II-3-2  Interface table.

   It is through this table that the network program informs the handler
   with the location and length of the emitting data.

   This table could be a ring table with 2 pointers: one for filling,
   the other for extracting.  They are respectively updated by the
   network and the handler program.


















 
RFC 7                      Host-IMP Interface                   May 1969


                      [Length] of the message
                           contained
                           in the buffer
                               ^
                               |
           +--------------+----------+
           | Buffer addr. | nb bytes |
           +--------------+----------+
           |              |          | <== Filling pointer
           +--------------+----------+         |
           |                         |         V
           |                         |
           //                        //
           |                         |
           |                         |
           |                         |
           +--------------+----------+
           | Buffer addr. | nb bytes | <== eEtracting pointer
           +--------------+----------+         |
           | Buffer addr. | nb bytes |         V
           +--------------+----------+



III.  Questions.

III-1.  Why is there not a simple control procedure between the HOST and
        the IMP?  What happens if a message, issued from the HOST,
        reaches the IMP with an error due to the transmission?

   From the BBN specifications it appears that this error will be
   transmitted as far [as] the receiving HOST.

   In that case must an HOST-HOST control procedure be provided?

III-2.  Where will the special channel hardware unit be connected
        (MIOP/SIOP)?

   How will this device be notified of an outgoing message end in order
   to start the padding?

   (The program will provide to the MIOP SIOP the number of bytes of the
   outgoing message, and will receive back an interrupt when the last
   byte is sent out.  Is it that signal which will be also sent to the
   special device?)

   Vice versa how does the Handler know the length of the incoming
   message?  From the contents of the previous one or should this




 
RFC 7                      Host-IMP Interface                   May 1969


   program always ready to receive a message of maximum length?  (Then
   an interrupt should be triggered when the real end is detected by the
   hardware).

III-3.  When does the Gordo documentation will be available in order to
        design the user-network program interface.  What are the
        mechanisms for program initiations, transferring parameters from
        one program to another, etc...