Network Working Group                                 John Davidson
Request for Comments #355                             UH-ALOHA SYSTEM
NIC # 10597                                           9 June 72
Category:  Local Echoing, Remote Echoing, Satellite
References:  RFC 346



                        RESPONSE TO NWG/RFC 346
	

                             John Davidson

                              June 9, 1972

   Long transmission delays such as those inherent in satellite
   communication are most certainly a cause for concern among users of
   remote interactive systems.  Since the University of Hawaii will, by
   the end of this year, be linked to the ARPANET via satellite, the
   consequences of such delays are perhaps of more immediate concern to
   us than to current members of the surface net.  Consequently the BCC
   500 research group here has been studying various solutions to the
   problems of buffer allocation, partitioned echoing, etc. re-introduced
   in RFC 346.

        Generally, the solutions come from extensions to the original
   design concepts of the BCC 500 distributed communication system.  The
   500 was designed to serve a large number of geographically-scattered
   users each of whom accessed the central computing facility through one
   of several remote concentrators.  [The concept is not too unlike that
   of users at different TIPs all accessing a single host.] Since it was
   felt that in full-duplex, character-by-character interaction, echo
   delays of any noticeable length should not be tolerated, a facility
   was provide whereby the concentrator could provide local (to the
   terminal) echoing when deemed appropriate.  (A character input/output
   microprocessor, the CHIO, in implicit conjunction with the terminal
   user's process executing in the CPU dictated when it was appropriate.)
   The problems associated with coordinating the concentrator and CHIO in
   the partioning of echoing were solved for the BCC 500, but are not
   immediately extensible to the asynchronous message transmissions of
   the ARPANET - especially with the introduction of satellite delays.
   As stated, we are working on some viable alternatives.

        It is not known, at present, what effects the incorporation of
   these partitioned echoing techniques might have on the existing net.
   Perhaps local echoing will become a function of User TELNETs; most
   certainly local echoing should be available in the TIP.  But could it
   be incorporated into the IMP so that TIP and User TELNETs can be used
   without change?  If so, what happens to the concentrator's local
   echoing capability in a system such as the BCC 500?

        These questions do not have immediate answers.  Other problems
   obviously exist because of the differences in serving system
   conventions for terminal control.  We, in conjunction with the ILLIAC
   group at NASA-AMES, are seeking solutions to such problems in general,
   with an eye toward their implementation

   on the net.  I would appreciate hearing of any other research being
   performed in this area, and will be happy to discuss the findings of
   our group with any interested parties.















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