rfc508.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.


RFC 508        Real-Time Data Transmission On The Arpanet     7 May 1973


   On-Line System.  The remaining three tests which failed did not do so
   at any regular time, bit-rate, or buffer size so no definite
   statements can be made about their source of delay.

   The overall picture presented by Table I is very promising.  In 96
   percent of the trials a communications link of the two host computers
   and a portion of the ARPA Network was able to take data from a real-
   time process operating as high as 30,000 bits/second.  Further
   encouragement is given by three additional tests which were carried
   out at 30,000 bps and a buffer size of 2,016 bits.  On 2/5/73 at 2:20
   P.M. a 5-minute test was executed with no gaps.  On 2/6/73 at 11:58
   A.M. the same test was executed for 8 minutes with no gaps.  The
   third test was conducted for 18 minutes on 2/7/73 at 11:53 A.M. with
   no gaps in the process.

   The tests were not carried out often enough or over a long enough
   period of time to obtain any statistical results or predictions. The
   measurement task is made somewhat difficult by the fact that the
   state of the overall communications link is never repeatable from one
   test to the next. For example, it was found that a test which failed
   could usually be repeated successfully, even when it was carried out
   within 15 seconds of the previous test.





























Pfeifer & MacAfee                                               [Page 6]

RFC 508        Real-Time Data Transmission On The Arpanet     7 May 1973


+-----+---------------------------------------------------------------+
|PRO- |                BUFFER SIZE (BITS)                             |
|CESS |                                                               |
|BIT  |---------------------------------------------------------------+
|RATE | 1008  | 2016  | 3024  | 4023  | 5040  | 6048  | 7056  | 8048  |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|5300 | 11:31 | 9:51  | 11:34 | 10:34 | 10:12 | 1:59  | 1:37  | 12:32 |
|     |  158  |  81   |  45   |  41   |  33   |  28   |  24   |   21  |
+-----+-------+-------+-------+-------+-------+-----------------------+
|6000 | 11:32 | 9:52  | 11:40 | 10:35 | 10:13 | 2:00  | 1:38  | 12:36 |
|     |  180  |  89   |  61   |  46   |  37   |  31   |  27   |  23   |
|     |       |-------|       |       |       |       |       |       |
|     |       | 174ms |       |       |       |       |       |       |
|     |       |   1   |       |       |       |       |       |       |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|7200 | 11:33 | 9:54  | 11:41 | 10:36 | 10:14 | 2:01  | 1:39  | 12:37 |
|     |  216  |  109  |  72   |  54   |  44   |  37   |  33   |  23   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|8400 | 11:34 | 7:55  | 11:42 | 10:37 | 10:14 | 2:02  | 1:40  | 12:38 |
|     |  245  |  126  |  82   |  63   |  51   |  42   |  37   |  32   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|9600 | 11:35 | 9:56  | 11:43 | 10:38 | 10:15 | 2:03  | 1:41  | 12:39 |
|     |  287  |  83   |  99   |  73   |  58   |  49   |  42   |  36   |
|     |       |-------|       |       |       |       |       |       |
|     |       | 8 sec |       |       |       |       |       |       |
|     |       |   1   |       |       |       |       |       |       |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|10800| 11:36 | 9:57  | 11:44 | 10:39 | 10:16 | 2:04  | 1:42  | 12:40 |
|     |  318  |  138  |  109  |  81   |  65   |  56   |  47   |  42   |
|     |       |-------|       |       |       |       |       |       |
|     |       |  3 sec|       |       |       |       |       |       |
|     |       |1.5 sec|       |       |       |       |       |       |
|     |       |100 ms |       |       |       |       |       |       |
|     |       |   2   |       |       |       |       |       |       |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|12000| 11:37 | 9:58  | 11:45 | 10:44 | 10:17 | 2:05  | 1:43  | 12:41 |
|     |  358  |  180  |  119  |   91  |   73  |  61   |  52   |  46   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|13200| 11:38 | 9:59  | 11:46 | 10:45 | 10:18 | 2:06  | 1:44  | 12:49 |
|     |  396  |  188  |  132  |  101  |   80  |  67   |  57   |  49   |
|     |       |-------|       |       |       |       |       |       |
|     |       | 438 ms|       |       |       |       |       |       |
|     |       | 269 ms|       |       |       |       |       |       |
|     |       | 100 ms|       |       |       |       |       |       |
|     |       |   2   |       |       |       |       |       |       |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+





Pfeifer & MacAfee                                               [Page 7]

