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Annotation of 43BSDReno/contrib/isode-beta/doc/practical-osi2/end-to-end.tex, revision 1.1

1.1     ! root        1: % run this through LaTeX with the appropriate wrapper
        !             2: 
        !             3: \dotopic{END-TO-END SERVICES}
        !             4: 
        !             5: 
        !             6: \begin{bwslide}
        !             7: \part* {OUTLINE}\bf
        !             8: 
        !             9: \begin{description}
        !            10: \item[PART I:]         CONCEPTS
        !            11: 
        !            12: \item[PART II:]                BUILDING BLOCKS
        !            13: 
        !            14: \item[PART III:]       ACHIEVING CONNECTIVITY
        !            15: 
        !            16: \item[PART IV:]                COMPARISON TO TCP/IP
        !            17: \end{description}
        !            18: \end{bwslide}
        !            19: 
        !            20: 
        !            21: \begin{bwslide}
        !            22: \ctitle        {A BIG ACKNOWLEDGEMENT}
        !            23: 
        !            24: \begin{nrtc}
        !            25: \item  MY INTEREST IN END-TO-END SERVICES IS ONLY AS A USER,
        !            26:        NOT A PROVIDER
        !            27: 
        !            28: \item  AS SUCH, I'D PREFER TO USE THEM AS A BLACK BOX
        !            29: 
        !            30: \item  UNFORTUNATELY, THIS APPROACH DOESN'T WORK IN PRACTICE
        !            31:     \begin{nrtc}
        !            32:     \item      THE LOWER-LAYERS AREN'T HOMOGENEOUS
        !            33:     \end{nrtc}
        !            34: 
        !            35: \item  THE PRACTICAL PERSPECTIVE PRESENTED HERE IS HEAVILY INFLUENCED BY
        !            36:     \begin{nrtc}
        !            37:     \item      STEPHEN E.~KILLE OF UNIVERSITY COLLEGE LONDON
        !            38:     \end{nrtc}
        !            39: 
        !            40: \item  AND HIS PAPER
        !            41:     \begin{nrtc}
        !            42:     \item      ``AN INTERIM APPROACH TO USE OF NETWORK ADDRESSES''
        !            43:     \end{nrtc}
        !            44: \end{nrtc}
        !            45: \end{bwslide}
        !            46: 
        !            47: 
        !            48: \begin{bwslide}
        !            49: \part  {CONCEPTS}\bf
        !            50: 
        !            51: \begin{nrtc}
        !            52: \item  BASIC TERMINOLOGY
        !            53: 
        !            54: \item  NETWORK SERVICE
        !            55: 
        !            56: \item  TRANSPORT SERVICE
        !            57: \end{nrtc}
        !            58: \end{bwslide}
        !            59: 
        !            60: 
        !            61: \begin{bwslide}
        !            62: \part* {BASIC TERMINOLOGY}\bf
        !            63: 
        !            64: \begin{nrtc}
        !            65: \item  END-TO-END SERVICES RESPONSIBLE FOR
        !            66:     \begin{nrtc}
        !            67:     \item      DATA TRANSFER
        !            68:     \end{nrtc}
        !            69: 
        !            70: \item  APPLICATION SERVICES RESPONSIBLE FOR
        !            71:     \begin{nrtc}
        !            72:     \item      INFORMATION TRANSFER
        !            73:     \end{nrtc}
        !            74: \end{nrtc}
        !            75: \end{bwslide}
        !            76: 
        !            77: 
        !            78: \begin{bwslide}
        !            79: \ctitle        {BASIC TERMINOLOGY (cont.)}
        !            80: 
        !            81: \begin{nrtc}
        !            82: \item  TERMINOLOGY DIFFERS BETWEEN NETWORKING COMMUNITIES
        !            83:     \begin{nrtc}
        !            84:     \item      WE'LL USE ``OSIFIED'' TERMINOLOGY
        !            85:     \end{nrtc}
        !            86: 
        !            87: \item  A NETWORK CONSISTS OF A COLLECTION OF SUBNETWORKS CONNECTED
        !            88:        BY INTERMEDIATE SYSTEMS AND POPULATED BY END-SYSTEMS
        !            89: 
        !            90: \item  DATA TRANSFER OCCURS BETWEEN TWO END-SYSTEMS,
        !            91:        POTENTIALLY GOING THROUGH ONE OR MORE INTERMEDIATE-SYSTEMS
        !            92:        IF THE END-SYSTEMS RESIDE ON DIFFERENT SUBNETWORKS
        !            93: \end{nrtc}
        !            94: \end{bwslide}
        !            95: 
        !            96: 
        !            97: \begin{bwslide}
        !            98: \ctitle        {THE NETWORK}
        !            99: 
        !           100: \vskip.5in
        !           101: \diagram[p]{figureE-2}
        !           102: \end{bwslide}
        !           103: 
        !           104: 
        !           105: \begin{bwslide}
        !           106: \ctitle        {END-SYSTEMs (ES)}
        !           107: 
        !           108: \begin{nrtc}
        !           109: \item  CONTAIN BOTH: 
        !           110:     \begin{nrtc}
        !           111:     \item      THE LOWER-LAYER PROTOCOLS NECESSARY FOR DATA TRANSFER, AND
        !           112: 
        !           113:     \item      THE UPPER-LAYER PROTOCOLS NECESSARY FOR INFORMATION TRANSFER
        !           114:     \end{nrtc}
        !           115: 
        !           116: \item  WHERE THE APPLICATIONS LIVE
        !           117: 
        !           118: \item  WHAT THE USERS ARE INTERESTED IN
        !           119: \end{nrtc}
        !           120: \end{bwslide}
        !           121: 
        !           122: 
        !           123: \begin{bwslide}
        !           124: \ctitle        {INTERMEDIATE-SYSTEMs (IS)}
        !           125: 
        !           126: \begin{nrtc}
        !           127: \item  CONTAIN ONLY:
        !           128:     \begin{nrtc}
        !           129:     \item      THE LOWER-LAYER PROTOCOLS NECESSARY FOR DATA TRANSFER
        !           130:     \end{nrtc}
        !           131: 
        !           132: \item  ULTIMATELY CONTAIN HIGHER-LAYER PROTOCOLS TO SUPPORT MANAGEMENT
        !           133: 
        !           134: \item  IN ADDITION TO PASSING ALONG APPLICATION DATA,
        !           135:        INTERMEDIATE-SYSTEMS COOPERATE AMONGST THEMSELVES
        !           136:     \begin{nrtc}
        !           137:     \item      e.g., EXCHANGE ROUTING DATA
        !           138:     \end{nrtc}
        !           139: \end{nrtc}
        !           140: \end{bwslide}
        !           141: 
        !           142: 
        !           143: \begin{bwslide}
        !           144: \part* {NETWORK SERVICE}\bf
        !           145: 
        !           146: \begin{nrtc}
        !           147: \item  NETWORK SERVICE IS RESPONSIBLE FOR MOVING DATA FROM ONE END-SYSTEM
        !           148:        TO ANOTHER
        !           149: 
        !           150: \item  UNFORTUNATELY, THERE ARE TWO DIFFERENT VIEWS AS TO WHAT THIS MEANS:
        !           151:     \begin{nrtc}
        !           152:     \item      CONNECTION-ORIENTED
        !           153: 
        !           154:     \item      CONNECTIONLESS-MODE
        !           155:     \end{nrtc}
        !           156: 
        !           157: \item  PERHAPS THE GREATEST ``RELIGIOUS'' ISSUE OF THE LAST DECADE
        !           158: \end{nrtc}
        !           159: \end{bwslide}
        !           160: 
        !           161: 
        !           162: \begin{bwslide}
        !           163: \ctitle        {CONNECTION-ORIENTED NETWORK SERVICE\\ (CONS)}
        !           164: 
        !           165: \begin{nrtc}
        !           166: \item  BASED ON THE NOTION OF ``RESERVATIONS'':
        !           167:     \begin{nrtc}
        !           168:     \item      ON CONNECTION REQUEST, MINIMUM REQUIREMENTS ARE STATED
        !           169:        \begin{nrtc}
        !           170:        \item   (e.g., THROUGHPUT)
        !           171:        \end{nrtc}
        !           172: 
        !           173:     \item      IF REQUEST IS GRANTED, THESE RESOURCES ARE RESERVED FOR THE
