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1.1 root 1: % -*- LaTeX -*- (really SLiTeX)
2:
3: \documentstyle[blackandwhite,landscape,oval,pagenumbers,small]{NRslides}
4:
5:
6: \font\xx=cmbx10
7: \font\yy=cmbx7
8:
9: \raggedright
10:
11: \input trademark
12: \let\tradeNAMfont=\relax
13: \let\tradeORGfont=\relax
14:
15: \begin{document}
16:
17: \title {Issues in Transition and Coexistence\\ for TCP/IP to OSI}
18: \author {Marshall T.~Rose\\ The Wollongong Group, Inc.}
19: \date {November 29, 1988}
20: \maketitlepage
21:
22:
23: \begin{bwslide}
24: \part* {AGENDA}\bf
25:
26: \begin{description}
27: \item[PART I:] MOTIVATION
28:
29: \item[PART II:] BACKGROUND
30:
31: \item[PART III:] PROTOCOL-BASED APPROACHES
32:
33: \item[PART IV:] RE-DEFINING THE PROBLEM
34:
35: \item[PART V:] SERVICE-BASED APPROACHES
36:
37: \item[PART VI:] EXAMPLES
38: \end{description}
39: \end{bwslide}
40:
41:
42: \begin{bwslide}
43: \part {MOTIVATION}\bf
44:
45: \begin{nrtc}
46: \item THERE ARE MANY TCP/IP NETWORKS TODAY; THERE WILL BE MORE TOMORROW
47:
48: \item BY THE TIME OSI BECOMES A WORTHWHILE OPERATIONAL ALTERNATIVE,
49: THERE WILL BE MANY MORE TCP/IP NETWORKS THAN THERE ARE TODAY!
50:
51: \item PROBLEM: HOW TO PROTECT INSTALLED BASE?
52:
53: \item PROBLEM: HOW TO TRANSITION GRACEFULLY?
54: \end{nrtc}
55: \end{bwslide}
56:
57:
58: \begin{bwslide}
59: \ctitle {GROWTH OF TCP/IP}
60:
61: \begin{nrtc}
62: \item SALES OF TCP/IP-BASED TECHNOLOGY
63: \begin{nrtc}
64: \item PARTICULARLY IN EUROPE
65: \end{nrtc}
66: CONTINUES TO GROW
67:
68: \item SEVERAL TECHNICAL AND MARKET ASPECTS CONTRIBUTE TO THIS PHENOMENA:
69: \begin{nrtc}
70: \item SUPERIORITY OF TCP/IP IN LOWER-LAYER CONNECTIVITY
71:
72: \item MATURITY OF TCP/IP PRODUCTS\\ (e.g., RANGE OF PLATFORMS)
73: \end{nrtc}
74:
75: \item ALTHOUGH OSI WILL DOMINATE, IT DOESN'T YET
76:
77: \item HENCE, TCP/IP IS BECOMING MORE FIRMLY ENTRENCHED
78: \end{nrtc}
79: \end{bwslide}
80:
81:
82: \begin{bwslide}
83: \ctitle {FEAR AND LOATHING IN THE MARKET}
84:
85: \begin{nrtc}
86: \item F.U.D. IN THE MARKETPLACE:
87: \begin{quote}\em
88: ``All marketing is fear, uncertainty, and doubt.''\\ \raggedleft
89: -- Einar Stefferud, Network Management Associates
90: \end{quote}
91:
92: \item WHAT THE VENDORS SAY:
93: \begin{quote}\em
94: ``$\ldots$ protection of your investment while assuring a path to an OSI
95: future.''\\ \raggedleft
96: -- Vendor A
97: \end{quote}
98: AND
99: \begin{quote}\em
100: ``$\ldots$ plans for a smooth, painless guaranteed migration to OSI standards
101: as they are approved.''\\ \raggedleft
102: --Vendor B
103: \end{quote}
104:
105: \item THE SAD TRUTH:
106: \begin{quote}\em
107: ``You can't win, and you can't quit, but you \underline{can} reduce the
108: pain.''\\ \raggedleft
109: -- Marshall Rose, The Wollongong Group
110: \end{quote}
111:
112: \end{nrtc}
113: \end{bwslide}
114:
115:
116: \begin{bwslide}
117: \part {BACKGROUND}\bf
118:
119: \begin{nrtc}
120: \item CONCEPTS
121:
122: \item TERMINOLOGY
123:
124: \item HISTORY
125:
126: \item METRICS FOR COMPARISON
127: \end{nrtc}
128: \end{bwslide}
129:
130:
131: \begin{bwslide}
132: \ctitle {THE FUNDAMENTAL ASSUMPTION}
133:
134: \begin{nrtc}
135: \item TCP/IP IS HERE TODAY, WIDELY INSTALLED, AND USEFUL
136:
137: \item OSI WILL EVENTUALLY REPLACE TCP/IP AS THE OFF-THE-SHELF TECHNOLOGY FOR
138: BUILDING INTEROPERABLE SYSTMS
139:
140: \item BOTH WILL BE SIMULTANEOUSLY WIDESPREAD FOR QUITE SOME TIME
141: \begin{nrtc}
142: \item DURING WHICH OSI WILL GAIN DOMINANCE
143: \end{nrtc}
144: \end{nrtc}
145: \end{bwslide}
146:
147:
148: \begin{bwslide}
149: \part* {CONCEPTS}\bf
150:
151: \begin{nrtc}
152: \item TRANSITION:
153: \begin{nrtc}
154: \item TO MOVE FROM ONE PROTOCOL SUITE TO ANOTHER
155: \end{nrtc}
156:
157: \item COEXISTENCE:
158: \begin{nrtc}
159: \item TO LIVE TOGETHER WITHOUT HOSTILITY OR CONFLICT DESPITE
160: DIFFERENCES
161: \end{nrtc}
162:
163: \item MIGRATION:
164: \begin{nrtc}
165: \item TO MOVE BACK AND FORTH, AS THE SEASONS CHANGE
166: \end{nrtc}
167: \end{nrtc}
168: \end{bwslide}
169:
170:
171: \begin{bwslide}
172: \ctitle {MAPPINGS}