RFC 508        Real-Time Data Transmission On The Arpanet     7 May 1973


|14400| 11:39 | 10:45 | 11:46 | 10:46 | 10:18 | 2:07  | 1:45  | 12:50 |
|     |  428  |  213  |  141  |  107  |  88   |  73   |  62   |  56   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|15600| 11:39 | 10:46 | 11:47 | 10:47 | 10:19 | 2:08  | 1:46  | 12:51 |
|     |  467  |  232  |  156  |  117  |  94   |  79   |  67   |  59   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|16800| 11:40 | 11:15 | 11:43 | 10:48 | 10:20 | 2:09  | 1:47  | 12:52 |
|     |  503  |  243  |  168  |  127  |  100  |  85   |  72   |  63   |
|     |       |-------|       |       |       |       |       |       |
|     |       | 190 ms|       |       |       |       |       |       |
|     |       | 128 ms|       |       |       |       |       |       |
|     |       |  29 ms|       |       |       |       |       |       |
|     |       |   3   |       |       |       |       |       |       |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|18000| 11:41 | 11:17 | 11:48 | 10:49 | 10:21 | 2:10  | 1:48  | 1:00  |
|     |  535  |  266  |  179  |  136  |  107  |  90   |  76   |  68   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|19200| 11:42 | 11:18 | 11:49 | 10:50 | 10:22 | 2:11  | 1:49  | 1:20  |
|     |  573  |  285  |  191  |  144  |  114  |  98   |  82   |  73   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|20400| 11:42 | 11:19 | 11:50 | 10:51 | 10:23 | 2:12  | 1:50  | 1:21  |
|     |  610  |  303  |  202  |  153  |  123  |  103  |  87   |  75   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|21600| 11:43 | 11:20 | 11:51 | 10:52 | 10:24 | 2:13  | 1:51  | 1:22  |
|     |  643  |  327  |  213  |  162  |  130  |  108  |  94   |  81   |
|     |       |       |       |       |       |       |       |-------|
|     |       |       |       |       |       |       |       | 98 ms |
|     |       |       |       |       |       |       |       | 30 ms |
|     |       |       |       |       |       |       |       |  5 ms |
|     |       |       |       |       |       |       |       | 10    |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|22800| 11:44 | 11:21 | 11:51 | 10:53 | 10:25 | 2:14  | 1:52  | 1:27  |
|     |  687  |  344  |  223  |  173  |  138  |  113  |  99   |  86   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|24000| 11:44 | 11:22 | 11:52 | 10:54 | 10:26 | 2:15  | 1:53  | 1:29  |
|     |  712  |  352  |  240  |  180  |  143  |  122  |  103  |  93   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|25200| 11:45 | 11:23 | 11:53 | 10:55 | 10:27 | 2:16  | 1:54  | 1:30  |
|     |  741  |  375  |  252  |  193  |  146  |  126  |  109  |  96   |
|     |       |       |       |       |-------|       |       |       |
|     |       |       |       |       | 149 ms|       |       |       |
|     |       |       |       |       |  70 ms|       |       |       |
|     |       |       |       |       |   2 ms|       |       |       |
|     |       |       |       |       |  13   |       |       |       |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+






Pfeifer & MacAfee                                               [Page 8]

RFC 508        Real-Time Data Transmission On The Arpanet     7 May 1973


|26400| 11:46 | 11:24 | 11:54 | 10:56 | 10:30 | 2:17  | 1:55  | 1:31  |
|     |  786  |  395  |  264  |  203  |  160  |  131  |  113  | 100   |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|27600| 11:47 | 11:27 | 11:55 | 10:57 | 10:31 | 2:18  | 1:56  | 1:32  |
|     |  819  |  410  |  276  |  213  |  167  |  140  |  119  |  104  |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|28800| 11:48 | 11:28 | 11:56 | 11:30 | 10:32 | 2:19  | 1:57  | 1:33  |
|     |  856  |  429  |  287  |  217  |  171  |  145  |  125  |  110  |
+-----+-------+-------+-------+-------+-------+-------+-------+-------+
|30000| 11:49 | 11:30 | 11:57 | 11:33 | 10:33 | 2:20  | 1:58  | 1:34  |
|     |  896  |  447 ||  299  |  224  |  180  |  151  |  129  |  112  |
+-----+-------+------|+-------+-------+-------+-------+-------+-------+
      | 2/7/73 (a.m.)||     2/6/73 (a.m.)     |     2/5/73 (p.m.)     |
      +--------------|+-----------------------+-----------------------+
                     V
        2/5/73            |  2/6/73           |  2/7/73
        5 min. test       |  8 min. test      |  10 min. test
        @ 2:20 pm         |  @ 11:53 am       |  @ 11:53 am
        no gaps           |  no gaps          |  no gaps
        4669 buffers sent | 7141 buffers sent | 16071 buffers sent


     +--              +--------+
     | time of day----|  9:35  |    Results of a test for transmitting
     | # buffers sent-|   76   |    data from a continuous external
     |                |--------|    process at UCSB (SEL 810B computer)
 KEY-| max. gap time--| 119 ms |    through the UCSB Host computer, over
     | avg. gap time--|  50 ms |    the ARPA network, and into a UCLA
     | min. gap time--|   2 ms |    (site 65) Host discard socket
     | # gaps (discon-|   3    |    (socket 9).  Each test (approx.) 30
     |  tinuity in    +--------+    sec.
     |  process)
     +--

VII. CONCLUSIONS

   Based upon the results of this experiment the following conclusions
   can be drawn:

      1) High bit-rate real-time processes can use the ARPA Network to
         transmit data for relatively long periods of time.

      2) Real-time processes accessing the Network through large-scale
         timesharing host computers can expect arbitrary delays or gaps,
         probably attributable to the host computers and not the
         Network.





Pfeifer & MacAfee                                               [Page 9]

RFC 508        Real-Time Data Transmission On The Arpanet     7 May 1973


      3) Techniques for handling gaps of 1/2 to 1 second may be possible
         but 8 second gaps, as measured in this experiment, will cause
         extreme hardship on any real-time process.

   This experiment has pointed up the need to conduct additional tests
   using a complete transmission link with actual data and with
   monitoring equipment at both the sending and receiving ends. Our
   current and future efforts are directed toward carrying out such
   experiments.

REFERENCES

[1]  "Interface Message Processors for the ARPA Computer Network",
      Quarterly Technical Report No. 16, 1 Oct 1972 to 31 Dec 1972,
      Bolt, Beraneck and Newman, Inc.

[2]   Semiannual Technical Summary on Graphics, Lincoln Laboratory,
      Massachusetts Institute of Technology, Nov 1971.

[3]   D.L. Retz, "An Interactive System for Signal Analysis: Design,
      Implementation, and Applications", CSL Report No 25, Computer
      Systems Lab, University of California, Santa Barbara, CA, 1972.


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Pfeifer & MacAfee                                              [Page 10]