        !           174:                CONNECTION'S DURATION
        !           175:     \end{nrtc}
        !           176: 
        !           177: \item  CO-MODE SERVICE PRIMITIVES
        !           178:     \begin{nrtc}
        !           179:     \item      N-CONNECT: CONNECTION ESTABLISHMENT
        !           180: 
        !           181:     \item      N-DATA (N-DATA-ACKNOWLEDGE): DATA TRANSFER 
        !           182: 
        !           183:     \item      N-EXPEDITED-DATA: EXPEDITED DATA TRANSFER
        !           184: 
        !           185:     \item      N-DISCONNECT: CONNECTION RELEASE
        !           186: 
        !           187:     \item      N-RESET: CONNECTION RESYNCHRONIZATION
        !           188:     \end{nrtc}
        !           189: \end{nrtc}
        !           190: \end{bwslide}
        !           191: 
        !           192: 
        !           193: \begin{bwslide}
        !           194: \ctitle        {CONS (cont.)}
        !           195: 
        !           196: \begin{nrtc}
        !           197: \item  GOOD POINTS:
        !           198:     \begin{nrtc}
        !           199:     \item      LOW OVERHEAD FOR DATA TRANSIT
        !           200: 
        !           201:     \item      IMMUNITY FROM OTHER NETWORK TRAFFIC
        !           202: 
        !           203:     \item      ACCOUNTABILITY
        !           204:     \end{nrtc}
        !           205: 
        !           206: \item  BAD POINTS:
        !           207:     \begin{nrtc}
        !           208:     \item      HIGH OVERHEAD FOR CONNECTION ESTABLISHMENT
        !           209: 
        !           210:     \item      QUESTIONABLE RECOVERY CHARACTERISTICS
        !           211: 
        !           212:     \item      IF RESOURCES ARE RESERVED, BUT NOT IN USE,
        !           213:                NEW CONNECTION REQUESTS ARE DENIED
        !           214:     \end{nrtc}
        !           215: \end{nrtc}
        !           216: \end{bwslide}
        !           217: 
        !           218: 
        !           219: \begin{bwslide}
        !           220: \ctitle        {CONNECTIONLESS-MODE NETWORK SERVICE\\ (CLNS)}
        !           221: 
        !           222: \begin{nrtc}
        !           223: \item  BASED ON THE NOTION OF ``COME AS YOU ARE'':
        !           224:     \begin{nrtc}
        !           225:     \item      NO CONNECTION REQUEST, JUST SEND DATA
        !           226: 
        !           227:     \item      TRANSPORT MUST DYNAMICALLY DETERMINE IF REQUIREMENTS ARE
        !           228:                BEING MET
        !           229:     \end{nrtc}
        !           230: 
        !           231: \item  CL-MODE SERVICE PRIMITIVES
        !           232:     \begin{nrtc}
        !           233:     \item      N-UNITDATA: DATA TRANSFER
        !           234:     \end{nrtc}
        !           235: \end{nrtc}
        !           236: \end{bwslide}
        !           237: 
        !           238: 
        !           239: \begin{bwslide}
        !           240: \ctitle        {CLNS (cont.)}
        !           241: 
        !           242: \begin{nrtc}
        !           243: \item  GOOD POINTS:
        !           244:     \begin{nrtc}
        !           245:     \item      LESS DELAY FOR INITIAL DATA TRANSIT
        !           246: 
        !           247:     \item      POTENTIALLY MORE ROBUST WITH CHANGES IN THE NETWORK
        !           248: 
        !           249:     \item      SQUEEZES ``LAST DROP'' FROM AVAILABLE RESOURCES
        !           250:     \end{nrtc}
        !           251: 
        !           252: \item  BAD POINTS:
        !           253:     \begin{nrtc}
        !           254:     \item      HIGHER OVERHEAD FOR DATA TRANSIT IF MULTIPLE SUBNETWORKS
        !           255:                ARE INVOLVED
        !           256: 
        !           257:     \item      REQUIRES WELL-BEHAVED USERS TO PREVENT OVER-SUBSCRIPTION
        !           258:     \end{nrtc}
        !           259: \end{nrtc}
        !           260: \end{bwslide}
        !           261: 
        !           262: 
        !           263: \begin{bwslide}
        !           264: \part* {TRANSPORT SERVICE}
        !           265: 
        !           266: \begin{nrtc}
        !           267: \item  TRANSPORT SERVICE IS RESPONSIBLE FOR MOVING DATA FROM ONE END-SYSTEM
        !           268:        TO ANOTHER~---~RELIABLY
        !           269:     \begin{nrtc}
        !           270:     \item      (WE'RE CONSIDERING ONLY CO-MODE TRANSPORT SERVICE)
        !           271:     \end{nrtc}
        !           272: 
        !           273: \item  IF CO-MODE NETWORK SERVICE IS USED, THIS IS TRIVIAL
        !           274: 
        !           275: \item  OTHERWISE, SOPHISTICATED ALGORITHMS ARE REQUIRED IN PROTOCOLS
        !           276:        WHICH IMPLEMENT TRANSPORT SERVICE
        !           277: \end{nrtc}
        !           278: \end{bwslide}
        !           279: 
        !           280: 
        !           281: \begin{bwslide}
        !           282: \ctitle        {TRANSPORT SERVICE (cont.)}
        !           283: 
        !           284: \begin{nrtc}
        !           285: \item  IMPORTANT IMPLICATION:\\
        !           286:     \begin{nrtc}
        !           287:     \item      AVAILABLE NETWORK SERVICE DETERMINES WHICH
        !           288:                TRANSPORT PROTOCOL CAN BE USED
        !           289: 
        !           290:     \item      HOWEVER, WHEN INITIATING A CONNECTION,
        !           291:                TRANSPORT SERVICE IS ACTIVE PRIOR TO NETWORK SERVICE!
        !           292:     \end{nrtc}
        !           293: \end{nrtc}
        !           294: \end{bwslide}
        !           295: 
        !           296: 
        !           297: \begin{bwslide}
        !           298: \ctitle        {CHOICE OF NETWORK SERVICE}
        !           299: 
        !           300: \begin{nrtc}
        !           301: \item  CHOICE OF NETWORK SERVICE IS ECO-POLITICAL NOT TECHNICAL
        !           302:     \begin{nrtc}
        !           303:     \item      EITHER APPROACH CAN BE MADE TO WORK WELL
        !           304:     \end{nrtc}
        !           305: 
        !           306: \item  CO-MODE NETWORK SERVICE IS MORE SUITED TOWARDS A COMMON-CARRIER MODEL
        !           307:     \begin{nrtc}
        !           308:     \item      ACCOUNTABILITY AND ISOLATION
        !           309:     \end{nrtc}
        !           310:     THIS IS TYPIFIED BY PUBLIC DATA NETWORKS
        !           311: 
        !           312: \item  CL-MODE NETWORK SERVICE IS MORE GENERAL
        !           313:     \begin{nrtc}
        !           314:     \item      ADAPTABILITY AND COOPERATION
        !           315:     \end{nrtc}
        !           316:     THIS IS TYPIFIED BY CLOSED COMMUNITY NETWORKS
        !           317: 
        !           318: \item  HOWEVER, THE TWO APPROACHES DON'T MIX WELL
        !           319: \end{nrtc}
        !           320: \end{bwslide}
        !           321: 
        !           322: 
        !           323: \begin{bwslide}
        !           324: \part  {BUILDING BLOCKS}\bf
        !           325: 
        !           326: \begin{nrtc}
        !           327: \item  ADDRESS FORMATS
        !           328: 
        !           329: \item  NETWORK BINDING
        !           330: 
        !           331: \item  TRANSPORT PROTOCOLS
        !           332: 
        !           333: \item  APPLICATION USE OF END-TO-END SERVICES
        !           334: 
        !           335: \item  EMULATION OF OSI END-TO-END SERVICES
        !           336: \end{nrtc}
        !           337: \end{bwslide}
        !           338: 
        !           339: 
        !           340: \begin{bwslide}
        !           341: \part* {ADDRESS FORMATS}\bf
        !           342: 
        !           343: \begin{nrtc}
        !           344: \item  HIERARHICALLY STRUCTURED
        !           345:     \begin{nrtc}
        !           346:     \item      ADDRESSING DOMAINS, SUB-DOMAINS
        !           347: 