173:
174: \begin{nrtc}
175: \item TRANSITION AND COEXISTENCE CAN BE DESCRIBED BY THE MAPPINGS THEY
176: REQUIRE
177:
178: \item SOME MAPPINGS ARE SIMPLE
179: \begin{nrtc}
180: \item i.e., SYNTACTIC CHANGES
181: \end{nrtc}
182:
183: \item SOME MAPPINGS ARE COMPLEX
184: \begin{nrtc}
185: \item i.e., SEMANTIC CHANGES
186: \end{nrtc}
187:
188: \item THE MORE COMPLEX THE MAPPING, THE GREATER THE LOSS OF INFORMATION OR
189: INTENT
190: \end{nrtc}
191: \end{bwslide}
192:
193:
194: \begin{bwslide}
195: \part* {TERMINOLOGY}\bf
196:
197: \begin{nrtc}
198: \item WE'LL FAVOR OSI TERMINOLOGY, BUT STILL NEED SOME INTERNET (TCP/IP)
199: TERMINOLOGY
200:
201: \item TWO BASIC TERMS
202: \begin{nrtc}
203: \item GATEWAY: GENERIC TO ANY LEVEL, COMPLEX
204:
205: \item BRIDGE: GENERIC TO ANY LEVEL, SIMPLE
206: \end{nrtc}
207: \end{nrtc}
208: \end{bwslide}
209:
210:
211: \begin{bwslide}
212: \ctitle {SERVICE SEMANTICS}
213:
214: \begin{nrtc}
215: \item STORE-AND-FORWARD
216: \begin{nrtc}
217: \item SERVICE SEMANTICS CARRIED MULTI-HOP VIA FORWARDERS
218: \end{nrtc}
219:
220: \item END-TO-END
221: \begin{nrtc}
222: \item SERVICE SEMANTICS CARRIED FROM ORIGINATOR TO RECIPIENT
223:
224: \item MAY BE SUPPORTED BY AN UNDERYLING STORE-AND-FORWARD SERVICE
225: \end{nrtc}
226: \end{nrtc}
227: \end{bwslide}
228:
229:
230: \begin{bwslide}
231: \ctitle {SERVICE SEMANTICS (cont.)}
232:
233: \vskip.5in
234: \diagram[p]{figure3}
235: \end{bwslide}
236:
237:
238: \begin{bwslide}
239: \ctitle {PROTOCOL SUITE}
240:
241: \begin{nrtc}
242: \item A COLLECTION OF PROTOCOLS RELATED:
243: \begin{nrtc}
244: \item ADMINISTRATIVELY, BY AN ORGANIZATION\\ (e.g., ISO/IEC); and,
245:
246: \item PHILOSOPHICALLY, BY A REFERENCE MODEL\\ (e.g., the ARM)
247: \end{nrtc}
248:
249: \item FOR OUR PURPOSES, THERE ARE ONLY TWO:
250: \begin{nrtc}
251: \item THE OSI SUITE OF PROTOCOLS
252:
253: \item THE INTERNET SUITE OF PROTOCOLS
254: \end{nrtc}
255: \end{nrtc}
256: \end{bwslide}
257:
258:
259: \begin{bwslide}
260: \ctitle {APPLICATIONS}
261:
262: \begin{nrtc}
263: \item APPLICATION CLASS
264: \begin{nrtc}
265: \item A SET OF APPLICATIONS RELATED TO A PARTICULAR ACTIVITY,
266: e.g., FILE TRANSFER, IRREGARDLESS OF PROTOCOL SUITE
267: \end{nrtc}
268:
269: \item APPLICATION INSTANCE
270: \begin{nrtc}
271: \item A MEMBER OF AN APPLICATION CLASS SPECIFIC TO A PARTICULAR
272: PROTOCOL SUITE, e.g., FTAM
273: \end{nrtc}
274: \end{nrtc}
275: \end{bwslide}
276:
277:
278: \begin{bwslide}
279: \part* {HISTORY}\bf
280:
281: \begin{nrtc}
282: \item A VERY BRIEF INTRODUCTION TO THE TWO PROTOCOL SUITES
283:
284: \item WE'LL ATTEMPT TO TAKE A NON-PARTISAN VIEW (ha!)
285: \end{nrtc}
286: \end{bwslide}
287:
288:
289: \begin{bwslide}
290: \ctitle {INTERNET SUITE}
291:
292: \begin{nrtc}
293: \item SPONSORED BY THE U.S.~DoD
294: \begin{nrtc}
295: \item GREW OUT OF EARLY (D)ARPA RESEARCH INTO SURVIVABLE NETWORKS
296: \end{nrtc}
297: BASIS FROM THE ARPANET REFERENCE MODEL (ARM)
298:
299: \item SPECIFIED IN ``REQUEST FOR COMMENTS'' SERIES (RFCs) AND
300: U.S.~MILITARY STANDARDS (MILSTDs)
301:
302: \item CURRENT GENERATION BASED ON
303: \begin{nrtc}
304: \item CONNECTION-ORIENTED TRANSPORT SERVICE,
305: PROVIDED BY THE TCP; AND,
306:
307: \item CONNECTIONLESS-MODE NETWORK SERVICE,
308: PROVIDED BY THE IP
309: \end{nrtc}
310:
311: \item MAJOR EMPHASIS ON CONNECTIVITY OF DIVERSE SUB-NETWORKS
312: \begin{nrtc}
313: \item EXCELLENT RESEARCH CONTINUES, TO THIS DAY, ON THESE ISSUES
314: \end{nrtc}
315: \end{nrtc}
316: \end{bwslide}
317:
318:
319: \begin{bwslide}
320: \ctitle {INTERNET SUITE (cont.)}
321:
322: \begin{nrtc}
323: \item SEVERAL PRODUCTION APPLICATIONS
324: \begin{nrtc}
325: \item SIMPLE MAIL TRANSFER PROTOCOL (SMTP)
326:
327: \item FILE TRANSFER PROTOCOL (FTP)
328:
329: \item TELNET (VIRTUAL TERMINAL PROTOCOL)
330:
331: \item DOMAIN NAME SYSTEM (DNS)
332: \end{nrtc}
333: ALL OF WHICH ARE RATHER SIMPLE
334:
335: \item APPLICATIONS CONTAIN THEIR OWN IMPLICIT SESSION AND PRESENTATION
336: MECHANISMS
337:
338: \item NOT SURPRISING, CONSIDERING THAT THESE APPLICATIONS ARE ALL BASED ON
339: 15~YEAR OLD MODELS!
