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1.1 root 1: \documentstyle [small,blackandwhite] {NRslides}
2:
3: \author {S.E. Kille \\
4: Department of Computer Science \\
5: University College London}
6:
7: \date {October 1988}
8: \raggedright
9: \title {ISODE --- Further Comments}
10:
11: \begin {document}
12:
13: \maketitlepage
14:
15: \begin {bwslide}
16: \ctitle {Overview}
17: \begin {itemize}
18: \item To complement Marshall Rose's talk
19: \item To give a European perspective
20: \item To give some more details on lower layers and ASEs (other talks focus
21: on the applications)
22: \end {itemize}
23: \end {bwslide}
24:
25: \begin {bwslide}
26: \ctitle {Coding Approaches}
27: \begin {itemize}
28: \item Procedural interfaces corresponding to service definitions
29: \begin {itemize}
30: \item Easy to understand
31: \item Flexible
32: \item General
33: \item Sometimes wrong (e.g. RTS)
34: \end {itemize}
35:
36: \item Full implementations of the protocols and services
37:
38: \item All ASEs and lower layers can be used asynchronously
39: \begin {itemize}
40: \item Must be suitable support from Transport or Network interface (e.g.,
41: Sockets)
42: \item Needs to have sufficient kernel buffering for OPDU writes
43: \item ISODE deals with OPDU read buffering
44: \end {itemize}
45:
46: \item Flexible layering
47: \end {itemize}
48: \end {bwslide}
49:
50:
51:
52: \begin {bwslide}
53: \ctitle {What about the X.25}
54: \begin {itemize}
55:
56: \item X.25/CONS is essential for real OSI
57: \begin {itemize}
58: \item Statement of religion
59: \item TCP/IP or TP4/CLNS are not suitable/desirable for WANs
60: \end {itemize}
61:
62: \item Current implementations
63: \begin {itemize}
64: \item SUNOS + SUNLINK X.25
65: \item Vax + BSD UNIX + UBC Code + DMF 32
66: \item Vax + Ultrix + CAMTEC Dexpand with X.25 or Pink Book (latter is not a
67: product).
68: \item Straightforward to add in others
69: \begin {itemize}
70: \item Easiest if socket-like interface
71: \item Device-like interface possible
72: \end {itemize}
73:
74: \end {itemize}
75: \end {itemize}
76: \end {bwslide}
77:
78:
79: \begin {bwslide}
80: \ctitle {What about the X.25 (2)}
81:
82: (or why TCP/IP is used on UNIX LANs)
83:
84:
85: \begin {itemize}
86:
87: \item Problems with UNIX X.25
88: \begin {itemize}
89: \item Not sufficient coverage
90: \item No standard interface
91: \item Poor performance
92: \item Not robust
93: \item Some interfaces will not allow for asynchronous working
94: \item Problem with the implementations, not X.25
95: \end {itemize}
96:
97: \item What is needed
98: \begin {itemize}
99: \item Standard interface (POSIX transport may give this)
100: \item Pink Book
101: \item Realistic Performance
102: \end {itemize}
103:
104: \item ISODE supports X.25, but X.25 does not support ISODE
105:
106: \end {itemize}
107: \end {bwslide}
108:
109: \begin {bwslide}
110: \ctitle {Transport}
111: \begin {itemize}
112: \item TP0 is a part of ISODE
113: \item TP0++ over TCP in ISODE
114: \begin {itemize}
115: \item RFC 1006
116: \item Best choice in LAN environment (currently)
117: \end {itemize}
118:
119: \item Straightforward to interface to other Transport {\em Services}
120:
121: Variety of application disciplines:
122: \begin {itemize}
123: \item Use of Transport Daemon (tsapd)
124: \item Application Servers
125: \item Callback
126: \item Multithreading
127: \end {itemize}
128:
129: \item TP0 extensively tested
130: \end {itemize}
131: \end {bwslide}
132:
133: \begin {bwslide}
134: \ctitle {Session}
135:
136: \begin {itemize}
137: \item Full Session Protocol and Service implemented
138: \item Substantial interworking tests
139: \item Version 2 (88) in ISODE 4.0
140: \end {itemize}
141:
142: \end {bwslide}
143:
144:
145: \begin {bwslide}
146: \ctitle {Presentation}
147: \begin {itemize}
148: \item Most of Protocol and Service implemented