        !           348:     \item      UNAMBIGUOUS PREFIXES
        !           349:     \end{nrtc}
        !           350: 
        !           351: \item  MAIN GOAL: FACILITATE ALLOCATION
        !           352: 
        !           353: \item  NO IMPLICATIONS ON ``HOW TO GET THERE''
        !           354:     \begin{nrtc}
        !           355:     \item      BUT STRUCTURE MAY FACILITATE ROUTING DECISIONS
        !           356:     \end{nrtc}
        !           357: \end{nrtc}
        !           358: \end{bwslide}
        !           359: 
        !           360: 
        !           361: \begin{bwslide}
        !           362: \ctitle        {ADDRESS FORMATS (cont.)}
        !           363: 
        !           364: \begin{nrtc}
        !           365: \item  AN ADDRESSING AUTHORITY DEFINES STRUCTURE OF DOMAIN
        !           366:     \begin{nrtc}
        !           367:     \item      TERMED AN ABSTRACT SYNTAX
        !           368:     \end{nrtc}
        !           369:     AND ALSO ALLOCATES VALUES
        !           370: 
        !           371: \item  A TRANSFER SYNTAX DEFINES HOW ADDRESSES ARE ENCODED
        !           372: \end{nrtc}
        !           373: \end{bwslide}
        !           374: 
        !           375: 
        !           376: \begin{bwslide}
        !           377: \ctitle        {TOP-LEVEL}
        !           378: 
        !           379: \begin{nrtc}
        !           380: \item  ADDRESS IS DIVIDED INTO TWO PARTS:
        !           381:     \begin{nrtc}
        !           382:     \item      INITIAL DOMAIN PART (IDP), AND
        !           383: 
        !           384:     \item      DOMAIN SPECIFIC PART (DSP)
        !           385:     \end{nrtc}
        !           386: \end{nrtc}
        !           387: 
        !           388: \diagram[p]{figureE-3}
        !           389: \end{bwslide}
        !           390: 
        !           391: 
        !           392: \begin{bwslide}
        !           393: \ctitle        {TOP-LEVEL (cont.)}
        !           394: 
        !           395: \begin{nrtc}
        !           396: \item  AUTHORITY AND FORMAT IDENTIFIER (AFI) DEFINES HOW
        !           397:     \begin{nrtc}
        !           398:     \item      IDI IS INTERPRETED, AND
        !           399: 
        !           400:     \item      HOW DSP IS FORMATTED
        !           401:        \begin{nrtc}
        !           402:        \item   (DECIMAL/BINARY ABSTRACT SYNTAX)
        !           403:        \end{nrtc}
        !           404:     \end{nrtc}
        !           405: 
        !           406: \item  INITIAL DOMAIN IDENTIFIER (IDI) SAYS WHO OWNS THE DSP
        !           407:     \begin{nrtc}
        !           408:     \item      MIGHT BE VARIABLE LENGTH
        !           409: 
        !           410:     \item      MIGHT HAVE (SIGNIFICANT) LEADING ZEROS
        !           411:     \end{nrtc}
        !           412: 
        !           413: \item  DOMAIN SPECIFIC PART (DSP) IS JUST THAT
        !           414: \end{nrtc}
        !           415: \end{bwslide}
        !           416: 
        !           417: 
        !           418: \begin{bwslide}
        !           419: \ctitle        {EXAMPLE 1:\\ X.121 ADDRESS}
        !           420: 
        !           421: \begin{nrtc}
        !           422: \item  AN X.121 ADDRESS MAY BE ENCODED USING
        !           423:     \begin{nrtc}
        !           424:     \item      AFI = 36
        !           425: 
        !           426:     \item      IDI = X.121 ADDRESS (UP TO 14~DIGITS)
        !           427:     \end{nrtc}
        !           428: \end{nrtc}
        !           429: 
        !           430: \diagram[p]{figureE-4}
        !           431: \end{bwslide}
        !           432: 
        !           433: 
        !           434: \begin{bwslide}
        !           435: \ctitle        {EXAMPLE 2:\\ ICD ADDRESS}
        !           436: 
        !           437: \begin{nrtc}
        !           438: \item  AN INTERNATIONALLY RECOGNIZED ENTITY MAY ALLOCATE ADDRESSES USING
        !           439:     \begin{nrtc}
        !           440:     \item      AFI = 47
        !           441: 
        !           442:     \item      IDI = INTERNATIONAL CODE DESIGNATOR (4~DIGITS)
        !           443:     \end{nrtc}
        !           444: \end{nrtc}
        !           445: 
        !           446: \diagram[p]{figureE-5}
        !           447: \end{bwslide}
        !           448: 
        !           449: 
        !           450: \begin{bwslide}
        !           451: \ctitle        {EXAMPLE 3:\\ LOCAL ADDRESS}
        !           452: 
        !           453: \begin{nrtc}
        !           454: \item  ANYONE MIGHT USE A ``LOCAL'' ADDRESSING FORMAT
        !           455:     \begin{nrtc}
        !           456:     \item      AFI = 49
        !           457: 
        !           458:     \item      IDI = NULL (0~DIGITS)
        !           459:     \end{nrtc}
        !           460: \end{nrtc}
        !           461: 
        !           462: \diagram[p]{figureE-6}
        !           463: \end{bwslide}
        !           464: 
        !           465: 
        !           466: \begin{bwslide}
        !           467: \part* {NETWORK BINDING}\bf
        !           468: 
        !           469: \begin{nrtc}
        !           470: \item  HOW DOES DATA GO FROM ORIGINATING TO DESTINATION END-SYSTEM?
        !           471:     \begin{nrtc}
        !           472:     \item      i.e., HOW IS ROUTING ACCOMPLISHED?
        !           473:     \end{nrtc}
        !           474: 
        !           475: \item  NETWORK SERVICE AT ORIGINATING END-SYSTEM DECIDES ``NEXT HOP''
        !           476: 
        !           477: \item  IF DESTINATION END-SYSTEM IS ON SAME SUBNETWORK,
        !           478:        THEN NEXT HOP IS DESTINATION END-SYSTEM
        !           479: 
        !           480: \item  OTHERWISE, NEXT HOP IS AN INTERMEDIATE SYSTEM (ON THE SAME SUBNETWORK)
        !           481:        WHICH IS ``CLOSER'' TO THE DESTINATION END-SYSTEM
        !           482: \end{nrtc}
        !           483: \end{bwslide}
        !           484: 
        !           485: 
        !           486: \begin{bwslide}
        !           487: \ctitle        {DETERMINING THE NEXT HOP}
        !           488: 
        !           489: \begin{nrtc}
        !           490: \item  NETWORK ADDRESSES DO NOT CONTAIN ROUTING INFORMATION
        !           491:     \begin{nrtc}
        !           492:     \item      IN THEORY, AT LEAST
        !           493:     \end{nrtc}
        !           494: 
        !           495: \item  INTERMEDIATE-SYSTEMS MAINTAIN ROUTING TABLES WHICH TELL
        !           496:        ``HOW TO GET THERE''
        !           497: 
        !           498: \item  SO, ONCE THE DESTINATION END-SYSTEM'S SUBNETWORK HAS BEEN REACHED,
        !           499:        NEED A WAY OF DETERMINING ``WHERE IT IS'' ON A PARTICULAR
        !           500:        SUBNETWORK
        !           501: \end{nrtc}
        !           502: \end{bwslide}
        !           503: 
        !           504: 
        !           505: \begin{bwslide}
        !           506: \ctitle        {SUBNETWORK POINT OF ATTACHMENT (SNPA)}
        !           507: 
        !           508: \begin{nrtc}
        !           509: \item  A NODE (ES or IS) IS ATTACHED TO A SUBNETWORK AT A
        !           510:     \begin{nrtc}
        !           511:     \item      SUBNETWORK POINT OF ATTACHMENT (SNPA)
        !           512:     \end{nrtc}
        !           513: 
        !           514: \item  NEED A WAY TO MAP BETWEEN A NETWORK ADDRESS
        !           515:        AND ITS CORRESPONDING SNPA
        !           516: 
        !           517: \item  THE PROBLEM:
        !           518:     \begin{nrtc}
        !           519:     \item      ROUTING IS A NETWORK-WIDE FUNCTION,
        !           520: 
        !           521:     \item      SO INFORMATION MUST BE COHERENT NETWORK-WIDE
        !           522:     \end{nrtc}
        !           523: \end{nrtc}
        !           524: \end{bwslide}
        !           525: 