340: \end{nrtc}
341: \end{bwslide}
342:
343:
344: \begin{bwslide}
345: \ctitle {INTERNET PROTOCOLS}
346:
347: \vskip.5in
348: \diagram[p]{figure4}
349: \end{bwslide}
350:
351:
352: \begin{bwslide}
353: \ctitle {OSI SUITE}
354:
355: \begin{nrtc}
356: \item SPONSORED BY THE INTERNATIONAL COMMUNITY
357: \begin{nrtc}
358: \item IN PARTICULAR THE ISO
359: \end{nrtc}
360: BASIS FROM THE OSI REFERENCE MODEL (OSIRM)
361:
362: \item SPECIFIED IN ``STANDARDS'' (ISO/IEC) AND RECOMMENDATIONS (CCITT)
363:
364: \item BASED ON
365: \begin{nrtc}
366: \item CONNECTION-ORIENTED TRANSPORT SERVICE,
367: PROVIDED BY ONE OF FIVE DIFFERENT TPs; DEPENDING ON
368:
369: \item THE NETWORK SERVICE AVAILABLE (CONS or CLNS)
370: \end{nrtc}
371:
372: \item DIFFICULT TO IDENTIFY THE ``MAJOR'' EMPHASIS
373: \end{nrtc}
374: \end{bwslide}
375:
376:
377: \begin{bwslide}
378: \ctitle {OSI SUITE (cont.)}
379:
380: \begin{nrtc}
381: \item SEVERAL INTERESTING APPLICATIONS
382: \begin{nrtc}
383: \item MESSAGE HANDLING SYSTEMS (MHS)
384:
385: \item FILE TRANSFER, ACCESS AND MANAGEMENT (FTAM)
386:
387: \item VIRTUAL TERMINAL (VT)
388:
389: \item DIRECTORY SERVICES (DS)
390: \end{nrtc}
391:
392: \item APPLICATIONS EVOLVING QUITE HEAVILY OVER THE LAST FEW YEARS
393:
394: \item MUCH MORE AMBITIOUS THAN THEIR INTERNET COUNTERPARTS
395: \end{nrtc}
396: \end{bwslide}
397:
398:
399: \begin{bwslide}
400: \ctitle {OSI PROTOCOLS}
401:
402: \vskip.5in
403: \diagram[p]{figure5}
404: \end{bwslide}
405:
406:
407: \begin{bwslide}
408: \ctitle {A BRIEF COMPARISON}
409:
410: \begin{nrtc}
411: \item NOTE THAT CONCERNS DIFFER
412: \begin{nrtc}
413: \item NETWORK USERS: APPLICATION-LEVEL FUNCTIONALITY
414:
415: \item NETWORK ADMINISTRATORS: NETWORK AND TRANSPORT ISSUES
416: \end{nrtc}
417:
418: \item FOR APPLICATIONS, ONCE IMPLEMENTED, THE OSI SUITE IS SUPERIOR
419:
420: \item FOR NETWORK/TRANSPORT ISSUES, THE INTERNET SUITE IS SUPERIOR:
421: \begin{nrtc}
422: \item TSDU(PACKET) ORIENTATION PREVENTS USE OF SOPHISTICATED
423: CONGESTION COLLAPSE ALGORITHMS
424:
425: \item SIMPLISTIC RETRANSMISSION ALGORITHMS
426:
427: \item INAPPROPRIATE END-TO-END CHECKSUM
428: \end{nrtc}
429: \end{nrtc}
430: \end{bwslide}
431:
432:
433: \begin{bwslide}
434: \part* {METRICS FOR COMPARISON}\bf
435:
436: \begin{nrtc}
437: \item CAN JUDGE A TRANSITION/COEXISTENCE SCHEME USING DIFFERENT
438: CRITERIA
439:
440: \item THE FOUR WE'LL FOCUS ON ARE ALL SUBJECTIVE;
441: \begin{nrtc}
442: \item TECHNICAL SOLUTIONS DO NOT EXIST IN A VACUUM
443:
444: \item THEY MUST BE EVALUATED IN THE CONTEXT OF A TARGET ENVIRONMENT
445: \end{nrtc}
446: \end{nrtc}
447: \end{bwslide}
448:
449:
450: \begin{bwslide}
451: \ctitle {METRICS FOR COMPARISON (cont.)}
452:
453: \begin{nrtc}
454: \item PERFORMANCE:
455: \begin{nrtc}
456: \item THROUGHPUT, LATENCY
457:
458: \item EFFECT ON OTHER APPLICATIONS
459: \end{nrtc}
460:
461: \item FLEXIBILITY:
462: \begin{nrtc}
463: \item RANGE OF APPLICABILITY
464: \end{nrtc}
465: \end{nrtc}
466: \end{bwslide}
467:
468:
469: \begin{bwslide}
470: \ctitle {METRICS FOR COMPARISON (cont.)}
471:
472: \begin{nrtc}
473: \item TRANSPARENCY:
474: \begin{nrtc}
475: \item USAGE CONTINUITY
476:
477: \item SEAMLESS USER INTERFACE
478: \end{nrtc}
479:
480: \item AMENABILITY:
481: \begin{nrtc}
482: \item MANAGEABILITY
483: \end{nrtc}
484: \end{nrtc}
485: \end{bwslide}
486:
487:
488: \begin{bwslide}
489: \ctitle {SEVERAL CANDIDATES}
490:
491: \begin{nrtc}
492: \item PROTOCOL-BASED APPROACHES
493: \begin{nrtc}
494: \item DUAL STACK
495:
496: \item APPLICATION GATEWAYS
497:
498: \item TRANSPORT GATEWAYS
499: \end{nrtc}
500:
501: \item SERVICE-BASED APPROACHES
502: \begin{nrtc}
503: \item TRANSPORT-SERVICE BRIDGES
504:
505: \item NETWORK TUNNELS
506: \end{nrtc}
507:
508: \item NONE OF THESE TECHNIQUES ARE SPECIFIC TO THE PROBLEM OF
509: \begin{nrtc}
510: \item INTERNET $\mapsto$ OSI
511: \end{nrtc}
512: \end{nrtc}
513: \end{bwslide}
514:
515:
516: \begin{bwslide}
517: \part {PROTOCOL-BASED APPROACHES}\bf
518:
519: \begin{nrtc}
520: \item THE ``STANDARD'' METHODS USED TO INTERCONNECT DIFFERENT
521: PROTOCOL STACKS
522:
523: \item THESE EMPHASIZE THE PROTOCOLS IN EACH STACK
524:
525: \item HENCE THEY REINFORCE THE BOUNDARIES BETWEEN TCP/IP AND OSI
526: \end{nrtc}
527: \end{bwslide}
528:
529:
530: \begin{bwslide}
531: \part* {DUAL STACK}\bf
532:
533: \begin{nrtc}
534: \item PUT BOTH PROTOCOL SUITES IN ALL HOSTS
535:
536: \item WORKS WELL, IF YOU CAN CHANGE EVERYTHING ON THE NETWORK
537: \begin{quote}\em
538: ``Nice work, if you can get it.''\\ \raggedleft
539: -- Groucho Marx, Monkey Business, Paramount Pictures (1931)
540: \end{quote}
541: \end{nrtc}
542: \end{bwslide}
543:
544:
545: \begin{bwslide}
546: \ctitle {DUAL STACK (cont.)}
547:
548: \vskip.5in
549: \diagram[p]{figure1}
550: \end{bwslide}
551:
552:
553: \begin{bwslide}
554: \ctitle {TALKING TO UNI-STACK HOSTS}
555:
556: \begin{nrtc}
557: \item QUESTION: HOW TO DECIDE WHICH APPLICATION INSTANCE,
558: \begin{nrtc}
559: \item APPL-$\alpha$ OR APPL-$\gamma$,
560: \end{nrtc}
561: TO USE?