149: \item IS
150: \item Simple and Full encoding
151: \item X.410 mode
152: \item Some interworking (FTAM + VTP)
153: \end {itemize}
154:
155: \end {bwslide}
156:
157:
158:
159: \begin {bwslide}
160: \ctitle {ASN.1}
161:
162: \begin {itemize}
163: \item Not bound to presentation layer
164: \item Special Tools (discussed elsewhere)
165: \item Abstract representation as C structures as intermediate form
166: \item Used extensively
167: \item Tools have handled a wide range of specifications
168: \end {itemize}
169: \end {bwslide}
170:
171: \begin {bwslide}
172: \ctitle {ACSE}
173: \begin {itemize}
174: \item Full implementation (lots of parameters)
175: \item The interface used by the application
176: \item AE Titles still a problem
177: \begin {itemize}
178: \item OBJECT IDENTIFIER used by stub directory
179: \item Distinguished Name will be used in QUIPU context
180: \end {itemize}
181:
182: \end {itemize}
183: \end {bwslide}
184:
185:
186:
187: \begin {bwslide}
188: \ctitle {RTS}
189: \begin {itemize}
190: \item 1988 and 1984 (X.410)
191: \item Some interworking tests of X.410 done
192: \item Not spooled (i.e. RTS application has to do the work)
193: \item New interface being done
194: \end {itemize}
195: \end {bwslide}
196:
197:
198: \begin {bwslide}
199: \ctitle {ROS}
200:
201:
202: \begin {itemize}
203: \item Full implementation
204: \item ROSY/POSY facilitate use
205: \item Various versions
206: \begin {itemize}
207: \item X.410
208: \item ECMA ROS (BCS Session)
209: \item 1988 ROS (RTS optional)
210: \end {itemize}
211:
212: \item Common interface, except for initialisation
213:
214: \item ECMA ROS used by THORN
215:
216: \item 1988 ROS (no RTS) used by other ROS applications
217: \end {itemize}
218: \end {bwslide}
219:
220:
221:
222: \begin {bwslide}
223: \ctitle {Performance}
224: \begin {itemize}
225: \item Full implementation leads to large processes:
226: \begin {itemize}
227: \item Minimum 300kbyte
228: \item DSA 500 kbyte
229: \item FTAM 800 kbyte
230: \end {itemize}
231:
232: \item Substantial effort to avoid byte copying
233: \begin {itemize}
234: \item qbufs
235: \item PPPPPP
236: \end {itemize}
237:
238: \item Low bulk transfer overheads
239: \begin {itemize}
240: \item ROS is 12\% slower than raw TCP
241: \item FTAM is 8\% slower than Arpanet FTP
242: \item More CPU intensive
243: \item X.25 too slow to be relevant
244: \end {itemize}
245:
246: \item Initialisation not so fast
247: \begin {itemize}
248: \item Typically a few seconds
249: \item Paging in process is a big overhead
250: \end {itemize}
251:
252: \end {itemize}
253: \end {bwslide}
254:
255:
256: \begin {bwslide}
257: \ctitle {How good is it really?}
258: \begin {itemize}
259: \item Does not claim to be production quality
260: \item Better than much ``production software'' I have seen
261: \item Code Quality
262: \begin {itemize}
263: \item Few comments
264: \item Well structured
265: \item Long variable names
266: \item Documented (700 pages)
267: \item Careful version control
268: \item Thorough testing of releases
269: \end {itemize}
270:
271: \item Ideal for experimentation and early services
272:
273: \item Possible drawbacks for products
274: \begin {itemize}
275: \item Lower layers and ASEs not tuned for specific applications
276:
277: \item ASN.1 Tools
278: \begin {itemize}
279: \item Good overall functionality, but
280: \item Too much code output
281: \item Memory based
282: \item Need SOPY
283: \end {itemize}
284:
285: \end {itemize}
286:
287:
288: \end {itemize}
289:
290: \end {bwslide}
291:
292: \begin {bwslide}
293: \ctitle {Other Applications}
294: \begin {itemize}
295: \item NRS Lookup Protocol
296: \item IDIST (ROS based RDIST)
297: \item Management Protocols
298: \item ODA/ODIF
299: \end {itemize}
300:
301: \end {bwslide}
302:
303:
304: \end {document}
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