GIVEN TO THE ASSOCIATION CONTROL SERVICE
        !           704:        ELEMENT (ACSE), WHICH ESTABLISHES THE ASSOCIATION
        !           705: 
        !           706: \item  ACSE PASSES THE ADDRESS TO THE PRESENTATION SERVICE,
        !           707:        WHICH USES THE PRESENTATION SELECTOR
        !           708: 
        !           709: \item  THE REMAINDER IS GIVEN TO THE SESSION SERVICE,
        !           710:        WHICH USES THE SESSION SELECTOR
        !           711: 
        !           712: \item  THE REMAINDER IS GIVEN TO THE TRANSPORT SERVICE
        !           713: \end{nrtc}
        !           714: \end{bwslide}
        !           715: 
        !           716: 
        !           717: \begin{bwslide}
        !           718: \ctitle        {STEP 2 (cont.)}
        !           719: 
        !           720: \begin{nrtc}
        !           721: \item  TRANSPORT SERVICE LOOKS AT EACH NETWORK ADDRESS AND MUST DECIDE
        !           722:     \begin{nrtc}
        !           723:     \item      WHICH MODE NETWORK SERVICE WILL BE USED FOR THIS ADDRESS
        !           724:     \end{nrtc}
        !           725: 
        !           726: \item  TRANSPORT SERVICE SELECTS A TRANSPORT PROTOCOL BASED ON THE
        !           727:        DERIVED NETWORK SERVICE AND THE COMMUNICATIONS QUALITY OF SERVICE (QOS)
        !           728:        DESIRED BY THE APPLICATION
        !           729: 
        !           730: \item  THIS COMBINATION
        !           731:     \begin{nrtc}
        !           732:     \item       (NETWORK SERVICE+TRANSPORT PROTOCOL)
        !           733:     \end{nrtc}
        !           734:        IS TERMED A
        !           735:     \begin{nrtc}
        !           736:     \item      TRANSPORT SERVICE STACK (TS-STACK)
        !           737:     \end{nrtc}
        !           738: \end{nrtc}
        !           739: \end{bwslide}
        !           740: 
        !           741: 
        !           742: \begin{bwslide}
        !           743: \ctitle        {STILL MORE ON\\ STEP 2}
        !           744: 
        !           745: \begin{nrtc}
        !           746: \item  IN MANY ENVIRONMENTS ONLY A SINGLE MODE OF NETWORK SERVICE AND A
        !           747:        SINGLE TRANSPORT PROTOCOL ARE AVAILABLE 
        !           748: 
        !           749: \item  THIS IMPLIES THAT ONLY A SUBSET (OR PERHAPS NONE) OF THE
        !           750:        NETWORK ADDRESSES WILL BE USABLE AT THE ORIGINATING END-SYSTEM
        !           751: \end{nrtc}
        !           752: \end{bwslide}
        !           753: 
        !           754: 
        !           755: \begin{bwslide}
        !           756: \ctitle        {STEP 3:\\ ORDER NETWORK ADDRESSES}
        !           757: 
        !           758: \begin{nrtc}
        !           759: \item  THE NETWORK ADDRESSES ARE THEN ORDERED BY PREFERENCE
        !           760: 
        !           761: \item  PREFERENCE IS BASED BOTH ON COMMUNICATIONS-QOS AND ``CLOSENESS''
        !           762:        OF NETWORK ADDRESSES
        !           763: 
        !           764: \item  FOR EXAMPLE:
        !           765:     \begin{nrtc}
        !           766:     \item      TWO NETWORK ADDRESSES, EACH IMPLYING A CO-MODE NETWORK
        !           767:                SERVICE, MIGHT BE PRESENT
        !           768: 
        !           769:     \item      ONE OF THE NETWORK ADDRESS MIGHT BELONG TO A PRIVATE
        !           770:                NETWORK, WHILST THE OTHER BELONGS TO A PDN
        !           771: 
        !           772:     \item      THE TRANSPORT SERVICE MIGHT PREFER THE PRIVATE NETWORK,
        !           773:                FOR COST REASONS
        !           774:     \end{nrtc}
        !           775: \end{nrtc}
        !           776: \end{bwslide}
        !           777: 
        !           778: 
        !           779: \begin{bwslide}
