RFC 65 (rfc65) - Page 1 of 2

Comments on Host/Host Protocol document #1

Network Working Group                                        Dave Walden
Request for Comments: 65                       A/S Norsk Data-Elektonikk
                                                         August 29, 1970


  Comments on Host-Host Protocol Document No. 1 (S. Crocker - 8/3/70)

   Page 3.   Eliminate marking.  Instead, make all regular messages into
   two message: The first containing just the leader and indicating that
   the data follows in the second (next) message.  Do this both from the
   source Host to its IMP and from the destination IMP to its Host.
   Thus, no more hunting for the beginning of the data is necessary.
   Once this adjustment is made, an additional simplification is
   available.  If the maximum message length is a common multiple of the
   word sizes of all the computers in the network (perhaps 2880*2 bits),
   successive messages of long files can be dropped in place without
   shifting.

   Page 4.   Control messages should be sent to and from the _control
   socket_  -- not over the control link.  The concept of the control
   link causes a great big, unnecessary special case.

   Page 5.   Assigning sockets permanently to certain network resources
   should be encouraged and a directory of the socket/resource
   associations should be available somewhere in the network, perhaps in
   physical book form at each site.

   Page 6.  Links have no Host-Host purpose other than identifying a
   connection so that socket numbers don't have to be included in all
   messages and to simplify table look-ups in the NCPs.  However, since
   there are possibly 512 links* with the same number, links don't aid
   table look-ups very much.  Also finding the next available link to a
   particular destination is very ugly .  Therefore, I suggest limiting
   the number of links to a total of n (where n = 32, 64, or 256 or some
   other good number) for all destinations.  In other words, a
   particular link is only in use to one destination at a time(actually
   from one destination at a time since the receiver picks the link to
   be used for a connection).  This change makes picking the next
   available link very simple and,I feel,is a worthwhile change if only
   for this reason.  The question of simplifying table look-ups is a
   little more complex.  It is easy to use the link directly as an index
   into tables in the receive portion of the NCP since the receiver
   picks the link.  But a hash table or linear search or something is
   still necessary in the send portion of the NCP.  This too can be
   fixed with the following changes.  Add to STR a _pseudo link_  chosen
   by the sender. This link is sent in all non-control messages in the 8
   --------------------------------------
   *A destination number is 9 bits.



Walden