562:
563: \item TWO ANSWERS:
564: \begin{nrtc}
565: \item DEPEND ON THE USER TO KNOW AND INVOKE THE RIGHT PROGRAM
566:
567: \item DEVELOP A GENERIC APPLICATION WHICH SUPPORTS BOTH CLASSES
568: \end{nrtc}
569:
570: \item IN THE LATTER CASE, NEED AN UP-TO-DATE DIRECTORY TO DO THIS RELIABLY
571: \end{nrtc}
572: \end{bwslide}
573:
574:
575: \begin{bwslide}
576: \ctitle {GENERIC APPLICATION INSTANCE}
577:
578: \vskip.5in
579: \diagram[p]{figure6}
580: \end{bwslide}
581:
582:
583: \begin{bwslide}
584: \ctitle {AN IMPLEMENTATION OF DUAL-STACK}
585:
586: \begin{nrtc}
587: \item ENVIRONMENT: \unix/~SVR3 (STREAMS)
588:
589: \item ACCESS TO LOWER-LAYER PROTOCOLS VIA TRANSPORT LAYER INTERFACE (TLI)
590:
591: \item NOTE THAT ALTHOUGH TLI PROVIDES A UNIFORM INTERFACE,
592: IT DOES NOT PROVIDE A UNIFORM SERVICE:
593: \begin{nrtc}
594: \item PACKET- vs. STREAM-ORIENTATION
595:
596: \item GRACEFUL RELEASE
597:
598: \item EXPEDITED vs. URGENT DATA
599:
600: \item ADDRESSING
601: \end{nrtc}
602: \end{nrtc}
603: \end{bwslide}
604:
605:
606: \begin{bwslide}
607: \ctitle {GENERIC APPLICATION INSTANCE}
608:
609: \vskip.5in
610: \diagram[p]{figure11}
611: \end{bwslide}
612:
613:
614: \begin{bwslide}
615: \ctitle {SCORECARD}
616:
617: \begin{nrtc}
618: \item PERFORMANCE: NO DEGRADATION
619:
620: \item FLEXIBILITY: GOOD
621:
622: \item TRANSPARENCY:
623: \begin{nrtc}
624: \item ASSUMING REMOTE SYSTEM SUPPORTS AT LEAST ONE OF THE PROTOCOL
625: STACKS, THEN HIGH TRANSPARENCY BY USING COMMON SERVICE
626: INTERFACE
627: \end{nrtc}
628:
629: \item AMENABILITY:
630: \begin{nrtc}
631: \item BOTH END- AND INTERMEDIATE-SYSTEMS MUST RUN BOTH PROTOCOLS
632:
633: \item INTRODUCES ADMINISTRATIVE PROBLEMS AS THERE ARE NOW TWO
634: LOGICAL NETWORKS
635: \begin{nrtc}
636: \item MANAGEMENT OF BOTH \underline{PLUS} CONTENTION BETWEEN THEM
637: \end{nrtc}
638: \end{nrtc}
639: \end{nrtc}
640: \end{bwslide}
641:
642:
643: \begin{bwslide}
644: \part* {APPLICATION GATEWAYS}\bf
645:
646: \begin{nrtc}
647: \item A WELL-KNOWN, BUT LITTLE-UNDERSTOOD TECHNOLOGY
648: \begin{nrtc}
649: \item USED IN MESSAGE HANDLING QUITE A BIT
650: \end{nrtc}
651:
652: \item MOST ARE QUITE TERRIBLE
653: \begin{quote}\em
654: ``Sometimes when you try to turn an apple into an orange you get back a
655: lemon.''\\ \raggedleft
656: -- Michael Padlipsky, The Elements of Networking Style (1985)
657: \end{quote}
658: \end{nrtc}
659: \end{bwslide}
660:
661:
662: \begin{bwslide}
663: \ctitle {APPLICATION GATEWAYS (cont.)}
664:
665: \vskip.5in
666: \diagram[p]{figure2}
667: \end{bwslide}
668:
669:
670: \begin{bwslide}
671: \ctitle {IMPERFECT MAPPINGS}
672:
673: \begin{nrtc}
674: \item BECAUSE THEY ARE AT THE HIGHEST LAYER IN THE STACK,
675: APPLICATION GATEWAYS TEND TO PERFORM SEMANTIC MAPPINGS
676:
677: \item THESE ARE ACCOMPANIED BY A LOSS OF INFORMATION
678:
679: \item SOMETIMES THE LOSS IS ONLY ANNOYING
680: \begin{nrtc}
681: \item e.g., ``FUNNY LOOKING'' MAIL ADDRESSES
682: \end{nrtc}
683:
684: \item SOMETIMES THE LOSS IS CATASTROPHIC
685: \begin{nrtc}
686: \item e.g., ROUTING LOOPS
687: \end{nrtc}
688: \end{nrtc}
689: \end{bwslide}
690:
691:
692: \begin{bwslide}
693: \ctitle {AN IMPLEMENATION OF APPLICATION-GATEWAY}
694:
695: \begin{nrtc}
696: \item TWO KINDS OF IMPLEMENATIONS
697:
698: \item STAGING (TRUE STORE-AND-FORWARD):
699: \begin{nrtc}
700: \item TOP-LEVEL PROTOCOL TRANSACTIONS ARE GROUPED AT THE GATEWAY
701:
702: \item REQUIRES LOCAL STORAGE, BUT MAY PERMIT BETTER MAPPINGS
703: \end{nrtc}
704:
705: \item IN-SITU (VIRTUAL END-TO-END):
706: \begin{nrtc}
707: \item NO PROTOCOL TRANSACTIONS ARE GROUPED
708:
709: \item MAPPINGS ARE ``ON THE FLY''\\ (AND PERHAPS LESS PRECISE)
710:
711: \item END-TO-END RESPONSE IS FASTER
712: \end{nrtc}
713: \end{nrtc}
714: \end{bwslide}
715:
716:
717: \begin{bwslide}