        !           780: \ctitle        {STEP 4:\\ ATTEMPT CONNECTIONS}
        !           781: 
        !           782: \begin{nrtc}
        !           783: \item  FOR EACH NETWORK ADDRESS:
        !           784:     \begin{nrtc}
        !           785:     \item      THE APPROPRIATE TRANSPORT PROTOCOL ENGINE IS STARTED,
        !           786:                AND THE NETWORK SERVICE INVOKED
        !           787: 
        !           788:     \item      ONCE A TRANSPORT CONNECTION IS ESTABLISHED,
        !           789:                THE REMAINDER OF THE NETWORK ADDRESSES ARE IGNORED
        !           790:     \end{nrtc}
        !           791: \end{nrtc}
        !           792: \end{bwslide}
        !           793: 
        !           794: 
        !           795: \begin{bwslide}
        !           796: \part* {EMULATION OF OSI END-TO-END SERVICES}\bf
        !           797: 
        !           798: \begin{nrtc}
        !           799: \item  IS IT POSSIBLE TO PROVIDE
        !           800: 
        !           801: \item  A SOLUTION IS OFFERED BY LAYERING
        !           802:     \begin{nrtc}
        !           803:     \item      THE OSI TRANSPORT \underline{SERVICE} IS VERY SIMPLE
        !           804:     \end{nrtc}
        !           805: 
        !           806: \item  CAN WE BUILD TS-STACKS USING NON-OSI PROTOCOLS?
        !           807: \end{nrtc}
        !           808: \end{bwslide}
        !           809: 
        !           810: 
        !           811: \begin{bwslide}
        !           812: \ctitle        {SERVICE EMULATOR AT TRANSPORT}
        !           813: 
        !           814: \vskip.5in
        !           815: \diagram[p]{figureE-13}
        !           816: \end{bwslide}
        !           817: 
        !           818: 
        !           819: \begin{bwslide}
        !           820: \ctitle        {APPROACH:\\ TRANSPORT SERVICE CONVERGENCE PROTOCOL}
        !           821: 
        !           822: \begin{nrtc}
        !           823: \item  USE THE CONNECTION-ORIENTED TRANSPORT SERVICE PROVIDED BY
        !           824:        THE NON-OSI PROTOCOL SUITE
        !           825: 
        !           826: \item  DEFINE A ``TSCP'' WHICH SMOOTHS OVER THE DIFFERENCES IN THE SERVICES
        !           827:        OFFERED
        !           828:     \begin{nrtc}
        !           829:     \item      IN PRACTICE, THESE ARE QUITE SMALL
        !           830:     \end{nrtc}
        !           831: 
        !           832: \item  FOR EXAMPLE, THE RFC1006 METHOD DEFINES A TSCP FOR TCP/IP NETWORKS
        !           833: \end{nrtc}
        !           834: \end{bwslide}
        !           835: 
        !           836: 
        !           837: \begin{bwslide}
        !           838: \ctitle        {OSI TRANSPORT SERVICES\\ ON TOP OF THE DoD TCP (cont.)}
        !           839: 
        !           840: \vskip.25in
        !           841: \diagram[p]{figureE-14}
        !           842: \end{bwslide}
        !           843: 
        !           844: 
        !           845: \begin{bwslide}
        !           846: \part  {ACHIEVING CONNECTIVITY}\bf
        !           847: 
        !           848: \begin{nrtc}
        !           849: \item  THE REAL WORLD OF OSI
        !           850: 
        !           851: \item  INTERIM USE OF NETWORK ADDRESSES
        !           852: 
        !           853: \item  TRANSPORT BRIDGING
        !           854: \end{nrtc}
        !           855: \end{bwslide}
        !           856: 
        !           857: 
        !           858: \begin{bwslide}
        !           859: \ctitle        {NOW THE HARD PART}
        !           860: 
        !           861: \begin{nrtc}
        !           862: \item  A LOT OF FLEXIBILITY IS AVAILABLE
        !           863: 
        !           864: \item  BUT PRACTICALLY, CAN THIS BE MADE TO WORK?
