RFC355 - Response to NWG/RFC346

Network Working Group John Davidson

Request for Comments #355 UH-ALOHA SYSTEM

NIC # 10597 9 June 72

Category: Local Echoing, Remote Echoing, Satellite

References: RFC346

RESPONSE TO NWG/RFC346

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

in RFC346.

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.

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