        !           526: 
        !           527: \begin{bwslide}
        !           528: \ctitle        {MAPPING TO SNPA}
        !           529: 
        !           530: \begin{nrtc}
        !           531: \item  TWO WAYS TO ACHIEVE DYNAMIC MAPPINGS
        !           532: 
        !           533: \item  RUN A PROTOCOL (ES-IS) ON THE SUBNETWORK
        !           534: 
        !           535: \item  USE A LOCAL TABLE
        !           536: 
        !           537: \item  OTHERWISE MUST EMBED THE SNPA IN THE NETWORK ADDRESS
        !           538:     \begin{nrtc}
        !           539:     \item      LOSES A LOT OF FLEXIBILITY
        !           540:     \end{nrtc}
        !           541:        (AND PRONE TO CONFIGURATION ERRORS)
        !           542: \end{nrtc}
        !           543: \end{bwslide}
        !           544: 
        !           545: 
        !           546: \begin{bwslide}
        !           547: \part* {TRANSPORT PROTOCOLS}\bf
        !           548: 
        !           549: \begin{nrtc}
        !           550: \item  AVAILABLE NETWORK SERVICE DETERMINES CHOICE OF TRANSPORT PROTOCOL
        !           551: 
        !           552: \item  OSI PROVIDES 5 TRANSPORT PROTOCOLS, TP0--TP4
        !           553:     \begin{nrtc}
        !           554:     \item      CLASSES 0--3 WORKS WITH A CO-MODE NETWORK SERVICE
        !           555: 
        !           556:     \item      CLASS 4 WORKS WITH BOTH CO/CL-MODE NETWORK SERVICES
        !           557:     \end{nrtc}
        !           558: \end{nrtc}
        !           559: \end{bwslide}
        !           560: 
        !           561: 
        !           562: \begin{bwslide}
        !           563: \ctitle        {NETWORK CLASSES}
        !           564: 
        !           565: \begin{nrtc}
        !           566: \item  ``A'' --- LOW LOSS, ERRORS SIGNALLED
        !           567: 
        !           568: \item  ``B'' --- ERRORS SIGNALLED
        !           569: 
        !           570: \item  ``C'' --- ERRORS NOT SIGNALLED
        !           571:     \begin{nrtc}
        !           572:     \item      LOSS
        !           573: 
        !           574:     \item      DUPLICATION
        !           575: 
        !           576:     \item      RE-ORDERING
        !           577: 
        !           578:     \item      CORRUPTION
        !           579:     \end{nrtc}
        !           580:     OF DATA
        !           581: \end{nrtc}
        !           582: \end{bwslide}
        !           583: 
        !           584: 
        !           585: \begin{bwslide}
        !           586: \ctitle        {PROTOCOLS USING\\ CO-MODE NETWORK SERVICE}
        !           587: 
        !           588: \begin{nrtc}
        !           589: \item  TP0: SIMPLE CLASS
        !           590:     \begin{nrtc}
        !           591:     \item      NOTHING MORE THAN TRANSPORT ADDRESSING AND SEGMENTATION
        !           592: 
        !           593:     \item      ``A'' NETWORKS
        !           594:     \end{nrtc}
        !           595: 
        !           596: \item  TP1: BASIC ERROR RECOVERY CLASS
        !           597:     \begin{nrtc}
        !           598:     \item      RECOVER FROM NETWORK RESETS\\ (MAY INVOLVE RE-ROUTING)
        !           599: 
        !           600:     \item      ``B'' NETWORKS
        !           601:     \end{nrtc}
        !           602: \end{nrtc}
        !           603: \end{bwslide}
        !           604: 
        !           605: 
        !           606: \begin{bwslide}
        !           607: \ctitle        {PROTOCOLS USING\\ CO-MODE NETWORK SERVICE (cont.)}
        !           608: 
        !           609: \begin{nrtc}
        !           610: \item  TP2: MULTIPLEXING CLASS
        !           611:     \begin{nrtc}
        !           612:     \item      MULTIPLEX OVER A SINGLE NETWORK CONNECTION
        !           613: 
        !           614:     \item      OPTIONAL FLOW CONTROL   
        !           615: 
        !           616:     \item      ``A'' NETWORKS
        !           617:     \end{nrtc}
        !           618: 
        !           619: \item  TP3: ERROR RECOVERY AND MULTIPLEXING CLASS
        !           620:     \begin{nrtc}
        !           621:     \item      ALL OF THE ABOVE
        !           622: 
        !           623:     \item      ``B'' NETWORKS
        !           624:     \end{nrtc}
        !           625: \end{nrtc}
        !           626: \end{bwslide}
        !           627: 
        !           628: 
        !           629: \begin{bwslide}
        !           630: \ctitle        {PROTOCOLS WHICH CAN USE\\ CL-MODE NETWORK SERVICE}
        !           631: 
        !           632: \begin{nrtc}
        !           633: \item  TP4: ERROR DETECTION AND RECOVERY CLASS
        !           634:     \begin{nrtc}
        !           635:     \item      RELIABILITY THROUGH RETRANSMISSION
        !           636: 
        !           637:     \item      ``C'' NETWORKS
        !           638:     \end{nrtc}
        !           639: \end{nrtc}
        !           640: \end{bwslide}
        !           641: 
        !           642: 
        !           643: \begin{bwslide}
        !           644: \part* {APPLICATION USE OF END-TO-END SERVICES}\bf
        !           645: 
        !           646: \begin{nrtc}
        !           647: \item  APPLICATION IDENTIFIES APPLICATION ENTITY WHICH PROVIDES
        !           648:        DESIRED SERVICE
        !           649:     \begin{nrtc}
        !           650:     \item      e.g., AN FTAM APPLICATION IDENTIFIES A FILESTORE SERVICE
        !           651:                PROVIDED BY A PARTICULAR APPLICATION ENTITY    
        !           652:     \end{nrtc}
        !           653: 
        !           654: \item  THE APPLICATION ENTITY IS IDENTIFIED BY ITS DISTINGUISHED NAME IN
        !           655:        THE OSI DIRECTORY
        !           656: \end{nrtc}
        !           657: \end{bwslide}
        !           658: 
        !           659: 
        !           660: \begin{bwslide}
        !           661: \ctitle        {STEP 1:\\ MAP DISTINGUISHED NAME\\ TO PRESENTATION ADDRESS}
        !           662: 
        !           663: \begin{nrtc}
        !           664: \item  ESTABLISH ASSOCIATION TO DIRECTORY SERVICE AGENT (DSA)
        !           665:        USING DIRECTORY ACCESS PROTOCOL (DAP)
        !           666: 
        !           667: \item  RETRIEVE THE \verb"presentationAddress" ATTRIBUTE FROM
        !           668:        THE OBJECT WITH THE GIVEN DISTINGUISHED NAME
        !           669: \end{nrtc}
        !           670: 
        !           671: \begin{quote}\small\begin{verbatim}
        !           672: PSAPaddr ::=
        !           673:     SEQUENCE {
        !           674:         pSelector[0]
        !           675:             OCTET STRING
        !           676:             OPTIONAL,
        !           677: 
        !           678:         sSelector[1]
        !           679:             OCTET STRING
        !           680:             OPTIONAL,
        !           681: 
        !           682:         tSelector[2]
        !           683:             OCTET STRING
        !           684:             OPTIONAL,
        !           685: 
        !           686:         nAddresses[3]
        !           687:             SET OF (1..MAX) OCTET STRING
        !           688:     }
        !           689: \end{verbatim}\end{quote}
        !           690: \end{bwslide}
        !           691: 
        !           692: 
        !           693: \begin{bwslide}
        !           694: \ctitle        {STEP 2:\\ DETERMINE USE OF NETWORK ADDRESSES}
        !           695: 
        !           696: \begin{nrtc}
        !           697: \item  PRESENTATION ADDRESS IS GIVEN TO THE ASSOCIATION CONTROL SERVICE
        !           698:        ELEMENT (ACSE), WHICH ESTABLISHES THE ASSOCIATION
        !           699: 
        !           700: \item  ACSE PASSES THE ADDRESS TO THE PRESENTATION SERVICE,
        !           701:        WHICH USES THE PRESENTATION SELECTOR
        !           702: 