        !           865: \end{nrtc}
        !           866: \end{bwslide}
        !           867: 
        !           868: 
        !           869: \begin{bwslide}
        !           870: \part* {THE REAL WORLD OF OSI}\bf
        !           871: 
        !           872: \begin{nrtc}
        !           873: \item  THE ``REAL WORLD'' DEPENDS ENTIRELY WHERE YOU LIVE
        !           874: 
        !           875: \item  A COMMUNITY IS A COLLECTION OF END-SYSTEMS SHARING COMPATIBLE
        !           876:        TS-STACKS AND CONNECTED TOGETHER
        !           877: 
        !           878: \item  WHAT KIND OF OSI COMMUNITIES EXIST TODAY?
        !           879: \end{nrtc}
        !           880: \end{bwslide}
        !           881: 
        !           882: 
        !           883: \begin{bwslide}
        !           884: \ctitle        {COMMUNITY 1:\\ INTERNATIONAL X.25}
        !           885: 
        !           886: \begin{nrtc}
        !           887: \item  X.121 FORMAT ADDRESSES ARE USED
        !           888: 
        !           889: \item  NETWORK PROTOCOL IS X.25(80) WHICH DOES NOT PROVIDE TRUE
        !           890:        OSI NETWORK SERVICE
        !           891:     \begin{nrtc}
        !           892:     \item      EVENTUALLY UPGRADING TO X.25(84)
        !           893:     \end{nrtc}
        !           894: 
        !           895: \item  TP0 IS FAVORED TRANSPORT PROTOCOL
        !           896: 
        !           897: \item  TS-STACKS:
        !           898: \end{nrtc}
        !           899: 
        !           900: \diagram[p]{figureE-7}
        !           901: \end{bwslide}
        !           902: 
        !           903: 
        !           904: \begin{bwslide}
        !           905: \ctitle        {COMMUNITY 2:\\ PRIVATE X.25}
        !           906: 
        !           907: \begin{nrtc}
        !           908: \item  SIMILAR TO INTERNATIONAL X.25 COMMUNITY,
        !           909:        BUT OWNED BY A PARTICULAR ENTERPRISE
        !           910:     \begin{nrtc}
        !           911:     \item      e.g., THE U.K.~JOINT ACADEMIC NETWORK (JANET)    
        !           912:     \end{nrtc}
        !           913: 
        !           914: \item  ADDRESSES ARE X.121-BASED, BUT ARE PRIVATELY ALLOCATED
        !           915:     \begin{nrtc}
        !           916:     \item      THUS THE X.121 NETWORK ADDRESS FORMAT CAN'T BE USED
        !           917:     \end{nrtc}
        !           918: 
        !           919: \item  TS-STACKS:
        !           920: \end{nrtc}
        !           921: 
        !           922: \diagram[p]{figureE-7}
        !           923: \end{bwslide}
        !           924: 
        !           925: 
        !           926: \begin{bwslide}
        !           927: \ctitle        {COMMUNITY 3:\\ VARIANT U.S. USE OF X.25}
        !           928: 
        !           929: \begin{nrtc}
        !           930: \item  X.25 TREATED AS A SUBNETWORK PROTOCOL
        !           931: 
        !           932: \item  CL-MODE NETWORK SERVICE RUN OVER THIS
        !           933: 
        !           934: \item  TS-STACKS:
        !           935: \end{nrtc}
        !           936: 
        !           937: \diagram[p]{figureE-9}
        !           938: \end{bwslide}
        !           939: 
        !           940: 
        !           941: \begin{bwslide}
        !           942: \ctitle        {COMMUNITY 4:\\ CONS-BASED LANS}
        !           943: 
        !           944: \begin{nrtc}
        !           945: \item  CO-MODE NETWORK SERVICE OFFERRED OVER 8802 SUBNETWORK
        !           946: 
        !           947: \item  BASICALLY ``X.25 OVER ETHERNET'' (LLC2)
        !           948: 
        !           949: \item  TS-STACKS:
        !           950: \end{nrtc}
        !           951: 
        !           952: \diagram[p]{figureE-10}
        !           953: \end{bwslide}
        !           954: 
        !           955: 
        !           956: \begin{bwslide}
        !           957: \ctitle        {COMMUNITY 5:\\ CLNS-BASED LANS}
        !           958: 
        !           959: \begin{nrtc}
        !           960: \item  CL-MODE NETWORK SERVICE OFFERRED OVER 8802 SUBNETWORK
        !           961: 
        !           962: \item  COMMONLY TERMED ``MAP/TOP LANs'' (LLC1)
        !           963: 
        !           964: \item  TS-STACKS:
        !           965: \end{nrtc}
        !           966: 
        !           967: \diagram[p]{figureE-11}
        !           968: \end{bwslide}
        !           969: 
        !           970: 
        !           971: \begin{bwslide}
        !           972: \ctitle        {COMMUNITY 6:\\ TCP/IP-BASED INTERNET USING RFC1006}
        !           973: 
        !           974: \begin{nrtc}
        !           975: \item  RFC1006 DEFINES A MAPPING FROM THE OSI TRANSPORT SERVICE ONTO THE DoD
        !           976:        TCP
        !           977:     \begin{nrtc}
        !           978:     \item      (A TRANSPORT SERVICE CONVERGENCE PROTOCOL)
        !           979:     \end{nrtc}
        !           980: 
        !           981: \item  PROBLEM: WHAT FORMAT TO USE NETWORK ADDRESS?