718: \ctitle {A STAGING IMPLEMENTATION}
719:
720: \vskip.5in
721: \diagram[p]{figure12}
722: \end{bwslide}
723:
724:
725: \begin{bwslide}
726: \ctitle {AN IN-SITU IMPLEMENTATION}
727:
728: \vskip.5in
729: \diagram[p]{figure13}
730: \end{bwslide}
731:
732:
733: \begin{bwslide}
734: \ctitle {SCORECARD}
735:
736: \begin{nrtc}
737: \item PERFORMANCE: USUALLY POOR, BUT ACCEPTABLE FOR STORE-AND-FORWARD
738: APPLICATIONS
739: \begin{nrtc}
740: \item TYPICALLY ALSO INTRODUCES ADDITIONAL NETWORK TRAFFIC
741: \end{nrtc}
742:
743: \item FLEXIBILITY: NONE; EACH A-GWY IS A SPECIAL-PURPOSE SOFTWARE BOX
744:
745: \item TRANSPARENCY:
746: \begin{nrtc}
747: \item TO SERVICE: OFTEN LOSES SIGNIFICANT FUNCTIONALITY
748:
749: \item TO USERS: POSSIBLE, BUT NOT LIKELY (e.g., IN AN FTAM/FTP A-GWY,
750: USERS EMBED HOSTNAMES IN FILENAMES)
751: \end{nrtc}
752:
753: \item AMENABILITY:
754: \begin{nrtc}
755: \item REQUIRES NO END-SYSTEM MODIFICATION
756:
757: \item MAY INTRODUCE ADMINISTRATIVE PROBLEMS
758: \end{nrtc}
759: \end{nrtc}
760: \end{bwslide}
761:
762:
763: \begin{bwslide}
764: \part* {TRANSPORT GATEWAYS}\bf
765:
766: \begin{nrtc}
767: \item IDEA: GATEWAY AT THE TRANSPORT LAYER SO AS TO AVOID NEEDING
768: MULTIPLE APPLICATION GATEWAYS
769: \begin{quote}\em
770: ``We could do it, but it would be wrong.''\\ \raggedleft
771: -- Richard Nixon
772: \end{quote}
773:
774: \item ALTHOUGH THE OSI (TP4) AND INTERNET (TCP) TRANSPORT PROTOCOLS DIFFER,
775: THE SERVICE IS QUITE SIMILAR
776:
777: \item HENCE, IT IS TECHNICALLY FEASIBLE TO PERFORM THE MAPPINGS
778: \begin{nrtc}
779: \item (ALTHOUGH IT'S A LOT OF HARD WORK)
780: \end{nrtc}
781: \end{nrtc}
782: \end{bwslide}
783:
784:
785: \begin{bwslide}
786: \ctitle {TRANSPORT GATEWAYS (cont.)}
787:
788: \vskip.5in
789: \diagram[p]{figure14}
790: \end{bwslide}
791:
792:
793: \begin{bwslide}
794: \ctitle {THE OBVIOUS QUESTION}
795:
796: \begin{nrtc}
797: \item WHAT APPLICATION DO YOU RUN WHEN USING THIS?
798: \begin{nrtc}
799: \item CAN'T RUN INTERNET APPLICATIONS IN THE OSI NETWORK,
800: SINCE THE TRANSPORT GATEWAY YIELDS OSI TRANSPORT SEMANTICS
801:
802: \item CAN'T RUN OSI APPLICATIONS IN THE INTERNET NETWORK,
803: SINCE THE TRANSPORT GATEWAY YIELDS INTERNET TRANSPORT SEMANTICS
804: \end{nrtc}
805:
806: \item THIS APPROACH FAILS BECAUSE IT PRESENTS DIFFERENT SERVICE SEMANTICS
807: IN EACH NETWORK
808: \end{nrtc}
809: \end{bwslide}
810:
811:
812: \begin{bwslide}
813: \part {RE-DEFINING THE PROBLEM}\bf
814:
815: \begin{nrtc}
816: \item BY THE TIME OSI-BASED NETWORKS ARE TRULY WIDESPREAD,
817: TCP/IP-BASED NETWORKS WILL ALREADY OFFER A MIX OF SERVICES:
818: \begin{nrtc}
819: \item SUCH AS FTAM AND MHS, IN ADDITION TO FTP AND SMTP
820: \end{nrtc}
821:
822: \item IN OTHER WORDS, THE TRANSITION TO OSI BEGINS WITH NEW APPLICATIONS ON
823: HOSTS AND NO CHANGES TO THE NETWORK
824: \end{nrtc}
825: \end{bwslide}
826:
827:
828: \begin{bwslide}
829: \ctitle {WOULD THIS REALLY HAPPEN?}
830:
831: \begin{nrtc}
832: \item RECALL THAT USERS ARE INTERESTED IN \underline{SERVICES} NOT
833: \underline{PROTOCOLS}
834:
835: \item THE OSI APPLICATIONS ARE MUCH RICHER THAN THEIR INTERNET COUNTERPARTS
836:
837: \item IN CONTRAST, AT THE LOWER-LAYERS THE INTERNET SUITE ``WORKS BETTER''
838: \begin{nrtc}
839: \item AS SUCH, IT IS UNLIKELY TO BE REPLACED BY THE OSI LOWER-LAYERS
840: FOR QUITE SOME TIME
841: \end{nrtc}
842: \end{nrtc}
843: \end{bwslide}
844:
845:
846: \begin{bwslide}
847: \ctitle {ONLY ONE LITTLE PROBLEM$\ldots$}
848:
849: \begin{nrtc}
850: \item HOW TO RUN THE OSI UPPER-LAYERS IN A TCP/IP-BASED NETWORK?
851:
852: \item A SOLUTION IS OFFERED BY LAYERING
853: \begin{nrtc}
854: \item THE OSI TRANSPORT \underline{SERVICE} IS VERY SIMPLE
855:
856: \item CAN WE PROVIDE AN EMULATION OF THAT SERVICE USING TCP?