        !           703: \item  THE REMAINDER IS GIVEN TO THE SESSION SERVICE,
        !           704:        WHICH USES THE SESSION SELECTOR
        !           705: 
        !           706: \item  THE REMAINDER IS GIVEN TO THE TRANSPORT SERVICE
        !           707: \end{nrtc}
        !           708: \end{bwslide}
        !           709: 
        !           710: 
        !           711: \begin{bwslide}
        !           712: \ctitle        {STEP 2 (cont.)}
        !           713: 
        !           714: \begin{nrtc}
        !           715: \item  TRANSPORT SERVICE LOOKS AT EACH NETWORK ADDRESS AND MUST DECIDE
        !           716:     \begin{nrtc}
        !           717:     \item      WHICH MODE NETWORK SERVICE WILL BE USED FOR THIS ADDRESS
        !           718:     \end{nrtc}
        !           719: 
        !           720: \item  TRANSPORT SERVICE SELECTS A TRANSPORT PROTOCOL BASED ON THE
        !           721:        DERIVED NETWORK SERVICE AND THE COMMUNICATIONS QUALITY OF SERVICE (QOS)
        !           722:        DESIRED BY THE APPLICATION
        !           723: 
        !           724: \item  THIS COMBINATION
        !           725:     \begin{nrtc}
        !           726:     \item       (NETWORK SERVICE+TRANSPORT PROTOCOL)
        !           727:     \end{nrtc}
        !           728:        IS TERMED A
        !           729:     \begin{nrtc}
        !           730:     \item      TRANSPORT SERVICE STACK (TS-STACK)
        !           731:     \end{nrtc}
        !           732: \end{nrtc}
        !           733: \end{bwslide}
        !           734: 
        !           735: 
        !           736: \begin{bwslide}
        !           737: \ctitle        {STILL MORE ON\\ STEP 2}
        !           738: 
        !           739: \begin{nrtc}
        !           740: \item  IN MANY ENVIRONMENTS ONLY A SINGLE MODE OF NETWORK SERVICE AND A
        !           741:        SINGLE TRANSPORT PROTOCOL ARE AVAILABLE 
        !           742: 
        !           743: \item  THIS IMPLIES THAT ONLY A SUBSET (OR PERHAPS NONE) OF THE
        !           744:        NETWORK ADDRESSES WILL BE USABLE AT THE ORIGINATING END-SYSTEM
        !           745: \end{nrtc}
        !           746: \end{bwslide}
        !           747: 
        !           748: 
        !           749: \begin{bwslide}
        !           750: \ctitle        {STEP 3:\\ ORDER NETWORK ADDRESSES}
        !           751: 
        !           752: \begin{nrtc}
        !           753: \item  THE NETWORK ADDRESSES ARE THEN ORDERED BY PREFERENCE
        !           754: 
        !           755: \item  PREFERENCE IS BASED BOTH ON COMMUNICATIONS-QOS AND ``CLOSENESS''
        !           756:        OF NETWORK ADDRESSES
        !           757: 
        !           758: \item  FOR EXAMPLE:
        !           759:     \begin{nrtc}
        !           760:     \item      TWO NETWORK ADDRESSES, EACH IMPLYING A CO-MODE NETWORK
        !           761:                SERVICE, MIGHT BE PRESENT
        !           762: 
        !           763:     \item      ONE OF THE NETWORK ADDRESS MIGHT BELONG TO A PRIVATE
        !           764:                NETWORK, WHILST THE OTHER BELONGS TO A PDN
        !           765: 
        !           766:     \item      THE TRANSPORT SERVICE MIGHT PREFER THE PRIVATE NETWORK,
        !           767:                FOR COST REASONS
        !           768:     \end{nrtc}
        !           769: \end{nrtc}
        !           770: \end{bwslide}
        !           771: 
        !           772: 
        !           773: \begin{bwslide}
        !           774: \ctitle        {STEP 4:\\ ATTEMPT CONNECTIONS}
        !           775: 
        !           776: \begin{nrtc}
        !           777: \item  FOR EACH NETWORK ADDRESS:
        !           778:     \begin{nrtc}
        !           779:     \item      THE APPROPRIATE TRANSPORT PROTOCOL ENGINE IS STARTED,
        !           780:                AND THE NETWORK SERVICE INVOKED
        !           781: 
        !           782:     \item      ONCE A TRANSPORT CONNECTION IS ESTABLISHED,
        !           783:                THE REMAINDER OF THE NETWORK ADDRESSES ARE IGNORED
        !           784:     \end{nrtc}
        !           785: \end{nrtc}
        !           786: \end{bwslide}
        !           787: 
        !           788: 
        !           789: \begin{bwslide}
        !           790: \part* {EMULATION OF OSI END-TO-END SERVICES}\bf
        !           791: 
        !           792: \begin{nrtc}
        !           793: \item  IS IT POSSIBLE TO PROVIDE OSI APPLICATIONS IN NON-OSI NETWORKS?
        !           794: 
        !           795: \item  A SOLUTION IS OFFERED BY LAYERING
        !           796:     \begin{nrtc}
        !           797:     \item      THE OSI TRANSPORT \underline{SERVICE} IS VERY SIMPLE
        !           798:     \end{nrtc}
        !           799: 
        !           800: \item  CAN WE BUILD TS-STACKS USING NON-OSI PROTOCOLS?
        !           801: \end{nrtc}
        !           802: \end{bwslide}
        !           803: 
        !           804: 
        !           805: \begin{bwslide}
        !           806: \ctitle        {SERVICE EMULATOR AT TRANSPORT}
        !           807: 
        !           808: \vskip.5in
        !           809: \diagram[p]{figureE-13}
        !           810: \end{bwslide}
        !           811: 
        !           812: 
        !           813: \begin{bwslide}
        !           814: \ctitle        {APPROACH:\\ TRANSPORT SERVICE\\ CONVERGENCE PROTOCOL}
        !           815: 
        !           816: \begin{nrtc}
        !           817: \item  USE THE CONNECTION-ORIENTED TRANSPORT SERVICE PROVIDED BY
        !           818:        THE NON-OSI PROTOCOL SUITE
        !           819: 
        !           820: \item  DEFINE A ``TSCP'' WHICH SMOOTHS OVER THE DIFFERENCES IN THE SERVICES
        !           821:        OFFERED
        !           822:     \begin{nrtc}
        !           823:     \item      IN PRACTICE, THESE ARE QUITE SMALL
        !           824:     \end{nrtc}
        !           825: 
        !           826: \item  FOR EXAMPLE, THE RFC1006 METHOD DEFINES A TSCP FOR TCP/IP NETWORKS
        !           827: \end{nrtc}
        !           828: \end{bwslide}
        !           829: 
        !           830: 
        !           831: \begin{bwslide}
        !           832: \ctitle        {OSI TRANSPORT SERVICES\\ ON TOP OF THE TCP}
        !           833: 
        !           834: \vskip.25in
        !           835: \diagram[p]{figureE-14}
        !           836: \end{bwslide}
        !           837: 
        !           838: 
        !           839: \begin{bwslide}
        !           840: \part  {ACHIEVING CONNECTIVITY}\bf
        !           841: 
        !           842: \begin{nrtc}
        !           843: \item  THE REAL WORLD OF OSI
        !           844: 
        !           845: \item  INTERIM USE OF NETWORK ADDRESSES
        !           846: 
        !           847: \item  TRANSPORT BRIDGING
        !           848: \end{nrtc}
        !           849: \end{bwslide}
        !           850: 
        !           851: 
        !           852: \begin{bwslide}
        !           853: \ctitle        {NOW THE HARD PART}
        !           854: 
        !           855: \begin{nrtc}
        !           856: \item  A LOT OF FLEXIBILITY IS AVAILABLE
        !           857: 
        !           858: \item  BUT PRACTICALLY, CAN THIS BE MADE TO WORK?
        !           859: \end{nrtc}
        !           860: \end{bwslide}
        !           861: 
        !           862: 
        !           863: \begin{bwslide}
        !           864: \part* {THE REAL WORLD OF OSI}\bf
        !           865: 
        !           866: \begin{nrtc}
        !           867: \item  THE ``REAL WORLD'' DEPENDS ENTIRELY WHERE YOU LIVE
        !           868: 
        !           869: \item  A COMMUNITY IS A COLLECTION OF END-SYSTEMS SHARING COMPATIBLE
        !           870:        TS-STACKS AND CONNECTED TOGETHER
        !           871: 
        !           872: \item  WHAT KIND OF OSI COMMUNITIES EXIST TODAY?