        !           982: 
        !           983: \item  TS-STACKS:
        !           984: \end{nrtc}
        !           985: 
        !           986: \diagram[p]{figureE-12}
        !           987: \end{bwslide}
        !           988: 
        !           989: 
        !           990: \begin{bwslide}
        !           991: \ctitle        {COMMUNITY 7:\\ TCP/IP-BASED LAN USING RFC1006}
        !           992: 
        !           993: \begin{nrtc}
        !           994: \item  SIMILAR TO INTERNET COMMUNITY,
        !           995:        BUT ON AN ISOLATED TCP/IP LAN
        !           996:     \begin{nrtc}
        !           997:     \item      e.g., A CAMPUS NETWORK RUNNING TCP/IP LOCALLY AND HAVING A
        !           998:                CONNECTION TO A PDN
        !           999:     \end{nrtc}
        !          1000: 
        !          1001: \item  TS-STACKS:
        !          1002: \end{nrtc}
        !          1003: 
        !          1004: \diagram[p]{figureE-12}
        !          1005: \end{bwslide}
        !          1006: 
        !          1007: 
        !          1008: \begin{bwslide}
        !          1009: \ctitle        {COMMUNITY INTEROPERATION}
        !          1010: 
        !          1011: \begin{nrtc}
        !          1012: \item  SO, THERE ARE (AT LEAST) SEVEN DIFFERENT COMMUNITIES IN THE OSI WORLD
        !          1013: 
        !          1014: \item  IDEALLY WOULD LIKE THIS INTERWORKING MATRIX:
        !          1015: \end{nrtc}
        !          1016: 
        !          1017: \diagram[p]{figureE-15}
        !          1018: \end{bwslide}
        !          1019: 
        !          1020: 
        !          1021: \begin{bwslide}
        !          1022: \ctitle        {COMMUNITY INTEROPERATION (cont.)}
        !          1023: 
        !          1024: \begin{nrtc}
        !          1025: \item  COMMUNITY 7 IS ISOLATED BY LACK OF CONNECTIVITY
        !          1026: \end{nrtc}
        !          1027: 
        !          1028: \diagram[p]{figureE-16}
        !          1029: \end{bwslide}
        !          1030: 
        !          1031: 
        !          1032: \begin{bwslide}
        !          1033: \ctitle        {COMMUNITY INTEROPERATION (cont.)}
        !          1034: 
        !          1035: \begin{nrtc}
        !          1036: \item  PRIVATE X.25 AND RFC1006--BASED COMMUNITIES NEED DIFFERENT ADDRESS
        !          1037:        SPACE
        !          1038: \end{nrtc}
        !          1039: 
        !          1040: \diagram[p]{figureE-17}
        !          1041: \end{bwslide}
        !          1042: 
        !          1043: 
        !          1044: \begin{bwslide}
        !          1045: \ctitle        {REAL WORLD CONNECTIVITY MATRIX}
        !          1046: 
        !          1047: \begin{nrtc}
        !          1048: \item  IN PRACTICE, CONS-BASED LANS DON'T INTEROPERATE WITH CONS-BASED WANS 
        !          1049:     \begin{nrtc}
        !          1050:     \item      ROUTING OF CONS-BASED SUBNETWORKS ISN'T WIDELY IMPLEMENTED
        !          1051:                OUTSIDE OF X.75
        !          1052:     \end{nrtc}
        !          1053: \end{nrtc}
        !          1054: 
        !          1055: \diagram[p]{figureE-18}
        !          1056: \end{bwslide}
        !          1057: 
        !          1058: 
        !          1059: \begin{bwslide}
        !          1060: \ctitle        {COMMUNITY INTEROPERATION (cont.)}
        !          1061: 
        !          1062: \begin{nrtc}
        !          1063: \item  CLNS-BASED AND CONS-BASED TS-STACKS DON'T ALWAYS INTEROPERATE
        !          1064:     \begin{nrtc}
        !          1065:     \item      IT IS NOT ENOUGH TO START WITH TP4 AND DOWN-NEGOTIATE
        !          1066:     \end{nrtc}