857: \end{nrtc}
858: \end{nrtc}
859: \end{bwslide}
860:
861:
862: \begin{bwslide}
863: \ctitle {SERVICE EMULATOR AT TRANSPORT}
864:
865: \vskip.5in
866: \diagram[p]{figure7}
867: \end{bwslide}
868:
869:
870: \begin{bwslide}
871: \ctitle {THE OSI TRANSPORT SERVICE}
872:
873: \begin{nrtc}
874: \item ALTHOUGH THE SERVICE IS VERY SIMPLE, THERE ARE ACTUALLY FIVE DIFFERENT
875: ISO PROTOCOLS WHICH CAN BE USED (TP0$\ldots$TP4)
876:
877: \item PROTOCOLS CAN BE DIVIDED INTO TWO CLASSES, BASED ON THE UNDERLYING
878: NETWORK SERVICE
879: \begin{nrtc}
880: \item A CONNECTION-ORIENTED NETWORK SERVICE (CONS), e.g., X.25
881:
882:
883: \item A CONNECTIONLESS-MODE NETWORK SERVICE (CLNS), e.g., CLNP
884: \end{nrtc}
885: \end{nrtc}
886: \end{bwslide}
887:
888:
889: \begin{bwslide}
890: \ctitle {OSI TRANSPORT SERVICES\\ ON TOP OF THE DoD TCP}
891:
892: \begin{nrtc}
893: \item IDEA: TAKE THE SIMPLEST PROTOCOL (TP0) AND DEFINE A MAPPING ONTO
894: THE DoD TCP
895:
896: \item{} [RFC983], PUBLISHED IN APRIL OF 1986, WAS A FIRST ATTEMPT AT THIS
897:
898: \item TWO VERSIONS AND 13 MONTHS LATER, [RFC1006] GOT IT RIGHT, TELLING
899: ``HOW TO SPEAK TP0 OVER THE TCP''
900:
901: \item NOTE: THIS APPROACH IS NOT UNIQUE TO TCP/IP-BASED NETWORKS!
902: \end{nrtc}
903: \end{bwslide}
904:
905:
906: \begin{bwslide}
907: \ctitle {OSI TRANSPORT SERVICES\\ ON TOP OF THE DoD TCP (cont.)}
908:
909: \vskip.25in
910: \diagram[p]{figure8}
911: \end{bwslide}
912:
913:
914: \begin{bwslide}
915: \part {SERVICE-BASED APPROACHES}\bf
916:
917: \begin{nrtc}
918: \item BACK TO OUR PREDICATION:
919: \begin{nrtc}
920: \item TCP/IP-BASED NETWORKS WILL OFFER A MIX OF SERVICES
921: \end{nrtc}
922: \end{nrtc}
923: \end{bwslide}
924:
925:
926: \begin{bwslide}
927: \ctitle {OBSERVATION}
928:
929: \begin{nrtc}
930: \item GIVEN THE ABOVE ASSUMPTION, IT SHOULD BE NOTED THAT:
931: \begin{nrtc}
932: \item WE HAVE TWO COMMUNITIES USING THE SAME APPLICATIONS
933: (OSI), AND
934:
935: \item ONLY THE UNDERLYING ``TS-STACK'' WILL DIFFER BETWEEN THE TWO:
936: \begin{nrtc}
937: \item IN THE OSI COMMUNITY: TP4/CLNP/$\ldots$
938:
939: \item IN THE TCP COMMUNITY: [RFC1006]/TCP/IP/$\ldots$
940: \end{nrtc}
941: \end{nrtc}
942:
943: \item THIS LEADS US TO POSTULATE AN INTERESTING COEXISTENCE
944: STRATEGY:
945: \begin{nrtc}
946: \item LET'S RUN OSI APPLICATIONS, END-TO-END, BETWEEN THE TWO
947: \end{nrtc}
948:
949: \item IN A SENSE, THIS IS A HYBRID OF THE TWO PREVIOUS APPROACHES,
950: INTENDED TO MINIMIZE THE DISADVANTAGES OF EACH
951: \begin{nrtc}
952: \item SAME APPLICATION PROTOCOL,\\
953: BUT DIFFERENT UNDERYLING LAYERS
954: \end{nrtc}
955: \end{nrtc}
956: \end{bwslide}
957:
958:
959: \begin{bwslide}
960: \part* {TRANSPORT-SERVICE BRIDGES}\bf
961:
962: \begin{nrtc}
963: \item INTRODUCE A TRANSPORT ENTITY CALLED THE ``TS-BRIDGE''
964: \begin{quote}\em
965: ``Users are interested in services, not protocols.''\\ \raggedleft
966: -- Marshall Rose, The Wollongong Group
967: \end{quote}
968:
969: \item THE TS-BRIDGE ``COPIES'' SERVICE PRIMITIVES FROM ONE COMMUNITY TO THE
970: OTHER, e.g.:
971: \begin{nrtc}
972: \item UPON RECEIVING A T-CONNECT.INDICATION PRIMITIVE FROM ONE
973: TS-STACK,
974:
975: \item IT ISSUES A T-CONNECT.REQUEST PRIMITIVE TO THE OTHER TS-STACK
976: \end{nrtc}
977: \end{nrtc}
978: \end{bwslide}
979:
980:
981: \begin{bwslide}
982: \ctitle {TRANSPORT-SERVICE BRIDGES (cont.)}
983:
984: \vskip.5in
985: \diagram[p]{figure9}
986: \end{bwslide}
987:
988:
989: \begin{bwslide}
990: \ctitle {THE TS-BRIDGE AND THE OSI MODEL}
991:
992: \begin{nrtc}
993: \item THE TS-BRIDGE IS A LEVEL-FOUR ROUTER
994:
995: \item POTENTIAL PROBLEMS:
996: \begin{nrtc}
997: \item THE TS-BRIDGE MAINTAINS STATE AS TO THE EXISTING CONNECTIONS
998:
999: \item TWO CHECKSUMS, AND NEITHER REALLY END-TO-END
1000:
1001: \item \underline{MAY} THWART SOPHISTICATED BACK-PRESSURE TECHNIQUES
1002: \end{nrtc}
1003: \end{nrtc}
1004: \end{bwslide}
1005:
1006:
1007: \begin{bwslide}
1008: \ctitle {TRANSPARENT USE OF TS-BRIDGES}
1009:
1010: \begin{nrtc}
1011: \item BY JUDICIOUS USE OF DIRECTORY SERVICES, SELECTION OF THE
1012: TS-BRIDGE CAN BE MADE TRANSPARENT ON BOTH ENDPOINTS
1013:
1014: \item CONSIDER A ``TYPICAL'' PRESENTATION ADDRESS:
1015: \[\begin{tabular}{ll}
1016: network address:& CLNP 470005001700$\ldots$5301\\
1017: transport selector:& 1\\
1018: session selector:& ``FTAM''\\
1019: presentation selector:& null
1020: \end{tabular}\]
1021:
1022: \item A SLIGHTLY DIFFERENT ENTRY IS RETURNED FOR HOSTS IN THE
1023: OPPOSITE COMMUNITY:
1024: \[\begin{tabular}{ll}
1025: network address:& ts-bridge's network address\\
1026: transport selector:& \begin{tabular}[t]{ll}
1027: network address:&
1028: CLNP 47 $\ldots$\\
1029: transport selector:& 1
1030: \end{tabular}\\
1031: session selector:& ``FTAM''\\
1032: presentation selector:& null
1033: \end{tabular}\]
1034: \end{nrtc}
1035: \end{bwslide}
1036:
1037:
1038: \begin{bwslide}
1039: \ctitle {ANOTHER PROBLEM SOLVED:\\ ISO CONS versus CLNS}
1040:
1041: \begin{nrtc}
1042: \item IN GENERAL, THE TS-BRIDGE SHOWS HOW TO PERFORM
1043: ``IMPEDENCE MATCHING'' BETWEEN TWO PROTOCOLS WHICH OFFER THE
1044: SAME SERVICE INTERFACE, e.g., OUR USE IS:
1045: \begin{nrtc}
1046: \item PROTOCOLS: TP4/CLNP AND TP0/TCP
1047:
1048: \item SERVICE: OSI TRANSPORT SERVICE
1049: \end{nrtc}
1050:
1051: \item THIS IS SUSPICIOUSLY SIMILAR TO THE ISO TP4/CLNS vs. TP0/CONS PROBLEM:
1052: \begin{nrtc}
1053: \item PROTOCOLS: TP4/CLNP AND TP0/X.25
1054:
1055: \item SERVICE: OSI TRANSPORT SERVICE
1056: \end{nrtc}
1057:
1058: \item THE TS-BRIDGE WILL ALSO WORK IN THIS ENVIRONMENT WITHOUT
1059: MEANINGFUL LOSS OF GENERALITY:
1060: \begin{nrtc}
1061: \item EXPEDITED DATA IS NEGOTIATED AWAY, AND
1062:
1063: \item INITIAL USER DATA RESULTS IN DISCONNECT
1064: \end{nrtc}
1065: \end{nrtc}
1066: \end{bwslide}
1067:
1068:
1069: \begin{bwslide}
1070: \ctitle {AN IMPLEMENTATION OF THE TS-BRIDGE}
1071:
1072: \begin{nrtc}
1073: \item AT UNIFORUM IN FEBRUARY, 1988, THE
1074: \begin{nrtc}
1075: \item TP4/CLNP to TP0/TCP
1076: \end{nrtc}
1077: ``IMPEDENCE MATCHING'' WAS DEMONSTRATED
1078:
1079: \item CURRENTLY, ALL THREE TS-STACKS
1080: \begin{nrtc}
1081: \item TP4/CLNP, TP0/X.25, TP0/TCP
1082: \end{nrtc}
1083: ARE BEING BRIDGED (ON A SINGLE HOST)
1084: \end{nrtc}
1085: \end{bwslide}
1086:
1087:
1088: \begin{bwslide}
1089: \ctitle {SCORECARD}
1090:
1091: \begin{nrtc}
1092: \item PERFORMANCE: FAIR; WHEN TS-BRIDGE IS MADE INTO A KERNEL-RESIDENT
1093: STREAMS MODULE IT SHOULD IMPROVE DRAMATICALLY
1094:
1095: \item FLEXIBILITY: HIGH; INDEPENDENT OF ANY APPLICATION
1096:
1097: \item TRANSPARENCY: TOTAL
1098:
1099: \item AMENABILITY:
1100: \begin{nrtc}
1101: \item TCP END-SYSTEMS MUST RUN ``NEW'' PROTOCOLS
1102: \begin{nrtc}
1103: \item BUT, NO MODIFICATIONS REQUIRED TO END-SYSTEM KERNELS
1104: \end{nrtc}
1105:
1106: \item MAY INTRODUCE ADMINISTRATIVE PROBLEMS (WHICH SHOULD BE SOLVED
1107: DYNAMICALLY BY DIRECTORY SERVICES)
1108: \end{nrtc}
1109: \end{nrtc}
1110: \end{bwslide}
1111:
1112:
1113: \begin{bwslide}
1114: \part* {NETWORK TUNNELS}\bf
1115:
1116: \begin{nrtc}
1117: \item IDEA: ENCAPSULATE CLNP INSIDE OF IP, TREATING IP AS SIMPLY A DATA LINK
1118: PROTOCOL
1119: \begin{quote}\em
1120: ``Encapsulation complies with the layering concept, but violates the notion
1121: of absolute levels.''\\ \raggedleft
1122: -- Danny Cohen and Jon Postel, ``The ISO Reference Model and Other Protocol
1123: Architectures'' (1983)
1124: \end{quote}
1125:
1126: \item NS-TUNNEL PERFORMS AS A ROUTER, REMOVING ONE DATA LINK HEADER AND
1127: ADDING ANOTHER
1128: \end{nrtc}
1129: \end{bwslide}
1130:
1131:
1132: \begin{bwslide}
1133: \ctitle {TUNNELING}
1134:
1135: \vskip.5in
1136: \diagram[p]{figure18}
1137: \end{bwslide}
1138:
1139:
1140: \begin{bwslide}
1141: \ctitle {NETWORK TUNNELS}
1142:
1143: \vskip.5in
1144: \diagram[p]{figure10}
1145: \end{bwslide}
1146:
1147:
1148: \begin{bwslide}
1149: \ctitle {INTERESTING FEATURES}
1150:
1151: \begin{nrtc}
1152: \item NO STATE MAINTAINED BY NS-TUNNEL
1153:
1154: \item A TRUE END-TO-END CHECKSUM
1155: \end{nrtc}
1156: \end{bwslide}
1157:
1158:
1159: \begin{bwslide}
1160: \ctitle {POTENTIAL PROBLEMS}
1161:
1162: \begin{nrtc}
1163: \item REQUIRES COMMON HIGHER-LEVEL PROTOCOLS (TRANSPORT AND ABOVE) ON BOTH
1164: END-SYSTEMS, BUT DOES NOT REQUIRE ALL INTERVENING ROUTERS TO USE THE
1165: SAME NETWORK PROTOCOL
1166:
1167: \item THE TCP END-SYSTEM IMPLEMENTATION CHOICES ARE SIMILAR TO NETBIOS OVER
1168: TCP [RFC1001/1002]
1169: \end{nrtc}
1170: \end{bwslide}
1171:
1172:
1173: \begin{bwslide}
1174: \ctitle {AN IMPLEMENATION OF AN NS-TUNNEL}
1175:
1176: \begin{nrtc}
1177: \item HAVEN'T SEE ANY YET
1178:
1179: \item REALLY NEED A LOT OF CLNP-BASED NETWORKS BEFORE THIS IS OF USE
1180:
1181: \item THIS WILL HAPPEN AT THE END OF THE TRANSITION PERIOD
1182: \end{nrtc}
1183: \end{bwslide}
1184:
1185:
1186: \begin{bwslide}
1187: \ctitle {SCORECARD}
1188:
1189: \begin{nrtc}
1190: \item PERFORMANCE: NO WORSE THAN TYPICAL CLNP-ROUTER (AND PROBABLY A LOT
1191: BETTER TOO!)
