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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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