        !          1067: \end{nrtc}
        !          1068: 
        !          1069: \diagram[p]{figureE-19}
        !          1070: \end{bwslide}
        !          1071: 
        !          1072: 
        !          1073: \begin{bwslide}
        !          1074: \ctitle        {THE MYTH OF TRANSPORT NEGOTIATION}
        !          1075: 
        !          1076: \begin{nrtc}
        !          1077: \item  IF INITIATOR SELECTS TP4, MUST ALSO DECIDE CONS/CLNS
        !          1078:     \begin{nrtc}
        !          1079:     \item      IF CLNS IS USED, THEN MUST STAY WITH TP4
        !          1080: 
        !          1081:     \item      IF CLNS ISN'T USED, THEN CAN'T TALK TO CLNS-BASED LAN    
        !          1082:     \end{nrtc}
        !          1083: \end{nrtc}
        !          1084: \end{bwslide}
        !          1085: 
        !          1086: 
        !          1087: \begin{bwslide}
        !          1088: \part* {INTERIM USE OF NETWORK ADDRESSES}\bf
        !          1089: 
        !          1090: \begin{nrtc}
        !          1091: \item  WANT TO ACCOMODATE ALL OSI COMMUNITIES IN OSI DIRECTORY
        !          1092: 
        !          1093: \item  PROBLEM: ALL ADDRESSES MUST CONFORM TO DIRECTORY DEFINED SYNTAX
        !          1094: 
        !          1095: \item  PROBLEM: ALL ADDRESSES MUST BE GLOBALLY UNIQUE YET LOCALLY
        !          1096:        INTERPRETABLE
        !          1097: \end{nrtc}
        !          1098: \end{bwslide}
        !          1099: 
        !          1100: 
        !          1101: \begin{bwslide}
        !          1102: \ctitle        {CONFORMANCE TO\\ DIRECTORY DEFINED SYNTAX}
        !          1103: 
        !          1104: \begin{nrtc}
        !          1105: \item  A PROBLEM FOR THE PRIVATE X.25 AND RFC1006--BASED COMMUNITIES
        !          1106: 
        !          1107: \item  TAKE A PART OF THE SPACE ASSIGNED TO TELEX ADDRESSES
        !          1108:     \begin{nrtc}
        !          1109:     \item      NO ONE WILL USE TELEX AFI FOR NETWORK ADDRESSES
        !          1110:     \end{nrtc}
        !          1111: 
        !          1112: \item  SUB-DIVIDE THIS ADDRESS SPACE FOR EACH COMMUNITY, e.g.,
        !          1113:     \begin{nrtc}
        !          1114:     \item      AFI = 54
        !          1115: 
        !          1116:     \item      IDI = 00728722
        !          1117:     \end{nrtc}
        !          1118: \end{nrtc}
        !          1119: 
        !          1120: \diagram[p]{figureE-8}
        !          1121: \end{bwslide}
        !          1122: 
        !          1123: 
        !          1124: \begin{bwslide}
        !          1125: \ctitle        {INTERPRETATION OF ADDRESSES}
        !          1126: 
        !          1127: \begin{nrtc}
        !          1128: \item  FROM EACH NETWORK ADDRESS
        !          1129:     \begin{nrtc}
        !          1130:     \item      COMMUNITY (TS-STACK, IDENTITY OF NETWORK) MUST BE DEDUCIBLE
        !          1131: 
        !          1132:     \item      NETWORK-SPECIFIC INFORMATION (i.e., SNPA) MUST BE DEDUCIBLE
        !          1133:     \end{nrtc}
        !          1134: \end{nrtc}
        !          1135: \end{bwslide}
        !          1136: 
        !          1137: 
        !          1138: \begin{bwslide}
        !          1139: \part* {TRANSPORT BRIDGING}\bf
        !          1140: 
        !          1141: \begin{nrtc}
        !          1142: \item  PROBLEM: SUPPOSE THE ORIGINATING END-SYSTEM DETERMINES THAT
        !          1143:        IT IS IN A DIFFERENT COMMUNITY THAN THE DESTINATION END-SYSTEM
        !          1144: 
        !          1145: \item  FROM A PURIST PERSPECTIVE:
        !          1146:     \begin{nrtc}
        !          1147:     \item      INTEROPERATION CAN NOT OCCUR!