        !           873: \end{nrtc}
        !           874: \end{bwslide}
        !           875: 
        !           876: 
        !           877: \begin{bwslide}
        !           878: \ctitle        {COMMUNITY 1:\\ INTERNATIONAL X.25}
        !           879: 
        !           880: \begin{nrtc}
        !           881: \item  X.121 FORMAT ADDRESSES ARE USED
        !           882: 
        !           883: \item  NETWORK PROTOCOL IS X.25(80) WHICH DOES NOT PROVIDE TRUE
        !           884:        OSI NETWORK SERVICE
        !           885:     \begin{nrtc}
        !           886:     \item      EVENTUALLY UPGRADING TO X.25(84)
        !           887:     \end{nrtc}
        !           888: 
        !           889: \item  TP0 IS FAVORED TRANSPORT PROTOCOL
        !           890: 
        !           891: \item  TS-STACKS:
        !           892: \end{nrtc}
        !           893: 
        !           894: \diagram[p]{figureE-7}
        !           895: \end{bwslide}
        !           896: 
        !           897: 
        !           898: \begin{bwslide}
        !           899: \ctitle        {COMMUNITY 2:\\ PRIVATE X.25}
        !           900: 
        !           901: \begin{nrtc}
        !           902: \item  SIMILAR TO INTERNATIONAL X.25 COMMUNITY,
        !           903:        BUT OWNED BY A PARTICULAR ENTERPRISE
        !           904:     \begin{nrtc}
        !           905:     \item      e.g., THE U.K.~JOINT ACADEMIC NETWORK (JANET)    
        !           906:     \end{nrtc}
        !           907: 
        !           908: \item  ADDRESSES ARE X.121-BASED, BUT ARE PRIVATELY ALLOCATED
        !           909:     \begin{nrtc}
        !           910:     \item      THUS THE X.121 NETWORK ADDRESS FORMAT CAN'T BE USED
        !           911:     \end{nrtc}
        !           912: 
        !           913: \item  TS-STACKS:
        !           914: \end{nrtc}
        !           915: 
        !           916: \diagram[p]{figureE-7}
        !           917: \end{bwslide}
        !           918: 
        !           919: 
        !           920: \begin{bwslide}
        !           921: \ctitle        {COMMUNITY 3:\\ VARIANT U.S. USE OF X.25}
        !           922: 
        !           923: \begin{nrtc}
        !           924: \item  X.25 TREATED AS A SUBNETWORK PROTOCOL
        !           925: 
        !           926: \item  CL-MODE NETWORK SERVICE RUN OVER THIS
        !           927: 
        !           928: \item  TS-STACKS:
        !           929: \end{nrtc}
        !           930: 
        !           931: \diagram[p]{figureE-9}
        !           932: \end{bwslide}
        !           933: 
        !           934: 
        !           935: \begin{bwslide}
        !           936: \ctitle        {COMMUNITY 4:\\ CONS-BASED LANS}
        !           937: 
        !           938: \begin{nrtc}
        !           939: \item  CO-MODE NETWORK SERVICE OFFERRED OVER 8802 SUBNETWORK
        !           940: 
        !           941: \item  COMMONLY TERMED ``X.25 OVER ETHERNET'' (LLC2)
        !           942: 
        !           943: \item  TS-STACKS:
        !           944: \end{nrtc}
        !           945: 
        !           946: \diagram[p]{figureE-10}
        !           947: \end{bwslide}
        !           948: 
        !           949: 
        !           950: \begin{bwslide}
        !           951: \ctitle        {COMMUNITY 5:\\ CLNS-BASED LANS}
        !           952: 
        !           953: \begin{nrtc}
        !           954: \item  CL-MODE NETWORK SERVICE OFFERRED OVER 8802 SUBNETWORK
        !           955: 
        !           956: \item  COMMONLY TERMED ``MAP/TOP LANs'' (LLC1)
        !           957: 
        !           958: \item  TS-STACKS:
        !           959: \end{nrtc}
        !           960: 
        !           961: \diagram[p]{figureE-11}
        !           962: \end{bwslide}
        !           963: 
        !           964: 
        !           965: \begin{bwslide}
        !           966: \ctitle        {COMMUNITY 6:\\ TCP/IP-BASED INTERNET USING RFC1006}
        !           967: 
        !           968: \begin{nrtc}
        !           969: \item  RFC1006 DEFINES A MAPPING FROM THE OSI TRANSPORT SERVICE ONTO THE TCP
        !           970: 
        !           971: \item  PROBLEM: WHAT FORMAT TO USE NETWORK ADDRESS?
        !           972: 
        !           973: \item  TS-STACKS:
        !           974: \end{nrtc}
        !           975: 
        !           976: \diagram[p]{figureE-12}
        !           977: \end{bwslide}
        !           978: 
        !           979: 
        !           980: \begin{bwslide}
        !           981: \ctitle        {COMMUNITY 7:\\ TCP/IP-BASED LAN USING RFC1006}
        !           982: 
        !           983: \begin{nrtc}
        !           984: \item  SIMILAR TO INTERNET COMMUNITY,
        !           985:        BUT ON AN ISOLATED TCP/IP LAN
        !           986:     \begin{nrtc}
        !           987:     \item      e.g., A CAMPUS NETWORK RUNNING TCP/IP LOCALLY AND HAVING A
        !           988:                CONNECTION TO A PDN
        !           989:     \end{nrtc}
        !           990: 
        !           991: \item  TS-STACKS:
        !           992: \end{nrtc}
        !           993: 
        !           994: \diagram[p]{figureE-12}
        !           995: \end{bwslide}
        !           996: 
        !           997: 
        !           998: \begin{bwslide}
        !           999: \ctitle        {COMMUNITY INTEROPERATION}
        !          1000: 
        !          1001: \begin{nrtc}
        !          1002: \item  SO, THERE ARE (AT LEAST) SEVEN DIFFERENT COMMUNITIES IN THE OSI WORLD
        !          1003: 
        !          1004: \item  IDEALLY WOULD LIKE THIS INTERWORKING MATRIX:
        !          1005: \end{nrtc}
        !          1006: 
        !          1007: \diagram[p]{figureE-15}
        !          1008: \end{bwslide}
        !          1009: 
        !          1010: 
        !          1011: \begin{bwslide}
        !          1012: \ctitle        {COMMUNITY INTEROPERATION (cont.)}
        !          1013: 
        !          1014: \begin{nrtc}
        !          1015: \item  COMMUNITY 7 IS ISOLATED BY LACK OF CONNECTIVITY
        !          1016: \end{nrtc}
        !          1017: 
        !          1018: \diagram[p]{figureE-16}
        !          1019: \end{bwslide}
        !          1020: 
        !          1021: 
        !          1022: \begin{bwslide}
        !          1023: \ctitle        {COMMUNITY INTEROPERATION (cont.)}
        !          1024: 
        !          1025: \begin{nrtc}
        !          1026: \item  PRIVATE X.25 AND RFC1006--BASED COMMUNITIES NEED DIFFERENT ADDRESS
        !          1027:        SPACE
        !          1028: \end{nrtc}
        !          1029: 
        !          1030: \diagram[p]{figureE-17}
        !          1031: \end{bwslide}
        !          1032: 
        !          1033: 
        !          1034: \begin{bwslide}
        !          1035: \ctitle        {REAL WORLD CONNECTIVITY MATRIX}
        !          1036: 
        !          1037: \begin{nrtc}
        !          1038: \item  IN PRACTICE, CONS-BASED LANS DON'T INTEROPERATE WITH CONS-BASED WANS 
        !          1039:     \begin{nrtc}
        !          1040:     \item      ROUTING OF CONS-BASED SUBNETWORKS ISN'T WIDELY IMPLEMENTED
        !          1041:                OUTSIDE OF X.75
        !          1042:     \end{nrtc}
        !          1043: \end{nrtc}
        !          1044: 
        !          1045: \diagram[p]{figureE-18}
        !          1046: \end{bwslide}
        !          1047: 
        !          1048: 
        !          1049: \begin{bwslide}
        !          1050: \ctitle        {COMMUNITY INTEROPERATION (cont.)}
        !          1051: 
        !          1052: \begin{nrtc}
        !          1053: \item  CLNS-BASED AND CONS-BASED TS-STACKS DON'T ALWAYS INTEROPERATE
        !          1054:     \begin{nrtc}
        !          1055:     \item      IT IS NOT ENOUGH TO START WITH TP4 AND DOWN-NEGOTIATE