1192:
1193: \item FLEXIBILITY: HIGH (INDEPENDENT OF ANY APPLICATION)
1194:
1195: \item TRANSPARENCY: TOTAL
1196:
1197: \item AMENABILITY: TCP END-SYSTEMS MUST RUN BOTH TRANSPORT PROTOCOLS
1198: \end{nrtc}
1199: \end{bwslide}
1200:
1201:
1202: \begin{bwslide}
1203: \part {EXAMPLES}\bf
1204:
1205: \begin{nrtc}
1206: \item DoD OSI IMPLEMENTATION PLAN
1207:
1208: \item GENERIC EXAMPLE
1209:
1210: \item CONCLUSIONS
1211: \end{nrtc}
1212: \end{bwslide}
1213:
1214:
1215: \begin{bwslide}
1216: \part* {DoD OSI\\ IMPLEMENTATION PLAN}\bf
1217:
1218: \begin{nrtc}
1219: \item IMPLEMENT CAPABILITY TO USE OSI IN DoD INTERNETWORK ENVIRONMENT
1220: \begin{nrtc}
1221: \item OSI-POSIX PROJECT
1222: \end{nrtc}
1223:
1224: \item PROVIDE THE CAPABILITY FOR DoD AND OSI PROTOCOLS TO INTEROPERATE
1225: \begin{nrtc}
1226: \item FTAM-FTP GATEWAY
1227:
1228: \item MHS-SMTP GATEWAY
1229: \end{nrtc}
1230: \end{nrtc}
1231: \end{bwslide}
1232:
1233:
1234: \begin{bwslide}
1235: \ctitle {OSI-POSIX PROJECT}
1236:
1237: \begin{nrtc}
1238: \item GOAL: ACCELLERATE THE UBIQUITY OF OSI
1239:
1240: \item APPROACH: OPENLY AVAILABLE, COMPLETE OSI IMPLEMENTATION FOR NEXT MAJOR
1241: RELEASE OF BERKELEY \unix/
1242:
1243: \item FOR MORE DETAILS:
1244: \begin{quote}
1245: OSI PROTOCOLS WITHIN AN OPENLY AVAILABLE, POSIX-CONFORMANT, BERKELEY UNIX
1246: ENVIRONMENT
1247: \end{quote}
1248: APPEARING IN ConneXions, OCTOBER, 1988
1249: \end{nrtc}
1250: \end{bwslide}
1251:
1252:
1253: \begin{bwslide}
1254: \diagram[p]{figure15}
1255: \end{bwslide}
1256:
1257:
1258: \begin{bwslide}
1259: \diagram[p]{figure16}
1260: \end{bwslide}
1261:
1262:
1263: \begin{bwslide}
1264: \part* {GENERIC EXAMPLE}\bf
1265:
1266: \begin{nrtc}
1267: \item TWO PRONGS:
1268: \begin{nrtc}
1269: \item FAVOR USE OF OSI APPLICATIONS OVER TCP ON LAN MESH
1270:
1271: \item LOCATE APPLICATION GATEWAYS AND A TS-BRIDGE ON ALL NODES
1272: WITH WAN ATTACHMENETS
1273: \end{nrtc}
1274:
1275: \item AWAIT OSI LOWER-LAYERS TO BECOME COMPETITIVE
1276: \end{nrtc}
1277: \end{bwslide}
1278:
1279:
1280: \begin{bwslide}
1281: \ctitle {GENERIC EXAMPLE (cont.)}
1282:
1283: \begin{nrtc}
1284: \item EACH ATTACHMENT LOCUS SHOULD SUPPORT COEXISTENCE SERVICES
1285:
1286: \item IF RESOURCES PERMIT, SELECT ONE OTHER SYSTEM TO SUPPORT THESE
1287: SERVICES FOR USE BY LOCAL UNI-STACK HOSTS
1288:
1289: \item THIS ``COVERS ALL BASES'' BY HANDLING ALL POSSIBLE OSI COMBINATIONS
1290: WITH A BIT OF EXTRA REDUNDANCY
1291:
1292: \item MIGHT REQUIRE A BIT OF SOPHISTICATED USE FROM THE DIRECTORY
1293: \end{nrtc}
1294: \end{bwslide}
1295:
1296:
1297: \begin{bwslide}
1298: \ctitle {A LAN OF MANY COLORS}
1299:
1300: \vskip.5in
1301: \diagram[p]{figure17}
1302: \end{bwslide}
1303:
1304:
1305: \begin{bwslide}
1306: \part* {CONCLUSIONS}\bf
1307:
1308: \begin{quote}\em
1309: ``Optimality differs according to context.''\\ \raggedleft
1310: -- Michael Padlipsky, The Elements of Networking Style (1985)
1311: \end{quote}
1312: \end{bwslide}
1313:
1314:
1315: \begin{bwslide}
1316: \ctitle {CONCLUSIONS (cont.)}
1317:
1318: \begin{nrtc}
1319: \item TCP/IP-BASED NETWORKS WILL OFFER OSI APPLICATIONS
1320:
1321: \item COEXISTENCE IN THE SHORT TERM:
1322: \begin{nrtc}
1323: \item TS-BRIDGE MINIMIZES SOFTWARE INVESTMENT
1324: \end{nrtc}
1325:
1326: \item COEXISTENCE IN THE LONG TERM:
1327: \begin{nrtc}
1328: \item NS-TUNNEL MAXIMIZES PERFORMANCE AND ROBUSTNESS
1329: \end{nrtc}
1330:
1331: \item IF/WHEN THERE ARE NO MORE TCP/IP-BASED NETWORKS, THEN THE
1332: COEXISTENCE PERIOD IS OVER, AND TRANSITION IS A NON-ISSUE!
1333: \end{nrtc}
1334: \end{bwslide}
1335:
1336:
1337: \end{document}
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