        !          1148:     \end{nrtc}
        !          1149: 
        !          1150: \item  FROM A PRAGMATIC PERSPECTIVE:
        !          1151:     \begin{nrtc}
        !          1152:     \item      IGNORE THE CURSED MODEL AND BUILD A LEVEL-4 RELAY
        !          1153:     \end{nrtc}
        !          1154: \end{nrtc}
        !          1155: \end{bwslide}
        !          1156: 
        !          1157: 
        !          1158: \begin{bwslide}
        !          1159: \ctitle        {TS-BRIDGES}
        !          1160: 
        !          1161: \begin{nrtc}
        !          1162: \item  ALTHOUGH MANY DIFFERENT TS-STACKS EXIST,
        !          1163:        THEY ALL PROVIDE THE SAME TRANSPORT SERVICE
        !          1164: 
        !          1165: \item  SO, IT IS STRAIGHT-FORWARD TO BUILD A BOX THAT:
        !          1166:     \begin{nrtc}
        !          1167:     \item      KNOWS NOTHING ABOUT TRANSPORT PROTOCOLS, BUT
        !          1168: 
        !          1169:     \item      KNOWS HOW TO USE THE RELATIVELY SIMPLE OSI TRANSPORT SERVICE
        !          1170:     \end{nrtc}
        !          1171: 
        !          1172: \item  A TS-BRIDGE ``COPIES'' SERVICE PRIMITIVES FROM ONE TS-STACK TO THE
        !          1173:        OTHER, e.g.,
        !          1174:     \begin{nrtc}
        !          1175:     \item      UPON RECEIVING A T-CONNECT.INDICATION PRIMITIVE FROM ONE
        !          1176:                TS-STACK,
        !          1177: 
        !          1178:     \item      IT ISSUES A T-CONNECT.REQUEST PRIMITIVE TO THE OTHER TS-STACK
        !          1179:     \end{nrtc}
        !          1180: \end{nrtc}
        !          1181: \end{bwslide}
        !          1182: 
        !          1183: 
        !          1184: \begin{bwslide}
        !          1185: \ctitle        {TS-BRIDGES (cont.)}
        !          1186: 
        !          1187: \vskip.5in
        !          1188: \diagram[p]{figureE-1}
        !          1189: \end{bwslide}
        !          1190: 
        !          1191: 
        !          1192: \begin{bwslide}
        !          1193: \ctitle        {THE PROBLEMS OF LEVEL-4 RELAYS}
        !          1194: 
        !          1195: \begin{nrtc}
        !          1196: \item  THE TS-BRIDGE MAINTAINS STATE AS TO THE EXISTING CONNECTIONS
        !          1197: 
        !          1198: \item  EACH TS-STACK PROVIDES A CHECKSUM,
        !          1199:        NEITHER OF WHICH IS REALLY END-TO-END
        !          1200:     \begin{nrtc}
        !          1201:     \item      (CHECKSUM AT EITHER TRANSPORT OR NETWORK SERVICE)
        !          1202:     \end{nrtc}
        !          1203: 
        !          1204: \item  THIS ALSO DEFEATS TRANSPORT-LEVEL ENCRYPTION
        !          1205: 
        !          1206: \item  \underline{MAY} THWART SOPHISTICATED BACK-PRESSURE TECHNIQUES
        !          1207: \end{nrtc}
        !          1208: \end{bwslide}
        !          1209: 
        !          1210: 
        !          1211: \begin{bwslide}
        !          1212: \ctitle        {USE OF THE TS-BRIDGE}
        !          1213: 
        !          1214: \begin{nrtc}
        !          1215: \item  MUST NOW SUBTLY MODIFY TRANSPORT SERVICE OF ORIGINATING END-SYSTEM
        !          1216:     \begin{nrtc}
        !          1217:     \item      STEP 2: DETERMINE USE OF NETWORK ADDRESSES
        !          1218:     \end{nrtc}
        !          1219: 
        !          1220: \item  IF NO USABLE NETWORK ADDRESSES ARE AVAILABLE
        !          1221: 
        !          1222: \item  THEN SELECT A TS-BRIDGE WHICH SERVICES THE OSI COMMUNITY FOR ONE OF
        !          1223:        THE NETWORK ADDRESSES
