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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

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 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

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 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.

       [ This RFC was put into machine readable form for entry ]
       [ into the online RFC archives by BBN Corp. under the   ]
       [ direction of Alex McKenzie.                      1/97 ]

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