rfc619.txt

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    December was therefore five times as large as it was in August.

2.  Traffic matrix.  The overall mean round trip delay depends on the
    traffic matrix.  If most of the messages are sent over distances of
    0 or 1 hop the overall round trip delay will be small.  The heavy
    traffic between AMES and AMST over a high-speed circuit in August
    contributed to the small overall mean round trip delay.

3.  Network topology.  The mean round trip delay depends on the number
    of hops between source-IMP and destination-IMP and therefore on the
    network topology.  Disregarding line or IMP failures, the mean
    number of hops for a message in August and December was,
    respectively, 3.24 and 4.02.





Naylor & Opderbeck                                              [Page 5]

RFC 619           Mean Round-Trip Times in the ARPANET        March 1974


4.  Averaging.  The network load, given in number or messages per
    minute, represents an average over a seven-day period.  Even though
    this number may be small, considerable queuing delays could have
    been incurred during bursts of traffic.

5.  Host delays.  The round trip delay includes the transmission delay
    of the first packet from the destination-IMP to the destination-
    HOST; therefore, the mean round trip delay may be influenced by HOST
    delays that are independent of the network load.










































Naylor & Opderbeck                                              [Page 6]

RFC 619           Mean Round-Trip Times in the ARPANET        March 1974


                   Table 1 Mean Round Trip Delay as a
                     Function of the Number of Hops

      #MESSAGES/MINUTE  #SITE PAIRS     MEAN ROUND TRIP DELAY
HOPS   AUG      DEC     AUG     DEC     AUG     DEC    DEC
                                                WITH   W/OUT
                                                STAT   STAT
                                                RPTS   RPTS
O       646.9   378.3    39      45      27      44      41

1       487.6   288.7    86     100      25      65      50

2       191.0   143.1   118     138      70     119      80

3       380.7   226.9   148     168      95     131     112

4       218.5   274.1   176     196     102     167     119

5       276.3   185.6   204     228     109     217     134

6       183.8   136.3   210     258     175     355     167

7       333.6   212.7   218     256     178     301     240

8       156.7   161.1   160     234     222     365     241

9        59.0   160.3   102     208     270     308     218

10       0.6     29.9   40      124     331     939     410

11       1.0     18.9   20       46     344     998     699

12       -       10.2    -       20      -      992     655

13       -        0.01   -        4      -      809     809
















Naylor & Opderbeck                                              [Page 7]

RFC 619           Mean Round-Trip Times in the ARPANET        March 1974


     Table 2  Mean Round Trip Delays for Messages from a Given Site

               #MESSAGES/MINUTE       MEAN ROUND TRIP DELAY
    SITE      AUGUST    DECEMBER   AUGUST   DECEMBER  DECEMBER
                                                WITH   WITHOUT
                                              STATUS    STATUS
                                             REPORTS   REPORTS
 1  UCLA        50.7      40.3       130         282       165
 2  SRI        377.3     147.9        45         189       174
 3  UCSB        80.2      70.3       120         221       161
 4  UTAH        27.0      46.2       136         247       169
 5  BBN        120.4     128.3       110         133       133
 6  MIT        120.6      96.9       126         160       150
 7  RAND        29.3      34.2       127         323       208
 8  SDC          1.7       2.4       521        2068       131
 9  HARV        50.3      96.0       105          88        72
10  LL           4.4       6.7       201         602       187
11  STAN        49.7      39.7       173         300       191
12  ILL         26.8      53.4       158         216       165
13  CASE        57.6       2.5       138        1592       335
14  CMU         61.1      59.5       153         220       170
15  AMES       242.4     114.1        43         120        81
16  AMST       304.0     163.0        39          94        67
17  MTRT        89.5      60.0       126         199       142
18  RADT        27.7      29.1       145         273       160
19  NBST        98.4      48.2       118         213       152
20  ETAT        24.1      20.6       119         280       119
21  LLL          -         6.8         -         721       169
22  ISI        372.0     304.4       110         147       142
23  USCT       298.1     210.3        60          92        70
24  GWCT        10.5      14.1       144         381       102
25  DOCT         5.5       7.0       236         791       171
26  SDAT        14.7      22.9       164         322       177
27  BELV         1.3       2.4       243        1469       466
28  ARPT        57.9      64.3        84         150        93
29  ABRD         1.3       2.4       183        1402       554
30  BBNT        40.8      10.0        75         372       124
31  CCAT       177.7      86.7        83         147       115
32  XROX        56.8      71.7        79         136        78
33  FNWT         2.3       3.5       347        1466       174
34  LBL          1.2       2.7       384        1653       621
35  UCSD        11.9      19.3       237         413       205
36  HAWT        27.5       5.2       654         569       476
37  RMLT        10.4      13.0       122         387        97
40  NCCT         -        59.3         -         110        97
41  NSAT         0.6       3.4      1022        1870      1056
42  LONT         -        20.8         -         998       848
43  TYMT         -         3.7         -        1352       157



Naylor & Opderbeck                                              [Page 8]

RFC 619           Mean Round-Trip Times in the ARPANET        March 1974


44  MIT2         -         5.6         -         720       100
45  MOFF         -         2.4         -        1982       447
46  RUTT         -        22.4         -         271       153
47  WPAT         -         2.7         -        1399       380















































Naylor & Opderbeck                                              [Page 9]

RFC 619           Mean Round-Trip Times in the ARPANET        March 1974


      Table 3  Mean Round Trip Delay for Messages to a Given Site
               #MESSAGES/MINUTE    MEAN ROUND TRIP DELAY
    SITE      AUGUST    DECEMBER    AUGUST    DECEMBER
 1  UCLA        57.1      43.5       134         209
 2  SRI        382.3     149.4        45         158
 3  UCSB        61.1      59.1       117         138
 4  UTAH        28.1      50.4       128         159
 5  BBN        160.8     149.2       185         110
 6  MIT        150.4     107.1       116         130
 7  RAND        22.6      25.0        95         161
 8  SDC          1.7       0.8       149         174
 9  HARV        59.3      98.3       101          70
10  LL           4.6       5.2       195         202
11  STAN        65.3      40.6       135         162
12  ILL         29.1      69.8       156         149
13  CASE        52.6       4.0       127         262