        !          1224:     \begin{nrtc}
        !          1225:     \item       RECALL, OSI COMMUNITY EQUALS TS-STACK PLUS CONNECTIVITY
        !          1226:     \end{nrtc}
        !          1227: \end{nrtc}
        !          1228: \end{bwslide}
        !          1229: 
        !          1230: 
        !          1231: \begin{bwslide}
        !          1232: \ctitle        {USE OF THE TS-BRIDGE (cont.)}
        !          1233: 
        !          1234: \begin{nrtc}
        !          1235: \item  ENCODE THE NETWORK ADDRESS AND TRANSPORT SELECTOR AS AN OCTET STRING,
        !          1236:        CALL THIS THE NEW TRANSPORT SELECTOR
        !          1237: 
        !          1238: \item  USE THE NETWORK ADDRESS OF THE TS-BRIDGE FOR THE REMAINING STEPS
        !          1239: 
        !          1240: \item  WHEN TS-BRIDGE RECEIVES CONNECTION,
        !          1241:        IT SIMPLY DECODES TRANSPORT SELECTOR TO FIND ADDRESS OF
        !          1242:        DESTINATION END-SYSTEM
        !          1243: \end{nrtc}
        !          1244: \end{bwslide}
        !          1245: 
        !          1246: 
        !          1247: \begin{bwslide}
        !          1248: \ctitle        {TS-BRIDGE ADDRESSING}
        !          1249: 
        !          1250: \vskip.5in
        !          1251: \diagram[p]{figureE-20}
        !          1252: \end{bwslide}
        !          1253: 
        !          1254: 
        !          1255: \begin{bwslide}
        !          1256: \part  {COMPARISON TO TCP/IP}\bf
        !          1257: 
        !          1258: \begin{nrtc}
        !          1259: \item  NETWORK SERVICE
        !          1260: 
        !          1261: \item  TRANSPORT SERVICE
        !          1262: \end{nrtc}
        !          1263: \end{bwslide}
        !          1264: 
        !          1265: 
        !          1266: \begin{bwslide}
        !          1267: \ctitle        {COMPARISONS}
        !          1268: 
        !          1269: \begin{nrtc}
        !          1270: \item  ALL COMPARISONS ARE PARTISAN IN NATURE
        !          1271: 
        !          1272: \item  HOWEVER, WITHOUT BIAS OR LOSS OF GENERALITY,\\ I CAN HONESTLY STATE:
        !          1273:     \begin{nrtc}
        !          1274:     \item      THE OSI LOWER-LAYERS ARE CURRENTLY INCOHERENT
        !          1275:     \end{nrtc}
        !          1276: \end{nrtc}
        !          1277: \end{bwslide}
        !          1278: 
        !          1279: 
        !          1280: \begin{bwslide}
        !          1281: \part* {NETWORK SERVICE}\bf
        !          1282: 
        !          1283: \begin{nrtc}
        !          1284: \item  THE INTERNET PROTOCOL (IP) PROVIDES A CL-NETWORK SERVICE
        !          1285:     \begin{nrtc}
        !          1286:     \item      SIMILAR TO CLNP,\\ BUT MUCH MORE EFFICIENT
        !          1287:     \end{nrtc}
        !          1288: 
        !          1289: \item  THE LEAST COMMON DENOMINATOR, USABLE OVER BOTH WANs AND LANs
        !          1290:     \begin{nrtc}
        !          1291:     \item      BEST EFFORT DELIVERY
        !          1292: 
        !          1293:     \item      RELIABILITY RESPONSIBILITY OF TRANSPORT SERVICE
        !          1294:     \end{nrtc}
        !          1295: \end{nrtc}
        !          1296: \end{bwslide}
        !          1297: 
        !          1298: 
        !          1299: \begin{bwslide}
        !          1300: \ctitle        {ARE TWO OSI NETWORK SERVICES\\ ONE TOO MANY?}
        !          1301: 
        !          1302: \begin{nrtc}
        !          1303: \item  IN A WORD: YES
        !          1304: 
        !          1305: \item  OSI COMMUNITIES ARE SEPERATED BY TS-STACKS AND CONNECTIVITY
