RFC 914 (rfc914) - Page 1 of 22

Thinwire protocol for connecting personal computers to the Internet

Network Working Group                                    David J. Farber
Request for Comments: 914                                   Gary S. Delp
                                                         Thomas M. Conte
                                                  University of Delaware
                                                          September 1984

                          A Thinwire Protocol
                   for connecting personal computers
                            to the INTERNET

Status of this Memo

   This RFC focuses discussion on the particular problems in the
   ARPA-Internet of low speed network interconnection with personal
   computers, and possible methods of solution.  None of the proposed
   solutions in this document are intended as standards for the
   ARPA-Internet.  Rather, it is hoped that a general consensus will
   emerge as to the appropriate solution to the problems, leading
   eventually to the adoption of standards.  Distribution of this memo
   unlimited.

What is the Problem Anyway ?

   As we connect workstations and personal computers to the INTERNET,
   many of the cost/speed communication tradeoffs change.  This has made
   us reconsider the way we juggle the protocol and hardware design
   tradeoffs.  With substantial computing power available in the $3--10K
   range, it is feasible to locate computers at their point of use,
   including in buildings, in our homes, and other places remote from
   the existing high speed connections.  Dedicated 56k baud lines are
   costly, have limited availability, and long lead time for
   installation.  High speed LAN's are not an applicable interconnection
   solution.  These two facts ensure that readily available 1200 / 2400
   baud phone modems over dialed or leased telephone lines will be an
   important part of the interconnection scheme in the near future.
   This paper will consider some of the problems and possibilities
   involved with using a "thin" (less than 9600 baud) data path.  A trio
   of "THINWIRE"  protocols for connecting a personal computer to the
   INTERNET are presented for discussion.

   Although the cost and flexibility of telephone modems is very
   attractive, their low speed produces some major problems.  As an
   example, a minimum TCP/IP Telnet packet (one character) is 41 bytes
   long.  At 1200 baud, the transmission time for such a packet would be
   around 0.3 seconds.  This is equivalent to using a 30 baud line for
   single character transmission.  (Throughout the paper, the assumption
   is made that the transmission speed is limited only by the speed of
   the communication line.  We also assume that the line will act as a
   synchronous link when calculating speed.  In reality, with interrupt,
   computational, and framing overhead, the times could be 10-50%
   worse.)

   In many cases, local echo and line editing can allow acceptable


Farber & Delp & Conte