RFC 64 (rfc64) - Page 2 of 4

Getting rid of marking

RFC 64                   Getting Rid of Marking


we first have to shift the whole message. We must detect the firsl 1
following the leader, and from this determine that we must shift the
message 4 bits to the left. This takes approximately 12 �sec per double
word, which makes 1,5 msec per full regular message. This is not huge,
but still it is about one-third of the time it will take to translate
the message in internal code.

1.2 Inefficiency in transmission

      More important is the inefficiency resulting from adding
unnecessary bits to the message, especially if it turns out that one
character messages are used. Figure 1.2 shows the example of a 1
character text sent by the sigma 7, which results in transmitting 112
bits to carry 8 bits of information, thus leading to an efficiency
factor of 0.07. Supression of marking would

                            -----------------------------------
   Sigma 7                  |           leader                |
                            -----------------------------------
   Message                  |00000000000000000000000000000001 |
                            -----------------------------------
                            | text | 000000000000000000000000 |
                            -----------------------------------
   16 bits of padding       | 1000000000000000 |
   added by sending IMP     --------------------

                                figure 1.2

increase this efficiency to 0.10. For a 32 bit text (length of some
control commands), it would increase the efficiency form 0.28 to 0.4.
For one packet messages, the efficiency would still be increased by 3%.

2. A remedy.

      This is a suggested modification of the Host-Imp users interface
which has been tentatively sketched on diagrams extracted form BBN 1822
report.