        !          1306: 
        !          1307: \item  CONNECTIVITY ISN'T A TECHNICAL ISSUE
        !          1308: 
        !          1309: \item  BUT, TS-STACKS ARE, SO:
        !          1310:     \begin{nrtc}
        !          1311:     \item      IF THERE WAS A SINGLE NETWORK SERVICE,
        !          1312:                THEN THERE COULD BE A SINGLE TRANSPORT PROTOCOL
        !          1313:     \end{nrtc}
        !          1314: \end{nrtc}
        !          1315: \end{bwslide}
        !          1316: 
        !          1317: 
        !          1318: \begin{bwslide}
        !          1319: \part* {TRANSPORT SERVICE}\bf
        !          1320: 
        !          1321: \begin{nrtc}
        !          1322: \item  THE TRANSMISSION CONTROL PROTOCOL (TCP) PROVIDES A CO-TRANSPORT
        !          1323:        SERVICE
        !          1324: 
        !          1325: \item  SEVERAL DIFFERENCES FROM THE OSI TRANSPORT SERVICE
        !          1326:     \begin{nrtc}
        !          1327:     \item      TCP IS STREAM-ORIENTED
        !          1328: 
        !          1329:     \item      TCP USES GRACEFUL RELEASE
        !          1330: 
        !          1331:     \item      TCP USES URGENT DATA
        !          1332:     \end{nrtc}
        !          1333: 
        !          1334: \item  THESE ARE DIFFERENCES, NOT PROS AND CONS
        !          1335: \end{nrtc}
        !          1336: \end{bwslide}
        !          1337: 
        !          1338: 
        !          1339: \begin{bwslide}
        !          1340: \ctitle        {COMPARISON OF PROTOCOLS}
        !          1341: 
        !          1342: \begin{nrtc}
        !          1343: \item  REALLY CAN COMPARE ONLY THE TCP AND TP4
        !          1344: 
        !          1345: \item  TP4 PACKET ORIENTATION PREVENTS USE OF SOPHISTICATED CONGESTION
        !          1346:        COLLAPSE ALGORITHMS
        !          1347: 
        !          1348: \item  TP4 PACKET ORIENTATION HELPS BUFFER MANAGEMENT,
        !          1349:        POSSIBLY MORE EFFICIENT
        !          1350: 
        !          1351: \item  TP4 RETRANSMISSION ALGORITHMS ARE SIMPLISTIC
        !          1352: 
        !          1353: \item  TP4 END-TO-END CHECKSUM IS INAPPROPRIATE
        !          1354: \end{nrtc}
        !          1355: \end{bwslide}
        !          1356: 
        !          1357: 
        !          1358: \begin{bwslide}
        !          1359: \ctitle        {TRANSPORT BRIDGING}
        !          1360: 
        !          1361: \begin{nrtc}
        !          1362: \item  UNNECESSARY IN TCP/IP WORLD
        !          1363:     \begin{nrtc}
        !          1364:     \item      COMMON NETWORK PROTOCOL
        !          1365: 
        !          1366:     \item      UNIFORM NETWORK ADDRESS FORMAT
        !          1367:     \end{nrtc}
        !          1368: \end{nrtc}
        !          1369: \end{bwslide}
        !          1370: 
        !          1371: 
        !          1372: \begin{bwslide}
        !          1373: \part* {CONCLUSIONS}\bf
        !          1374: 
        !          1375: \begin{nrtc}
        !          1376: \item  DEPRESSING
        !          1377:     \begin{nrtc}
        !          1378:     \item      WORLD-WIDE OSI ``CAN'T HAPPEN''
        !          1379: 
        !          1380:     \item      THIS WILL CURTAIL USE OF WONDERFUL APPLICATIONS
        !          1381:     \end{nrtc}
        !          1382: 
        !          1383: \item  FORTUNATELY, CLOSED COMMUNITIES WILL BE RELATIVELY IMMUNE
        !          1384: \end{nrtc}
        !          1385: \end{bwslide}
        !          1386: 

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