        !          1056:     \end{nrtc}
        !          1057: \end{nrtc}
        !          1058: 
        !          1059: \diagram[p]{figureE-19}
        !          1060: \end{bwslide}
        !          1061: 
        !          1062: 
        !          1063: \begin{bwslide}
        !          1064: \ctitle        {THE MYTH OF TRANSPORT NEGOTIATION}
        !          1065: 
        !          1066: \begin{nrtc}
        !          1067: \item  IF INITIATOR SELECTS TP4, MUST ALSO DECIDE CONS/CLNS
        !          1068:     \begin{nrtc}
        !          1069:     \item      IF CLNS IS USED, THEN MUST STAY WITH TP4
        !          1070: 
        !          1071:     \item      IF CLNS ISN'T USED, THEN CAN'T TALK TO CLNS-BASED LAN    
        !          1072:     \end{nrtc}
        !          1073: \end{nrtc}
        !          1074: \end{bwslide}
        !          1075: 
        !          1076: 
        !          1077: \begin{bwslide}
        !          1078: \part* {INTERIM USE OF NETWORK ADDRESSES}\bf
        !          1079: 
        !          1080: \begin{nrtc}
        !          1081: \item  WANT TO ACCOMODATE ALL OSI COMMUNITIES IN OSI DIRECTORY
        !          1082: 
        !          1083: \item  PROBLEM: ALL ADDRESSES MUST CONFORM TO DIRECTORY DEFINED SYNTAX
        !          1084: 
        !          1085: \item  PROBLEM: ALL ADDRESSES MUST BE GLOBALLY UNIQUE YET LOCALLY
        !          1086:        INTERPRETABLE
        !          1087: 
        !          1088: \item  SOLUTION: KILLE'S INTERIM APPROACH
        !          1089: \end{nrtc}
        !          1090: \end{bwslide}
        !          1091: 
        !          1092: 
        !          1093: \begin{bwslide}
        !          1094: \ctitle        {CONFORMANCE TO\\ DIRECTORY DEFINED SYNTAX}
        !          1095: 
        !          1096: \begin{nrtc}
        !          1097: \item  A PROBLEM FOR THE PRIVATE X.25 AND RFC1006--BASED COMMUNITIES
        !          1098: 
        !          1099: \item  TAKE A PART OF THE SPACE ASSIGNED TO TELEX ADDRESSES
        !          1100:     \begin{nrtc}
        !          1101:     \item      NO ONE WILL USE TELEX AFI FOR NETWORK ADDRESSES
        !          1102:     \end{nrtc}
        !          1103: 
        !          1104: \item  SUB-DIVIDE THIS ADDRESS SPACE FOR EACH COMMUNITY, e.g.,
        !          1105:     \begin{nrtc}
        !          1106:     \item      AFI = 54
        !          1107: 
        !          1108:     \item      IDI = 00728722
        !          1109:     \end{nrtc}
        !          1110: \end{nrtc}
        !          1111: 
        !          1112: \diagram[p]{figureE-8}
        !          1113: \end{bwslide}
        !          1114: 
        !          1115: 
        !          1116: \begin{bwslide}
        !          1117: \ctitle        {INTERPRETATION OF ADDRESSES}
        !          1118: 
        !          1119: \begin{nrtc}
        !          1120: \item  FROM EACH NETWORK ADDRESS
        !          1121:     \begin{nrtc}
        !          1122:     \item      COMMUNITY (TS-STACK, IDENTITY OF NETWORK) MUST BE DEDUCIBLE
        !          1123: 
        !          1124:     \item      NETWORK-SPECIFIC INFORMATION (i.e., SNPA) MUST BE DEDUCIBLE
        !          1125:     \end{nrtc}
        !          1126: \end{nrtc}
        !          1127: \end{bwslide}
        !          1128: 
        !          1129: 
        !          1130: \begin{bwslide}
        !          1131: \part* {TRANSPORT BRIDGING}\bf
        !          1132: 
        !          1133: \begin{nrtc}
        !          1134: \item  PROBLEM: SUPPOSE THE ORIGINATING END-SYSTEM DETERMINES THAT
        !          1135:        IT IS IN A DIFFERENT COMMUNITY THAN THE DESTINATION END-SYSTEM
        !          1136: 
        !          1137: \item  FROM A PURIST PERSPECTIVE:
        !          1138:     \begin{nrtc}
        !          1139:     \item      INTEROPERATION CAN NOT OCCUR!
        !          1140:     \end{nrtc}
        !          1141: 
        !          1142: \item  FROM A PRAGMATIC PERSPECTIVE:
        !          1143:     \begin{nrtc}
        !          1144:     \item      IGNORE THE CURSED MODEL AND BUILD A LEVEL-4 RELAY
        !          1145:     \end{nrtc}
        !          1146: 
        !          1147: \item  FOR AN AMUSING READ, TRY ISO/DTR10172
        !          1148: \end{nrtc}
        !          1149: \end{bwslide}
        !          1150: 
        !          1151: 
        !          1152: \begin{bwslide}
        !          1153: \ctitle        {TS-BRIDGES}
        !          1154: 
        !          1155: \begin{nrtc}
        !          1156: \item  ALTHOUGH MANY DIFFERENT TS-STACKS EXIST,
        !          1157:        THEY ALL PROVIDE THE SAME TRANSPORT SERVICE
        !          1158: 
        !          1159: \item  SO, IT IS STRAIGHT-FORWARD TO BUILD A BOX THAT:
        !          1160:     \begin{nrtc}
        !          1161:     \item      KNOWS NOTHING ABOUT TRANSPORT PROTOCOLS, BUT
        !          1162: 
        !          1163:     \item      KNOWS HOW TO USE THE RELATIVELY SIMPLE OSI TRANSPORT SERVICE
        !          1164:     \end{nrtc}
        !          1165: 
        !          1166: \item  A TS-BRIDGE ``COPIES'' SERVICE PRIMITIVES FROM ONE TS-STACK TO THE
        !          1167:        OTHER, e.g.,
        !          1168:     \begin{nrtc}
        !          1169:     \item      UPON RECEIVING A T-CONNECT.INDICATION PRIMITIVE FROM ONE
        !          1170:                TS-STACK,
        !          1171: 
        !          1172:     \item      IT ISSUES A T-CONNECT.REQUEST PRIMITIVE TO THE OTHER TS-STACK
        !          1173:     \end{nrtc}
        !          1174: \end{nrtc}
        !          1175: \end{bwslide}
        !          1176: 
        !          1177: 
        !          1178: \begin{bwslide}
        !          1179: \ctitle        {TS-BRIDGES (cont.)}
        !          1180: 
        !          1181: \vskip.5in
        !          1182: \diagram[p]{figureE-1}
        !          1183: \end{bwslide}
        !          1184: 
        !          1185: 
        !          1186: \begin{bwslide}
        !          1187: \ctitle        {THE PROBLEMS OF LEVEL-4 RELAYS}
        !          1188: 
        !          1189: \begin{nrtc}
        !          1190: \item  THE TS-BRIDGE MAINTAINS STATE AS TO THE EXISTING CONNECTIONS
        !          1191: 
        !          1192: \item  EACH TS-STACK PROVIDES A CHECKSUM,
        !          1193:        NEITHER OF WHICH IS REALLY END-TO-END
        !          1194:     \begin{nrtc}
        !          1195:     \item      (CHECKSUM AT EITHER TRANSPORT OR NETWORK SERVICE)
        !          1196:     \end{nrtc}
        !          1197: 
        !          1198: \item  THIS ALSO DEFEATS TRANSPORT-LEVEL ENCRYPTION
        !          1199: 
        !          1200: \item  \underline{MAY} THWART SOPHISTICATED BACK-PRESSURE TECHNIQUES
        !          1201: \end{nrtc}
        !          1202: \end{bwslide}
        !          1203: 
        !          1204: 
        !          1205: \begin{bwslide}
        !          1206: \ctitle        {AND WHAT ABOUT?}
        !          1207: 
        !          1208: \begin{nrtc}
        !          1209: \item  ACCOUNTING
        !          1210: 
        !          1211: \item  ACCESS CONTROL
        !          1212: 
        !          1213: \item  LOAD BALANCING
        !          1214: 
        !          1215: \item  CONCATENATION OF TS-BRIDGES
        !          1216: 
        !          1217: \item  and so on$\ldots$
        !          1218: \end{nrtc}
        !          1219: \end{bwslide}
        !          1220: 
        !          1221: 
        !          1222: \begin{bwslide}
        !          1223: \ctitle        {USE OF THE TS-BRIDGE}
        !          1224: 
        !          1225: \begin{nrtc}
        !          1226: \item  MUST NOW SUBTLY MODIFY TRANSPORT SERVICE OF ORIGINATING END-SYSTEM
        !          1227:     \begin{nrtc}
        !          1228:     \item      STEP 2: DETERMINE USE OF NETWORK ADDRESSES
