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Network Working Group                                 John DavidsonRequest for Comments #355                             UH-ALOHA SYSTEMNIC # 10597                                           9 June 72Category:  Local Echoing, Remote Echoing, SatelliteReferences:RFC 346                        RESPONSE TO NWG/RFC 346                             John Davidson                              June 9, 1972                                                                [Page 1]

   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   inRFC 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                                                                [Page 2]

   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 ]                                                                [Page 3]