        !          1229:     \end{nrtc}
        !          1230: 
        !          1231: \item  IF NO USABLE NETWORK ADDRESSES ARE AVAILABLE
        !          1232: 
        !          1233: \item  THEN SELECT A TS-BRIDGE WHICH SERVICES THE OSI COMMUNITY FOR ONE OF
        !          1234:        THE NETWORK ADDRESSES
        !          1235:     \begin{nrtc}
        !          1236:     \item       RECALL, OSI COMMUNITY EQUALS TS-STACK PLUS CONNECTIVITY
        !          1237:     \end{nrtc}
        !          1238: \end{nrtc}
        !          1239: \end{bwslide}
        !          1240: 
        !          1241: 
        !          1242: \begin{bwslide}
        !          1243: \ctitle        {USE OF THE TS-BRIDGE (cont.)}
        !          1244: 
        !          1245: \begin{nrtc}
        !          1246: \item  ENCODE THE NETWORK ADDRESS AND TRANSPORT SELECTOR AS AN OCTET STRING,
        !          1247:     \begin{nrtc}
        !          1248:     \item      (USING KILLE'S STRING FORMAT)
        !          1249:     \end{nrtc}
        !          1250:        CALL THIS THE NEW TRANSPORT SELECTOR
        !          1251: 
        !          1252: \item  USE THE NETWORK ADDRESS OF THE TS-BRIDGE FOR THE REMAINING STEPS
        !          1253: 
        !          1254: \item  WHEN TS-BRIDGE RECEIVES CONNECTION,
        !          1255:        IT SIMPLY DECODES TRANSPORT SELECTOR TO FIND ADDRESS OF
        !          1256:        DESTINATION END-SYSTEM
        !          1257: \end{nrtc}
        !          1258: \end{bwslide}
        !          1259: 
        !          1260: 
        !          1261: \begin{bwslide}
        !          1262: \ctitle        {TS-BRIDGE ADDRESSING}
        !          1263: 
        !          1264: \vskip.5in
        !          1265: \diagram[p]{figureE-20}
        !          1266: \end{bwslide}
        !          1267: 
        !          1268: 
        !          1269: \begin{bwslide}
        !          1270: \part  {COMPARISON TO TCP/IP}\bf
        !          1271: 
        !          1272: \begin{nrtc}
        !          1273: \item  NETWORK SERVICE
        !          1274: 
        !          1275: \item  TRANSPORT SERVICE
        !          1276: \end{nrtc}
        !          1277: \end{bwslide}
        !          1278: 
        !          1279: 
        !          1280: \begin{bwslide}
        !          1281: \ctitle        {COMPARISONS}
        !          1282: 
        !          1283: \begin{nrtc}
        !          1284: \item  ALL COMPARISONS ARE PARTISAN IN NATURE
        !          1285: 
        !          1286: \item  HOWEVER, WITHOUT BIAS OR LOSS OF GENERALITY,\\ I CAN HONESTLY STATE:
        !          1287:     \begin{nrtc}
        !          1288:     \item      THE OSI LOWER-LAYERS ARE CURRENTLY INCOHERENT
        !          1289:     \end{nrtc}
        !          1290: \end{nrtc}
        !          1291: \end{bwslide}
        !          1292: 
        !          1293: 
        !          1294: \begin{bwslide}
        !          1295: \part* {NETWORK SERVICE}\bf
        !          1296: 
        !          1297: \begin{nrtc}
        !          1298: \item  THE INTERNET PROTOCOL (IP) PROVIDES A CL-NETWORK SERVICE
        !          1299:     \begin{nrtc}
        !          1300:     \item      SIMILAR TO CLNP, BUT MORE EFFICIENT
        !          1301:     \end{nrtc}
        !          1302: 
        !          1303: \item  THE LEAST COMMON DENOMINATOR, USABLE OVER BOTH WANs AND LANs
        !          1304:     \begin{nrtc}
        !          1305:     \item      BEST EFFORT DELIVERY
        !          1306: 
        !          1307:     \item      RELIABILITY RESPONSIBILITY OF TRANSPORT SERVICE
        !          1308:     \end{nrtc}
        !          1309: \end{nrtc}
        !          1310: \end{bwslide}
        !          1311: 
        !          1312: 
        !          1313: \begin{bwslide}
        !          1314: \ctitle        {ARE TWO OSI NETWORK SERVICES\\ ONE TOO MANY?}
        !          1315: 
        !          1316: \begin{nrtc}
        !          1317: \item  IN A WORD: YES
        !          1318: 
        !          1319: \item  OSI COMMUNITIES ARE SEPERATED BY TS-STACKS AND CONNECTIVITY
        !          1320: 
        !          1321: \item  CONNECTIVITY ISN'T A TECHNICAL ISSUE
        !          1322: 
        !          1323: \item  BUT, TS-STACKS ARE, SO:
        !          1324:     \begin{nrtc}
        !          1325:     \item      IF THERE WAS A SINGLE NETWORK SERVICE,
        !          1326:                THEN THERE COULD BE A SINGLE TRANSPORT PROTOCOL
        !          1327:     \end{nrtc}
        !          1328: \end{nrtc}
        !          1329: \end{bwslide}
        !          1330: 
        !          1331: 
        !          1332: \begin{bwslide}
        !          1333: \part* {TRANSPORT SERVICE}\bf
        !          1334: 
        !          1335: \begin{nrtc}
        !          1336: \item  THE TRANSMISSION CONTROL PROTOCOL (TCP) PROVIDES A CO-TRANSPORT
        !          1337:        SERVICE
        !          1338: 
        !          1339: \item  SEVERAL DIFFERENCES FROM THE OSI TRANSPORT SERVICE
        !          1340:     \begin{nrtc}
        !          1341:     \item      TCP IS STREAM-ORIENTED
        !          1342: 
        !          1343:     \item      TCP USES GRACEFUL RELEASE
        !          1344: 
        !          1345:     \item      TCP USES URGENT DATA
        !          1346:     \end{nrtc}
        !          1347: 
        !          1348: \item  THESE ARE DIFFERENCES, NOT PROS AND CONS
        !          1349: \end{nrtc}
        !          1350: \end{bwslide}
        !          1351: 
        !          1352: 
        !          1353: \begin{bwslide}
        !          1354: \ctitle        {COMPARISON OF PROTOCOLS}
        !          1355: 
        !          1356: \begin{nrtc}
        !          1357: \item  REALLY CAN COMPARE ONLY THE TCP AND TP4
        !          1358: 
        !          1359: \item  TP4 PACKET ORIENTATION PREVENTS USE OF SOPHISTICATED CONGESTION
        !          1360:        COLLAPSE ALGORITHMS
        !          1361: 
        !          1362: \item  TP4 PACKET ORIENTATION HELPS BUFFER MANAGEMENT,
        !          1363:        POSSIBLY MORE EFFICIENT
        !          1364: 
        !          1365: \item  TP4 RETRANSMISSION ALGORITHMS ARE SIMPLISTIC
        !          1366: 
        !          1367: \item  TP4 END-TO-END CHECKSUM IS INAPPROPRIATE
        !          1368: \end{nrtc}
        !          1369: \end{bwslide}
        !          1370: 
        !          1371: 
        !          1372: \begin{bwslide}
        !          1373: \ctitle        {TRANSPORT BRIDGING}
        !          1374: 
        !          1375: \begin{nrtc}
        !          1376: \item  UNNECESSARY IN TCP/IP WORLD
        !          1377:     \begin{nrtc}
        !          1378:     \item      COMMON NETWORK PROTOCOL
        !          1379: 
        !          1380:     \item      UNIFORM NETWORK ADDRESS FORMAT
        !          1381:        \begin{nrtc}
        !          1382:        \item   (ALL IN 32--BITS!)
        !          1383:        \end{nrtc}
        !          1384:     \end{nrtc}
        !          1385: \end{nrtc}
        !          1386: \end{bwslide}
        !          1387: 
        !          1388: 
        !          1389: \begin{bwslide}
        !          1390: \part* {CONCLUSIONS}\bf
        !          1391: 
        !          1392: \begin{nrtc}
        !          1393: \item  DEPRESSING
        !          1394:     \begin{nrtc}
        !          1395:     \item      WORLD-WIDE OSI ``CAN'T HAPPEN''
        !          1396: 
        !          1397:     \item      THIS WILL CURTAIL USE OF WONDERFUL APPLICATIONS
        !          1398:     \end{nrtc}
        !          1399: 
        !          1400: \item  FORTUNATELY, CLOSED COMMUNITIES WILL BE RELATIVELY IMMUNE
        !          1401: \end{nrtc}
        !          1402: \end{bwslide}
        !          1403: 

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